Download GEOL 2311

GEOL 2311
Mineralogy Final Exam
Name: Key
Score: ________/ 200
Class Totals:
Lecture: ____/480; Lab & Field Trip:____/511; Extra Credit: _____
Total Points:_____/991; Total %: ______; Final Grade________
Instructions for EXTRA CREDIT – for questions that ask you to circle the true
statements, you will receive ½ pt extra credit for false statements that you can add or
change a word or phrase to make the statement true (e.g., isometric minerals typically
display anisotropic optical properties. isotropic )
First Third
1) Circle all the statements that are true about the definition of a mineral (3 pts)
A) naturally occurring
D) not necessarily fixed composition
B) formed mostly by inorganic processes
E) random chemical arrangement
C) definite chemical composition
F) highly ordered atomic structure
2) A mineral is named and classified mainly by what criteria? (circle one, 2 pts)
a) its major cations
b) its crystal class
c) its major anionic component
d) its space group symmetry
3) Name a mineral that contains the following common elements as a major chemical
component. (8 pts; OK to name a mineral more than once)
Si (silica) ______________________________
Al (aluminum) _____________________________
Ti (titanium) _____________________________
Mg (magnesium) ___________________________
Ca (calcium) _____________________________
K (potassium) ___________________________
P (phosphorous) ____________________________
Cl (chlorine) _____________________________
4) Circle all the statements that are true about atoms, elements, and isotopes (3 pts)
A) most mass of an atom is contained in the nucleus
B) the nucleus is composed of protons and neutrons
C) an element is defined by the number of protons, known as the atomic number
D) in a stable, non-ionized atom, the number of protons, and electrons and neutrons
are all equal.
E) the isotopic number of an element is defined by the total number of protons and
neutrons
F) isotopes of a particular element have similar different atomic weights but different
similar chemical properties
Pg score _____
5) The diagram below displays the types and number of electron subshell orbitals that
exist in each of the principal electron shells (K, L, M, N…) of atoms. The element
argon (atomic number 18) is a noble gas, which means that it has all of its subshell
orbitals filled to capacity with electrons. Knowing this, what are the electron
capacities of the S and the P subshell orbitals? (2 pts)
S____2____
P ____6____
6) Referring to the partial periodic table below for help, give the most common valence
(or oxidation) state (e.g. +4, -1, …) for the following elements: (8 pts)
Si _+4
Mg_+2
O __-2
Na_+1
Al_+3
Cl_-1
Mg_XX_
Ti _+4 (hint TiO2 is rutile)
7) Sulfur (S) can be an anion or a cation. What is its valance state as a cation?_+6
What is its valance state as an anion?__-2 (2 pts)
8) Circle the true statements about elements in the periodic table (3 pts)
A) the electronegativity of elements increase across a row
B) the 1st ionization potential of elements increase across a row
Pg score _____
C) the atomic radius of cations increase decrease across a row
D) the atomic radius of elements increase down a column
E) the atomic radius of a particular element is fixed variable, regardless of the type
and number of elements that surround it
F) the elements in shaded boxes are considered non-metallic elements
9) Circle the true statements about bonding in minerals (4 pts)
A) Covalent bonds are the weakest strongest type of bond
B) Ionic bonds are formed from elements that exchange outer electrons whereas
covalent bonds form by sharing outer electrons
C) Different types of bonds commonly occur in the same mineral
D) The greater the difference in electronegativity between two elements, the greater
the tendency to create ionic bonds
E) Metallic bonds can be thought of as element nuclei and inner electron shells in a
“sea” of unbound electrons
F) The strength of a bond is inversely proportional to its hardness
G) Atomic nuclei and inner electron shells in a “sea” of unbound electrons is
definition of Van der Waals metallic bonds
H) Hydrogen bonds form by the polarization of the hydrogen-oxygen bond in a water
molecule
10) Circle the true statements about packing of ions in minerals (3 pts)
A) The coordination number is dependent on the cation:anion radius ratio
B) A radius ratio of 1 favors octahedral (6-fold) 12-fold or close packed coordination
C) Cubic coordination occurs for cations that have 8 nearest anion neighbors
D) In most minerals, the main anionic element is iron oxygen
E) Tetrahedral coordination occurs for cations that have 3 4 nearest anion neighbors
F) Hexagonal-close packed coordination occurs where ions are stacked in an A-B-C
A-B configuration
11) The strength of an ionic bond between a cation and and anion is proportional to its
electrostatic valence (e.v.), which is defined as what? (circle one, 2 pts)
A) the ratio of the valence number of the cation to its coordination number.
