Download Common Rocks (Chapter 2)

GEOLOGY 306 Laboratory
Instructor: TERRY J. BOROUGHS
NAME:
Common Rocks (Chapter 2)
For this assignment you will require: a streak plate, glass plate, magnet, dilute hydrochloric (HCl) acid,
microscope, and various mineral samples (all provided by instructor). Objectives for chapter 2: you should be able
to recognize, name, and describe individual minerals within rocks; be able to examine a rock and determine if it is an
igneous, sedimentary, or metamorphic rock; list and define the terms used to describe the textures of igneous,
sedimentary, and metamorphic rocks; use a classification key to identify a rock; recognize and name some of the
common rocks by sight.
IGNEOUS ROCK TERMS:
TEXTURAL TERMS:
Pegmatitic
Phaneritic
Aphanitic
Porphyritic
Glassy
Frothy
Vesicular or Cellular
Fragmental/Pyroclastic
:
:
:
:
:
:
:
:
very coarse-grained, larger than your thumb (> 1-inch)
coarse-grained, easily seen, uniform size
fine-grained, uniform size
phenocrysts in a finer grained matrix
similar to glass
glassy & vesicular, many small vesicles, foamy-looking
many visible vesicles
particles, ash, fragments of rock, etc. fused together
Please note! If a sample has a porphyritic texture, the term porphyritic is added to the rock name. (i.e.,
PORPHYRITIC GRANITE, PORPHYRITIC BASALT, PORPHYRITIC RHYOLITE.)
COMPOSITIONAL TERMS:
FELSIC
INTERMEDIATE
MAFIC
ULTRAMAFIC
:
:
:
:
light colored
medium shades
dark colored
rare (composition of the mantle)
SEDIMENTARY ROCK TERMS:
GRAIN SIZE
FINE-GRAINED:
MEDIUM-GRAINED:
COARSE-GRAINED:
You will not be able to see individual grains. Mudstone (shale) belongs in this group.
You will be able to see individual grains. Sandstone belongs in this category.
Grains are larger than 2 mm. Conglomerates and breccias belong in this group.
CLASSIFICATION (ORIGIN AND RESULTING TEXTURES)
INORGANIC DETRITAL / CLASTIC: Sample is composed of grains of pre-existing minerals or rocks cemented
together. Conglomerate, sandstone, and shale belong to this group.
Non-Clastic: CHEMICAL OR BIOLOGICAL: Chemical sediments are formed by the precipitation of minerals (from a
solution) during the evaporation of water (usually ocean water). In addition, sedimentary rocks can be
formed by biological processes. Limestone, rock salt, dolostone, rock gypsum, and coal belong to
these groups of chemical and biological sediments.
SORTING: due to the settling of grains in water. Poorly and well-sorted varieties and those that are somewhere in
between. E.g. Med. – Well sorted or Med. – Poorly sorted.
POORLY SORTED:
INTERMEDIATE SORTING:
WELL SORTED:
A wide variety of grain sizes and shapes are present.
Sorting is intermediate between poorly sorted and well sorted.
Most grains are the same size and shape.
ROUNDING: due to the abrasion and erosion of corners on fragments. Well rounded and angular as well as those
that are somewhere in between. E.g. Sub-rounded or sub-angular.
WELL ROUNDED:
SUB-ROUNDED
SUB-ANGULAR:
ANGULAR:
grains are spherical.
grains are have mostly rounded surfaces, but are not spherical:
grains are mostly angular, but have some rounded surfaces.
grains have jagged edges and are not spherical.
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CEMENT:
to become a rock, clastic (detrital) sediments must be cemented together. The most common types of
cements in sedimentary rocks are:
SILICEOUS:
CALCAREOUS:
FERRUGINOUS:
••••
colorless or white, chemical composition is SiO2. The same chemical composition as
QUARTZ.
chemical composition is the same as CALCITE. Calcareous cement will "FIZZ" when HCL
acid is applied.
contains iron. There are two types of ferruginous cement that you should be able to
identify: LIMONITE (yellow-brown) and HEMATITE (red-brown).
IN ADDITION, SOME SEDIMENTARY ROCKS CONTAIN FOSSILS OF PLANTS AND/OR ORGANISMS.
IN GENERAL, IF A ROCK CONTAINS FOSSILS, THEN THE TERM FOSSILIFEROUS IS PLACE BEFORE
THE ROCK NAME. (I.E. FOSSILIFEROUS LIMESTONE, FOSSILIFEROUS SANDSTONE, ETC.)
