Download Physical Geology Laboratory Manual - e

GE-101
Physical Geology
Laboratory Manual
Printed by
The QCC Press
page 1 OUT
Physical Geology
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
LABORATORY OUTLINE
GE-101
Text: Laboratory Manual for GE-101 : Frishman, Rance, Scal
COMMON ROCK FORMING MINERALS AND ROCKS
page
1
Physical properties of common rock forming minerals
2
Quiz 1
Igneous rocks
17
Quiz 2
Sediments and sedimentary rocks
29
Quiz 3
Metamorphic rocks
43
Quiz 4
Review of common minerals and rocks
55
3.
4.
5.
6.
3
TEST 1 minerals and rocks
TOPOGRAPHIC MAPS
7.
Contour lines and topographic profiles
Film and Quiz 9: “Beach - a river of sand”
Homework
55
64
66
8.
Quiz 10
Topographic maps, Areal photographs
Homework
67
TEST 2
72
9.
Areal photographs topographic maps and profiles
ORE MINERALS
10.
11.
Quiz 5
Ore minerals, physical properties
73
Quiz 6
Ore minerals, chemical properties
87
Homework: Collection of soil sample for Soil Science laboratories 12 and 13
98
SOIL SCIENCE
12.
13.
Quiz 7
Soil science, physical
99
Quiz 8
Soil science, chemical
109
Please note: Bring a pencil to every laboratory. Laboratory results may be refused unless they are in
pencil. The last laboratory period 14 is omitted in lieu of the required field trip. Laboratory quizzes will be
given at the beginning of the laboratory. Missed quizzes cannot be made up.
This MANUAL will be collected and graded at the end of the term.
page 2
INT
THE ROCK CYCLE
There are three types of rocks. They are: igneous, sedimentary, and metamorphic. These types of
rock have different origins. One type of rock can become another type. The Rock Cycle (Figure 1) is a
description of how Earth’s materials can be cycled. On Earth, rocks do not last forever but their material
can be cycled into forming other rocks and this can happen again, and again, in several ways.
Figure 1
A simple description of the rock cycle is: An igneous rock, such as a granite, becomes exposed at
Earth’s surface. Mechanical weathering breaks up the granite into rock fragments and mineral grains.
This process is aided by chemical weathering that changes feldspar and ferromagnesian minerals, but not
quartz, to clay and dissolved salts. These materials together are the components of soil. Soil is eroded
(removed by denudation and leaching) and its components are separated and sorted as they are
transported to where they accumulate as sediments such as: gravel, sand, mud, and salt deposits. In time,
sediments lithify (harden) to sedimentary rock such as: conglomerate, sandstone, shale, and limestone.
Burial causes the temperature of the sedimentary rock, and the pressure on it, to increase. The rock
recyrstallizes, but it does not melt in doing so, and with a new appearance it is called a metamorphic rock
such as: quartzite, slate, schist, gneiss, and marble. Deeper burial and radioactive heating can cause rock
to melt to a magma. Magma is buoyant and so it will rise to intrude at higher levels or erupt at Earth’s
surface as a lava. In both places, it cools and hardens to an igneous rock.
Other pathways are given in Figure 1 for the cycling of Earth’s materials from one rock type to
another or as a replacement of itself.
Sun’s radiant energy drives the rock cycle at Earth's surface. Within Earth, primordial and
radioactive-mineral’s emitted heat drives the rock cycle.
page 3
GE-101 Sect:
Physical Geology
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Instructor:
Date:
/
Your name:
Laboratory module: Physical properties of rock forming minerals
Objectives: After completing this laboratory you should be able to:
1.
Distinguish between minerals and non-minerals.
2.
Understand the difference between crystal faces and crystal cleavages..
3.
Recall several or the most common rock forming minerals.
EQUIPMENT CHECK LIST (Report any missing items to the laboratory proctor)
Material
Description
MINERALS
Mineral hand specimens without crystal faces.
A reference collection of 6 identified museum
specimens with crystal faces 1
1 set
CHEMICALS
Dilute (5%) hydrochloric acid in a dropper bottle
2
GEOLOGICAL
EQUIPMENT
Window glass, 3" square plate with beveled edges
(for hardness tests)
Calcite cleavage blocks (for hardness tests)
Streak plate (unglazed porcelain plate)
Pocket knife (blades blunted)
Hand lens
1
Ask proctor for location and handling procedure
per
Student
per
Table
1
1
1
2
MIN
/
page 4
Section I
MIN
MINERALS
Minerals are defined to be naturally occurring, inorganic, crystalline substances. A mineral's name
is a class name that refers simultaneously to two criteria: chemical composition and symmetry of internal
crystal structure. Symmetry of internal crystal structure is fixed for each mineral. Chemical composition
can either be fixed or can have any value within a range: limited by the crystal structure and the
requirement that the symmetry of the crystal structure remains unchanged. Minerals can be distinguished
less specifically by their physical and chemical properties. Procedures, either elementary or advanced,
exist whereby the composition, physical properties or chemical properties of a mineral can be determined.
Determinations of the symmetry of internal crystal structure and the arrangement of component atoms can
be obtained by advanced X-ray methods.
A mineral's symmetry of internal structure can be partly discerned in the external geometric form
of its crystals, when these are found, or in the way some can be found to break in a regular manner.
A mineral is said to exhibit crystal faces when it is bounded by smooth, flat, surfaces which can be
argued to be a product of unrestricted crystal growth. A crystal grows by the orderly bonding of compatible
material to its exterior surfaces. Crystal faces will not be present when a crystal has grown to fill an
unyielding preexisting space or when the crystal faces have subsequently been broken away.
A mineral is said to exhibit crystal cleavage when smooth, planar parting surfaces are found where
a portion of a crystal has been broken away or can be seen to divide it internally. Not all minerals exhibit
cleavage. When a mineral is broken in a direction other than that of cleavage the resulting irregular surface
is called a fracture surface.
As early as 1600, R. J. Haüy (Ah-you-ee) recognized the existence of crystal faces and cleavage,
when present, could be explained if each mineral crystal is made from a systematic arrangement and
holding together of building blocks (see Figure 2). In 1920, W. L. Bragg showed that crystalline substances
diffract X-rays in a way that is consistent with the idea that all minerals are constructed of building blocks
(later called unit-cells) of a definable symmetry. In principle, a unit-cell constitutes the smallest possible
sample of a mineral.
Figure 2
page 5
Exercise 1
MIN
EVALUATION QUESTIONS
What by definition is necessarily true of a mineral?
Summarize (after discussion with your laboratory instructor) why each of the following substances is or is
not a mineral:
Synthetic ruby
Potassium
Garnet
Native Silver
Coal
Crude oil
Graphite
Glacial ice
Flint
Natural volcanic glass
Quartz
Granite
Can differently named minerals have the same composition? (yes, no) Explain.
What can be said to be the same, and unvarying, in all samples of the same mineral?
What are crystal faces?
How do crystals grow?
Give two reasons why mineral species need not be bounded by crystal faces.
What is crystal cleavage?
Do all minerals exhibit cleavage? (yes, no) Explain.
Can crystals be divided into smaller and smaller pieces indefinitely? (yes, no) Explain.
page 6
MIN
Section II
Exercise 2
CLEAVAGE AND FRACTURE
The given minerals are fragments broken out of larger specimens. As a result they are not bounded by
crystal faces. Your problem is to examine the given set of identified minerals with the purpose of
classifying them by the way they have broken.
Procedure: Work with one specimen at a time. Record your results in Table 1.
Step 1. Write mineral specimen numbers in each stage of the classification.
Stage 0. Pick up a mineral specimen and note the specimen number.
Stage 1. Cleavage is present if, when the mineral is turned, reflected light is seen to flash off
several stepped flat surfaces simultaneously. Otherwise, the mineral has no cleavage. See Figure 3.
Stage 2a. If cleavage is present, minerals that cleave in: (see Figure 3, page 8)
One direction - break into flakes or thin slabs
Two directions - break into slabs, columns or blades with rough ends
Three directions - break into regular blocks
Four directions - break into four sided pyramids
Six directions - break to yield flat surfaces, seemingly in every direction
Stage 2b. If cleavage is not present, then the mineral fracture can be described as:
Conchoidal - exampled by the way glass can break to yield curved and shell-like fracture surfaces
Uneven - breaks to yield rough, irregular, shiny surfaces
Earthy - breaks to yield rough, irregular, dull or powdery looking surface
Splintery - breaks into splinters or hair-like fibers
Stage 3. For minerals with two or three cleavage directions, note whether cleavages meet at (or
approximately at) right angles or at distinctly oblique angles.
Step 2. Check your results against the key provided by your laboratory instructor and investigate the
reasons for any errors.
Figure 3
Perfect cleavage is easily recognized, for it characteristically develops a smooth, even surface which will reflect
light (arrows) like a mirror (A). Cleavage planes may occur in a step-like manner, however, and appear at first
to be an irregular fracture. If the specimen is rotated in front of a light, the small parallel cleavage planes will
reflect light in the same manner as a large, smooth cleavage surface (B). An uneven fracture will not
concentrate light in any particular direction (C).
page 7
Table 1
CLASSIFICATION (CLEAVAGE OR FRACTURE)
Cleavage present
One direction
Two directions
At right angles
At oblique angles
Three directions
At right angles (cubic)
At oblique angles (rhombohedral)
Four directions
Six directions
Fracture only
Conchoidal
Uneven
Earthy
Splintery
Stage 0
Stage 1
Stage 2
Stage 3
MIN
page 8
MIN
(A) One direction of cleavage.
(B) Two directions of cleavage that
intersect at 90° angles. Feldspar is an
example.
(D) Three directions of cleavage that
intersect at 90° angles (cubic). Halite is
an example.
(F) Four directions of cleavage. Diamond
is an example.
(C) Two directions of cleavage that do
not intersect at 90° angles. Amphibole is
an example.
(E) Three directions of cleavage that do
not intersect at 90° angles
(rhombohedral). Calcite is an example.
(G) Six directions of cleavage. Sphaierite
is an example.
Figure 3 Possible types or mineral cleavage. After R. D. Dailmeyer, Physical Geology
Laboratory Manual, Dubuque, Iowa: Kendall-Hunt Publishing Company, 1978.
page 9
Exercise 3
MIN
HARDNESS
A mineral's hardness is a measure of its ability to withstand abrasion and scratching by other substances. In
Mohs hardness scale, materials are ordered according to increasing relative hardness on a scale that runs
from 1 (talc) through 10 (diamond). In terms of this scale, the hardness of skin is about 1.5, a finger nail is
up to 2.5, a knife blade is near 6.5, window glass is 5.5 and a streak plate is near 6.5.
Your problem is to determine the relative hardness of the given minerals by comparison to window glass.
Procedure: Work with one specimen at a time. Record your results in Table 2.
Step 1. Write mineral specimen numbers in each stage of the classification.
Stage 0. Pick up a mineral specimen and note the specimen number.
Stage 1. Place a glass slab on the table (CAUTION: do not hold it in your hand) and see if
you can scratch 1 it with the mineral. If you cannot, the mineral's hardness is less than 5.5 but if you can its
hardness is 5.5 or more. (Your instructor may ask you to skip stages 2 and 3 at this time.)
If time permits: further subdivide the soft minerals by testing their relative hardeness first with your finger
nail and then against the mineral calcite (hardness 3).
Stage 2. Try scratching the specimen with your finger nail using a cutting (do not pull your
nail towards you but use a side to side) motion. If the specimen can be so scratched, it is softer than a
finger nail. If the specimen cannot be so scratched proceed to Stage 3.
Stage 3. See if the smooth cleavage surface of a calcite crystal can be scratched by a sharp
edge of the mineral. If the mineral does not leave a scratch its hardness is less than 3 but if it does its
hardness is 3 or more.
Step 2. Check your results against the key provided by your laboratory instructor and investigate the
reasons for any errors.
1
Rub any powder away with your finger tip. If there is a scratch, it should be deep enough for you to catch your
finger nail in it.
Table 2
H. less than 5.5
(SOFTER THAN GLASS)
H. less than 2.5
H. 2.5 or more
H. between 2.5 and 3
H. more than 3 and less than 5.5
H. more than 5.5
(HARDER THAN GLASS)
Stage 0
Stage 1
Stage 2
Stage 3
page 10
Exercise 4
MIN
LUSTER and COLOR TONE
The color tone of some of the common rock forming minerals is light and for others it is dark. None of the
common rock forming minerals look metallic and their luster is described as nonmetallic. Your problem is
to sort these specimens according to their color tone. Any which look like metals, or which look dull or
earthy, will not be common rock forming minerals, and these are identified differently according to their
streak (see page 14).
Procedure: Work with one specimen at a time. Record your results in Table 3.
Step 1. Write mineral specimen numbers in each stage of the classification.
Stage 0. Pick up a mineral specimen and note the specimen number.
Stage 1. Decide whether the mineral is:
Nonmetallic in its luster (if it is, go to Stage 2),
Metallic in its luster (looks unquestionally like what one might buy as a
metal), or is Earthy (dull)
Stage 2. If the mineral is nonmetallic, decide if it is:
Leucocratic - meaning: light colored (specifically in geology this most often
means: colorless, white, light gray, pink, orange, yellow, blue)
Melanocratic - meaning: dark colored (specifically in geology this most often
means: black, brown, brownish red, green)
Step 2. Check your results against the key provided by your laboratory instructor and investigate
the reasons for any errors.
Table 3
Nonmetallic
Leucocratic
Melanocratic
Metallic or Earthy (dull)
Stage 0
Stage 1
Stage 2
page 11
MIN
Section III
Exercise 5
IDENTIFICATION OF THE COMMON ROCK FORMING MINERALS
You have examined the given common ruck forming minerals for luster, color tone, relative hardness, and
the presence or absence of cleavage. These few physical properties can go a long way toward
distinguishing the several common rock forming minerals. Your problem is to name each of them.
Procedure: Work with one specimen at a time.
Step 1. Refer to your data in Tables 1, 2 and 3.
Write mineral specimen numbers in each stage of:
Table 4 for identification of minerals with nonmetallic luster (pages 12, and 13), and in
Table 5 for identification of minerals with metallic luster or with an earthy (dull) luster
(page 14).
page 12
TABLE 4
LEUCOCRATIC
LUSTER: NONMETALLIC
HARDER
THAN
GLASS
CLEAVAGE
PRESENT
Good cleavage in 2 directions at approx. 90°;
pearly to vitreous luster
FELDSPAR GROUP
Potassium feldspars
KAISi3O8 - Pink, white or
green
Plagioclase feldspars
NaAISi3O8 to CaAl7SiO2
White, blue-gray; striations
on some cleavage planes
CLEAVAGE
ABSENT
SOFTER
THAN
GLASS
CLEAVAGE
PRESENT
CLEAVAGE
ABSENT
Conchoidal fracture; transparent to translucent;
vitreous luster; when present, 6-sided prismatic
crystals
QUARTZ SiO2 (silica)
Varieties:
Milky: white and opaque
Smoky: gray to black
Rose: light pink
Amethyst: violet
Conchoidal fracture; waxy luster
CRYPTOCRYSTALLINE
QUARTZ, SiO2
Agate: banded
Flint: dark color
Chert: light colored
Jasper: red
Opal: waxy luster
Perfect cubic cleavage; colorless to white;
soluble in water; salty taste
HALITE
NaCl
Perfect cleavage in 1 direction; poor in 2 others
GYPSUM
CaSO, • 2H,0
Perfect cleavage in 1 direction, producing thin
elastic sheets;
MUSCOVITE
KAl2(AISi3O10)(OH)2
Perfect cleavage in 3 directions at approx. 75 º,
effervesces in HC1
CALCITE
CaCO3
Cleavage as in calcite; effervesces in HCl only if
powdered
DOLOMITE
CaMg(CO3)2
Good cleavage in 4 directions; colors: yellow,
blue, green, or violet; transparent to translucent;
cubic crystals
FLUORITE
CaF
Green to white; soapy feel; pearly luster, H =1;
foliated or compact masses; one direction of
cleavage, forms thin scales and shreds
TALC
MgAl2,Si3O10)(OH)2
White to red; earthy mimics; crystals so small no
cleavage; becomes plastic when moistened,
earthy odor
KAOLINITE
Al6Si4O10(OH)3
MIN
page 13
TABLE 4 continued
MELANOCRATIC
HARDER
THAN
GLASS
LUSTER: NONMETALLIC
CLEAVAGE
PRESENT
CLEAVAGE
ABSENT
SOFTER
THAN
GLASS
MIN
CLEAVAGE
PRESENT
Cleavage in 2 directions at approx. 90°;
dark green to black, short prismatic
8-sided crystals
PYROXENE GROUP
Complex Ca, Mg, Fe. Al silicates
Cleavage in 2 directions at approx. 60°;
dark green to black or brown; long
prismatic 6-sided crystals; shinier than
pyroxene
AMPHIBOLE GROUP
Complex Ca, Mg, Fe. Al silicates;
most commonly HORNBLENDE
Olive green; commonly to small glassy
grains; conchoidal fracture: transparent
to translucent, glassy luster
OLIVINE
(Fe, Mg)2SiO4
Red, brown or yellow; glassy luster;
conchoidal fracture, commonly occurs
in well formed 12-sided crystals
GARNET GROUP
Fe, Mg, Ca, Al silicates
Brown to black; l perfect cleavage; thin
flexible elastic sheets
BIOTITE
K, Mg, Fe, Al silicate
Very dark green to brown; 1 cleavage
direction: commonly occurs to foliated
or scaly masses; nonelastic plates;
CHLORITE
Hydrous Mg, Fe, Al silicate
Yellowish brown to black; resinous luster;
cleavage in 6 directions; yellowish
brown or nearly white streak
SPHALERITE
ZnS
page 14
MIN
The following minerals are usually not volumetrically abundant. But when they are, they are conspicuous.
TABLE 5
METALLIC
OR
EARTHY
(DULL)
LUSTER: METALLIC OR EARTHY (DULL)
RED
STREAK
Red to black to steel grey. Earthy, sometimes oolitic or
botryoidal masses.
HEMATITE
Micaceous variety - specular
YELLOW
to
BROWN
STREAK
Yellow brown, brown to black. Often in radiating forms.
GOETHITE
Fe2O3• nH2O
Bog iron ore.
GREEN
Green. Earthy, sometimes botryoidal masses.
MALACHITE
Cu2CO3(OH)2
BLACK
STREAK
Black. Strongly magnetic. Cubic crystals but usually in
granular masses.
MAGNETITE
FeO-Fe203
Lead grey. Cubic crystals. H =2.5.Sp. Gr.=7.4-7.6. Cleavage
perfect cubic. Luster bright silver metallic. Easily recognized
by good cubic cleavage, high specific gravity, and softness.
GALENA
PbS
Steel grey to black. Cleavage, perfect, one direction. H =1-2,
so greasy feel and writes on paper.
GRAPHITE
C
Pale brass yellow. Cubic crystals. H =6-6.5. Fracture uneven.
Crystals have striated faces. Also massive. ‘Fool's Gold.’
PYRITE
FeS2
Brass yellow, often tarnished to bronze or purple. Brittle.
Tetragonal crystals. H =3.5-4.
CHALCOPYRITE
CuFeS2
DISCUSSION: TO DISTINGUISH BETWEEN CRYSTAL FACES AND CLEAVAGE OR FRACTURE SURFACES
The museum collection of identified minerals shows the unbroken crystal form of several of the minerals with which you have been
working. Discuss with your laboratory instructor what features can distinguish a crystal face from a cleavage or fracture surface.
page 15
MINERALS
Multiple choice questions
Petrology is the scientific study of
a. the earth.
b. minerals.
c. rocks.
d. oil and gas.
A mineral can be
a. a liquid.
b, chert.
c. naturally occurring.
d, organic.
All minerals with the same name have the same
a. composition.
b. internal crystal structure.
c. crystal form.
d. solid solution.
The volume of the Earth's crust which is made of
silicates is about
a. 5%
b. 10%
c. 40%
d. 90%
The volume of the Earth's crust which is made of
nonsilicates is
a. 5%
b. 8%
c. 39%
d. 92%
The geometric arrangement of atoms in crystals is
because
a. these are solids.
b. of chemical bonds.
c. of the atom's sizes.
d. all of the above except (a).
An amorphous solid is not
a. flint.
b. obsidian.
d. coal.
e. calcareous shell.
Crystal faces result from
a. crystal growth.
b. the complete infi1ling of a geode.
c. cleavage.
e. none of the above.
MIN
Your name:
date:
The law of constancy of interfacial angles is true
because
a. the size of the crystal faces are equal.
b. the shape of the crystal is unvaried.
c. the internal. geometric arrangement of the
component atoms is fixed.
d. none of the above.
The habit (shape due to growth) of garnet or pyroxene
is
a. columnar.
b. granular, eight sided.
c. blade shaped.
d. fibrous, felted.
Abraham Werner's mineral classification system is
a. natural, as it is based on composition and crystal
structure.
b. artificial, as it is based on only easily observed
pbysica1 properties.
c. quantitative, as it is based on S.G. and hardness.
d. alchemy based on solubility.
Werner's mineral classification system does not use
a. luster.
b. smell.
c. fusibility.
e. sound.
A mineral's luster is judged to be metallic
a. subjectively, based on familiarity with the look of
metals.
b. objectively. based on the color of highlights.
c. because it is opaque and shiny,
d. because it is a good conductor of electricity.
Tbe terms adamantine. glassy, resinous, or earthy
apply to minerals that are
a. metallic.
b. organic.
c. non-metallic.
d. amorphous.