B) the ratio of the valence numbers of the cation and anion
C) the cation/anion radius ratio
D) the difference between the valence numbers of the cation and anion.
12) Circle the true statements about phase equilibrium of minerals (4 pts)
A) A mineral is said to be in equilibrium with its environment when it is at its lowest
energy for the conditions of pressure and temperature
B) All substances strive to be at their greatest state of order disorder
C) Variables such as mass and volume are dependent on the amount of material
present
D) Variables such as temperature, pressure, and compositional proportions are also
not dependent on the amount of material present
E) In a one component system, an invariant point, where the degrees of freedom are
zero, occurs where two three phases are in equilibrium according to the phase
rule (F = C – Φ + 2; this equation is correct). 0=1-3+2
Pg score _____
F) In a two-component phase diagram for igneous systems, compositions is typically
plotted against pressure temperature
G) Subsolidus exsolution is cause by unmixing of components in a solid solution
mineral as it cools down and the atomic structure becomes more ordered
H) Phase diagrams for metamorphic systems are typically compositional diagrams
that show equilibrium mineral phases at a particular pressure and temperature.
13) Indicate for the six phases on
this compositional diagram
whether they show complete
solid solution, limited solid
solution, and no solid solution?
(6 pts)
Tridymite - No
Albite - Complete
Orthoclase - Complete
Nepheline - Limited
Leucite - Limited
Kalsilite - Limited
Second Third
14) Circle the true statements about external crystal symmetry (4 pts)
A) External crystal symmetry involves symmetry operations that lack translation
B) The main external symmetry operations are rotation axes, center of symmetry and
rotoinversion. And mirror planes
C) There are 64 32 possible combinations of symmetry operations that define external
symmetry of crystals
D) The 222 point group (or crystal class) occurs in triclinic orthorhombic crystal
system
E) Crystals containing a combination of 4-fold, 3-fold and 2-fold rotation axes can
only occur in the isometric crystal system
F) Mirror planes (m) perpendicular to a rotational axis (#) is portrayed in the
Hermann-Maugin notation by #/m
G) Six-fold and three-fold rotation axes are common in the hexagonal system
H) Isometric crystals have the greatest symmetry, and tetragonal triclinic crystals
have the least symmetry.
15) Give the Hermann-Maugin notation for these tetragonal point groups (3 pts)
422
4/m2/m2/m
4mm
Pg score _____
16) Indicate which crystal system corresponds to each point group (4 pts)
Point Group
Crystal System
4mm
Tetragonal
622
Hexagonal
4/m32/m
Isometric
2/m
Monoclinic
17) Circle the true statements about crystallographic axis and crystal systems (3 pts)
A) Isometric crystals have mutually perpendicular axes of unequal lengths
B) Hexagonal crystals have 4 axes, one (C) being different length than the other 3
C) Triclinic crystals have non-perpendicular axes of unequal length
D) Tetragonal crystals have mutually perpendicular axes with two of equal length
E) Monoclinic crystals have axes of unequal length and two that have a non-90° angle
F) Orthorhombic crystals have mutually perpendicular axes of unequal lengths
18) What crystal face would qualify as the “unit
face” in this crystal? (give face intercepts)
(2 pts)
1 :1:1
19) Label the Miller
indicies of the shaded
faces for the three
crystals (3 pts)
Miller Indicies
(1 0 1 0)
( 1 1 2 0)
(1 1 2 1)
Pg score _____
20) What is the Miller index of the upper face
(2 pts)
(1/2 : 1/2 : 3/2)*2 = 1 : 1 : 3
21) What is the zone axis of faces m’,
a, m, and b? (2 pts)
[001]
22) Circle the true statements about twinning (3 pts)
A) Twins are symmetrical intergrowth of two or more crystals related to a symmetry
operation (twin element) that is otherwise absent in a single crystal
B) Twin elements include mirrors, rotation axes (usually 2-fold) and roto-inversion
C) Penetration twins form by reflective symmetry across a mirror plane rotation axes
D) Contact twins form by rotational axes mirror plane/reflection symmetry
E) Albite twinning is a type of multiple polysynthetic twinning
F) Twinning only occurs in the isometric all crystal systems
23) Circle the true statements about 2D lattice symmetry (3 pts)
A) A 2D unit cell is defined as the smallest grouping that define the basic ordering of
an array of motifs or atoms.