METAMORPHIC ROCK TERMS:
GRAIN SIZE
FINE-GRAINED:
MEDIUM-GRAINED:
COARSE-GRAINED:
You will not be able to see individual grains.
You will be able to see individual grains, up to 2 mm.
Grains are larger than 2 mm.
FOLIATION
FOLIATED:
A layered structure is developed in the rock. Folding and shearing may also be present.
Foliated rocks contain parallel planes of platy minerals that have aligned due to the effects
of pressure and recrystallization.
NONFOLIATED:
Shows no layering. Exhibits a more uniform appearance.
THE FOLLOWING QUESTIONS REFER TO CHAPTER 2 IN YOUR MANUAL
(Read the questions from your manual and place your answers in the following spaces provided.)
1.
Use Figures 2.4. 2.5, 2.7, 2.9, 2.10, 2.11, 2.13, 2.19, 2.20, 2.21 (8th edition) for this question. Of
igneous, sedimentary, and metamorphic rocks which two of the three basic rock types appear to
made of inter-grown (interlocking) crystals?
2.
Which one of the two rock types you listed in question 1 have mineral grains or crystals aligned or
arranged so that they point in the same direction in a linear, line-like manner?
3.
Which one of the two rock types you listed in question 1 have the mineral crystals in most of the
rocks arranged in a dense interlocking mass with no alignment?
4.
Of the three rock types (igneous, sedimentary, or metamorphic) rocks are most often contain
haphazardly arranged pieces or fragments, rather than crystals? (Select the best answer)
5.
The igneous rock illustrated in Figure 2.9 A (8th edition) is made of large mineral crystals that are all
about the same size. The rock formed from magma that cooled (slowly, rapidly) and (inside,
on/near the surface of) the Earth. (Select the best answers).
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6.
The rock shown in Figure 2.9 C (8th edition) is made of mineral crystals that are all small and not
identifiable without a microscope. The rock formed from magma that cooled (slowly, rapidly) and
(inside, on/near the surface of) the Earth. (Select the best answers).
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7.
The igneous rock in Figure 2.9 G (8th edition) has a porphyritic texture. The large crystals are
called________ and the surrounding smaller crystals are called_____
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8.
The rocks in Figures 2.9 A and C (8th edition) have nearly the same mineral composition. What fact
about the mineral crystals in the rocks makes their appearances so different? What caused this
difference?
9.
Skip
10. Estimate the percentage of dark minerals contained in the igneous rock in Figure 2.11 D (8th edition)
(You may find the color index at the at the bottom of Figure 2.10 (8th edition), “Igneous & Rock
Identification Key,” helpful) The rock’s color is (light, medium, dark, or very dark). Select the best
answer.
11. skip
12. Use the specimens provided in the rock identification portion of this lab and identify the igneous
rocks, samples 1 through 11.
13. skip Questions 13 through 15
16. Of the samples provided for question 18 (samples 12 through 22), how many of the Sedimentary
rock samples are Crystalline versus how many contain shells or shell fragments?
Crystalline
Shells or shell fragments
17. Skip
18. Use the specimens provided in the rock identification portion of this lab and identify the sedimentary
rocks, samples 12 through 22.
19. Figure 2.13 C (8th edition) is the rock sandstone that formed from sand. Where on Earth do you find
sand, the primary material of sandstone, being deposited today?
20. Use Figure 2.16 (8th edition) to name the environment(s) where, in the past, the sediment for the
following sedimentary rocks may have been deposited. Use the following table:
Rock type:
Original Sediment
Rock salt:
(precipitated halite)
Bituminous Coal
(carbon)
Fossilferous Limestone:
(coral)
Travertine
(precipitated calcite)
Quartz Sandstone:
(wind faceted sand)
Environment(s)
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21. What characteristic can be used to distinguish Conglomerate from Breccia? (In other words, how
would you tell them apart?)
22. From the rocks illustrated in Figure 2.19 A and C (8th edition), the (slate, schist) resulted from more
intensive heat and pressure. Select the best answer.
23. From the metamorphic rocks in Figure 2.19 B and D (8th edition), the (phyllite, gneiss) shows the
minerals separated into light and dark bands. Select the best answer. (The foliated-banded
texture of the rock that you have selected often results from the most intensive heat and pressure
during metamorphism)
24. skip
25. Use the specimens provided in the rock identification portion of this lab and identify the metamorphic
rocks, samples 23 through 31.