A mineral's specific color can not be
a. diagnostic.
b. reflection.
c. very varied.
d. an indication of composition.
page 16
The streak. of a mineral is the color of the
a. polished mineral.
b. acid treated mineral.
c. crushed mineral.
d. cleavage surface.
The streak. of a mineral is most useful for
distinguishing between
a. non-metallic minerals.
b. metallic minerals.
c. native metals.
d. precious stones.
In Mobs's hardness scale
quartz is:
window glass is:
calcite is:
a. 2
b. 3
c. 5.5
d. 7
MIN
A drop of cold dilute HCl causes effervescence when
placed, where the following mineral has been newly
scratched:
a. halite.
b. gypsum.
c. fluorite.
d. dolomite.
In thin section, viewed in transmitted light
leucocratic minerals are:
melanocratic minerals are:
metallic minerals are:
a. colorless or shadowed gray.
b. white.
c. yellow. blue. pink. or green.
d. opaque.
In hand specimens
melanocralic minerals are usually:
leucocratic minerals are usually:
a. colorless.
b. white. gray. blue, pink, or yellow.
c. black. green, brown, or red.
d. metallic.
The cleavage of
dolomite is:
mica is:
pyroxene is:
a. good in one direction.
b. good in two directions at right angles.
c. cubic.
d. rhombohedral.
A native element is
a. common to a region (indigenous).
b. a crystalline metal or a nonmetal.
c. chemically combined with water.
d. a compound of different elements.
Student mineral collections are usually arranged
according to
a. composition.
b. S. G. (specific gravity).
c. hardness.
d. color.
The metal Al can be extracted economically from an
ore deposit of
a. talc.
b. bauxite.
c. orthoclase.
d. quartz.
The fracture of quartz. olivine. and garnet is
a. hackly.
b. splintery.
c. earthy.
d. conchoidal.
Ore-minerals are mostly
a. silicates.
b. precious metals.
c. nonsilicates.
d. harder than quartz.
A nugget of gold is easy to distinguish because of its
a. magnetism.
b. taste.
c. heft.
d. feel.
page 17
GE-101 Sect:
Physical Geology
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Instructor:
Date:
Your name:
Laboratory module:
Igneous rocks
Objectives: After completing this laboratory you should be able to:
1.
Describe the growth of crystals from a melt a.nd relate your findings to a genetic
classification of the igneous rocks on the criterion of their texture.
2.
Ascertain the probable compositional range of any given igneous rock,
3.
Name igneous rocks on the dual criteria of their texture and composition.
EQUIPMENT CHECK LIST (Report any missing items to the laboratory proctor)
Material
Description
IGNEOUS
ROCKS
Hand specimens
CHEMICALS
Thymol crystals
GEOLOGICAL
EQUIPMENT
Tweezers or measuring spoon (0.5 gm.),
for handling thymol
Petri dish, pyrex
Hot plate
Ice in water in pan
Paper towels1
Binocular microscope
Lens paper1
Knife blade
1
per
Student
per
Table
1 set
2 gms
1 jar
1
1
1
1
1
1
Available in laboratory room
HOMEWORK: Review the properties of the eight common igneous rock forming minerals.
IGN
/
/
page 18
Section I
IGN
IGNEOUS ROCKS
Igneous rocks originate from the solidification of magmas or lavas (molten or partially molten
portions of the earth). At depth: magmas rise under the force of gravity when their density is less than
that of the overlying column of rock. Emplaced at higher levels within the earth: intrusive magmas
solidify to form plutonic rocks. Erupted by volcanism at the earth's surface: extrusive magmas are
referred to as lavas. Volcanism is aided by the expansion of gases evolved from a magma under reduced
pressure near the earths surface and because of partial crystallization (water is left out of the high
temperature minerals). Lavas solidify (congeal) to form volcanic rocks.
Textural varieties of igneous rocks can be related to variations in the solidification history of
parent magmas or lavas.
Magmas of high viscosities are usually emplaced as irregularly shaped plutons: batholiths, stocks
and laccoliths (see Figure 3.1). These cool relatively slowly because of their size and, shape. Magmas of
low viscosities are usually emplaced as tabular plutons: dikes, sills, laccoliths, and lopoliths. These can
cool relatively rapidly when they are thin. Textural varieties of plutonic rocks are related mostly to
magma cooling rates: slow cooling allows for the growth of large crystals whereas fast cooling prevents
the growth of large crystals. Plutonic rocks are characterized by a mosaic of interlocking crystals most of
which can be seen, in a hand specimen, without the aid of a microscope: texture called phaneritic.
Lavas are subject to rapid heat loss and degassing at the earth's surface. Nevertheless, before
congealing, lavas of low viscosities can flow large distances and spread to build plateaus and shield
volcanoes. Lavas of high viscosities flow relatively short distances and build steep sided volcanoes, puys
and spines. Textural varieties of volcanic rocks are related mostly to lava viscosities: low viscosity
promotes crystal growth whereas high viscosity inhibits crystal growth. Volcanic rocks are characterized
by much of their substance being either (1) crystalline but so fine grained that component crystals cannot
be seen in a hand specimen without the aid of a microscope: texture called aphanitic, or (2) a natural
glass: texture called glassy.
Additional igneous rock textural types develop when the history of magma or lava solidification
is complex; involving, for example, a time of slow cooling and partial crystallization followed by a time
of fast cooling and solidification. Hand specimens of such rocks can show early formed large crystals
called phenocrysts, embedded in a later solidified fine grained crystalline or glassy rock, called
groundmass: texture called porphyritic.
Cont. on p.20 –>
Figure 3.1. Intrusive igneous rock bodies. The laccolith and sills are concordant with
the enclosing sedimentary beds, and the batholith and dikes are discordant.
page 19
IGN
Exercise 1 EVALUATION QUESTIONS
Define magma.
At depth, what can cause a magma to rise?
What are igneous rocks called that are inferred to have solidified from intrusive magmas?
What can aid the eruption of lavas?
What are solidified lavas called?
Describe igneous rock textures called:
phaneritic
aphanitic
glassy
What two factors can influence crystal size in igneous rocks?
Are all igneous rocks crystalline? (yes, no) Explain.
In porphyritic igneous rocks, are phenocrysts:
the first formed or the last formed crystals?
noticeably larger or smaller than any ground mass crystals?
Can the groundmass of a porphyritic rock be phaneritic, aphanitic or a glass? (yes, no) Explain.
page 20
IGN
Only eight of all the known elements are abundant in the earth's crust. Igneous rocks
made from these elements occur wherever a magma (a wholly or partially molten portion of the
earth) has solidified. The eight elements: oxygen, silica, aluminum, potassium, sodium,
calcium, iron and magnesium, occur in different proportions in different igneous rocks. Some
igneous rocks are natural glasses, others are aggregates of mineral crystals in which the elements
exist in chemical combinations with each other. Crystalline igneous rocks are usually made of
more than one type of mineral. This is because the chemical composition of any one mineral is
narrowly limited by its crystalline structure.
Eight igneous rock forming minerals are common: quartz, white mica, K-feldspar,
plagioclase, dark mica, hornblende, pyroxene, olivine. No one igneous rock, however, contains
all of these minerals. Minerals which coexist in any one igneous rock are determined by the
percentage abundance of silica in the whole rock. The suggestion here is that in the original
magma, the metalloids silica and aluminum and the nonmetal oxygen combine to behave as an
acid in the presence of metals (potassium, sodium, calcium, iron, magnesium) which behave as
bases. Acids and bases react to build the rock minerals. While such reasoning is by way of
analogy only, a rock that contains much silica is called "acidic" (60 to 100 % SiO2)*, and one
that contains relatively little is called "basic" (40 to 50% SiO2). Igneous rocks of "intermediate"
(50 to 60% SiO2) and of "ultrabasic" (0 to 40% SiO2) composition are also recognized.
In order to divide crystalline igneous rocks into groups of similar chemical composition,
it is usually sufficient either to compare the percentage abundance of common rock forming
minerals in each or, alternatively, to recognize the presence or absence of one of those minerals.
Not counted are minerals which make up less than one percent of the rock. These are called
accessory minerals. For example, quartz (a major component of acidic igneous rocks) can occur
in a basic igneous rock only as an accessory mineral. Also, garnet, atypical of most igneous
rocks, sometimes occurs as an accessory mineral in felsic igneous rocks.
Common igneous rock accessory minerals which are invariably present, but which are
usually hard to see without a microscope, are: magnetite, ilmenite, rutile, and zircon.
*In reporting the chemical composition of a rock, element abundances are quoted as their oxide
abundances as are determined by quantitative chemical analysis.
page 21
IGN
List the eight most abundant elements in the earth's crust:
Why does a crystalline igneous rock usually contain more than one type of mineral?
Can all eight common igneous rock forming minerals coexist in a single rock? (yes, no) Explain.
Which of the eight most abundant crustal elements are nonmetals or metalloids?
Define "acidic" igneous rock:
Can an ultrabasic igneous rock have no silica? (yes, no) Explain.
To divide crystalline igneous rocks into groups of similar chemical composition, is it necessary
to obtain a quantitative chemical analysis of each rock? (yes, no) Explain.
Define accessory mineral:
page 22
IGN
Section II
Exercise 2
CRYSTALLIZATION OF A MELT
Igneous rocks melt at very high temperatures. In this exercise, thymol, an organic
crystalline solid, substitutes for igneous rock because it melts at just above normal room
temperature and, therefore, it can be easily and safely studied. Your problem is to determine
what textural features of a crystalline solid would indicate a history of slow crystallization or of
fast crystallization of a melt.
Step 1. TO OBSERVE SLOW CRYSTALLIZATION
Turn on a hot plate and set to lowest heat. Locate a petri dish (pyrex) and place about 2
gms. of thymol crystals in it. (CAUTION: use measuring spoon or tweezers to handle thymol for
although it is not poisonous, it can irritate the eyes and skin.)
Place the petri dish containing the thymol on the hot plate. Tilt the dish from side to side
occasionally so the melting thymol spreads evenly. (Note: if the thymol fumes excessively, the
hot plate was not set to its lowest heat.) Remove the petri dish when a few specks of crystal
remain. (Note: if you have completely melted the thymol add a tiny bit more.) Place the petri
dish on the stage of a binocular microscope and observe at low magnification. When you see
crystals begin to grow, increase the magnification, adjust the focus and the light, and study, in
detail, the order and manner of crystal growth. (Note: you can repeat the experiment by simply
reheating the petri dish.)
Step 2. TO OBSERVE FAST CRYSTALLIZATION
Partly fill a bowl with water and some ice cubes. Place a paper towel flat on the table
nearby. Heat the petri dish containing the thymol as before. When only a few specks of crystal
thymol remain, remove the petri dish immediately and float it on the top of the iced water in the
bowl. The thymol should crystallize rapidly. Remove, dry base of petri dish on the paper towel
and set it on the microscope stage.
Clean up: Do not try to wash the petri dishes: thymol is insoluble in water. Simply cover and
stack the used dishes.
EVALUATION
Describe in your own words what textural features of a crystal aggregate that has solidified from
a melt, indicates a history of:
Slow crystallization
Fast crystallization
First formed crystals in the aggregate tend to be (circle those which are true):
larger
smaller
anhedral (irregular shape)
euhedral (exhibits crystal form)
page 23
Exercise 3
IGN
IDENTIFICATION OF IGNEOUS ROCK TEXTURES
Igneous rocks result from the solidification of magma or lava. A continuum of possible
textures exists that can be broadly related to the circumstances of solidification. Your problem is
to sort the given igneous rocks according to the identification scheme given in Table 1 and to
learn their textural class names.
Procedure: Work with one hand specimen at a time. Record your results in Table 1.
Step 1. Write the hand specimen number in each stage of the identification. Read the
footnotes to Table 1 as you proceed.
Igneous rocks composed of crystals that can be seen with the naked eye (generally 1-10
mm) are said to have a phaneritic texture (from the Greek word for visible). Phaneritic igneous
rocks with very large grains (generally larger than 1 cm) have a pegmatitic texture. Igneous
rocks composed of crystals too small to be seen with the naked eye (generally less than 1 mm)
have an aphanitic texture (from the Greek word for invisible).
Igneous rocks composed of volcanic glass have a hyaline texture (from the Greek word
for glass) or glassy texture.
Some igneous rocks have two distinct sizes of crystals: these have a porphyritic texture
in which the large crystals are called phenocrysts, and the smaller, more numerous crystals are
called the matrix, or groundmass. There are also porphyritic-aphanitic textures, meaning that the
phenocrysts occur in an aphanitic matrix, and porphyritic-phaneritic textures, meaning that the
phenocrysts occur in a phaneritic matrix.
Vesicles are gas bubbles trapped in a rock. Igneous rocks with vesicles have a vesicular
texture. Occasionally, lavas contain so many vesicles that they are frothy, like whipped egg
whites. Upon cooling, a frothy texture can result in the occurrence of scoria (dark color) or
pumice (light color). Pumice has so many tiny vesicles that it floats on water!
Pyroclasts (from the Greek, "fire broken") are fragmented rocky materials that have been
mechanically transported during explosive volcanic eruptions. They include fragments of
volcanic ash (pyroclasts <2 mm), lapilli or cinders (pyroclasts 2-64 mm), and volcanic bombs
(pyroclasts >64 mm. Igneous rocks composed of pyroclasts have a pyroclastic texture. They
include tuff (composed of volcanic ash) and volcanic breccia (composed chiefly of cinders and
volcanic bombs).
Step 2. Check your results against the key provided by your laboratory instructor and
investigate the reasons for any errors.
Footnotes to Table 1
(1) Each visible crystal (mineral grain) will be fairly uniform in color: its outline may be
irregular or geometric. In a rock, minerals of different color are easily distinguished. When a
rock has a uniform color, rotate it in the light and look for small flat reflective surfaces. If seen,
these are cleavage surfaces of individual crystals (mineral grains).
(2) The smaller crystals (if these exist in the hand specimen) may have geometric outlines.
(3) The smaller crystals have irregular outlines. The rock is made of
(a) some large crystals set in a groundmass small crystals, or
(b) crystals of not greatly contrasting sizes.
(4) The crystals that can be seen, have geometric outlines.
(5) The rock is uniform in color and dull and:
(a) is solid throughout
(b) has spherical voids in it but is relatively heavy (some of the voids may have been
filled with a secondary mineralization—the fillings are called amygdales)
(c) is shiny
(d) has finely alternating dull light colored and shiny dark colored layers
(e) is frothy and noticeably light in weight.
page 24
IGN
Table 1
IDENTIFICATION SCHEME
Mineral grains
can be seen by
the unaided eye.
These crystals
make up more
than 1 percent of
the volume of
the handspecimen.
(1)
TEXTURAL PROBABLE
TYPE
ORIGIN
one or a few very large crystals make
up most of the hand specimen
(2)
Many crystals:
the rock is seen
everywhere to
be made of
crystals
(3)
Stage 0
Stage 1
Phaneritic
Crystals of greatly
contrasting size
(3a)
Porphyritic
Crystals are of
approximately
equant size
(3b)
Phaneritic
Crystals seen are separated by rock
in which crystals cannot be seen
(4)
Mineral grains
cannot be seen
or any crystals
that can be seen
make up less
than 1 percent of
the volume of
the hand
specimen.
Pegmatitic
Phaneritic
Porphyritic
Aphanitic
Rock is solid throughout. Dull in
appearance.
(5a)
Aphanitic
Rock has rounded voids or
amygdales in it and is heavier than
water
(5b)
Vesicular
Rock is shiny and fractures
conchoidally
(5c)
Glassy
Rock is finely layered
(5d)
Glassy
Rock looks frothy and is lighter than
water
(5e)
Vesicular
Rock is composed of fragments
Pyroclastic
Stage 2
P
L
U
T
O
N
I
C
Stage 3
V
O
L
C
A
N
I
C
page 25
Section III
IGN
IGNEOUS ROCK NAMES
Exercise 4
Igneous rocks are classified using the dual criteria of texture and composition (for the
latter, a color index is used when no minerals can be seen).
Procedure: Work with one hand specimen at a time. Record your results in Table 2.
Step 1. Write the hand specimen number in each stage of the identification.
Stage 1. For each specimen, you have already identified the texture. This gives you the
row in Table 2 in which the rock's name will occur.
Stage 2. Decide on the column in Table 2 in which the rock's name will occur.
Igneous rocks composed mostly of quartz, potassium feldspar, and plagioclase
are classified as felsic (light-colored).
Igneous rocks composed mostly of the dark-colored ferromagnesian minerals
(i.e., minerals containing much iron and magnesium) are classified as mafic
(usually black, brown, or deep red in color).
Igneous rocks composed equally of felsic and mafic minerals are classified as
intermediate (gray).
Igneous rocks are composed entirely of ferromagnesian minerals are classified
as ultramafic (usually green or brown in color).
Also, mineral composition of an igneous rock can be approximated using a color index,
which is the percentage (by visual estimation) of dark minerals in the rock:
Fine grained felsic rocks tend to be pink, white, or pale brown
Fine-grained intermediate rocks tend to be greenish-gray
Fine-grained mafic rocks tend to be dark-gray-to-black.
Step 2. The igneous rock's name is where the row and column cross (Step 1). Also note:
Textural terms such as porphyritic and vesicular can be used as adjectives. For example,
one might identify a pinkish, fine-grained, igneous rock as a rhyolite. However, if it contains
scattered phenocrysts, it is a porphyritic rhyolite. Similarly, a basalt with vesicles is a vesicular
basalt.
An igneous rock which has a pegmatitic texture is named, for example: granite
pegmatite, syenite pegmatite, and so on.
page 26
Table 2.
IGN
Classification and Identification Chart for Hand Specimens of IGNEOUS ROCKS
composition
felsic
acidic
light or the color of the K-feldspar
phaneritic
t
e
x
t
u
r
e
aphanitic
VEIN
QTZ.
quartz
(vitreous
to greasy
luster)
GRANITE
visible
quartz
(glassy, gray
color),
K-feldspar
(any color)
RHYOLITE
may have
phenocrysts
of
quartz
and/or
muscovite
SYENITE
(pink color)
orthoclase
feldspar
mafic
intermediate
gray color
basic
usually black color
ultrabasic
green color
DIORITE
(light gray) no
visible quartz,
feldspar,
hornblende
ANORTHOSITE
(gray color)
plagioclase
feldspar,
GABBRO
(black color)
plagioclase
(striated)
feldspar,
pyroxene,
PERIDOTIT
E olivine
(green),
pyroxene
(brown)
ANDESITE
may have
phenocrysts
of amphibole
or feldspar
BASALT
(black color, sometimes dark red
color)
may have phenocrysts
of
pyroxene or olivine
KOMATIITE
DUNITE
olivine
(green)
glassy
OBSIDIAN - massive glass (typically looks lustrous black, but can be of any color (often red or colorless), breaks with a shiny
conchoidal fracture
vesicular
PUMICE - volcanic gas-frothed lava that is light in color, can usually float on
water, and is associated with andesitic volcanism
layered
WELDED TUFF (rhymes with "woof") - pyroclastic (fragmental), fine grained
volcanic ash which, near the volcano, can be partly molten so that the shards
weld into a solid rock called welded tuff or ash-flow tuff. These are built of thin,
alternating, dark (obsidian-like) and light (pumice-like) layers
pyroclastic
TUFF, LAPILLI, VOLCANIC BRECCIA, AGGLOMERATE
SCORIA - like pumice, but with larger
vesicles (gas bubble holes), dark in color
(black or rusty brown), and associated with
basaltic volcanism
KIMBERLITE
page 27
IGN
BOWEN'S REACTION SERIES
Bowen studied the order in which minerals crystallize from a basaltic melt. In this, at
high temperature, two sequences of minerals coexist (Figure 3.2). The minerals which exist, as
temperature is lowered, is determined by reactions with the melt. In one sequence, a polymer
[SiO4]4- in the presence of Fe3+ and Mg2+ ions with lowering temperature gives Bowen's
discontinuous reaction series. In the other sequence, the polymer [Si2Al2O]2- becomes the
polymer [Si3AlO8]1- anwith a substitution of Na1+ for Ca2+ ions with lowering temperature gives
Bowen's continuous reaction series.
In the discontinuous series (olivine6pyroxene6amphibole6biotite), each mineral has a
different structure. The higher temperature mineral in each case dissolves upon the
crystallization of the lower temperature mineral in the sequence.
In the continuous series, the plagioclase structure stays the same but its composition
changes, through a continuum, from being calcium rich at high temperature to being sodium rich
at low temperature.
HIGH
11250C
T
E
M
P
E
R
A
T
U
R
E
6000C
Olivine (monomer, first to crystallize)
`
Ca-plagioclase (3-D open)
Pyroxene (chain)
b
`
Ca,Na-plagioclase (3-D open)
Amphibole (double chain)
b
`
Na-plagioclase (3-D open)
Biotite mica (sheet
`
b
K-feldspar (3-D open)
9
Muscovite mica (sheet)
9
Quartz (3-D solid, last to crystallize)
LOW
Figure 3.2 Bowen's reaction series
MAGMATIC DIFFERENTIATION
Bowen realized that any igneous rock could be derived by a process of magmatic
differentiation of basaltic magma. As this mafic magma cools the first formed crystals are
olivine. These minerals are rich in iron and magnesium and relatively poor in silicon. With
respect to these elements, the remaining uncrystallized melt is depleted in the first two and is
enriched in the third and so it will be more felsic than the original magma. If the olivine is
removed from contact with the remaining liquid, either by settling out as a layer of olivine or by
the a mechanism of filter pressing whereby the remaining liquid is forced away to accumulate by
itself elsewhere, the olivine cannot change to pyroxene because there is no liquid with which it
can react at lower temperatures and an igneous rock made of olivine (called dunite), close in
composition to peridotite, persists. If the remaining liquid continues to cool, minerals of
pyroxene and calcium rich plagioclase will crystallize. The remaining melt becomes even more
felsic. Again this liquid can be separated leaving behind a rock close to gabbro in composition.