B) Only More than one type of unit cell can be defined in a 2D array
C) Besides translation, screw axes glide lines are the other type of symmetry
operation that distinguishes 2D lattice symmetry from point group symmetry of
single crystals
D) A rectangular plane lattice has orthogonal axes of unequal length
E) Hexagonal plane lattices involve 3- or 6-fold rotation axes
F) Glide lines involve mirror line and translation symmetry operations
24) Screw axes involve a combination of what two symmetry operations? (2 pts)
rotation and translation
Pg score _____
25) Determine which of the 17 possible plane groups of 2D symmetry illustrated below
applies to the two tessellation drawings on the next page. (2 pts)
A) P2gg
B) P6
Also, on each drawing, outline a unit cell and draw the symmetry elements contained
within it. (6 pts)
Pg score _____
26) Match the 3D space group with the crystal system (11 pts)
Space Group
Crystal System
F23
Isometric
R3m
Hexagonal
P2/b21/c21/m
Orthorhombic
C2/m
Monoclinic
P42/m21/b2/c
Tetragonal
F4132
Isometric
P63mc
Hexagonal
P4/m
Tetragonal
P1
Triclinic
I212121
Orthorhombic
I43d
Isometric
Last Third
27) Circle the true statements about the nature of light (6 pts)
A) Light is a form of electromagnetic radiation
B) Light can be characterized as a transverse wave form that travels in a straight line
C) The frequency amplitude of light is manifest in the brightness of the light
D) The velocity of light is its wavelength multiplied by its frequency
E) Light speeds up slows down as it passes through denser substances
F) The short long wavelength of visible light is in the red end of the spectrum
28) Circle the true statements about reflection, refraction, and relief (8 pts)
A) Light is reflected at the same angle as the incident angle
B) Refraction occurs when light passes from one substance into another and results in
its changing velocity and being bent.
C) The index of refraction measures the degree to which light is slowed down relative
to the speed of light in a vacuum
D) The critical angle of refraction is the incident angle at which the light will not be
bent be reflected
E) A mineral in an oil grain mount will show high relief only if it has a higher
different index of refraction than the oil
F) The dark outline of a mineral with high relief is caused by the refraction of light at
the grain boundary
G) In a Becke line test, the bright line moves toward the substance with the lower
higher index of refraction
H) In a grain mount where the index of refraction of the oil and the mineral are
similar, one might observe a dispersion of the color spectrum at the grain
boundaries.
29) What does an optical indicatrix portray in a mineral? (2 pts) It is a 3-d map of how
the index of refraction of light varies with vibration direction in a mineral
Pg score _____
30) How can isotropic minerals be recognized under the microscope? (2 pts) They will
be fully extinct under cross polarized light
31) Name two ways anisotropic minerals can be recognized under the microscope?(2 pts)
It will display interference colors under cross polarized light
It goes to extinction 4 times in a 360° rotation of the stage
32) For these uniaxial indicatricies:
A) What crystal systems display this
type of optics? (2 pts)
uniaxial
B) What is the sign of the indicatrix on
the right? (1 pt) +
C) What is another name for the C-axis
(1 pt) optic axis or the ε vibration
direction
D) Is light vibrating in the ω direction
the fast or slow ray in the left
diagram? (1 pt) slow
33) Circle the true statements about optical properties of anisotropic minerals (8 pts)
A) Interference colors indicate the retardation of light which is a product of
birefringence and the thickness of the mineral
B) A particular mineral of a constant thickness will always show the same variable
interference colors regardless of depending on its orientation
C) Maximum birefringence is the difference in the maximum and minimum index of
refraction of a mineral
D) When birefringence = 0, the mineral is sliced through principal circular section of
the indicatrix
E) To find an optic axis figure, one searches for a mineral that displays the highest
lowest interference colors.
F) A random section through the indicatrix shown in question 32 will always have
one of the vibration directions parallel to ω.
