Lecture Midterm Study Flashcards
amorphous
lacking a crystalline structure (think obsidian)
mineraloids
mineral-like things that lack a long-range crystal structure
metamict
disrupted crystal structure
tektites
impact melt glasses from meteorites
fulgurites
produced by lightning strikes
clinkers
burning coal bed fuses surrounding rock (forming ash glasses)
mineral group
a set of minerals with the same basic structure but different compositions
pseudotachylite
frictional melt at fault zone from intense shearing
specific gravity (G)
density of a material divided by the density of water at 4deg C
packing index (def)
how tightly the ions are packed in a mineral
packing index (formula)
(V_ions / V_cell) * 100
brittle
breaks or powders easily
malleable
can be pounded out into thin sheets
ductile
can be drawn into a wire
sectile
may be cut smoothly with a knife
elastic
if bent, will spring back
flexible
if bent, will not spring back
parting
stress-derived, not cleavage-controlled
the ‘chromophore’ elements
Ti, V, Cr, Mn, Fe, Co, Ni, Cu
color centers
depend on having electrons mislocated throughout the structure (i.e. occupying ion spots)
play of color
iridescence
luminescence
material absorbs one form of energy and reemits it as visible light
triboluminescence
material becomes faintly luminous if struck, crushed, scratched, or rubbed
thermoluminescent/incandescent
material emits visible light energy as a consequence of being heated
photoluminescent
material emits light in response to being exposed to visible or UV light
diamagnetic
no element in the mineral contains unpaired electrons
paramagnetic
mineral in which magnetic moments of constituent atoms are not mutually aligned (i.e. magnetic moments go everywhere)
ferromagnetic
mineral with retained magnetic polarity because magnetic moments are systematically aligned
exchange coupling
locks the magnetic moment of adjacent ions into parallel alignment
ferrimagnetic
magnetic, but some atoms/ions in adjacent sites have antiparallel magnetic moments (e.g. Magnetite)
antiferromagnetic
antiparallel spins completely cancel out to yield zero net magnetic moment
piezoelectric
when deformed, mineral will generate a voltage, so that a positive charge is generated on one side and a negative charge on the other
electrostriction
the application of a voltage in a piezoelectric mineral to produce a deformation
pyroelectric
change in temperature causes displacement of positive and negative charges and the development of a voltage
Steno’s Law
The angles between crystal faces of a given mineral species are constant
Hauy found this…
Minerals are made up of stacked blocks (unit cells)
Number of Bravais lattices
14
Number of crystal systems
6
Number of point groups (possible unit cell symmetries)
32
Number of space groups
230
How you get space groups
Translating the Bravais lattices through 3D space
Hauy’s Law
Crystal faces cut the crystallographic axes in simple, whole-number ratios
Bravais’ Law
A face is more commonly developed in a crystal if it intersects a larger number of lattice points
Weiss Indices
mno
Miller Indices
(hkl)
Cubic Close-Packing
ABA
Hexagonal Close-Packing
ABC
Pauling’s Coordination Principle
Cations are bound to ions within a polyhedra; the bigger the cation, the larger the CN
Pauling’s Electrostatic Valency Principle
In a stable ionic structure, the total strength of the valency bonds that reach an anion from all neighboring cations is equal to the charge of the anion
Pauling’s Sharing Polyhedral Elements Principle
Sharing of edges and faces decreases stability of ionic structures; In a crystal containing different cations, those with large valence and small coordination number tend not to share polyhedral elements
Retardation (Delta)
= d (n_s - n_f)
Birefringence
The difference between the indices of refraction of the slow and fast rays
Interference colors are produced by…
…are produced by interference between the 2 waves (fast and slow) in an anisotropic mineral
Extinction angle (EA)
The angle between the length or cleavage of a mineral and one of the mineral’s vibration directions
With accessory plate, if retardations ADD…
slow (plate) on slow (mineral)
With accessory plate, if retardations CANCEL…
slow (plate) on fast (mineral)
Length Slow
The slow ray vibrates more-or-less parallel to the length of an elongate mineral (Positive Elongation)
Length Fast
The fast ray vibrates more-or-less parallel to the length of an elongate mineral (Negative Elongation)
Pleochroism
Anisotropic property; change of color on rotation (with only lower polarizer)
Index of Refraction (Definition)
A measure of how much the light will be bent, is a function of velocity (high means low velocity)
Index of Refraction (Formula)
n = V_vacuum / V_mineral
Frequency (Formula)
V / λ
Wave Normal
A line drawn at right angles to the wave front
Snell’s Law gives you…
The angle that the light is bent upon passing from material 1 to material 2 is found by…
Snell’s Law (Formula)
Sin(θ1) / Sin(θ2) = n_2 / n_1