In short, by continuing this process, nature can produce diorite and ultimately granite.
Alternatively, the partial melting of peridotite will produce a melt of basaltic
composition. In short, the partial melting of an igneous rock will produce a magma which is
more felsic than the whole rock. In this way the partial melting of continental crustal rocks
(which on average have an andersitic composition) can yield granitic magmas.
page 28
Igneous rock classification (modern simplified)
IGN
page 29
IGNEOUS ROCKS
multiple choice review questions
Your name:
A magma is
a. a stone.
b. an igneous rock.
c. partly molten stony earth material.
d. hardened earth material.
Date:
The composition of igneous rock is
indicated by
a. its temperature.
b. the coexistence of quartz and olivine.
c. its color.
d. the size of its crystals.
Lava can be
a. intrusive.
b. extrusive.
c. a volcano.
d. plutonic.
An igneous texture is "granitic" when it
a. is unlayered.
b. has oriented crystals.
c. is an interlocking mosaic of crystals.
d. all of the above.
Natural glass rarely forms when a melt has
a. cooled and crystallized quickly.
b. a low viscosity.
c. a high silica content.
d. degassed.
The texture of an igneous rock with
phenocrysts is
a. glassy.
b. phaneritic.
c. aphanitic.
d. porphyritic.
Aphanitic is a description of the texture of
a. natural glass.
b. crystalline volcanics.
c. lava.
d. granite.
Vesicles originate when the volatile content
of a lava
a. dissolves.
b. bubbles out of solution.
c. forms pipes at the base of a flow.
d. none of the above.
Plutonic igneous rocks are
a. a mythical Gr. god.
b. intrusive.
c. extrusive.
d. chilled country rock.
Plutonic igneous rock is characterized by
a. glassy interiors and coarse grained
margins
b. vesicles
c. veins formed from residual liquids
d. pillows
IGN
Felsic igneous rocks are mostly
a. K-feldspar (orthoclase).
b. Ca-Na-plagioclase.
c. plagioclase feldspar and ferromagnesians.
d. ferromagnesians.
An igneous rock composed of 25% quartz,
50% orthoclase, and 5% Na-plagioclase is
a. granite.
b. diorite.
c. gabbro.
d. peridotite.
Plagioclase in a gabbro is typically
a. minor.
b. 25%
c. 40%
d. 60%
An igneous rock composed of 80% olivine,
20% pyroxene and plagioclase is
a. granite.
b. diorite.
c. gabbro.
d. peridotite.
page 30
The silica content of diorite or andesite is
said to make it
a. acidic.
b. intermediate.
c. basic.
d. ultrabasic.
The color of gabbro or basalt is
characteristically
a. white.
b. gray.
c. black.
d. green.
An example of an igneous rock made of
more than one mineral is
a. syenite.
b. basalt.
c. dunite.
d. vein quartz.
Visible quartz is always present in
a. granite.
b. diorite.
c. gabbro.
d. rhyolite.
Olivine phenocrysts are often present in
a. rhyolite.
b. andesite.
c. basalt.
d. all of the above.
Amphibole phenocrysts identify an igneous
rock to be a
a. rhyolite.
b. andesite.
c. basalt.
d. komatiite.
Scoria is different from obsidian because it
is
a. a welded tuff.
b. vesicular.
c. dark in color.
d. pumice.
IGN
Obsidian is typically
a. dull black.
b. conchoidally fractured.
c. vesicular, and floats on water.
d. a thin flow.
A sill is a
a. dome shaped extension of a batholith.
b. tabulate pluton that cuts across structures
in the
country rock.
c. tabulate pluton that is conformable with
structures in the country rock.
d. large spoon shaped pluton.
Extensive fissure flows of basalt build
a. plateau basalts.
b. composite volcanoes.
c. puys.
d. basaltic cinder cones.
Alternating flows of andesite and layers of
ash, are characteristic of
a. plateau basalts.
b. shield volcanoes.
c. composite volcanoes.
d. puyes.
Magmatic differentiation can involve
a. partial melting.
b. removal of first formed crystals.
c. cooling.
d. all of the above.
The partial melting of andesite can produce
a magma with the composition of
a. peridotite.
b. gabbro.
c. diorite.
d. granite.
page 31
GE-101 Sect:
Physical Geology
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Instructor:
Date:
/
Your name:
Laboratory module: Sediments and sedimentary rocks
Objectives: After completing this laboratory you should be able to:
1.
Explain how the composition and texture of sedimentary rocks can be indicative of
their origin.
2.
Describe and name a variety of detrital sediments and sedimentary rocks.
3.
Describe and name a variety of chemical sediments and sedimentary rocks.
EQUIPMENT CHECK LIST (Report any missing items to the laboratory proctor)
Material
Description
SEDIMENTS
Hand specimens
(A) detrital
(B) chemical
(sterilized: anhydrite, bittern salt, halite chips)1
1 set
1 set
CHEMICALS
Dilute (5%) hydrochloric acid in a dropper bottle
2
GEOLOGICAL
EQUIPMENT
Window glass, 3" square plate with beveled edges
(for hardness test)
Streak plate
Pocket knife (blades blunted)
Hand lens
AND
SEDIMENTARY
ROCKS
SPECIAL
EQUIPMENT
Wood matches
Alcohol burner
Wire (steel, thin gauge), 1 roll1
Wire holder1
Pliers (wire cutting and shaping)1
1
Available in laboratory room
per
Student
per
Table
1
1
2
2
1 box
2
4
2
/
SED
page 32
SED
Section I SEDIMENT, SEDIMENTS AND SEDIMENTARY ROCKS
Sediment. In the singular the word is usually applied to material in suspension in water or recently
deposited from suspension. In the plural, the word is applied to all kinds of deposits from the water of
streams, lakes, or seas, and in a more general sense to deposits of wind and ice. Such deposits that have been
consolidated are called sedimentary rocks. (Bryan)
Weathering produces the materials of sediments: the dissolved salts and particulate components of soils.
In the zone of weathering, accumulations of these products are soils or colluvium1. These are not considered
to be sediments because, by definition: a sediment is an accumulation of any materials that can be argued to
have undergone significant, prior, transportation by wind, moving water, moving ice or gravity.
Sediments whose material originated as dissolved weathering products are called chemical sediments.
Dissolved materials can be removed from solution: by evaporation of the dissolving medium, by chemical
precipitation or by biochemical mechanisms. In order for a chemical sediment to accumulate, its substance
can be removed from solution either during transportation or at the site of sedimentation.
Sediments whose material originated as particulate weathering products are called detrital sediments. In
order for a detrital sediment to accumulate, its substance must be eroded from the zone of weathering and be
transported, without being wholly dissolved, and be deposited by settling or coming to rest at the site of
deposition.
Particles of any size that have undergone transportation as solid particles are called clasts2. Class names
for clast size ranges are: boulder, cobble, pebble, granule, sand, silt and clay:
Size range (millimeters)
Clast size
>256
64 - 256
4 - 64
2-4
Boulder
Cobble
Pebble
Granule
1/16 - 2
Sand
1/256 - 1/16
<256
Silt
Clay
Sedimentary rocks are divided into two categories: detrital and chemical. Detrital sedimentary rocks
originate by the lithification of detrital sediments. Lithification can result from: the compaction of clasts,
interlocking of clast boundaries (by their recrystallization) or the precipitation between clasts of cementing
material from circulating ground waters. Chemical sedimentary rocks originate: by the direct crystallization
of transported, dissolved, material on a substrate, by the replacement and concomitant lithification of a
sediment by transported, dissolved, material or by the lithification of chemical sediments.
Chemical sedimentary rocks that are not accumulations of clasts have a nonclastic (crystalline or
amorphous) texture. Other chemical sedimentary rocks, for example a collection of shells, and all detrital
sedimentary rocks have a clastic texture.
1
Colluvium, for example talus, is not a sediment because it is material that is currently undergoing
transportation by mass wasting (ongoing downslope movement caused by gravity that acts as a body force).
2
A clast, by definition, must have undergone prior transportation. A crystal which grows and stays in place
is not, for example, called a clast.
page 33
SED
Sedimentary rocks visible in hand specimens or outcrops give the geologist clues to the rock's origin and
environment of deposition. A list of some of the more common features is given below:
a. Particle Size: The size of the particles is an indication of the energy of the transporting
medium. For example, swift streams carry cobbles; wind and waves transport sand
grains; and gentle currents carry, in suspension, clay particles far out to sea.
b. Stratification: Strata, beds, or layers are formed by repeated depositional events, or by a
change in the material supplied to the depositional site. Stratification is the most common feature of
sedimentary rocks.
c. Cross-Bedding: Each stratum is built of beds that are steeply inclined to the horizontal.
These form where a prograding depositional surfaces are at an angle to the
accumulating stratum, such as on the foreset face of a sand dune, river bar, or delta, or where sediment is
delivered from different directions as runnel infillings of a braided stream.
d. Concretions: A localized concentration of cementing material, these are usually resistant to
erosion and may stand out from the rock surface as lumps or bulges.
e. Jointing: A regular pattern of cracks usually perpendicular to bedding planes caused by
breakage due to the weight of overlying rocks.
f. Ripple Marks: Small waves or ripples formed by the movement of water or wind over the
surface of the sediment prior to solidification.
g. Fossils: Any evidence of past life preserved in the rock. May be bone or shell
fragments, footprints, leaf imprints, or organic materials replaced by silica or other
chemicals.
h. Color: Most colors, including red, brown, ochre, green, and purple, are due to various
iron compounds. Black is commonly caused by organic material, and white usually
indicates some salt, clay (i.e., kaolinite), or silica.
i. Cements: Precipitated calcium carbonate, iron oxides (as hematite and limonite), and colloidal
silica (as chert and drusy quartz), are the most common cements in clastic sedimentary rocks
Very angular
Angular
Sub-angular
Sub-rounded
Rounded
Well-rounded
Figure 2.1 Terms for degree of rounding of sand-sized clasts as seen through a hand lens.
Very well sorted
Well sorted
Moderately sorted
Poorly sorted
Figure 2.2 Terms for degrees of sorting.
Very poorly sorted
page 34
Exercise 1
SED
EVALUATION QUESTIONS
What are sediments?
What is a clast?
What is the size range of clasts in pure sand?
Describe three ways that dissolved material can be removed from solution.
What are detrital sediments?
Shell fish can remove dissolved calcium carbonate from water to build their shells. Later some shells can be
moved by water currents to accumulate as sediments. Would such sediments be chemical or detrital?
Describe three lithification mechanisms.
Is it possible to have a chemical sedimentary rock that is not a lithified accumulation of clasts? (yes, no)
Explain.
Do all detrital sedimentary rocks have a clastic texture? (yes, no) Explain.
page 35
Figure 2.3. Sedimentary environments
SED
page 36
Section II
SED
DETRITAL SEDIMENTARY ROCKS
Exercise 2
Detrital sedimentary rocks are aggregates of transported, broken, former rocks or silicate mineral fragments.
All have a clastic texture, therefore. Their composition can be simple or complex. Detrital sedimentary
rocks are classified by dividing them into textural types and further subdividing them into compositional
varieties. Each type or variety within a type is named. Your problem is to name each detrital sedimentary
rock specimen in the given set A..
Procedure: Work with one specimen at a time. Record your results in Table 2.
Step 1. Write rock specimen numbers in each stage of the classification.
Stage 0. Pick up a detrital sedimentary rock specimen and note, the specimen number.
Stage 1. Decide what sized clast (Figure 2.4) makes up most of the rock's volume. If these are:
Larger than sand sized - textural type is:
conglomerate if the clasts are sub-rounded to well rounded (Figure 2.1) or
breccia if the clasts are sub-angular to angular (Figure 2.1).
Sand sized - textural type is:
sandstone. If gravel sized clasts are present, they must make up less than 50% of
the rock's volume.
Silt sized - grains are too small to be seen individually, but when a smooth looking part
of the specimen, is rubbed with the finger tip, it has a gritty feel. Textural type is;
siltstone.
Clay size - grains are too small to be seen individually and when a smooth looking part
of the specimen is rubbed with the finger tip, it feel smooth. Textural type is;
mudstone (if the specimen exhibits little tendency to break into thin sheets) or
shale (if it does tend to break into thin sheets).
Stage 2. Read in Table 2 the compositional varieties listed beside the specimen's
type. Decide which one best describes the specimen.
textural
Step 2. Check your results against the key provided by your laboratory instructor and investigate the reasons
for any error.
Clast diameter
1/16 mm
Clay sized (smooth feel)
to silt sized (gritty feel)
Fine sand
2 mm
Sand
Figure 2.4
Coarse sand
Gravel
Boulders>
page 37
Table 2.
SED
Classification of DETRITAL SEDIMENTARY ROCKS
Textural type
Compositional variety
Rock Name
Environments of sedimentation
Gravel (granules
to boulders)
Rounded clasts often of vein
quartz, or a recognizble rock,
set in finer material such as
sandstone or siltstone.
Conglomerate
High energy environments:
stream and river beds,
submarine canyons.
Occasional large rounded or
soled clasts of a variety of
rocks set in silt or argillite.
Massive structure.
Tillite
Glaciers. Widespread deposits
formed by continental ice
sheets.
Angular clasts often of chert,
or of any other rock type, set in
finer material such as
sandstone, siltstone or clay.
Breccia
Little or no transport of clasts.
Deposited by flash
floods/mudflows, landsliding,
and limestone cavern collapse.
Quartz grains may be angular
or rounded, clear or frosted.
Will scratch glass. May be
stained with iron oxide. May
have some feldspar.
Quartz
sandstone
Sand dunes, beach faces,
offshore bars. Settings where
durable quartz is winnowed
from less stable or less resistant
grains.
Contains 25% or more
orthoclase (pink) and quartz.
Grains usually angular and
coarse. May resemble the
granite from which it was
derived. May have micas.
Arkose
Typically, the weathered debris
of granite deposited on local
alluvial fans or floodplains.
Gray or greenish-gray, dense,
fine-grained sandstone.
Quartz rare; feldspars and rock
fragments common. Usually
has angular sand-size particles
in dark silt or clay matrix.
Graywacke
Rapid deposition in offshore
marine locales by submarine
slumping or underwater
mudflows, usually in
tectonically active zones.
Dark red color as ferruginous
cement covers sand grains.
Ferruginous
sandstone
Continental diagenic.
Silt
Fine-grained rock with slightly
gritty feel. Will separate along
bedding planes with difficulty.
Siltstone
Moderately high energy
aqueous environments: rivers,
nearshore marine.
Mud
Mostly clay, mica flakes may
be visible.
Mudstone
Low energy aqueous
environments: lagoons, lakes.
Clay
Smooth feel due to very small
(clay-size) particles.
Splits easily along closely
spaced bedding planes.
Shale
Low energy aqueous
environments: continental
shelves, lagoons, deep marine,
lakes.
Sand sized grains
(make up at least
50% of the
specimen.)
page 38
SED
Section III CHEMICAL SEDIMENTARY ROCKS
Exercise 3
Chemical sedimentary rocks, made from material formerly in aqueous solution, characteristically have
simple, non-silicate, chemical compositions. Their textures can show great variations and can be either clastic
or nonclastic. Chemical sedimentary rocks are classified by dividing them into compositional types and further
subdividing them into textural varieties. Each type or variety within a type is named.
Your problem is to
name each chemical sedimentary rock specimen in the given set B.
Procedure: Work with one specimen at a time. Record your results in Table 3.
Step 1. Write rock specimen numbers in each stage of the identification.
Stage 0. Pick up a chemical sedimentary rock specimen and note the specimen number.
Stage 1. Work progressively through the following and stop when the composition is positively
identified. Then go to Stage 2.
a) Place one drop of dil. HCl (dilute hydrochloric acid) on the specimen. Look carefully at the drop to
see if there is any effervescence (bubbling). If effervescence is seen the composition is Calcite.
b) With the point of a knife, scratch the specimen in a small area so that a little powder is produced on
the specimen where it was scratched (if you cannot scratch the specimen, go to (f). Place one drop of dil. HCl
on the specimen where it was scratched. Look carefully to see if there is any effervescence. If effervescence is
seen the composition is Dolomite.
c) If the color of the specimen is black or dark brown [if not go directly to (d)] see what happens when
a small chip of it (chips will be provided and are obtained by breaking a specimen with a hammer) is heated by
a flame. Method: Light an alcohol burner. Place 3 inches of wire in a wire holder and with pliers twist a small
loop at the free end. Place the chip on the loop and hold it just above the tip of the alcohol burner flame. If the
chip ignites and burns to an ash, or if it melts and gives off a bituminous odor, the composition is Hydrocarbon.
d) Rub the specimen on a streak plate. If the streak is black the composition is Pyrolusite. If the streak
is red or reddish brown, the composition is Hematite. If the streak is deep yellow or yellowish brown,the
composition is Limonite.
e) Scratch the specimen with your finger nail, If it can be gauged easily it is: i) Hydrated Silica if a drop
of dil. HCl soaks in rapidly without effervescing, or ii) Gypsum if a drop of dil. HCl does not soak in and there
is no effervescence. If you cannot scratch it with you finger nail, go to (f).
f) Rub the specimen (press it down hard) on a piece of plate glass held flat on the table. Examine the
result and accordingly go A, B or C:
A) If the sharp edges or points on the specimen cannot scratch the glass (that is, any powder
of the specimen left on the glass can be rubbed away with your finger tip without the glass beneath showing any
scratch marks) then taste a (sterilized) chip of the specimen (WARNING: do not attempt to chew it). If the chip
has no distinct taste, the composition is Anhydrite. If the chip tastes like common table salt, the composition
is Halite. If the chip tastes bitter, its composition is one of the Bittern Salts.
B) If the specimen scratches glass with difficulty the composition is Hydrated silica (if the
specimen looks opaline), Colophane (if dull, concentrically banded and too fine grained for individual grains
to be seen) or Apatite (if individual grains can be seen).
C) If the specimen scratches glass making a grating sound and leaving pronounced scratches
in the surface of the glass, the composition is Chalcedony (where the specimen in too fine grained for individual
grains to be seen) or Quartz (where individual crystal grains can be seen).
Stage 2. Read in Table 3 the textural varieties listed beside the specimen's compositional type. Decide
which one best describes the apecimen.
page 39
Table 3
Classification of
SED
CHEMICAL SEDIMENTARY ROCKS
Compositional type
Textural variety
Name
Calcite
CaCO3
reacts with HCl
Chalk-like, fine grained, noticeably light heaft (easily
gouged by finger nail)
Chalk
Uniformly fine grained (harder than finger nail)
Lithographic
limestone
Fine grained, looks powdery, may be nodular, has
irregular small openings
Calcareous
tufa
Distinctly layered, may have small openings
Travertivne
Cemented shell hash
Coquina
Some shells, mostly unbroken, embedded in the rock
Shelly
limestone
Spherules, sand sized, embedded in the rock. May make
up most of the rock.
Oolitic
limestone
Spherules, larger than sand sized, (commonly pea-sized)
make up most of the rock.
Pisolitic
limestone
Irregularly shaped, interlocking, crystal grains in an
otherwise fine grained rock
Common
limestone
Dolomite
(Ca, Mg)CO3
reacts with HCl
where scratched
Fine to medium grained, no shells
Dolostone
Fine to medium grained, shells visible
Dolomitized
limestone
Hydrocarbon
Hx , Cy
Pitch-like (melts on heating giving off bituminous odor)
Asphalt
Matted plant fragments and organic muck, pliable when
damp (burns, smokily, to ash without melting)
Peat
Coaly, plant fragments visible, dull luster, not pliable
when wet (burns smokily to ash without melting)
Lignite
Coaly, locally shiny where broken, dirties hands (burns
to ash without melting)
Bituminous
coal
Earthy luster, not well layered
Wad
Earthy luster, concentrically layered
Manganese
nodule
Pyrolusite
MnO
continued over >
page 40
Table 2 continued
CHEMICAL SEDIMENTARY ROCKS
Hematite
Fe2O3
Earthy luster, may be oolitic
Sedimentary
hematite
Limonite
Fe2O3 • H2O
Earthy luster
Bog iron ore
Gypsum
CaSO4• H2O
Massive or visibly crystalline
Rock gypsum
Anhydrite
CaSO4
Massive
Rock gypsum
Halite
NaCl
Massive or visibly crystalline
Rock salt
Bittern salts
Massive or visibly crystalline
Bittern salts
Collophane
Ca3(PO4)2 • H2O
Massive, may be colloform, commonly oolitic
Phosphorite
Hydrated silica
SiO2 • H2O
Chalk-like, fine grained, noticeably light heaft
(easily gouged by finger nail)
"Diatomite"
Massive, opaline (harder than finger nail)
Opal
Massive, not banded
Chert
Massive, concentrically banded
Agate
Visibly crystalline
Drusy quartz
Chalcedony
SiO2
Quartz
SiO2
Stage 0
Stage 1
SED
Stage 2
Step 2. Check your results against the key provided by your laboratory instructor and investigate the reasons
for any error.
Photo essay
page 41
SEDIMENTARY ROCKS
multiple choice review questions
Sediments are
a. sediment in transportation.
b. the accumulated product of weathering.
c. the deposited product of erosion.
d. none of the above.