THE FOLLOWING QUESTIONS REFER TO THE SUMMARY / REPORT PAGE FOR CHAPTER 2
(Read the questions from your manual and place your answers in the following spaces provided.)
1.
Write a brief definition of each of the three rock types:
Igneous:
Sedimentary:
Metamorphic:
2.
What unique factor about the arrangement of mineral crystals occurs in many metamorphic rocks?
3.
Describe the basic difference between detrital and chemical sedimentary rocks.
4.
Match each term or characteristic with the appropriate rock group:
A. Slaty texture
E. Glassy Texture
I. Evaporite deposits
M. Detrital rocks
B. Silt-size particles
F. Vesicular texture
J. Strata or beds
N. Felsic composition
C. Porphyritic texture
G. Lithification
K. Alignment of mineral grains
D. Foliated texture
H. Clastic Texture
L. Gneissic texture
Igneous Rocks:
Sedimentary Rocks:
Metamorphic Rocks:
4
O. Chemical rocks
5.
Of the three basic rock types, which one is most likely to contain fossils?
The following questions are for extra credit points!
6. Use the various tables and/or figures in your manual to identify the textures and composition of the
following rocks:
Rock type:
Texture (Use the terms from
Mineral content or description of composition,
pages 1 & 2 of this packet!)
e.g. felsic, etc.
Basalt:
Quartzite:
Coquina:
7.
What factor determines the size of the crystals in igneous rocks?
8.
What is a good chemical test to determine the primary mineral in limestone?
9.
What factor(s) determine(s) the size of crystals in metamorphic rocks?
10. If the sedimentary rock limestone is subjected to metamorphism, what metamorphic rock will likely
form?
11. Referring to Figure 2.25 (8th edition) Identify the rock’s name and to which basic rock group it
belongs.
Fig. 2.25 D (8th edition)
Name:
Rock Group:
Fig. 2.25 E (8th edition)
Name:
Rock Group:
Fig. 2.25 F (8th edition)
Name:
Rock Group:
12. Referring to Figure 2.23 A, B, & C (8th edition) identify whether each outcrop is igneous, sedimentary,
or metamorphic in origin.
A. Outcrop A:
B. Outcrop B:
C. Outcrop C:
CONTINUE ONTO THE ROCK IDENTIFICATION PORTION OF
THIS LAB LOCATED ON THE FOLLOWING PAGES!!
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ROCK LIST - This list will be used for the ROCK Lab
IGNEOUS ROCKS
ANDESITE
BASALT
DIORITE
GABBRO
GRANITE
OBSIDIAN
PUMICE
RHYOLITE
SCORIA (MEDIUM-LARGE VESICLES, LESS DENSE) and/or
VESICULAR BASALT (VERY LARGE VESICLES, VERY DENSE)
SEDIMENTARY ROCKS
BRECCIA
COAL
CONGLOMERATE
COQUINA
FLINT and/or CHERT
LIMESTONE (FOSSILIFEROUS)
SANDSTONE (ARKOSE, QUARTZ)
SHALE
TRAVERTINE
METAMORPHIC ROCKS


GNEISS
QUARTZITE
MARBLE
SCHIST
PHYLLITE
SLATE
Igneous rocks may include the following terms in front of their names: Porphyritic, Vesicular, etc. For example,
basalt is not the same as porphyritic basalt!
Sedimentary rocks may include the term, “Fossiliferous” in front of the rock name. For example, fossiliferous
shale is not the same as shale!
ROCK IDENTIFICATION PORTION
Samples 1 through 11 are igneous rocks, samples 12 through 22 are sedimentary
rocks and samples 23 through 31 are metamorphic rocks.
Igneous rocks:
1. What type of texture does this sample have?
.
Is this rock felsic, intermediate, or mafic?
.
ROCK NAME
2. What type of texture does this sample have?
.
Is this rock felsic, intermediate, or mafic?
.
ROCK NAME
.
3. What type of texture does this sample have?
.
Is this rock felsic, intermediate, or mafic?
.
ROCK NAME
.
4. What type of texture does this sample have?
.
Is this rock felsic, intermediate, or mafic?
.
ROCK NAME
6
.
.
5. What type of texture does this sample have?
.
Is this rock felsic, intermediate, or mafic?
.
ROCK NAME
.
6. What type of texture does this sample have?
.
Is this rock felsic, intermediate, or mafic?
.
ROCK NAME
.
7. What type of texture does this sample have?
ROCK NAME
.
.
8. What type of texture does this sample have?
.