34) For the figure to the right (1 pt each):
A) What is this optic figure? (circle one)
unixial optic axis
biaxial optic axis
uniaxial flash figure
acute bisectrix
B) What are the black bars called? isogyres
C) If this figure has a positive sign, in which
quadrants will the colors go down when a
gypsum plate is inserted? NW & SE
D) The color rings that encircle the cross are
called isochromes and represent what ?
Zones of equal retardation
Pg score _____
35) For the figures A & B below of sections through different biaxial indicatricies (1 pt
each)
A) Which displays a positive sign? A
B) What plane lies perpendicular to each optic axis? Circular section
C) In which will the Y axis be closer in length to the X axis? A
A
B
36) For this negative biaxial mineral,
indicate the section that will (1 pt ea.)
A) Give an optic axis figure YC
B) Give an acute bisectrix figure YZ
C) Give an obtuse bisectrix figure XY
D) Show maximum birefringence XZ
E) Show intermediate interference colors
Any other than XZ or YC
37) By what two methods can the 2V angle of a biaxial mineral be estimated? (2 pts)
1) Curvature of the isogyre
2) Separation of the isogyres
Pg score _____
38) Name the types of extinction angles that would be generated by these three crystal
configurations (3 pts)
Symmetrical
Parallel
Inclined
39) Name three types of minerals that occur as metallic native elements (3 pts)
gold, silver, copper, platinum, palladium, osmium, iridium, iron
40) Name 4 metals for which sulfide minerals are the most common source of ore (4 pts)
Copper, iron, nickel, lead, zinc, cobalt, molybdenum, mercury
41) Name two copper-bearing sulfide minerals (2 pts)
Chalcopyrite, covellite, chalcocite, diginite, bornite
42) The spinel group of oxides has the general formula of XY2O4.
A) Cations of what valence state typically occupy the X site +2 (1pt)
B) Give an example of such an cation Fe+2, Mg, Be (1pt)
C) Cations of what valence state typically occupy the Y site +3 (1pt)
D) Give an example of such an cation Fe+3, Al, Cr (1pt)
43) Red corundum is ruby; blue corundum is sapphire. What attribute of corundum
makes these minerals good gemstones? (1 pt) Hardness ~9
44) What is the main anionic component of hydroxide minerals? (OH)- (1 pt)
Name a type of hydroxide mineral manganite, brucite, gibbsite, goethite, diaspore,
bauxite (1 pt)
45) Name an element that is a common anion in halides Cl, F, I, Br (1 pt)
Name a type of halide mineral halite, fluorite, sylvite (1 pt)
46) What common feature does carbonate, sulfate, and phosphate minerals share? (1 pt)
Have anionic complexes
Pg score _____
47) What is a common characteristic of most carbonates that aids in their identification?
(1 pt) hexagonal, soft, will effervesce with acid if scratched
48) What are two subtypes of sulfates? (2 pts) hydrous and anhydrous
49) What is the net charge of the PO4 anionic complex that occurs in phosphate minerals?
(1 pt) -3
50) What is the basic building block of all silicate minerals? (1 pt) silicon tetrahedra
51) Give two reasons why the Si-O bond is so strong in silicate minerals (2 pts)
1) it is a partially covalent bond
2) it has a high electrostatic valence (4/4 ~ 1)
52) Why don’t silica tetrahedral share edges or faces? (2 pts) repulsive forces of the
highly charged Si +4 cations
53) Match the silicate group name and the SiO unit composition to each silicon
tetrahedral arrangement. And name one common mineral from each group (21 pts)
Si Gp: Nesosilicates
SiO form: SiO4
Mineral
Si Gp: Inosilicate double
Si Gp: Sorosilicate
SiO form : Si4O11
SiO form: Si2O7
Mineral
Mineral
Si Gp: Cyclosilicate
SiO form: SiO3
Mineral
Si Gp Inosilicate single
SiO form: Si2O6
Mineral
Si Gp: Phyllosilicate
SiO form: Si2O5
Mineral
Si Gp: Tectosilicate
SiO form: SiO2
Mineral
Silicate group names: sorosilicates, tectosilicates, nesosilicates, inosilicates (single),
inosilicates (double), phyllosilicates, cyclosilicate
Si-O unit compositions: SiO2, SiO4, Si2O7, SiO3, Si2O6, Si4O11, Si2O5,
54) What is the main attribute by which pyroxenes are distinguished from amphiboles? (1
pt) Pyx - 90° cleavage; Amph – 120/60° cleavage
Pg score _____