Accumulations of transported clasts are
a. soils.
b. detrital sediments.
c. sedimentary rocks.
d. chemical sediments.
Chemical sediments can be
a. residual soils.
b. sea water.
c. hard water.
d. precipitates.
SED
Your Name:
Date:
Silt can be distinguished from clay because it
a. can be seen to be dust.
b. feels gritty between the fingers.
c. the clasts are smaller than 1/16 mm.
d. it cannot hold water.
In classifying a given chemical sedimentary rocks the
characteristic first considered is
a. clast size.
b. composition.
c. origin.
d. fabric.
Detrital sediments are immature if they are made of
clasts which are
a. sorted.
b. rounded.
c. easily weathered.
d. geologically young.
Chemical sediments can have a
fabric which is:
origin which is:
composition which is:
a. carbonate, sulphate, chloride.
b. evaporation, chemical precipitation,
organic extraction.
c. crystalline, dense, bioclastic.
d. none of the above.
A detrital sedimentary rock is mature if
a. the source of its clasts can be traced.
b. it is geologically old.
c. it contains easily weathered clasts.
d. its clasts are well rounded.
Lithification is never due to
a. cementation.
b. compaction.
c. dissolution.
d. recrystallization.
A detrital sedimentary rock that is made of clasts
that are mostly larger than 2 mm in diameter is a
a. conglomerate.
b. sandstone.
c. siltstone.
d. mudstone.
The age of a sedimentary rock is when it was
a. lithified.
b. sedimented.
c. exposed by erosion.
d. buried.
Sand sized clasts have a diameter that is larger than
a. 4 mm
b. 2 mm
c. 1/16 mm
d. 1/256 mm
A breccia is like a conglomerate except it
a. is a broken fragment.
b. contains large angular clasts.
c. contains angular small clasts and
rounded large clasts.
d. is a gritty sandstone.
Arkose sand is characterized by clasts of
a. quartz.
b. quartz, potassium feldspar, muscovite.
c. mafic volcanic rock, clay.
d. volcanic rock, silt, clay, glauconite.
Visible cement in detrital sedimentary rock is
a. washed in mud.
b. a chemical precipitate.
c. the matrix.
d. fine grained.
page 42
Clay lithifies to shale by being
a. cemented.
b. desiccated.
c. compacted.
d. recrystallized.
Loess is
a. dune sand.
b. a mixture of sand and silt.
c. a blanket of dust.
d. a lag deposit.
Buried sand does not lithify to sandstone by
a. cementing.
b. compaction.
c. partial recrystallization.
d. any of the above.
Oscillation ripples can be found
a. on dunes.
b. in shallow water environments.
c. in deep water environments.
d. on dune, or on submarine bar, slip faces.
Evaporite chemical sediments lithify by
a. cementation.
b. compaction.
c. recrystallization.
d. evaporation.
Current ripples
a. are diagnostic of shallow water
depositional environments.
b. are symmetrical in transverse cross section.
c. have crests that are transverse to the
current that forms them.
d. have crests that are parallel to the current
that forms them.
The most characteristic feature of sedimentary rock
seen in outcrop is their
a. stratification.
b. layers of different composition.
c. fossil content.
d. horizontality.
Sedimentary strata and layered igneous and
metamorphic rocks never have a common
a. composition.
b. texture.
c. resistance to weathering.
d. fossil content.
Large scale cross bedding is an internal feature of
a. stream bars.
b. dune sands.
c. loess.
d. turbidity current deposits.
Graded bedding is characteristic of
a. shallow water deposits.
b. deep water turbidites.
c. density inversions.
d. stream gradients.
Every sedimentary bed which is part of a stratum
a. is parallel to the stratum.
b. is at an angle to the stratum.
c. was eroded before burial or it is separated.
from the next by a paleosoil.
d. was once the surface of the earth.
Oolites
a. are detrital.
b. have the appearance of sandstones.
c. indicate deep water deposition.
d. are fossilized fish eggs.
Rare bedding plane features are
a. paleosoils.
b. ripple marks.
c. tracks and trails of animals.
d. desiccation mud-cracks.
Limestone is changed to dolostone by
a. prolonged weathering.
b. low temperature and pressure.
c. diagenesis.
d. micrite recrystallization.
Sand can be transported by wind
a. by sliding, rolling, and saltating.
b. in suspension.
c. by eolian floatation.
d. in solution.
SED
page 43
GE-101 Sect:
Physical Geology
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Instructor:
Date:
Your name:
Laboratory module:
Metamorphic rocks
Objectives: After completing this laboratory you should be able to
1.
Discuss the process of rock change called metamorphism.
2.
Understand that the texture of a metamorphic rock is related to its origin.
3.
Describe and name a variety of metamorphic rocks.
EQUIPMENT CHECK LIST (Report any missing items to the laboratory proctor)
Material
Description
per
Student
per
Table
METAMORPHIC
ROCKS
Hand specimens
1 set
CHEMICALS
Dilute (5%) hydrochloric acid in a dropper bottle
2
GEOLOGICAL
EQUIPMENT
Window glass, 3" square plate with beveled edges
(for hardness test)
Streak plate
Pocket knife (blades blunted)
1
1
2
MET
/
/
page 44
Section 1
MET
METAMORPHIC ROCKS
Rocks are chemical systems which at the time they originate are essentially in equilibrium with ambient
temperatures and pressures. Subsequently, ambient temperatures and pressures may change because of a
variety of causes such as: burial, heating, fold-mountain building, erosion of overburden, cooling, etc. As a
result, a rock may be caused to change. Rocks which can be argued to have changed within the earth
towards new equilibrium with such subsequently established conditions of temperature and pressure are
called metamorphic rocks: the process of change is called metamorphism. During metamorphism, a rock is
recrystallized without, or with, deformation while it remains essentially a solid: its bulk composition need
not change (if there is evidence that it has, the process is properly referred to as metasomatism) but its
substance must undergo physical rearrangements and chemical recombinations. Such adjustments are
promoted by the existence in the rock of pore fluids which allow solution, redistribution, mixing and
precipitation of mineral substances, and applied stresses which can change or rearrange chemical bonds in
minerals or plastically deform the rock.
Metamorphism which does not involve the plastic deformation of the effected rock is called contact
metamorphism. Metamorphism which does involve the plastic deformation of the effected rock is called
regional metamorphism.
page 45
Exercise 1
EVALUATION QUESTIONS
Do rocks originate essentially in, or out, of equilibrium with ambient temperatures and pressures?
Can metamorphic rocks originate, by definition, at Earth’s surface? (yes, no) Explain.
Name several causes of metamorphism.
Can metamorphism be recrystallization of a rock only? (yes, no) Explain.
What distinguishes metasomatism?
If heating, alone, evidently has caused a rock to recrystallize, what is the metamorphism called?
If plastic deformation is evident in a rock, what is the metamorphism called?
MET
page 46
Exercise 2
MET
NAME METAMORPHIC ROCKS
A metamorphic rock is type firstly according to its texture and secondly according to its composition. Each
type is named. Your problem is to name each specimen in the given set of metamorphic rocks.
Procedure: Work with one specimen at a time. Record your results in Table 1.
Step 1. Write rock specimen numbers in each stage of the classification.
Stage 0. Pick up a metamorphic rock specimen and note the specimen number.
Stage 1. Decide if the rock is:
Foliate - the rock is, any of the following:
a) made of thin sheets
b) breaks into thin sheets
c) seen to contain elongated minerals which are arranged to point all more or
less in the same direction
d) layered or banded in appearance
Nonfoliate - other than the above: the rock breaks into irregular blocks, it does not
have a well layered or banded appearance and should elongate crystals occur,
these point in all different directions.
Stage 2. Decide if the rock is:
Dense - in most of the rock, constituent mineral grains are too small to be
individually seen by the naked eye.
Granoblastic - most of the rock is made of mineral grains large enough to be
individually seen by the naked eye.
Stage 3. If the rock is:
Foliate, dense, you can assume that it is made mostly of silicate minerals unless it is
coal black in color. If this is so, make sure it is not a carbohydrate*.
Foliate, granoblastic, you can assume, as a first approximation, that it is made mostly
of silicate minerals. unless the rock is softer than steel and effervesces with
dilute hydrochloric acid (dil. HCl). If this is so, reclassify the specimen as
nonfoliate, granoblastic (see discussion, Section III)
Nonfoliate, dense, you can assume that it is made mostly of silicate minerals unless it
is coal black in color. In this case test to see if it is a carbohydrate*.
Nonfoliate, granoblastic , you can assume that it is made mostly of silicate minerals
unless the rock is softer than steel and effervesces with dilute hydrochloric
acid (dil. HCl). Test: see if you can scratch the rock with the point of a knife
(try to make a short scratch). If you can scratch the specimen, put a drop of
dil. HCl on the scratch mark and look closely for effervescence (bubbling). If
effervescence is seen, the test indicates carbonate.
continued page 48 6>
*Test for carbohydrate: rub the specimen on a streak plate. If it leaves a coal black streak it is a
carbohydrate. Go back to your table and reclassify the rock as nonfoliate in the Stage 1 column.
page 47
Table 1
Classification of
MET
METAMORPHIC ROCKS
Rock Name
Foliate
Dense
Granoblastic
Nonfoliate
Dense
Silicate
Silicate
Silicate
Dull luster
Slate
Satiny luster
Phyllite
Fissile
Schist
Layered or banded
Gneiss
Softer than glass
Serpentinite
Harder than glass
Hornfels
Carbohydrate
Granoblastic
Silicate
Anthracite
Red and green
minerals
Eclogite
Mostly green
minerals
Tactite
Mostly quartz
Metaquartzite
Pebbles in matrix
Metaconglomerate
Two or more
minerals
Granulite
Carbonate
Stage 0
Stage 1
Stage 2
Stage 3
Marble
Stage 4
page 48
MET
Stage 4. If the rock is:
Foliate, dense, silicate, decide if it is:
Dull in luster
Satiny in luster (the rock has a sheen)
Foliate, granoblastic, silicate, decide if it is:
Fissile - exhibits a tendency to break into thin, but not necessarily even, sheets or
into splintery blocks. Any porphyroblasts (crystals noticeably larger than the
average sized crystal in the rock) present tend to protrude or break free from the
rock's surface.
Nonfissile - exhibits little tendency to break into sheets or splinters. Any
porphyroblasts present do not tend to protrude or break free from the rock's
surface.
Nonfoliate, dense, silicate, decide if it is softer or harder than glass. Test: Lay a
glass plate on the table and pressing down on it with a point on the specimen
see if you can scratch it. Note: if the specimen slides greasily on the glass
and does make a grating sound, it is softer than the glass.
Nonfoliate, granoblastic, silicate, decide if it is made of:
Mostly green minerals.
Mostly quartz - glassy, fused looking grains, the rock as a whole has a greasy
luster where freshly broken.
Recognizable pebbles (Figure ) in a finer grained matrix.
Two or more minerals of not greatly dissimilar size.
Section III
Discussion:
NAMING THE VARIETIES OF METAMORPHIC ROCKS
Each type of metamorphic rock can be expected to contain certain minerals. For example,
silicate metamorphic rocks such as slate, phyllite, schist, gneiss, granulite, hornfels and so on,
commonly contain quartz and feldspar(s). These rocks can also contain other minerals such as
andalusite, biotite, chlorite, garnet, graphite hornblende, kyanite, muscovite, olivine, pyroxene,
sillimanite, staurolite, talc and others.
Varieties of metamorphic rock types are distinguished by prefixing the type name with the
names of minerals present which are not common to the type. For example, a schist which
contains biotite is called a biotite-schist or a gneiss which contains, say, biotite and garnet is called
a biotite-garnet-gneiss. The presence of quartz and feldspar is not mentioned because they are
commonly in these rocks. Also, in this regard, the absence of quartz and feldspar is not
mentioned. For example, a schist which is made only of talc is called a talc-schist.
page 49
METAMORPHIC ROCKS
Your name:
Metamorphic rock multiple choice review questions
Sediments have accumulated in places to
thicknesses of as much as
a. 12 km.
b. 30 km.
c. 100 km.
d. 700 km.
Sediments have evidently been subducted to
depths of
a. 2 km.
b. 30 km.
c. 100 km.
d. 700 km.
Crustal temperatures can be accounted for
by
a. heat from the mantle.
b. internal radioactive sources.
c. radiant heat from the sun.
d. (a) and (b).
Coal buried to a depth of 12 kilometers
becomes
a. china.
b. compacted.
c. graphite.
d. diamond.
Metamorphism changes a rock's
a. temperature.
b. pressure.
c. texture.
d. state.
Metamorphic rocks originate by the
crystallization or recrystallization of rocks
that were
a. igneous.
b. sedimentary.
c. metamorphic.
d. all of the above.
MET
Date:
Minerals of metamorphic rocks are more varied
than those of igneous rocks because
a. the chemical composition of metamorphic
rocks is not as limited as it is for
igneous rocks.
b. the temperature of metamorphism is
controlled by pressure.
c. the range of pressure is greater than that to
which igneous rocks are subjected.
d. all of the above.
The texture of a fine-grained metamorphic rock
is described as
a. dense.
b. granoblastic.
c. nonfoliated.
d. foliated.
Metasomatism is different from metamorphism
because the rock that results has
a. an unchanged texture.
b. a mineralized appearance.
c. the same composition as the original rock.
d. a different composition than the original rock.
A rock that is changed by metamorphism has
a. an unchanged texture.
b. a mineralized appearance.
c. the same composition as the original rock.
d. a different composition than the original rock.
An example of a dense contact metamorphic
rock is
a. hornfels.
b. meta-conglomerate.
c. marble.
d. skarn.
page 50
An example of a granoblastic foliated regional
metamorphic rock is
a. slate.
b. phyllite.
c. gneiss.
d. greenstone.
Progressively higher metamorphic grade is
a. gneiss 6 schist 6 slate.
b. slate 6 schist 6 gneiss.
c. slate 6 gneiss 6 phyllite.
d. schist 6 phyllite 6 slate.
In contact metamorphism, the sequence of
index minerals: chlorite, biotite, almandine,
staurolite, kyanite, and sillimanite, indicates
a. decreasing grade at constant pressure.
b. increasing grade at constant pressure.
c. increasing grade with decreasing pressure.
d. none of the above.
Andalusite, kyanite, and sillimanite are
a. index minerals for high temperature and
pressure.
b. polymorphs.
c. found in blue schist.
d. all of the above.
Cataclastic metamorphic rock is typically
a. low grade.
b. high grade.
c. mylonite.
d. tectonically fragmented.
MET
page 51
GE-101 Sect:
Physical Geology
Instructor:
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Your name:
MINERALS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Date:
/
REV
/
page 52
GE-101 Sect:
Physical Geology
Instructor:
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Your name:
IGNEOUS ROCKS
20
21
22
23
24
25
26
27
28
29
30
31
32
33
Date:
/
REV
/
page 53
GE-101 Sect:
Physical Geology
Instructor:
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Your name:
SEDIMENTARY ROCKS
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
Date:
/
REV
/
page 54
GE-101 Sect:
Physical Geology
Instructor:
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Your name:
METAMORPHIC ROCKS
56
57
58
59
60
61
62
63
64
Date:
/
REV
/
page 55
GE-101 Sect:
Physical Geology
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Instructor:
Date:
/
TOP
/
Your Name:
Laboratory: Contour lines and topographic maps
Objectives: After completing the following two laboratory periods you should be able to:
1.
Construct contour lines and topographic sections.
2.
Visualize the scenery portrayed by features and contours and in a topographic map.
3.
Anticipate several ways you might use a topographic map.
EQUIPMENT CHECK LIST
Material
Description
per
Student
TOPOGRAPHIC MAPS
AND
AERIAL PHOTOGRAPHS
USGS quadrangle maps
1
Book of aerial photographs
1
EQUIPMENT
Stereoscope
1
per
Table
page 56
TOP
TOPOGRAPHIC MAPS
A planimetric map gives a two dimensional view of the land that shows the position of natural
features such as rivers and lakes, and artificial features such as buildings and roads. The United States
Geological Survey (USGS) is the government agency responsible for preparing maps for land
development of the United States. To aid geological mapping, there are Landsat images, areal
photographs, and topographic maps.
A topographic map is a planimetric map that also shows the relief of the land surface by
contours: this three dimensional aspect is sometimes enhanced by hachures, tints and shadings.
Figure 1 illustrates how various features are depicted on a topographic map.
B
from USGS publication
Figure 1. The upper illustration (A) is a perspective view of a river valley and the adjoining hills.
The river flows into a bay which is partly enclosed by a hooked sandbar. On either side of the valley are
terraces through which streams have cut gullies. The hill on the right has a smoothly eroded form and gradual
slopes, whereas the one on the left rises abruptly in a sharp precipice from which it slopes gently, and forms an
inclined tableland traversed by a few shallow gullies. A road provides access to a church and two houses
situated across the river from a highway which follows the seacoast and curves up the river valley.
The lower illustration (B) shows the same features represented by symbols on a topographic map. A
spot height is marked by an X. The contour interval (the vertical distance between adjacent contours) is 20 feet.
page 57
TOP
TOPOGRAPHIC MAPS
Discussion: List several features of maps that make them usable.
MAP SCALES
The fundamental usefulness of maps derives from the fact that they represent the reduction of
vast areas down to a piece of paper we can easily handle. In order to interpret a map successfully, we
must know the amount of this reduction, and know how a unit measured on the map relates to actual
distance on the ground.
The amount of reduction is expressed on maps as the ratio scale; i.e., the distance on the map
is a certain fraction of that on the ground. Note that any system of units may be used, as the ratio
scale is unitless. A 1:24,000 scale means that any one linear unit measured on the map is equal to
24,000 of those units on the ground. Using one inch for the unit, one inch on such a map would
represent a distance of 24,000 inches, or 2,000 feet, on the ground. So for all maps printed at a ratio
scale of 1:24,000, the relation of map to ground units, the verbal scale, is one inch equals 2,000 feet,
1" = 2,000 '.
A graphic scale or bar scale is a plot of the verbal scale on the map. This scale, which is
printed at the bottom center of all U.S.G.S. maps, is actually a ruler for measuring map distances.
This scale will still be valid if the map on which it is printed is reduced or enlarged photographically,
although the ratio scale will not. Bar scales on USGS topographic quadrangle maps looks like this:
Figure 2. Three equivalent bar scales.
page 58
TOP
Most United States topographic maps are published by the U.S. Geological Survey in the form
of topographic quadrangle maps. A quadrangle is a section of the Earth's surface that is bounded by
lines of latitude on the north and south and by lines of longitude on the east and west .
The two most common sizes of quadrangle maps are 15-minute quadrangle maps and 71/2minute quadrangle maps; the numbers refer to the amount of area (in degrees of latitude and longitude)
that the maps depict. A 15-minute topographic map represents an area that measures 15 minutes of
latitude by 15 minutes of longitude. A 71/2-minute topographic map represents an area that measures
71/2 minutes of latitude by 71/2 minutes of longitude. Each 15-minute map can be divided into four
71/2-minute maps.
The direction of true geographic north is toward the top of the map (and it is always parallel to
the lines of longitude). Unfortunately, magnetic compasses are not attracted to the geographic North
Pole (true north pole), but rather to the magnetic north pole, which is located just west of Hudson Bay
in northern Canada. The angle formed between the direction of true geographic north and the direction of magnetic north is known as the magnetic declination. It is usually indicated in
diagrammatic form in the margin of a topographic map for a specific year.
The magnetic pole moves very slowly through time, so the declination is exact only for the
year listed on the map. Tables are available from which you can calculate correct declination for any
quadrangle and year.
Notes:
LATITUDE AND LONGITUDE
1.
Latitude lines, or parallels, are parallel to the Equator and measure distances north and south of
the Equator.
2.
Longitude lines, or meridians, pass through the North and South Poles. They measure distances
east and west of the Prime Meridian, which passes through Greenwich, England.
3.
Any point on the Earth's surface can be represented as an intersection of a line of latitude and a
line of longitude.
4.
Since all of North America is north of the Equator and west of the Prime Meridian, all latitudes
in the continental United States are north and all longitudes are west.
5.
Latitude and longitude are expressed in degrees, minutes, and seconds.
1 degree (0) = 60 minutes (')
1 minute = 60 seconds (")
3600 makes a complete circle.
page 59
TOP
The Public Land Survey System (PLS) was initiated in the late 1700s, and all but the original
thirteen states, and a few states derived from them, are covered by this system. Exceptions also occur in
some areas of the southwestern United States, where land surveys may be based upon Spanish land
grants, or in areas of rugged terrain, where surveys were never made.
The PLS system was established in each state by surveying one or more base lines, which are
east-west lines, and one or more principal meridians, which are north-south lines (see A in Figure 3).
Once the initial principal meridian and base lines were established, additional lines parallel to these were
surveyed with a six-mile spacing. This created a grid of squares with each square being six miles on a
side.
Squares along each east-west strip of the grid are referred to as townships and are numbered relative to the base line (Township I North, Township 2 North, etc.)
Figure 3. Standard land divisions used in the United States and Canada.
page 60
A tier is a 6-mile wide strip running east-west.
A range is a 6-mile wide strip running north-south.
A township is a square formed by the intersection of a tier and a range.
Figure 4 shows how a township is further subdivide.
A township is divided into 36 sections, each 1 mile square.
A section is divided into quarters; quarters may be divided into quarters again, and again.
Figure 4.
TOP
Map Margin Information
Map Margin Information
1. State plane coordinate
system grid tick 660,000 feet
north from origin within the
state plane grid system. This
coordinate system was
established by the U.S. Coast
and Geodetic Survey for use in
defining positions of points in
terms of plane rectangular (x,
y) coordinates. There is
usually one system for each
state and each state
determines the measurement
unit (i.e., feet or meters).