Is this rock felsic, intermediate, or mafic?
.
ROCK NAME
.
9. What type of texture does this sample have?
ROCK NAME
.
.
10. This sample has phenocrysts.
What type of texture does this sample have?
.
Is this rock felsic, intermediate, or mafic?
.
ROCK NAME
.
11. What type of texture does this sample have?
.
Is this rock felsic, intermediate, or mafic?
.
ROCK NAME
.
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Sedimentary rocks:
12. This rock WILL REACT WITH ACID!
Clastic, Chemical, or Biochemical in origin?
.
Is this rock fossiliferous?
.
What is the dominant mineral in this rock?
.
ROCK NAME
.
13. This is an important economic rock. It is a biochemical rock that is composed of increasingly
altered (compacted) plant remains.
ROCK NAME
.
14. This rock WILL REACT WITH ACID!
Clastic, Chemical, or Biochemical in origin?
.
Is this rock fossiliferous?
.
What is the dominant mineral in this rock?
.
ROCK NAME
.
15. These samples are composed of SILICA.
Clastic, Chemical, or Biochemical in origin?
.
Grain size? (Coarse, medium, fine)
ROCK NAME
.
16. Clastic, Chemical, or Biochemical in origin?
.
Grain size? (Coarse, medium, fine)
What is the dominant mineral in this rock?
ROCK NAME
8
.
.
17. This rock WILL REACT WITH ACID!
Clastic, Chemical, or Biochemical in origin?
.
Is this rock fossiliferous?
.
What is the dominant mineral in this rock?
.
Does this rock exhibit banding or layers?
.
ROCK NAME
.
18. This rock may be fissile (breaks easily or flakes off easily)
Grain size? (Coarse, medium, fine)
.
Clastic, Chemical, or Biochemical in origin?
.
ROCK NAME
.
19. Grain size? (Coarse, medium, fine)
.
Clastic, Chemical, or Biochemical in origin?
.
Sorting? (well, medium, or poorly sorted)
.
Rounding? (well-rounded, sub-rounded, sub-angular or angular)
.
What is the dominant mineral in these samples?
.
ROCK NAME
.
20. Grain size? (Coarse, medium, fine)
.
Clastic, Chemical, or Biochemical in origin?
.
Sorting? (well, medium, or poorly sorted)
.
Rounding? (well-rounded, sub-rounded, sub-angular or angular)
.
What is the dominant mineral in these samples?
.
ROCK NAME
.
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21. Clastic, Chemical, or Biochemical in origin?
.
Sorting? (well, medium, or poorly sorted)
.
Rounding? (well-rounded, sub-rounded, sub-angular or angular)
.
ROCK NAME
.
22. Grain size? (Coarse, medium, fine)
.
Clastic, Chemical, or Biochemical in origin?
.
Sorting? (well, medium, or poorly sorted)
.
Rounding? (well-rounded, sub-rounded, sub-angular or angular)
.
ROCK NAME
.
Metamorphic rocks:
23. Is it foliated?
.
Is it banded?
.
Grain size? (Coarse, medium, fine)
ROCK NAME
24. Grain size? (Coarse, medium, fine)
.
What is the dominant mineral in this rock?
.
Is it foliated?
.
ROCK NAME
.
25. Grain size? (Coarse, medium, fine)
.
Is it foliated?
ROCK NAME
10
.
.
Does it have a silky luster?
.
.
26. Grain size? (Coarse, medium, fine)
.
Is it foliated?
.
ROCK NAME
.
27. This is a monomineralic metamorphic rock, that WILL REACT WITH ACID.
What mineral is it composed of?
.
Is it foliated?
.
ROCK NAME
.
28. This is a monomineralic metamorphic rock. IT DOES NOT REACT WITH ACID. LOOK
CLOSELY AND YOU WILL NOTICE THE "SUGARY" APPEARANCE. This sample WILL
SCRATCH GLASS!
What mineral is it composed of?
.
Is it foliated?
.
ROCK NAME
.
29. Grain size? (Coarse, medium, fine)
.
What are some the minerals in this rock?
.
Is it foliated?
.
Does it contain porphyroblasts?
.
ROCK NAME
.
30. Grain size? (Coarse, medium, fine)
Is it foliated?
.
Is it banded?
.
ROCK NAME
.
31. This is a monomineralic metamorphic rock, that WILL REACT WITH ACID.
What mineral is it composed of?
Is it foliated?
.
.
ROCK NAME
THE END!!
.
HAVE A GNEISS DAY!
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