2. Latitude 39 degrees, 37
minutes, 30 seconds (north of
the Equator, which is at 0
degrees latitude).
3. Longitude 105 degrees, 15
minutes, 00 seconds (west of
Meridian of Greenwich, also
called Prime Meridian, which is
at 0 degrees longitude).
4. North American Datum of
1927 -- horizontal datum.
Required for GPS users.
Also identifies UTM (Universal
Transverse Mercator) zone and
state plane coordinate system.
6. State plane coordinate
system grid tick
2,080,000 feet east of origin.
5. GN – UTM grid north (at the
center of the map).
7. * true or geographic north–
points to the north geographic
pole.
8. MN – magnetic north – the
approximate direction (at the
center of the map) to the north
magnetic pole at the date
given, in this case 1980. The
direction to which a magnetic
compass needle points.
9. 12 ½ o east – magnetic
declination or variation of the
compass – the number of
degrees a compass needle at a
particular location bears away
from true north and points to
the north magnetic pole.
196 MILS – military angular
measurement.
10. Longitude again
– this is a 2.5 minute
geographic grid tick
at 105 degrees (understood),
12 minutes, 30 seconds west.
11. Adjoining USGS
quadrangle name “Indian
Hills.”
The notation “4963 II SW” is
the NGA (National
Geospatial-Intelligence
Agency, the Department of
Defense mapping agency)
sheet designator for the same
map.
12. Range 69 West – 69 th
range west of 6th Principal
Meridian (which is at Meades
Ranch, Kansas). Public Land
Subdivisions: In 1785
Congress adopted a plan for
surveying public lands.
According to this plan, land
was divided into townships
approximately six miles
square, which were further
subdivided into 36 sections
approximately one mile
square. Principal meridians
and base lines were
established as a reference
system for the township
surveys.
14. UTM easting value –
487,000 meters false easting
(Zone 13).
15. Map reference code:
39 – degrees north latitude
105 – degrees west longitude
[[Topographic map with
contour values in Feet 024 –
1:24,000 scale]]
13. UTM (Universal Transverse Mercator) easting
value – 486,000 meters false easting (last 3 zeroes
omitted for brevity) (Zone13)
16. ISBN – International
Standard Book Number.
17. UTM northing value–
4,386,000 meters north from
the Equator.
“Northings” in the southern
hemisphere begin with the
Equator value = 10,000,000
meters and decrease in value.
18. Section number 5.
See Public Land Subdivisions.
19. Township 4 South -- 4
townships south of base line
(Base Line of 1855, in this
case).
See Public Land Subdivisions.
20. Latitude again
– another 2.5 minute latitude
grid tick at:
39 degrees (understood),
40 minutes,
00 seconds (understood).
[is not included on this map]
NY Flushing 20130328 TM
SE corner
page 61
TOP
CONTOUR LINES
Contour lines are used to depict three-dimensional features on a flat piece of paper. Contours
show the shape of hills, mountains, and valleys, as well as their altitude. A contour is an imaginary line
on the ground, all points of which are at the same altitude or, put another way, a contour line is a line
connecting all points of equal elevation. The zero contour is the shoreline of the ocean halfway between
high tide and low tide (mean sea level). All points 10 feet above sea level would lie on the 10-foot
contour line; all points 20 feet above sea level would lie on the 20-foot contour line, and so on. In this
example the contour interval, which is the difference in elevation between two adjacent contours, is 10
feet. A contour interval is chosen to fit the relief of the landscape and the scale of the map; to show as
much relief as possible without cluttering the map with lines bunched too closely together. Commonly
used intervals are 5, 10, 20, 25, 40, 50, 80, and 100 feet.
Figure 5 shows contour lines drawn on a natural landscape. If this imaginary area complete with
contour lines were photographed from above, the resulting photo would be a topographic map. In fact,
modern topographic maps are created by sophisticated computer processing of vertical aerial
photographs.
Listed below are some rules summarizing the basic nature of contour lines which should be used when
constructing or interpreting a topographic map:
1. Contour elevations are exact multiples of the contour interval above the zero sea-level elevation.
2. The spacing of contours reflects the gradient or slope:
a. contour lines that are far apart indicate a gentle slope
b. contours that are close together indicate a steep slope
c. contours that merge indicate a vertical slope
3. Contours never cross, never branch, and never terminate.
4. All solid-line contours are multiples of the contour interval; e.g., if the contour interval is 10 feet,
the contours will be 10, 20, 30, 40, 50, etc. Usually every fifth contour, called an index
contour, is printed heavier for ease of reference.
5. Dashed contours represent elevations of half the normal interval, and are added in areas of low
relief to increase detail.
6. Contour lines crossing stream valleys or other channels form a "V" pointing upstream.
7. Jagged topography will make sharp angles in the contour lines; low, rolling landscapes will have
gently curving lines.
8. Contour lines will eventually close on themselves, although demonstrating this may require
consulting adjacent maps.
9. Normal contours enclose an area that is higher than the contour; i.e., all points that lie within such
a closed contour are above the level of that contour.
10. Depression contours enclose areas that have no outlet-closed basins. They are marked by
hachures on the inside.
11. Depression contours have the same elevation as the adjacent normal contour which encloses the
depression.
12. Contours must be counted consecutively, and none can be skipped; repeated contours adjacent to
one another indicate a change in slope direction, such as into a depression or across a stream.
13. Bench marks, points on contours, and spot elevations are exact.
14. Hilltop elevations may be estimated as being greater than the highest contour shown but less
than the next contour (imaginary) above. Similarly, the bottoms of drainages will be below
the lowest contour shown in the immediate area, as will the bottoms of depressions.
15. The elevation points between contours may be estimated by the position of the point. If the
point is midway between two contours, the elevation will be read as halfway between the
values of the two bracketing lines. The nearer the point is to a contour, the closer it is to the
elevation of that contour.
page 62
Figure 5.
TOP
Vertical exaggeration = ___________________
page 63
TOP
Figure 6.
Exercise 1. To practice drawing contour lines:
Stage 1 The map shown in Figure 6 shows spot elevations and drainage lines. Your problem is
to draw contours with a contour interval that will reveal the topography and allow the spot heights to be
eliminated.
Discussion: Why is a contour interval of 10 feet reasonable?
Map Scale: ½ inch = 1000 feet.
Vertical exaggeration of topographic profile = ____________
page 64
GE-220 Physical Geology
Instructor:
Your name
TOP
Seat no:
Film: "Beach - a river of sand"Objectives, questions and essays
CONSIDER THE MATERIALS OF BEACHES
Are beaches found to be made of any locally available material that can be moved by the
surf? (yes, no) For example:
What sized material (boulders, sand, clay), abundantly transported by streams, most often
accumulates on the beach?
____________
drifts out to sea?
____________
DESCRIBE THE BEACH SLOPE
What process shapes (restores) the beach profile? (Hint: what removed the sand castle?)
Define the terms:
beach face
surf zone
How did the beach look in the:
summer
winter
In what respects do waves differ from summer to winter?
ACCOUNT FOR THE DISTRIBUTION OF SAND ALONG A BEACH
Why do waves, on most days, pass through the surf zone at an angle?
Can sand be moved along the beach face by wave action? (yes, no)
page 65
TOP
Can sand be moved only back and forth by wave action in the surf zone? (yes, no)
Is the longshore current found to be almost entirely within the surf zone? (yes, no)
ILLUSTRATE THE EVIDENCE OF LONGSHORE TRANSPORT
How does sand trapped by groins (walls built out into the sea) indicate the direction of longshore
transport?
In general, does sand move north, or south, along the U. S.'s east and west coasts?
Why must a dredge work the year round:
in the Santa Barbara harbor
behind the breakwater at Santa Monica
ACCOUNT FOR THE DISAPPEARANCE OF "RIVERS OF SAND"
Why does the sand beach terminate 120 miles down tho coast from Santa Monica?
How can the construction of river dams affect the California sand beaches?
page 66
HOMEWORK Choose a contour interval to be __________ and draw contour lines in the map.
Figure 7.
TOP
page 67
Exercise 2.
TOP
Map for construction of topographic profiles
Map scale 1 inch = 1000 feet
Figure 8
Vertical exaggeration: ________________
page 68
Exercise 3. Hand in
Your name: ______________________________
date:
/
TOP
/
Refer to the topographic map on page 69. Complete this page
Locate: (1) a hill, (2) valleys, (3) ridges, (4) a depression, (5) a saddle or pass. (To record your
decisions, put the numbers in the map )
Write in spot height values for a, b, c, d, and e.
Shade the area which is lower than 460 feet elevation.
Draw streams (with a solid line or a blue pencil) in the valleys and draw an arrow beside each stream to
indicate its direction of flow.
Draw in ridge crests (with a dashed line or a brown pencil).
What is the elevation of the school (square block with flag)?
____________
What is the elevation of the house (square block)?
____________
What is the elevation of the top of the hill?
____________
What is the elevation of lake shore?
____________
What is the relief of the terrain in the map?
____________
How high is the hill above the adjacent ridge?
____________
What is the elevation of the bottom of the depression?
____________
How deep is the depression?
____________
page 69
GE-220
Your name:
Date:
/
/
Exercise 4.
A) Write in the contour elevations.
B) Draw a topographic profile across the map though the spot height and the dot labeled x.
TOP
page 70
Exercise 5.
TOP
MAP
TOPOGRAPHIC PROFILE
Map scale
Contour interval = _____________
feet
Vertical exaggeration of cross section = ____________
page 71
Exercise 6.
TOP
page 72
TEST 1
Topographic maps and profile
TOP
Your name:
Date:
Part I
QUESTIONS
1 Using the elevations and streams given in the supplied figure, construct
a topographic map with a contour :interval of 20 feet.
2 Indicate-with arrows on the map in which direction the streams flow.
3 What is the maximum relief in the area?
___________
4 What is the average gradient of the indicated stream?
___________
5 If standing at point A could one see point B?
___________
6 If standing at point A could one see point C?
___________
7 If standing at point C could one see point D?
___________
8 Construct a topographic profile along an east west line you label X-Y.
Part II (refer to quadrangle map supplied in laboratory)
The name of the quadrangle is: __________________________
9 Why is the map called a quadrangle and not a rectangle?
___________________________________________________
10 What is the scale of the map in fractional form?
___________
11 What is the scale of the map in inches-per-mile?
___________
12 How many feet on the ground does one inch on the map represent?
___________
13 What is the distance between the two places indicated on the map (see
information on blackboard)
___________
14 What is the elevation of the lowest of these two places?
___________
15 What is the elevation of the lowest place anywhere in the map?
___________
page 73 OPH
GE-101 Sect:
Physical Geology
QUEENSBOROUGH COMMUNITY COLLEGE Date:
The City University of New York
Instructor:
/
/
Your name:
Laboratory module:
Ore minerals, physical properties
Objectives: After completing this laboratory you should be able to:
1.
Evaluate how well color, streak and luster characterize mineral species.
2.
Measure the hardness and specific gravity of minerals.
3.
Use mineral identification tables.
EQUIPMENT CHECK LIST (Report any missing items to the laboratory proctor)
Material
Description
MINERALS
8 unknown hand specimens* and chips+ for
specific gravity determination
GEOLOGICAL
EQUIPMENT
Streak plates+
Calcite cleavage plates+
Glass plates (beveled edges)+
Jolly specific gravity balances (fitted with
heavy gauge springs)
SPECIAL
EQUIPMENT
Beakers, 250 ml, glass
per
student
per
table
1 set
1
1
1
1
1
*Selected from the following ore minerals:
arsenopyrite, azurite
bauxite, beryl, barite
celestite, cinnabar, cassiterite, cerussite, chalcopyrite, chalcosite, columbite, chromite,
cuprite
galena, goethite
hematite
limonite
malachite, magnetite, magnesite
orpiment
pyrolusite, (pyrite), (pyrrhotite)
realgar, rutile, rhodochrosite
sphalerite, siderite, spodumene, stibnite, strontianite
zircon
+Expendable
page 74 OPH
Section 1
Ore Minerals, physical properties
Practical workers had distinguished and named many hundreds of minerals using such
physical criteria as: color, hardness and specific gravity (heft), before it was determined that the
two criteria essential for the definition of a mineral species are chemical composition and
symmetry of internal crystal structure. Neither of these latter criteria, however, can be observed
at first hand. Not surprisingly, therefore, the geologist today, in the role of prospector, or even as
a guest in a friend's house, should still possess the facility of identifying most common minerals
by the direct inspection of hand specimens.
The founder of systematic mineralogy was Abraham Gottlob Werner (1749-1817). He
assembled a great body of information concerning all minerals and demonstrated to the
satisfaction of the mining world the utility of a systematic classification of minerals based upon
their easily observed physical properties.
A mineral's physical properties are those of its characteristic that affect our senses, which
are: sight, touch, smell, taste and hearing. Sight can give us a quick measure of a mineral's color,
streak and luster. Observation of crystal form or cleavage, when present, requires that individual
crystals can be seen. Streak is the color of a mineral after it has been crushed to a powder. In
many instances, the color of the streak is quite different from the color of the uncrushed mineral.
Minerals, that are granular on the scale of a powder, will have a dull or earthy luster unless they
are native metals in which case they will have a metallic luster where freshly broken. Minerals
that are visibly crystalline and show fresh (unweathered, untarnished) crystal faces, cleavage
surfaces or fracture surfaces, will have a non-metallic luster if they are transparent or even
slightly translucent, and a metallic luster if they are thoroughly opaque (even at their thinnest
edge). Touch is related to a mineral's hardness and specific gravity. Smell, hearing and taste,
though of more restricted application in the physical classification of minerals, can be decisive.
Color, streak and luster, cannot be used to distinguish between all minerals equally well,
nevertheless, these characteristics are so obvious that it is often advantageous to use them in
mineral identification as initial criteria. From one specimen to another of the same mineral:
color varies least if the mineral has a distinctly colored streak (included are most minerals that
can have a metallic luster), and color varies most if the mineral has an uncolored, pale gray or
white streak (included are most minerals of non-metallic luster).
Further subdivision of minerals in standard identification table can involve: hardness, a
characteristic readily measured in the field with little specialized equipment, and specific
gravity, a characteristic that is easy to measure in the laboratory.
page 75 OPH
Exercise 1
EVALUATION QUESTIONS
What two criteria are necessary and sufficient for the definition of mineral species?
Why is it important for geologists to try to distinguish between mineral species by observing
their physical properties?
Who has been credited with being the founder of mineralogy?
Define streak:
Is the color and the streak of a mineral usually the same? (yes, no) Explain.
Describe the luster of crushed minerals which are not native metals:
Can only native metals have a metallic luster? (yes, no) Explain.
Can a mineral with metallic luster have a non-metallic streak? (yes, no) Explain.
Do all minerals of non-metallic luster have an uncolored, pale gray or white streak? (yes, no)
Explain.
Name two physical properties of minerals which can be measured easily.
page 76 OPH
Section II
Exercise 2 COLOR AND STREAK
In order to distinguish one mineral from another, care must be taken not to place too
much reliance on color although the specific color can be diagnostic. Also, the color of the
streak is mostly uniform from one specimen to another of the same mineral. For minerals which
look like metals, but which are not, the streak is very different from the color of the uncrushed
mineral and this helps in their identification. For the common rock forming minerals, the streak
is uncolored, white or pale gray. Your problem is to describe the color and the streak of the
given minerals.
Procedure: Work with one mineral at a time. Record your results in Table 1. List specimen
numbers in order from smallest to largest.
Step 1. Characterize the overall color of the mineral as: black, dark gray, yellow, brown,
red, blue, green, uncolored, light gray or white and then go on to describe the specific color*.
Step 2. There are several common methods for testing the streak of a mineral: first by
crushing to a powder with a hammer, second by scratching it with a knife blade or file, third by
rubbing it on what is known as a streak plate (a piece of unglazed porcelain). Use the third
method as the streak is preserved on the streak plate and can be compared with those of other
minerals whose streaks can be made close to each other. Press the mineral firmly against the
streak plate and rub it back and forth several times along the same short line in order to develop
the full tone of the streak. In that way, if the mineral has a dark streak, you will not mistake it
through lack of rubbing for one that has a light streak. (Minerals, whose hardness exceeds that
of the streak plate, must be powdered.)
Describe the mineral streak as: black, dark gray, yellow, brown, red blue, green,
uncolored, light gray, or white and then go on to describe the specific streak*.
*Hint. Choose from the following possibilities:
Color, streak
Specific color, Specific streak
BLACK
black, pitch-, velvet-, iron-, yellowish-,
brownish-, reddish-, purplish or iridescent metallic-, grayish-
DARK GRAY
dark gray, lead gray, bluish lead gray, dark steel gray.
YELLOW
grayish-, pale-, light-, lemon-, canary-, honey-, straw-, wax-, wine-, sulfur-,
metallic golden-, brassy-, brownish-, orange-, reddish-.
BROWN
blackish-, dark-, dirty-, hair-, smokey-, grayish-, yellowish-, bronze,
reddish-, cinnamon-, clove-.
RED
blackish-, ruby-, dark-, yellowish-, aurora-, flesh-, peach-, orange-, brick-,
brownish-, maroon, copper-, light copper-, rose-, bright-, cochineal-, cherry-,
blood-, crimson-, scarlet-, purplish-, vermilion-, hyacinth-, red violet, pink.
continued –>
page 77 OPH
BLUE
blackish metallic-, indigo, deep-, grayish-, smoky-, lavender, lilac, violet,
amethystine, azure-, sky-, greenish-, light-.
GREEN
blackish-, dark-, olive-, yellowish-, brownish-, bluish-, apple-, emerald-,
grass-, pea-, leek-, pale-.
LIGHT GRAY
pearl-, pale-, yellowish-, brownish-, reddish-, pinkish,lavender-, bluish-,
light lead-, silver.
WHITE
milky-, tin-, milk-, snow-.
UNCOLORED
uncolored.
Table 1
Mineral
specimen
no.
Color
Specific color
Streak
Specific streak
page 78 OPH
Exercise 3 LUSTER
A mineral's luster, the way it reflects light, is related to its transparency. Opaque
minerals can have a metallic luster, although, many do not. All transparent to slightly
translucent minerals have a non-metallic luster. Only native metals can have a streak with a
metallic luster. All other minerals when granular on the scale of a powder have a non-metallic
luster. Your problem is to describe the luster of the given minerals.
Procedure: Work with one mineral at a time. Refer to your data in Table 1. Record your results
in Table 2. List specimen numbers in order from smallest to largest.
Step l. Describe the mineral's luster as metallic if its specific color was correctly described as:
iron black, lead grey, bluish lead gray, dark steel gray, metallic golden yellow, brassy
yellow, bronze, light copper red, silver or tin white and it is completely opaque to light
even where seen to be very thin. (Hint: Do not describe a mineral's luster to be metallic
unless you would be prepared to buy it without question, as a metal.)
Step 2. The mineral has a non-metallic luster. Describe its specific luster as:
adamantine = the brilliant luster of a diamond
vitreous = the luster of glass
resinous = the appearance of yellow to brown taffy, may be shiny
pitchy = the appearance of road tar, may be shiny
waxy = the appearance of candle wax
greasy = the appearance of an oiled surface
pearly = as mother of pearl
silky = as silk or satin (has a sheen)
dull = as earth
Table 2
Mineral
specimen no.
Luster
Specific luster
page 79 OPH
Exercise 4 HARDNESS
A mineral's hardness is a measure of its ability to withstand abrasion and scratching by
other substances. In Mohs hardness scale, ten minerals are ordered in degrees of increasing
relative hardness:
Diamond (10)
Corundum (9)
Topaz (8)
Quartz (7)
Feldspar (6)
Apatite (5)
Fluorite (4)
Calcite (3)
Gypsum (2)
Talc (1)
In terms of this scale, the hardness of skin is about 1.5, a fingernail is up to 2.5, a knife
blade is near 5.5, window glass is 5.5 and a streak plate is near 6.5. Your problem is to
determine by comparison to calcite, window glass and a streak plate the approximate hardness of
the given minerals.
Procedure: Work with one mineral at a time. Record your results in Table 3. List specimen
numbers in order from smallest to largest.
Step 1. See if the smooth cleavage surface of a calcite crystal can be scratched* by a
sharp edge of the mineral. If the mineral does not leave a scratch on the calcite its hardness is
less than 3 but if it scratches the calcite its hardness is 3 or more.
Step 2. If the mineral is of hardness 3 or more, place a glass slab flat on the table* and
see if you can scratch it with the mineral. If you cannot, the mineral's hardness is less than 5.5.
If you can the mineral's hardness is 5.5 or more.
*After rubbing any powder away with your finger tip, the scratch must be deep enough for
you to catch your finger nail in it. (CAUTION: do not hold the glass slab in your hand when
scratching it).
Table 3
Mineral
specimen no.
Hardness
page 80 OPH
Exercise 5 SPECIFIC GRAVITY
The specific gravity of a substance is its weight in air compared to the weight of an equal
volume of water. A mineral's specific gravity lies within a range limited by the possible
compositional variation. Minerals with otherwise similar physical properties can have specific
gravities that differ materially. Your problem is to determine the specific gravity of the given
minerals.
Procedure: CAUTION: Never touch the spring on the Jolly balance as this can be easily
damaged.
Work with one mineral at a time. Record your results in Table 4. List specimen numbers in
order from smallest to largest.
Step 1. Fill a 250 ml beaker with water. Place it on the beaker stand (see Fig. 12).
Step 2. Hold the pan hook (not the coiled part of the spring just below the whiskers and
with your free hand carefully straighten the whiskers so that they are level and parallel the
graduated mirror face.
Step 3. Raise beaker stand and beaker until pan 2 floats on the water. Push pan 2 into
the water with your finger tip. Raise the beaker stand a little more so that pan 2 is completely
immersed up to the vertical support wire below pan 1. (Note: pan 1 should not become wet
during this process. If at any time pan 1 does become wet, hold the pan, not the spring, and
dry it with a paper towel.)
Step 4. Look for the image of the whisker in the graduated mirror. Raise or lower your
level of sight until the whisker hides its own image in the mirror. Keeping that position, read the
level (to an 0.1 accuracy) of the whisker on the graduated mirror. Record this reading. Lower
the beaker stand and beaker to the base of the stand. Pan 2 will be left clear of the water. Do not
mind if some water splashes around.
Step 5. Hold pan 1 and place the dry mineral chip(s), on it. Support pan 1 beneath with
your finger tips and gently lower until the pan lifts away. Repeat Step 3. Repeat Step 4.
To achieve greatest accuracy, add or remove chips to bring the whisker near the bottom of the
graduated mirror. Repeat steps 3 and 4. Do not repeat step 5. Go to step 6.
Step 6. Hold pan 1 and take the mineral chip(s) off it. We these chips in the water in the
beaker. Hold pan 2 and place the wet mineral chips on it. Repeat steps 3 and 4. Hold pan 2 and
take the mineral chip(s) off it.
Note:For the next determination, start again at Step 5.
Step 7. Calculate the specific gravity for each mineral according to:
A = initial reading without mineral in pan 1 or pan 2.
B = reading with mineral in pan 1 in air.
C = reading with mineral in pan 2 in water.
D = weight of the mineral in air = B - A.
E = weight of an equal volume of water = B - C.
Specific Gravity = D/E.
page 81 OPH
Table 4
Mineral
specimen
no.
Readings
A
B
Calculations
C
D
E
Specific
gravity
page 82 OPH
Section III
Exercise 6 IDENTIFICATION OF MINERALS BY THEIR PHYSICAL PROPERTIES
You have examined the given minerals for color, streak, luster, hardness and specific gravity.
The same minerals could have been examined for crystallization, structure, cleavage, fracture,
tenacity and special characteristics such as taste, odor, magnetism and fluorescence. Your
problem is to name the given minerals.
Procedure: Refer to your data in Tables 1, 3 and 4. Work with one mineral at a time. Record
your results in Table 5. List specimen numbers in order from smallest to largest.
Step 1. Use the accompanying identification table (p. 77- 79) to narrow the choice of the
possible name(s). List these.
Step 2 (optional). If there is a choice between several minerals, read fuller descriptions
of their physical characteristics in a reference provided by your instructor. In column 2 of Table
5, underline the mineral name you finally choose and in column 3 record the physical
characteristics by which it is distinguished.
Table 5
Mineral
specimen no.
Possible minerals
Distinguishing physical characteristics
page 83 OPH
ORE MINERAL IDENTIFICATION TABLE
metallic
Note: minerals that can have a
luster are italicized 1
Color
Streak
H.
S.G.
Possible ore minerals(s)1
dark gray
to black
dark gray
to black
1-3
4.3 - 5.4
5.5 - 5.8
6.4 - 6.6
7.2 - 7.6
tetrahedrite, stibnite, pyrolusite
chalcocite
bismithinite
argentite, galena
3 - 5.5
4.1 - 4.3
4.9 - 5.2
8.0 - 10.0
chalcopyrite
bornite
uraninite
5.5 - 10
4.5 - 5.5
5.4 - 6.4
7.1 - 7.5
ilmenite, magnetite, franklinite
columbite
wolframite
1-3
3.9 - 4.2
4.3 - 5.4
5.7 - 6.1
8.5 - 9.0
sphalerite
tetrahedrite, hematite
cuprite
copper
3 - 5.5
4.2 - 6.4
7.1 - 7.5
manganite, chromite, ilmenite,
franklinite, columbite
wolframite
1-3
3.4 - 4.0
limonite
3 - 5.5
3.7 - 4.4
siderite, sphalerite, goethite
uncolored,
white, or
light gray
3 - 5.5
2.9 - 3.1
magnesite
dark gray
to black
1-3
4.5 - 4.6
4.9 - 5.2
7.1 - 7.5
pyrrhotite
bornite
wolframite
brown to
red
1-3
2.5 - 2.6
4.9 - 5.3
8.0 - 8.2
8.5 - 9.0
bauxite
hematite
cinnabar
copper
3 - 5.5
3.3 - 3.5
4.2 - 4.3
5.4 - 5.7
5.7 - 6.1
7.1 - 7.5
8.0 - 10.0
hematite
rutile
zincite
cuprite
wolframite
uraninite
5.5 - 10
3.3 - 3.5
4.2 - 4.3
hematite
rutile
brown to
red
yellow
brown to
red
page 84 OPH
brown to
red
continued
yellow
Uncolored
white or
light gray
yellow
dark gray
to black
yellow
uncolored
to white
1-3
3.4 - 4.0
limonite
3 - 5.5
3.7 - 3.9
3.9 - 4.2
siderite
sphalerite
5.5 - 10
4.2 - 4.3
6.8 - 7.6
rutile
cassiterite
1-3
2.5 - 2.6
4.3 - 4.7
bauxite
barite
3 - 5.5
3.3 - 3.6
3.9 - 4.0
5.9 - 6.2
rhodochrosite
celestite
scheelite
5.5 - 10
2.6 - 2.8
4.2 - 4.3
4.4 - 5.8
beryl
rutile
zircon
3 - 5.5
4.1 - 4.3
4.5 - 4.6
4.6 - 5.2
chalcopyrite
pyrrhotite
pentlandite, bornite
5.5 - 10
4.9 - 5.2
pyrite
1-3
3.4 - 4.0
15.6 - 19.3
orpiment, realgar, limonite
gold
3 - 5.5
3.9 - 4.4
4.9 - 5.0
5.4 - 5.7
sphalerite, goethite
greenockite
zincite
1-3
1.9 - 2.0
cerussite
3 - 5.5
2.9 - 3.1
3.3 - 3.6
3.6 - 3.8
3.9 - 4.0
4.1 - 4.5
5.9 - 6.2
magnesite
rhodochrosite
strontianite
celestite
smithsonite
scheelite
5.5 - 10
2.6 - 2.8
4.4 - 4.8
beryl
zircon
page 85 OPH
blue or
green
dark gray
to black
1-3
4.6
covellite
red
1-3
8.5 - 9.0
copper
blue or
green
1-3
3.0 - 3.1
4.6
5.5 - 5.8
annabergite
covellite
chalcocite
3 - 5.5
3.7 - 4.1
6.0 - 8.0
azurite, malachite
uraninite
3 5.5
2.0 - 2.2
3.1 - 3.2
3.9 - 4.0
4.1 - 4.5
5.9 - 6.2
anglesite
spodumene
celestite
smithsonite
scheelite
5.5 10
2.6 - 2.8
4.4 - 4.8
beryl
zircon
1-3
4.6 - 4.7
6.4 - 6.6
7.3 - 7.6
stibnite
bismuthinite
galena
3 - 5.5
5.9 - 6.4
6.4 - 6.6
asenopyrite, cobalt
smaltite
1-3
2.5
10.0 - 12.0
bauxite
silver
3 - 5.5
2.6 - 2.8
2.9 - 3.1
3.6 - 3.8
3.9 - 4.0
4.1 - 4.5
5.9 - 6.4
6.4 - 6.6
beryl
magnesite
strontianite
celestite
smithsonite, witherite
scheelite, anglesite
cerussite
5.5 - 10
4.4 - 4.8
6.0 - 7.0
zircon
spodumene
uncolored
white or
light gray
uncolored
white or
light gray
dark gray
to black
uncolored
white or
light gray
page 86 OPH
APPENDIX Setting up the Jolly Balance
Selected references for the identification of minerals:
page 87 OCH
GE-101 Sect:
Physical Geology
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Instructor:
Date:
/
/
Your name:
Laboratory module:
Ore minerals, chemical properties
Objectives: After completing this laboratory you should be able to:
1. Describe a method for grouping minerals by the way they can be made to dissolve.
2. Name and follow chemical procedures that indicate the presence of certain metal
elements in mineral solutions.
3. Describe the difference between a mineral's physical and its chemical properties.
EQUIPMENT CHECK LIST (Report any missing items to the laboratory proctor
Material
Description
SOILS
4 crushed unknowns* in bottles labeled by
specimen number. Each bottle contains a 0.25
gm measuring spoon.
CHEMICALS
Concentrated hydrochloric acid in half lidded
50 ml stoppered bottle in safety dish.
Reagents: Ammonium carbonate and
potassium iodine in dark bottles.
Distilled water in dropper bottle.
SPECIAL
EQUIPMENT
Test tubes (pyrex)
Test tube stand
Test tube holder
50 ml beakers
200 ml beaker
Glass rod (stirrer)
Pippets (droppers)
Filter funnels
Filter papers1
Alcohol burner
Spot test plate
Wire (steel, thin gauge)1
Wire holder1
Pliers (wire-cutting)1
per pair
Students
per
Table
1 set
1
1
1
4
1
1
4
1
1
5
4
1
1
*Selected from the following minerals: anhydrite, azurite, braunite, calamine, calcite, chrysocolla,
cuprite, forsterite, galena, goethite, greenockite, gypsum, halite, hematite, limonite,
magnesite, malachite, pyrolusite, rhodonite, scheelite, serpentine, siderite, smithsonite,
sphalerite, stibnite, strontianite, sylvite, trona, willemnite- witherite, wollastonite, zincite.
1
Available in laboratory room.
page 88 OCH
Section I
Minerals are known to be composed either of one or of several elements. Amongst the latter,
composition is fixed for some and for others it can vary, with respect to some of its components, through
a range limited only by the condition that the symmetry of internal crystal structure remains unchanged.
Museum mineral collections, for display and research, are usually arranged according to the one
criterion: composition. A classification scheme devised by Dana (see Appendix ) is commonly followed.
When presented with an unfamiliar mineral for identification, we are quite often apt to forget to
test for its chemical properties which yield, qualitatively, a partial chemical analysis. This may be
because our experience with minerals is such that, under natural conditions, they mostly seem to
effectively withstand rapid decomposition or dissolution (both are chemical properties) and because we
know chemical tests usually require that a substance first be got into solution. The cardinal point to
remember is that all minerals can be got into solution and most so relatively easily. This is particularly
true of the ore minerals. For practical reasons, the only ore minerals that 1) cannot be easily dissolved or
2) have complex compositions, are those for which no alternative is known or is available.
Minerals can be grouped according to the way they can be made to dissolve. We find
minerals that are:
(A) partially or completely dissolved in hydrochloric acid.
(B) not soluble in hydrochloric acid but dissolve in nitric acid.
(C) not soluble in hydrochloric or nitric acid but are at least partly decomposed and
dissolved by nitric acid
(D) not dissolved by any of the common acids but can be fused with soda or
potassium bisulfate.
In (A) are found those minerals that are water soluble; most of the phosphates, sulfates, borates
and tungstates: the metallic ore carbonates and most oxides, and many of the less stable silicates. In (B)
will be found a majority of the heavy metallic ore sulfides, while in (C) and (D) are most silicates and a
few metallic ore oxides.
For illustrative purposes in this module, minerals have been selected which occur in group (A)
and which have only one metal in their composition.
page 89 OCH
Exercise 1 EVALUATION QUESTIONS
Can a mineral be composed of only one element? (yes, no) Explain.
In a museum display, would you expect minerals to be arranged according to their composition,
symmetry of internal crystal structure, physical properties or chemical properties?
What is quantitative chemical analysis?
Describe two desirable characteristics of minerals which are ores.
Is the way a mineral can be made to dissolve a physical property or a chemical property?
What groups of metallic ore minerals characteristically dissolve in:
hydrochloric acid
nitric acid
Are some oxides insoluble in the common acids? (yes, no) Explain.
WARNING: WHEN YOU ENTER THE LABORATORY ROOM THERE WILL BE
CONCENTRATED ACID ON THE TABLE.
DO NOT PICK UP THE ACID BOTTLE. DO NOT REMOVE IT AT ANY TIME FROM ITS
SAFETY DISH.
page 90 OCH
Section II CHEMICAL PROPERTIES
Exercise 2 SOLUBILITY OF MINERALS IN HYDROCHLORIC ACID
Not all minerals are soluble in hydrochloric acid. The (crushed) minerals you have been given,
however, are known to be. Your problem is to observe under what conditions the given minerals can be
made to dissolve. (Note: If a mineral is soluble in water, it will also be soluble in hydrochloric acid.
However, minerals not soluble in water may yet be soluble in hydrochloric acid.)
Procedure: Work with the four crushed minerals. Keep them organized in order of increasing specimen
number. Record your results in Table 1.
Step 1. Hold a thoroughly clean test tube with a test tube holder clamped near its open end. With
a measuring spoon marked 0.25 gms, introduce one level measure of the finely crushed mineral into the
test tube. Return the measuring spoon to the same ar it came from. Concentrate on working
systematically (the spoon is inside the jar with the crushed mineral).
Step 2. Add 20 drops of water to the test tube, (A drop is an exact measure. Work accurately.)
Shake the test tube from side to side to mix contents while holding it with the holder. (Note: to prevent
spillage, only the bottom of the test tube should move vigorously from side to side.) If the contents of the
test tube looks muddy or opaque, solution of the mineral has not occurred. If solution has occurred, the
liquid should be transparent (colorless or colored) and not cloudy and there should be no (or very little)
powder left. If it did not dissolve, go to step 3, otherwise go to step 6.
Step 3. (CAUTION: do not pick up the acid-bottle.) Firmly hold the acid bottle down in its
safety dish and with your free hand, twist and lift out its stopper. The stopper also acts as a dropper.
(CAUTION: should you get any acid on your skin or clothes, you have five minutes to avoid serious
damage. Flood area with water and inform proctor without delay.)
Step 4. If the mineral did not dissolve in Step 2, add (to the contents of the same test tube) ten
drops of concentrated hydrochloric acid. In the diluted hydrochloric-acid, if the contents immediately
starts to effervesce (bubble), the gas evolved is carbon dioxide and the mineral will soon be dissolved.
Otherwise, go to Step 5.
Light an alcohol burner (or a gas burner).
Step 5. Add (to the contents of the same test tube) twenty drops of concentrated hydrochloric
acid. Bring to boil while shaking the test tube continuously as before for one minute. If while boiling a
fetid (rotten egg, stink bomb) odor is noticed, hydrogen sulfide gas is evolved. Remove the test tube from
the flame and after the boiling has died down note whether there is a residue in the bottom of the test
tube. If there be, look at it carefully to see whether slow bubbling can be seen. If so, chlorine gas is
evolved. Otherwise (and only an acrid smell can be noticed), no gas is evolved. If there is a residue, boil
contents again for one more minute as before. Note if the mineral is wholly or partly dissolved. When
partly dissolved, describe the residue as: some (of the original material), yellow (WO3), white (PbCl2) or
gelatinous (SiO2).
Step 6. Note the color of each solution obtained. Do not throw these solutions away. Keep
them for exercises 4 and 5.
Extinguish the alcohol (or turn off the gas) flame.
page 91 OCH
Table 1
MINERAL SOLUBILITY
Mineral
specimen
no.
Soluble
in1
Gas
evolved2
Degree of
solution3
1
water,
dilute HCl (hydrochloric acid) step 2,
concentrated HCI step 4.
2
CO2- carbon dioxide (effervescence in dil. HC1),
H2S - hydrogen sulfide (fetid odor),
Cl2- chlorine (slow effervescence in conc. HCl),
none (no gas evolved).
3
wholly dissolved,
partly dissolved
4
none,
some (of the original),
yellow (WO3),
white (PbC12),
gelatinous (SiO2)
Residue4
Color of
solution
page 92 OCH
Exercise 3 USE OF SOLUBILITY DATA
All the minerals you were given are wholly or partly soluble in hydrochloric acid. Your problem
is to further narrow down the choice of a possible mineral name for each unknown by using the data
obtained in exercise 2.
Procedure: Refer to Table 1. Work with data obtained for one specimen at a time. Classify each
mineral by writing its specimen number appropriately in each stage (1 to 4) of the scheme given in Table
2.
Table 2
Mineral
soluble in
Gas
evolved
Residue
Solution
Possible mineral and composition
water
none
none
colorless
Halite, NaCl
Sylvite, KCl
dil. HCl
CO2
none
colorless
Trona, Na2CO3.NaHCO3.2H20
Witherite, BaCO3
Strontianite, SrCO3
Calcite, CaCO3
Smithsonite, ZnCO3
Magnesite, MgCO3
color
Malachite, CuCO3.Cu(OH)3
Azurite, 2CuCO3.Cu(OH)3
Siderite, FeCO3
none or
some
color
Pyrolusite, MnO2
SiO2
color
Braunite, 3Mn2O3.MnSiO3
none or
some
colorless
Sphalerite, ZnS
color
Greenockite, CdS
PbCl
color
Galena, PbS
none or
some
colorless
Anhydrite, CaSO4
Gypsum, CaSO4.2H20
Zincite, ZnO
Willemnite, ZnSiO4
color
Stibnite, Sb2S3
Hematite, Fe2O3
Goethite, Fe2O3.H20
Limonite, Fe2O3.3H20
Cuprite, Cu2O
Chrysocolla, CuSiO3.2H20
Rhodonite, MnSiO3
WO3
colorless
Scheelite, CaWO3
SiO2
colorless
Wollastonite, CaSiO3
Calamine, 2ZnO.SiO2.H20
Serpentine, 3MgO.sao2.H20
Forsterite, Mg2SiO4
Stage 3
Stage 4
conc. HCl
Cl2
H2S
none
Stage 1
Stage 2
page 93 OCH
Section III
Exercise 4
SPOT TESTS
Once a mineral is in solution, spot can be made tests to distinguish directly between minerals and
groups of minerals on the chemical property of their metal content. The advantage is speed and economy
of materials used. In addition, during the complete qualitative chemical analysis of a mineral, virtually all
of the different specific reactions of the elements and many group tests can be carried out using drops of
the solutions obtained and reagents. Your problem is to test for the chemical properties of the mineral
solutions you obtained in Exercise 2 using the two reagents: ammonium carbonate and potassium
iodide.
Procedure: Work with the four mineral solutions. Keep them organized in order of increasing specimen
number. Record your results in Table 3.
Step 1. Dilute each mineral solution that was kept from Exercise 2 by adding twenty drops of
water to each test tube.
Step 2. Into 5 ml beakers, from each solution, filter (see over, page 88) off any residue and keep
the clear solutions that collect in the beakers. Label each beaker carefully. Place a clean dropper in each
beaker. After use (in the following) always return dropper to same beaker.
Step 3. Fill a large beaker with clean water. Place a clean glass stirring rod in it and a paper
towel nearby.
Step 4. Work in turn with each filtered solution. On a spot test plate, place three drops of the
solution into each of two side by side depressions: three drops in each depression. (Concentrate on
working systematically so that you can later recall where the various drops have been placed.)
Step 5. Place one drop of ammonium carbonate in the depression with one of the solutions. If a
precipitate (an opaque, muddy, deposit) is obtained, stir with a clean glass rod to mix and record it color.
If no precipitate has been obtained, carefully add one more drop of reagent. Again, if no precipitate is
obtained, add one more drop until 5 have been added. Add no more. Record the color of the precipitate
or solution (be sure to say which) after stirring.
Step 6. Repeat step 5 using the reagent potassium iodide in the place of ammonium carbonate.
Return to step 4 for next solution.
Table 3
Mineral
specimen
no.
Color of precipitate (ppt) or solution (sol). See below :Mineral solution with ammonium carbonate
Mineral solution with potassium iodide
*always indicate: ppt (for precipitate) or, sol (for solution) and describe the color choosing from:
black, brown, dark brown, yellow brown,
yellow, curdy yellow, pale yellow, bright yellow, reddish yellow, orange yellow,
red, dark red, yellow pink, pink, orange, orange red,
green, brown green, olive green, apple green,
amethyst, blue, dark blue,
white, dirty white, pinkish white,
colorless
page 94 OCH
Locate box of filter papers.
Take one circular sheet.
Fold the circular sheet in half.
Fold the folded sheet in half again.
Press open one side to form a cone.
Set the cone into a filter funnel.
Hold it open and in place.
Wet cone, thoroughly, with drops of
water.
Tip or shake out any excess water that
the filter paper has not absorbed.
Set the filter funnel, with wetted filter
paper cone, in a 50 ml beaker. It
is now ready for use.
Pour anything you wish to filter into
the center of the cone. Be careful
not to more than half fill cone at
any time.
The filtered solution will collect in
the beaker.
Figure 31. Filtering procedure.
page 95 OCH
Exercise 5 FLAME TESTS
Some minerals are found to impart a characteristic color to an otherwise colorless flame when heated in
that flame. This effect can be caused by any of several metals present in the mineral.
The flame test, as this is called can be used to analyze for any of these metals in a mineral. The flame test
is not effected by a mineral's solubility. Your problem is to carry out a flame test on each of the given
crushed minerals.
Procedure: Work with the filtered solution of one mineral at a time. Record your results in Table 4. List
specimen numbers in order from smallest to largest.
Step 1. Locate the wire cutting and shaping pliers and a roll of thin gauge steel wire. Cut off a
three inch length of wire and clamp one end firmly into a wire holder. Light the alcohol (or gas) burner.
Step 2. Heat end of the wire to glowing in the colorless part of the alcohol burner (or gas) flame.
Hold it in the invisible flame until no color (yellow) is imparted to the invisible flame when the tip of the
wire glows.
Step 3. Dip the tip of the wire into one of the solutions saved from Exercise 2. Then hold the tip
of the wire in the flame again. Note if a colored flame appears*. Repeat Step 2 and step 3 for each
solution. Record your results in Table 4.
Table 4
Mineral
specimen no
Flame color
Fig. 15
*Describe the color choosing from: None, or
intense yellow, orange, yellowish red, carmine, crimson, pale violet, livid blue, azure blue,
bluish green, pale green, yellowish green, pale greenish white.
page 96 OCH
Exercise 6 USE OF SPOT TEST AND FLAME TEST DATA
When a mineral contains only one metal in its composition, spot test and/or flame test data can
often indicate that metal directly. When a mineral contains several metals in its composition, a detailed
analytical procedure must be followed in order to separate out each-one. The crushed minerals you were
given have only one metal in their composition. Many ore minerals have this feature. Your problem is to
use the data obtained in exercises 4 and 5 to identify the metal component of each of the given minerals.
Procedure: Refer to Table 5 and by direct comparison of your data in Tables 3 and 4 determine the metal
in each mineral specimen. Write the specimen number beside the metal indicated in Table 5.
Table 5
Spot test
Flame test
Metal
indicated
ammonium carbonate
potassium iodide
brown ppt.
deep red sol
none
ferric iron, Fe
yellow orange sol.
none
manganic
manganese,
Mn
green ppt. or a
blue ppt. or sol.
dirty green
to brown ppt
azure blue with
green outline
copper,
Cu
dirty white ppt.
deep red sol.
none
ferrous iron,
Fe
white ppt.
orange sol.
none
cadmium,
Cd
yellow sol.
none
manganous
manganese,
Mn
colorless or
pale yellow sol.
bluish green
zinc,
Zn
colorless or
pale yellow sol.
pale green
stibnite,
Sb
yellowish green
barium,
Br
intense yellow
or orange
sodium,
Na
yellowish red
calcium,
Ca
crimson
strontium,
Sr
pale violet
potassium,
K
colorless sol.
Mineral
specimen
no.
page 97 OCH
Exercise 7
IDENTIFICATION OF MINERALS BY THEIR CHEMICAL PROPERTIES
In Exercise 3, you narrowed the choice of possible mineral names and compositions for each of the given
crushed mineral specimens. Your problem is to further narrow down this choice knowing the metal that
each has in its composition.
Procedure: List the minerals in order of increasing specimen number in Table 6. Consider one at a time:
Table 5 tells you the metal it contains. Then go to Table 2 and note which possible mineral(s) it could
be. Record your results in .
Table 6
Mineral
specimen no.
Possible mineral(s)
page 98
GE-101 Sect:
Physical Geology
Instructor:
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Date:
Your name:
HOMEWORK: Collection of soil sample
/
/
SPH
page 99
GE-101 Sect:
Physical Geology
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Instructor:
Date:
/
/
Your name:
Laboratory module: Soil science, physical
Objectives: After completing this laboratory you should be able to:
1. Describe the physical characteristics of soil.
2. Classify soils on the criterion of their texture.
3. Measure the porosity, permeability and capillarity of loose soils.
EQUIPMENT CHECK LIST (Report any missing items to the laboratory proctor
Material
Description
SOILS
1/2 lb sample (either to be collected and
dried by student - see Appendix E - or
to be provided)
Dispersing reagent in dropper bottle
Flocculating reagent in dropper bottle
Soil separation tubes graduated in mls
Stand to hold tubes
Beaker, 100 ml
1
Funnel, 4" upper diameter, plastic, narrow stem
Stand to hold funnel
Water bottle with dropper, 500 ml
Stop watch
*Cotton wool
*Calculator
CHEMICALS
GEOLOGICAL
EQUIPMENT
SPECIAL
EQUIPMENT
1
per
Student
1
per
Table
1
1
1
1
1
1
1
1
1
1
Cut off stem, short and at an angle, so that liquid does not become caught in it when used in these
exercises
*Available in laboratory.
SPH
page 100
SPH
Section I
Soils originate from the weathering of rock or sediments and exist at the earth's surface as
residual deposits. Soil supports the plant life of the land and hence most of its animals. The variety,
formation and changeability of soils; their physical and chemical nature, is the study of soil science.
Descriptive terms that distinguish the physical variety of soils such as: clayey, silty or sandy
soil, refer to the predominance of particles of a certain size range in the soil. For measurement and
analysis of this physical parameter, class names for particle size ranges have been devised for
determining the proportions of particles of each class in a given soil sample (see Figure 17). Loam
soils, for example, are certain mixtures of clay, silt and sand. In the physical classification of soils,
particles larger than sand size are taken to be foreign because they are not thought of, in themselves, as
being supportive of life. To compare soils of different textural types, only their sand, silt and clay size
fractions by volume are considered; foreign materials ("stones," root masses, etc.) are first removed.
Physical properties of soil, attributed in part to the size distribution of component particles,
are: ability to retain and ability to transmit water. In order that these properties can be studied
meaningfully, it is necessary to define: porosity, permeability and capillarity.
Porosity is a measure of the empty or void space in a material.
Permeability is a measure of the interconnection of pore spaces in a material.
Capillarity is a measure of the amount of water that can be held by surface tension in the
interconnected pore spaces of a material.
Particles
Class name
Boulder
Cobble
Pebble
Granule
Coarse sand
Medium sand
Fine sand
Silt
Clay
Figure 17.
Size range in mm.
greater than 256
64 - 256
4 - 64
2- 4
1/2 - 2
1/4 -1/2
1/16 - 1/4
1/256 - 1/16
less than 1/264
Table showing the size range of named classes of particles;
proposed by C. K. Wentworth in 1922.
page 101
SPH
Exercise 1 EVALUATION QUESTIONS
How do soils originate?
To human life, what is the most important aspect of soils?
According to Wentworth's scale:
How large can a sand sized particle be?
How small can a sand sized particle be?
Are clay sized particles necessarily the mineral clay? (yes, no) Explain.
What is loam?
Why is soil texture defined as the size distribution of particles in the soil which are less than 2 mm in
size?
Define:
Porosity
Permeability
Capillarity
This week:
start exercises 2, 4
complete exercises 1, 5, 6
Next week:
complete exercises 2, 3, 4
page 102
Section II
SPH
SOIL TEXTURE
Exercise 2 ELUTRIATION
Soil texture is defined as the size distribution of particles less than 2 mm in size in the soil. Several
methods exist called elutriation for performing wet mechanical analysis to determine a soil's textural
type. All are based on Stoke's Law which determines the velocity at which a spherical particle of a
given diameter and weight settles in a still liquid. Appendix F gives information on the time needed
for different sized soil particles to settle through 10 cm of water. Your problem is to separate by
elutriation the soil you collected, or that provided, into particle size classes: sand, silt, and clay.
Procedure: Note: the soil separation tubes are graduated in milliliters (ml). Record your results in
Table 1.
Step 1. Label the three soil separation tubes, or their caps, A through C and stand them in the
rack provided. Remove the caps.
Step 2. Add soil to tube A up to line 15. Note: gently tap the
bottom of the tube on a firm surface to pack and level the soil and eliminate air spaces.
Step 3. Locate a stop watch and practice timing 30 seconds.
Step 4. Using the graduated dropper in the Soil Dispersing Reagent add 1.0 ml of reagent to
the sample in tube A. Fill soil separation tube A up to line 50 with tap water, cap and shake for two
minutes to thoroughly mix the soil with the water.
Step 5. Simultaneously stop shaking tube and start stop watch. Remove the cap and place
tube A in the rack and leave undisturbed.
Step 6. After 30 seconds has elapsed on the stop watch, immediately, pour into tube B all the
muddy water off the sand settled in tube A. Place tubes A and B in stand and leave undisturbed.
Step 7. After 30 minutes (take a break or start work on exercise 5) has elapsed on the stop
watch, immediately pour into tube C all the muddy water off the slit settled in tube B. Place tubes B
and C in stand. Measure the volume of sand in tube A.
Step 8. To tube C, add 1 measure (1 ml) of Soil Flocculating Reagent cap tube and shake for
1 minute. Initial label and return capped tube to stand. Measure the volume of silt in tube B. Wash
out tubes A and B (see page 76).
Step 9. At any time after 24 hours (next week, for example), carefully measure, without
disturbing contents, the volume of the clay in tube C.
Table 1
Soil
sample
no.
Size fraction by volume (ml)
Sand in tube A
Silt in tube B
Clay in tube C
page 103
Exercise 3
SPH
NAMING A SOIL'S TEXTURAL TYPE
The classification of soil textural types is based on their sand, silt and clay fractions by volume. When
added, these three fractions have a total volume which is greater than that of the original soil sample.
This is because when mixed together in the soil, the smaller particles can fit between the larger
particles. Also, clay has a tendency to swell when wet. Your problem is to use the U. S. Department
of Agriculture's scheme (see Figure 32) to classify and name the textural type of the soil you collected,
or that provided.
Procedure: Refer to data recorded in Table 1 and to Figure 32. Record your results in Table 2.
Step 1. Calculate the following (show working):
Total volume of the sand, silt and clay separated by elutriation:
volume sand + volume silt + volume clay = Z
Percentage sand by volume separated by elutriation:
volume sand x 100 =
Z
X
Percentage silt by volume separated by elutriation:
volume silt x 100 = Y
Z
Step 2. Mark the calculated percentage sand (X) on the bottom side of the diagram
in Figure 32 and draw a vertical line into the diagram from that point.
Step 3. Mark the calculated percentage silt (Y) on the left side of the diagram in Figure 32
and draw a horizontal line into the diagram from that point.
Step 4. Note in which named area of the diagram in Figure 32 the vertical and horizontal lines
that you have drawn meet. This gives the soil's textural type name.
Table 2
Soil
sample no
Z
X
Y
Textural type name
page 104
Figure 32. Classification of soil textural types
SPH
page 105
SPH
Section III
Exercise 4
POROSITY
The volume of pore space expressed as a percentage of the total volume of a material is called
porosity. Your problem is to measure the porosity of a loose soil.
Procedure: Record your results in Table 3.
Step 1. Label a clean, dry, soil separation tube with your name and soil sample number.
Place approximately 25 ml of the soil in the tube
Step 2. Pour approximately 25 ml of water into a second soil separation tube. Hold the tube
vertically and exactly measure the volume (V1) of the water (see Figure 33a).
Step 3. Very slowly pour the measured volume of water onto the soil in the first tube. The
soil should first become wetted and then flooded without being stirred up. Gently tap the base of the
tube against the table to level soil but again not stir up. Cap the tube and place it where it will not be
disturbed.
Step 4. At any time after 24 hours (next week for example) carefully measure the volume (V2)
of the water-saturated soil (eliminate air pockets in the soil by tapping the base of the tube
straight down onto the table surface) and the volume (V3) of the saturated soil plus excess water (see
Figure 33b).
Figure 33
Step 5. Calculate the following (show working):
Volume of excess water: V3 - V2 = V4
Volume of water in soil pores: V1 - V4 = V5
Percentage porosity: (V5 / V2) x 100
Table 3
Soil
sample
no.
Measurements
V1
V2
V3
Calculations
V4
V5
% Porosity
page 106
Exercise 5
SPH
PERMEABILITY
Permeability is the capacity of a porous material to transmit water. Thus whereas porosity determines
the maximum amount of water that a particular material can hold, the rate of movement of water
through a material will depend on its permeability. Pore water can move only if the pore spaces are
interconnected. Your problem is to determine the permeability of a loose soil.
Procedure: Record your results in Table 4. Refer to Figure 34.
Step 1. In the neck of a funnel, place a small wad of cotton wool and wet it with a few drops
of water so that it stays in place but is not packed down. Set the funnel in a stand.
Step 2. Measure 25 ml of soil (V6) in a dry soil separation tube and tip it into the funnel on
top of the cotton wool. Level surface but do not pack down. Place a dry beaker beneath the funnel.
Step 3. Measure 50 ml of water in the soil separation tube. Set a stop watch to zero. Rapidly
pour the 50 ml of water (V7) on top of the sand in the funnel. Start stopwatch immediately and
measure the time it takes for the water to sink out of sight into the soil. Describe the permeability
as:
High — time measured was less than 1 minute
Moderate — time measured was 1 to 30 minutes
Low — time measured was more than 30 minutes+
+Stop measuring time after 35 minutes. Pour off any water still above soil into the beaker.
Figure 34
Step 4. Leave the beaker in place and wait until water stops flowing from funnel stem. Do
not discard water caught in beaker; keep for Exercise 6.
Table 4
Soil
sample
no
Volume of
soil in
funnel, V6
Volume of
water poured
on soil, V7
Time flow
through
funnel stem
Permeability
page 107
SPH
Exercise 6 CAPILLARITY
Water will not drain completely from a permeable material if the water supply is cut off. The material
will remain damp. When interconnected pore spaces are only partly filled with water, surface tension
holds the water back. Capillarity is a measure of how much water a permeable material can retain.
Your problem is to determine the capillarity of a loose soil.
Procedure: Record your results in Table 5. Refer to data in Table 4.
Step 1. Pour the water caught in the beaker during exercise 5 into a soil separation tube and
accurately measure its volume (V8).
Step 2. Calculate the volume of capillarity water held in soil:
V7 - V8 = V9
Step 3. Calculate the capillarity expressed as a percentage:
( V9 / V6 ) x 100
Table 5
Soil
sample no.
V8
V9
% Capillarity
Clean up procedure to be followed when discarding soil
Tap out as much soil into plastic garbage bin as you can.
Rinse tube in deep plastic bin filled with water.
Please do not allow any soil to get into sink as this will clog it.
Soak tubes in shallow plastic bin filled with hot water.
Return after 10 minutes to remove label and rinse off the gum under running water.
Stand washed tubes inverted in stand to drain.
page 108 SPH
Clean up procedure to be followed when discarding soil
Tap out as much soil into plastic garbage bin as you can.
Rinse tube in deep plastic bin filled with water.
Please do not allow any soil to get into sink as this will clog it.
Soak tubes in shallow plastic bin filled with hot water.
Return after 10 minutes to remove label and rinse off the gum under running water.
Stand washed tubes inverted in stand to drain.
page 109 SCH
GE-101 Sect:
Physical Geology
QUEENSBOROUGH COMMUNITY COLLEGE
The City University of New York
Instructor:
Date:
/
/
Your name:
Laboratory module: Soil science. chemical
Objectives: After completing this laboratory you should be able to:
1. Discuss why plants cannot be expected to grow well in any soil.
2. Decide on what proportions of fertilizer to apply to nutrient deficient soils.
3. Understand how and under what circumstances to adjust a soil's pH.
EQUIPMENT CHECK LIST (Report any missing items-to the laboratory proctor)
Material
Description
SOILS
2 ounce sample (either to be collected and dried by
student - see Appendix E - or to be provided).
Unknowns set of 3 in bottles:
labeled: high Utility, A, and B.
LaMOTTE
CHEMICAL
SOIL TEST
EQUIPMENT
per
student
per
table
1
1 set
Nitrogen extracting solution
Nitrogen indicator powder
Nitrogen color chart
1
1
1
Phosphorus extracting solution
Phosphorus indicator solution
Phosphorus tablets
Phosphorus color chart
1
1
1
1
Potassium extracting solution
Potassium indicator tablets
Potassium test solution
Potassium color chart
1
1
1
1
pH indicator solution
pH color chart
1
1
Measuring spoons, 0.5 g. and 0.2 g.
Test. tubes, flat bottomed, graduated in rnl.
Test tube caps
Pipette (eye dropper)
2
6
6
1
page 110 SCH
Section I
Soil originates where weathering keeps ahead of erosion or burial. Weathering involves
progressive fragmentation and chemical adjustment of rock or sediment to air and water at the earth's
surface. The rate of chemical adjustment at surface temperatures and pressures is slow on all but a
ecological time scale. During weathering, elements enter idol' aqueous solution in a soil's moisture where
they become available to plants for their nutrition. Plants are adapted to utilize or cope with such
elements in the proportions that are naturally available in their native habitat.
Primary elements for plant nutrition are: nitrogen, phosphorus and potassium. Where crops. lawn
clippings. cut flowers, etc., are removed from an area, depletion of the primary elements will exceed the
natural rate at which these elements enter the soil's moisture. Unless plants are allowed to grow and die in
their natural setting it is necessary to artificially fertilize the soil with soluble salts of the primary
elements in the proportions that they are used by the plants.
Secondary elements for plant nutrition are: sulfur, iron, calcium and magnesium. The availability
of these elements to plants is determined by a soil's pH which is the acidity or alkalinity of the soil's
moisture measured on a scale that runs from: 1 for extremely acid, to 7 for neutral, to 14 for extremely
alkaline. Usually, sulfur and iron are abundantly available to plants in acidic (sour) sons, whereas,
calcium and magnesium are abundantly available in alkaline (sweet) soils. Because plants utilize these
elements in relatively small quantities, it is tardy necessary to fertilize for these elements as weathering
can keep pace with their depletion. However, if the natural soil is acid and one desires to grow plants
adapted to, say, alkaline soils, the soil's pH must be adjusted on a year to year basis by the artificial
addition of suitable compounds to the soil.
page 111 SCH
Exercise 1
EVALUATION QUESTIONS
In human terms, can the ongoing, natural, forming of soils be viewed as a rapid or a slow process?
Under what circumstances are elements in soils available to plants for their nutrition?
Why is it that the chemistry of soil moisture will strongly influence which given plant will best grow?
Name the three primary elements of plant nutrition.
How is it possible for plats to live naturally without our aid?
Does a plant, in order to thrive, necessarily need each of the three primary elements in the same amounts?
(yes, no) Explain.
What will usually determine the proportions of secondary elements available for plant's nutrition?
Will plants adapted to sour soils require calcium and magnesium in abundance? (yes, no) Explain.
If a soil's pH is adjusted to make sulfur and iron abundantly available in the soil's moisture, would plants
adapted to sweet soil thrive? (yes, no) Explain.
page 112 SCH
Section II
PRIMARY ELEMENTS
Exercise 2
TO TEST FOR SOIL NITROGEN, PHOSPHORUS AND POTASSIUM
Plants use, in various amounts bar their growth. nitrogen, phosphorus, and potassium more than
any other elements in soil moisture. Your problem is to measure the availability of these elements to
plants in the soil you collected by comparison to a given hip fertility soil.
Procedure: Work with two soils: the given High Fertility Soil (in labeled glass jar) and yours. Do
the following tests: A (page 113), B (page 114), and C (page 115). Take test materials for one test at a time
and return these before proceeding to the next test. Note: the tests A, B, or C can be done in any order.
Record your results in Table 1.
Table 1
Soil
sample
High Fertility Soil
Your soil
Primary elements available to plants
Nitrogen level
Phosphorus level
Potassium level
page 113 SCH
A) NITROGEN TEST. For each soil sample:
Step 1. Select a graduated test tube and add Nitrogen Extracting Solution to line 7. Note:
Squeeze the bottle gently to insure a uniform flow of solution.
Step 2. Using the measuring spoon marked 0.5 g, add one measure of the soil to the test tube.
Step 3. Replace the cap on the test tube and gently shake the mixture of soil and extracting
solution for one minute.
Step 4. Without removing the cap, allow the tube to stand undisturbed for several minutes. This
allows soil particles to settle so that the liquid above the soil layer becomes reasonably clear.
Step 5. A pipette (eye dropper) is provided to transfer this clear solution to a second graduated
test tube. To accomplish this, squeeze the bulb of the pipette before insertion in the first test tube (this
prevents agitation of the clear solution). After insertion, release the pressure on the bulb and so draw up a
portion of the clear solution. Transfer this amount to the second test tube. Continue this procedure until
the levy of solution is even with line 3 of the second test tube.
Step 6. Use a clean measure spoon 0.25 g and add one measure of Nitrogen Indicator Powder to
the soil extract in the second test tube.
Step 7. Cap the test tube and gently shake this to agitate until the powder is dissolved. Allow
three minutes for the full color to develop.
Step 8. Compare the color of the liquid in the tube with the color printed on the Soil Nitrogen
Color Chart. Record the soil's nitrogen level accordingly as: high, medium, or low.
.
page 114 SCH
B) PHOSPHORUS TEST. For each soil sample:
Step 1. Select a graduated test tube and add Phosphorus Extracting Solution to line 6. Note:
Squeeze the bottle gently to insure a uniform flow of solution.
Step 2. Use the measuring spoon marked 0.5 g, add one measure of the soil to the test tube.
Step 3. Replace the cap on the test tube and gently shake the mixture of soil and extracting
solution for one minute.
Step 4. Without remove she cap, allow the tube to stand undisturbed for several minutes. This
allows soil particles to settle so that the liquid above the soil layer becomes reasonably clear.
Step 5. A pipette (eye dropper) is provided to transfer this clear solution to a second graduated
test tube. To accomplish this, squeeze the bulb of the pipette before insertion in the first test tube (this
prevent agitation of the clear solution). After insertion, release the pressure on the bulb and so draw up a
portion of the clear solute. Transfer this amount to the second test tube. Continue this procedure until the
level of solution is even with line 3 of the second test tube.
Step 6. Add six drops of the Phosphors Indicator Solution to the soil extract in the second test
tube. Recap and shake the test tube to mix.
Step 7. Add one Phosphorous Tablet to the mixture in the test tube.
Step 8. Recap the test tube and shake the mixture until the tablet dissolves.
Step 9. Compare the color of the liquid in the test tube with the colors printed on the Soil
Phosphorus Color Chart. Record the soil's phosphorus level accordingly as: high. medium. or low.
page 115 SCH
C) POTASSIUM TEST. For each soil sample:
Step 1. Select a graduated test tube and add Potassium Extracting Solution to line 8.
Note: Carefully direct the flow of solution into the test tube. Squeeze the bottle gently to insure a uniform
flow of the solution.
Step 2. Using the measuring spoon marked 0.5 g, add two measures of the soil to the test tube.
Step 3. Replace the cap on the test tube and gently shake the mixture of soil and extracting solution for one
minute.
Step 4. Without removing the cap, allow the tube to want undisturbed for several minutes. This allows soil
particles to settle so that the liquid above the soil layer becomes reasonably clear.
Step 5. A pipette (eye dropper) is provided to transfer this clear solution to a second graduated test tube.
To accomplish this, squeeze the bulb of the pipette before insertion in the first test tube (this prevents
agitation of the clear solution). After insertion, release the pressure on the bulb and so drew up a portion of
the clear solute. Transfer this amount to the second test tube. Continue this procedure until the levy of
solution is even with line 5 of the second test tube.
Step 6. Add one Potassium Indicator Tablet to the soil extracting the second test tube. Recap and shake the
test tube until the tablet dissolves. The solution should have the pill’s pale-purple color.
Step 7. The Potassium Test Solution is in a drop dispensing bottle. Carefully add five drops of the
Potassium Test Solution to the mixture in the test tube. Recap the test tube and shake to mix contents. See
if all the liquid in the test tube has changed to a blue color similar to the color chart. If not, add five more
drops of the Potassium Test Solution, shake to mix and see if the color change has taken place. Continue
this procedure until the color change does take place or you have added twenty five drops. Record the
potassium level of the sample as:
high— (5 or 10 drops needed for color change),
medium—(15 or 20 drops needed for color change) or
low—(25 drops needed for color change or no color change).
page 116 SCH
DISCUSSION
Nitrogen stimulates rapid, lush green growth. Lawn grass requires high soil nitrogen levels. On
the other hand, slow growing plants (for example. perennials) are adapted to low levels of soil nitrogen.
Phosphorus builds strong roots and stems and richly colored foliage and flowers. Potassium helps plants
resist diseases and cold.
Exercise 3
The percentage of nitrogen, phosphorus and potassium salts in commercial fertilizers is
identified (in the same order) by three numbers (for example: a fertilizer labeled 5-10-5 contains 5 per
cent nitrogen, 10 per cent phosphorus. and 5 per cent potassium). To fertilize an area spread 3 to 4 pounds
fertilizer per 100 square feet.
Given two fertilizers labeled 5-10-5 and 0-20-20. which would you use to provide optimum
nutrients for:
grass _______________________
(explain)
perennials _______________________ (explain)
page 117 SCH
Section III SECONDARY ELEMENTS
Exercise 4 TO TEST FOR SOIL pH
Plants are adapted to the soil pH of their native habitat. That is to say they need those secondary
elements which become abundantly available at a given pH level. Your problem is to test the two given
soils: labeled A and B soil and the soil you collected.
Procedure: Work with three soils: the given soils A and B and your soil. Record your results in Table 2.
Step 1. Select a graduated test tube and add pH Indicator Solution to line 4; Note; Carefully direct the flow
of solution into the test tube. Squeeze the bottle gently to insure a uniform flow of solution.
Step 2. Using the measuring spoon marked 0.5 g, add two measures of the soil to the test tube.
Step 3. Replace the cap on the test tube and gently shake the mixture of soil and pH indicator for one
minute.
Step 4. Without removing the cap, allow the tube to stand undisturbed for several minutes. This allows the
soil particles to settle so that the color of the liquid above the soil layer can be seen.
Step 5. Compare the color of the liquid layer with the colors of the pH Color Chart. Record the soil pH to
an accuracy of half a unit (for example, if the color is between pH 4.0 and 5.0, record the soil pH as 4.5).
Table 2
Soil sample no.
pH level
A
B
Your soil
DISCUSSION
A soil's pH determines the types and proportions of secondary elements available for plant
nutrition. Plants are adapted to require a soil's pH to be within certain, narrow, ranges. When a soil's
natural pH is artificially altered, in order to grow plants which require a soil of different pH, care must be
taken to use substances that not only adjust pH but which also add the necessary secondary elements to
the soil's moisture. For example:
to raise the soil's pH by I unit,
add 5 pounds of crushed dolomite - CaMg(CO3)2 - per 100 square feet of urea;
to lower the soil's pH by 1 unit,
add 3 pounds of iron sulfate - FeSO4 - per 100 square feet of area.
page 118 SCH
Exercise 5.
Examine the following list of plants and circle three which are adapted to the pH of the soil you
collected.
Plant
Required
soil pH
Asparagus
7.0 - 8.0
Babies' .breath
6.5 - 7.5
Beans
7.0 - 8.0
Blueberry
4.0 - 5.0
Canna
7.0 - 8.0
Clematis
6.0 - 7.0
Dahlia
7.0 - 8.0
English wall flower
6.0 - 8.0
Gentian
5.0 - 6.5
Heath
4.0 - 5.0
Lettuce
7.0 - 8.0
Louisiana iris
5.5 - 6.5
Pea
7.0 - 8.0
Penstemon
5.5 - 6.5
Welsh poppy
5.5 - 6.5
Exercise 6.
Explain ONE of the following (show your calculations);
i) If the soil you collected is neutral or alkaline, how could you adjust its pH in order to
grow blueberries?
ii) If the soil you collected is acid, how could you adjust its pH in order to grow peas?
___________________________________________________________________________________
___________________________________________________________________________________
___________________________________________________________________________________
BEFORE YOU LEAVE PLEASE CLEAN ALL Equipment:
a) Sort the used testing materials (tubes, caps, etc.) and put in proper place at front table.
b) Place conical tubes from last week's laboratory in one of the two wire mesh bins (by the
sink) and the caps in the other bin.
c) Wipe the worktable top with a paper towel.
d) Push chairs under tables
page 119
How a white lie has caught up with seismologists
Much to their dismay, people are learning that seismologists typically do not use the Richter scale to judge quake size.
"We're just recovering from decades of telling a white lie, that's all," says seismologist Thomas H. Heaton (president of the Seismological
Society of America and a USGS researcher in Pasadena, Calif.)
While seismologists generally do not use the original Richter magnitude scale, the measuring systems currently in vogue represent extensions of
the type that Charles Richter developed nearly 60 years ago. "[Richter] introduced it because he was tired of the newsman asking him about the
relative size of earthquakes," recalls veteran seismologist Bruce A. Bolt from the University of California, Berkeley. That explains why some
seismologists continue to use the term when addressing the press.
Prior to Richter's work, researchers in the United States had no way of judging an earthquake's absolute size, which remains the same no matter
where it is measured. Instead, they dealt with a concept called intensity, which describes the strength of shaking at a particular location.
In the early 1930s, Japanese seismologist Yiyoo Wadati devised a method of comparing the sizes of quakes. He would take seismic recordings
of various shocks and set them on an equal footing by factoring in the distance between the recording station and the earthquake. But this method
was not easily grasped by lay people, especially the reporters of quake-plagued southern California.
In 1935, Richter dressed up the Japanese method to create an earthquake index. Richter defined seismic magnitude in terms of a particular type
of recording device, called a Wood-Anderson seismograph, situated at a standard distance of 100 kilometers from an earthquake's epicenter.
Richter appropriated from astronomy the idea of a logarithmic scale - based on powers of 10 - to accommodate the incredible range of
earthquake sizes. (The smallest detectable tremors equal the energy of a brick dropped off a table, while monster quakes surpass the largest
nuclear explosions) By Richter's original definition, a shake of magnitude 1.0 would cause the arm of the Wood-Anderson machine to swing
one- thousandth of a millimeter. A magnitude 2.0 temblor would make the arm swing 10 times as much, or one- hundredth of a millimeter.
In theory, the scale had no upper limit. But in practice, magnitudes could not top 7.0. "You would never see an earthquake bigger than
magnitude 7 [on the original magnitude scale], or at least we hope you never would because everything would be dead," Heaton says.
Of course, scientists rarely had a Wood-Anderson seismograph stationed exactly 100 kilometers from an earthquake. But by comparing the
arrival of slow versus fast seismic waves at a recording station, they could calculate what one of the devices would have detected at the standard
distance.
The magnitude index, as originally defined, could only measure southern California earthquakes because Richter calibrated the scale for the
crust there. What's more, it only worked for jolts within a few hundred kilometers of a Wood-Anderson seismograph. This original magnitude
scale was based on waves with periods of 0.1 to 3.0 seconds became known as ML or local magnitude, when a more general magnitude
measurement, denoted as MS. was devised by Caltech's Beno Gutenberg and Richter to handle distant earthquakes. M, depends on measurements
of surface waves rippling through Earth's crust with a period of about 20 seconds.
Even the new and improved magnitude formula had problems, however, because deep earthquakes do not produce many surface waves. So
Gutenberg and Richter invented MB, measured from body waves, which travel through the planet's interior. This yardstick proved helpful in
distinguishing nuclear explosions from actual earthquakes.
In the 1970s, seismologists realized that all existing magnitude methods underestimated the energy of truly large earthquakes. To circumvent
this limitation, Hiroo Kanamori, a successor of Richter and Gutenberg at Caltech, created a magnitude scale, MW, that quantifies the total
amount of seismic wave energy released in an earthquake.
But because such calculations are difficult, scientists usually approximate the energy by computing a quantity called "seismic moment,"
determined from long period vibrations. In the case of great earth- quakes, these vibrations have cycles longer than 200 seconds. Seismologists
therefore refer to MW as the moment magnitude.
MW differs from all other types of magnitude in that it measures the earthquake source, Kanamori says. The Richter magnitude and most others
gauge only the strength of vibrations sensed at Earth's surface. But to calculate moment magnitude, seismologists use the long-period waves to
decipher the dimensions of the fault rupture that produced the quake. [seismic moment - the length of the fault rupture multiplied by the amount
of rock movement and then again by the stiffness of the rock] In other words, moment magnitude measures the cause rather than the effect.
page 120
Although researchers have developed more than a dozen other ways of calculating earthquake magnitude, moment magnitude remains the figure
of choice among seismologists, especially for earthquakes larger than magnitude 6.5.
Confused?
With ML, MS, MB, MW and a litany of other M, floating around, it's no wonder that many seismologists took the easy way out over the years by
giving reporters what they thought the media wanted. When pressed for details, researchers typically simplified the issue by calling any
magnitude a Richter magnitude, even though this term applies only to the local (ML) magnitudes determined by Richter's original formulation.
"The problem is that seismologists have used the term 'Richter scale' in a very loose way, and now it's catching up with them. We didn't use it
among ourselves because it doesn't mean anything," Heaton says.
Immediately after an earthquake, the USGS National Earthquake Information Center in Golden, Colo., releases a preliminary measurement,
which could be a surface wave magnitude, a body wave magnitude, or even a local magnitude (similar to Richter's original formulation except
that modern seismographs have replaced Wood-Anderson ones.) After determining the moment magnitude, they release this number, which may
fall above or below the preliminary one.
As for the use of the term "Richter scale," the USGS has dodged any decision. "The question of labeling these magnitudes as 'Richter scale' is a
matter of tradition, semantics, and personal perspective.
The USGS has no official scientific position on the use of the term," declares the July statement. The USGS' Heaton, who works across the
street from Richter's old Pasadena office, says he wants to avoid the term entirely. "You probably wouldn't catch us using the term 'Richter
magnitude' around here, even though this was the home of Richter."
As journalists get more seismically sophisticated, they may head off some of the confusion. The Associated Press recently retired the term
"Richter scale" in favor of the phrases "preliminary magnitude" and "moment magnitude. "
But simply tidying the terminology will not, on its own, help people better understand the size of an earthquake. After all, how can one number
convey the power of something equivalent to a colossal nuclear explosion?
Even moment magnitude does not suffice, says its inventor. "The problem is everyone thinks that a single number determines everything. It's
almost like asking how big you are," says Kanamori. "The question is whether you are asking height, weight, or width. Depending on how you
measure a person, the answer can be very different. In the case of earthquakes, it's even more complex.
Excerpted from ''Abandoning Richter" by Richard Monastersk in Science News, vol. 146, Oct. IS, 1994.
_________________________________________________________________________________________________________________
Quake comparisons
It is true that the Richter magnitude scale is logarithmic, but this does not mean a magnitude 8 quake is 10 times stronger than a magnitude 7.
One should estimate seismic energy E released by calculating:
log E = 11.8 + 1.5 M8
where M8 is the surface wave magnitude. Thus a magnitude 8 earthquake is not 10 times stronger than a magnitude 7, but rather about 30 times
stronger.
Bemhardt Saint-Eidukat in Science News p.58, vol.137, No.4, Jan. 27, 1990.
Page 121
For this exercise:
A) The earthquake seismograms (Time in seconds horizontal axis. Amplitude vertical axis.) are on pages
122 a, b, c.
B) Complete pages 122 d, e.
page 122 a
Eureka, CA seismograph station
page 122 b
Elko. NV seismograph station
page 122 c
Las Vegas, NV seismograph station
122d
122 e
Page 123
Page 124
page 125
World Distribution of Earthquakes.
FIGURE 5 World distribution of earthquakes for a nine-year period. (Data from NOAA)
Earth scientists have determined that the global distribution of earthquakes is not random but follows a few relatively
narrow belts that wind around the earth. Figure 5 illustrates the world distribution of earthquakes for a 9 year period.
Using Figure 5 and your text as references, answer questions 17 and 18.
17. List the locations of the three major belts of concentrated earthquake activity on the earth.
Belt 1: _________________________________
Belt 2: _________________________________
Belt 3: _________________________________
18. According to the text, with what earth phenomenon is the location of earthquake epicenters closely
correlated?
page 126
THE EARTH BEYOND OUR VIEW
The Earth's Interior Structure. The study of earthquakes has contributed greatly to earth scientists' understanding
of the internal structure of the earth. Variations in the travel times of P and S waves as they journey through the
earth provide scientists with an indication of changes in rock properties. Also, since S waves cannot travel through
fluids, the fact that they are not present in seismic waves that penetrate deep into the earth suggests a fluid zone
near the earth's center.
In addition to the lithosphere, the other major zones of the earth's interior include the asthenosphere, mantle,
outer core, and inner core. After you have reviewed these zones and the general structure of the earth's interior in
Chapter 11 of your text, use Figure 6 to answer questions 19-24.
Figure 6 P and S velocity distributions in the Earth's interior. Solid line after Jeffreys, dotted line after
Gutenburg (after Bullen)
19. The layer labeled A on Figure 6 is the solid, rigid, upper zone of the earth that extends from the surface
to a depth of about (100, 500, 1000) kilometers. Circle your answer.
a. Zone A is called the (core, mantle, lithosphere).
b. What are the approximate velocities of P and S waves in zone A?
P wave velocity: ________ km/sec
S wave velocity: ______ km/sec
c. The velocity of both P and S waves (increases, decreases) with increased depth in zone A. Circle your
answer.
d. List the two parts of the earth's crust that are included in zone A and briefly describe the composition
of each.
1) ____________ . _________________
2) ____________ . _________________
page 127
20. Zone B is the part of the earth's upper mantle that extends from the base of zone A to a depth of up to
(100, 700, 2000) kilometers in some regions of the earth. Circle your answer.
a. Zone B is called the (crust, asthenosphere, core).
b. The velocity of P and S waves (increases, decreases) immediately below zone A in the upper part of
zone B.
c. According to the text, the change in velocity of the S waves in zone B indicates that it consists of
(partially molten, entirely liquid) material.
21. Zone C (which includes the lower part of zone A and zone B) extends to a depth of __________ kilometers.
a. Zone C is called the earth's ________________ .
b. What fact concerning S waves indicates that zone C is not liquid?
_____________________________ .
c. What is the probable composition of zone C? ______________________________________________
.
22. Zone D extends from 2885 km to about (5100, 6100) kilometers.
a. Zone D is the earth's __________________________________________
b. What happens to S waves when they reach zone D and what does this indicate about the zone?
___________________________________________________________________________________
c. The velocity of P waves (increases, decreases) as they enter zone D. Circle your answer.
23. Zone E is the earth's ____________ ____________
a. Zone E extends from a depth of ____________ km to the ____________ of the earth.
b. What change in velocity do P waves exhibit at the top of zone E and what does this suggest about the
zone?
___________________________________________________________________________________
c. What is the probable composition of the earth's core?
_______________________________________
24. Label Figure 6 by writing the name of each interior zone at the appropriate letter.
page 128
The Earth's Internal Temperature.
Measurements of temperatures in wells and mines have shown that earth temperatures increase with depth.
The rate of temperature increase is called the geothermal gradient. Although the geothermal gradient varies from
place to place, it is possible to calculate an average. Table 2 shows an idealized average temperature gradient for
the upper earth compiled from many different sources.
25. Plot the temperature values from Table 2 on the graph in Figure 7. Then draw a single line that fits the
pattern of points from the surface to 200 km. Label the line, "temperature gradient."
TABLE 2 Idealized internal temperatures of the earth compiled from several sources.
Depth (kilometers) Temperature (0C)
0
25
50
75
100
150
200
200
6000
10000
12500
14000
17000
18000
Use the information in Table 2 to answer questions 26-29.
26. Refer to the graph in Figure 7. The rate of increase of the earth's internal temperature
(is constant, changes) with increasing depth. Circle your answer.
27. The rate of temperature increase from the surface to 100 km is (greater, less) than the rate of increase
below 100 km.
28. The temperature at the base of the lithosphere, which is about 100 kilometers below the surface, is
approximately (6000, 14000, 18000) degrees Celcius.
29. Use the data and graph to calculate the earth’s average temperature gradient (temperature change per km of
depth):
for the upper100 km is ____________ 0C/100 km: and for 100–200 km down is ____________ 0C/100 km.
TABLE 3 Melting temperatures of granite (with water) and basalt at various depths within the earth.
Granite (with water)
Depth (km)
0
5
10
20
40
Melting temp.(0C)
9500
7000
6600
6250
6000
Basalt
Depth (km)
0
25
50
100
150
Melting temp.(0C)
11000
11600
12500
14000
16000
Melting Temperatures of Rocks. Geologists have always been concerned with the conditions required for
pockets of molten rock (magma) to form near the surface, as well as at what depth within the earth a general
melting of rock may occur. The melting temperature of a rock changes as pressure increases deeper within the
earth. The approximate melting points of the igneous rocks, granite and basalt, under various pressures (depths)
have been determined in the laboratory and are shown in Table 3. Granite and basalt have been selected because
they are the common materials of the upper earth. Use the data in Table 3 to answer questions 30-35.
30. Plot the melting temperature data from Table 3 on the earth's internal temperature graph you have prepared
in Figure 7. Draw a different colored line for each set of points and label them "melting curve for wet
granite" and "melting curve for basalt. "
page 129
Figure 7 Graph for plotting temperature curves
Use the graphs you have drawn in Figure 7 to help answer questions 31-33.
31. Use Figure 7 and assume your earth temperature gradient is accurate. At approximately what depth
within the earth would wet granite reach its melting temperature and form granitic magma?
_______ _ km within the earth
Evidence suggests that the oceanic crust and the remaining lithosphere down to a depth of about 100 km are
similar in composition to basalt.
32. The melting curve for basalt in Figure 7 indicates that the lithosphere above approximately 75 km
(has, has not) reached the melting temperature for basalt and therefore should be (solid, molten). Circle your
answers.
33. Figure 7 indicates that basalt reaches its melting temperature within the earth at a depth of approximately
________ km. (Solid, Partly melted) basaltic material would be expected to occur below this depth. Circle
your answer.
34. What is the name of the zone within the earth that begins at a depth of about 100 km and may extend to
approximately 700 kilometers?
____________________________________________________________________________________
35. Why do scientists believe that the zone in quest. 34 is capable of "flowing," carrying the rigid lithosphere
along with it?
____________________________________________________________________________________
page 130
EARTHQUAKES AND EARTH TEMPERATURES - A PRACTICAL APPLICATION
The study of earthquakes and the earth's internal temperature has contributed greatly to the understanding of plate
tectonics. One part of the theory is that large, rigid slabs of the lithosphere are descending into the mantle where
they break up and melt, generating deep focus earthquakes during the process. Using earthquakes and earth
temperatures, earth scientists have confirmed that this major earth process is currently taking place near the island of
Tonga in the South Pacific and elsewhere.
Figure 8
Distribution of earthquake
foci in 1965 in the vicinity of
Tonga Island. (Data from B. Isacks,
J. Oliver,and L. R. Sykes)
illustrates the distribution
of earthquake foci during a
one-year period in the vicinity
of Tonga Island.
Use the figure to answer questions 36-40.
36. At approximately what depth do the deepest earthquakes occur in the area represented on Figure 8?
_____________ kilometers
37. The earthquake foci in the area are distributed (in a random manner, nearly along a line). Circle your answer.
38. Draw a line on Figure 8 that outlines the area of earthquakes within the earth.
39. Using previous information from this exercise, draw a line on Figure 8 at the proper depth that indicates
the top of the asthenosphere-the zone of partly melted or plastic earth material. Label the line you draw "top
of asthenosphere."
40. Remember that earthquakes only occur in solid, rigid material and refer to Figure 8. Why have earth
scientists been drawn to the conclusion of a descending slab of solid lithosphere being consumed into the
mantle near Tonga?
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________