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Correlation Course > Optical Mineralogy > Flashcards

Optical Mineralogy Flashcards

1
Q

_______ minerals will transmit light.

A

Transparent

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2
Q

_________ minerals block light from passing through them

A

opaque

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3
Q

T or F. Minerals that are darkly colored in hand sample will also appear to have color in thin section

A

T

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4
Q

_______ when a mineral changes color as it is rotated relative to the polarizer in plane polarized light

A

Pleochroism

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5
Q

_________ of a mineral characterizes the relationship between the speed of light in a vacuum and the speed of light in that material.

A

refractive index

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6
Q

Refractive index of kyanite ranges from ______.

A

1.712-1.734

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7
Q

Mineral _______ is related to the refractive index of the mineral. If a mineral has a refractive index that is much higher or lower than the surrounding materials, it will stand out relative to the surrounding material and will have thick or distinct .

A

relief

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8
Q

Refractive index > 0.12 different from surrounding media

A

High relief

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9
Q

Refractive index 0.04 – 0.12 different from surrounding media

A

Intermediate relief

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10
Q

Refractive index <0.04 different from surrounding media

A

Low relief

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11
Q

The relative refractive indices of two materials (minerals, glass, or epoxy) adjacent to each other in a thin section can be determined using ______.

A

Becke lines

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12
Q

Refers to the ideal crystal form, or the shape a mineral takes when left to grow without barriers or interference with other nearby mineral grains.

A

Mineral Form

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13
Q

Minerals show perfect or nearly perfect crystal faces

A

Euhedral

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14
Q

Minerals are rounded but still show the general characteristic shape of that mineral

A

Subhedral

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15
Q

Crystals are completely irregular in shape and do not resemble the characteristic form for that mineral.

A

Anhedral

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16
Q

The tendency of minerals to break along atomic planes of weakness within the crystal structure

A

Cleavage

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17
Q

Irregular cracks within a mineral. These can form within any mineral, but when only fractures appear in a mineral, it may indicate that it has poor or no cleavage.

A

Fractures

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18
Q

__________ minerals have crystal structures which have the same structure in every direction.

A

Isotropic

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19
Q

Isotropic minerals belong ____________ system.

A

Isometric

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20
Q

_________ crystal structures vary with direction.

A

Anisotropic

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21
Q

Anisotropic minerals belong to ____________.

A

hexagonal, tetragonal, orthorhombic, monoclinic, and triclinic crystal systems

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22
Q

PPL - Mineral appears dark
XPL - Mineral appears dark even when rotated

A

Opaque

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23
Q

PPL - Light passes through mineral
XPL - Mineral appears dark even when rotated

A

Isotropic

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24
Q

PPL - Light passes through mineral
XPL - Mineral exhibits interference colors and goes dark (extinct) every 90 degrees

A

Anisotropic

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25
A mineral with _________ will go extinct with the cleavage at an angle to these directions as the stage is rotated.
inclined extinction
26
A mineral with __________ will go extinct (dark) when the cleavage direction is parallel to the north-south and east-west directions as the stage is rotated.
parallel extinction
27
The color of a mineral under cross-polarized light is called its _____________
interference color
28
Interference colors categorized by _____________________ order colors
first, second, third, and fourth
29
This diagram displays the interference colors in the chart, with verbal descriptions of first-, second-, and third-order colors below the x-axis. The y-axis on the left side of the diagram is thickness of the mineral (or thin section) in micrometers.
Michel-Levy Interference Color Chart
30
______________ the phenomenon exhibited by certain materials in which an incident ray of light is split into two rays, called an ordinary ray and an extraordinary ray, which are plane-(linear) polarized in mutually orthogonal planes, or circular-polarized in opposite directions (left and right).
Birefringence (δn, or nγ – nα)
31
____________ occurs when a preexisting crystal undergoes a transformation due to a change in pressure or temperature. This commonly occurs in minerals that have different crystal structures and different symmetry at different temperatures or pressures.
Twinning
32
Due to compositional changes during crystal growth
Zoning
33
Spatial variation in birefringence caused by a bent crystal lattice.
Undulatory extinction
34
A process by which a solid solution phase unmixes into two separate phases in the solid state.
Exsolution lamellae
35
An intimate intergrowth of sodic and potassic feldspar resulting from subsolidus exsolution (unmixing of two minerals).
Perthite
36
An intergrowth arising due to exsolution where potassic feldspar is present as blebs or lamellae within a sodic feldspar.
Antiperthite
37
When sodic and potassic feldspars are in broadly equal abundance.
Mesoperthite
38
Perthite that can only be observed with the aid of microscope is known as __________.
Microperthite
39
Minerals that shows complete solid solution at higher temperatures, but do not show such solid solution at lower temperatures.
Exsolution
40
Intergrowth of branching rods of quartz set in a single crystal of plagioclase, neighbouring rod of quartz have the same lattice orientation and extinguish together. May also occur at grain boundaries of K-feldspar.
Myrmekite
41
An igneous texture in which an intergrowth of two minerals has the appearance of runic writing.
Graphic texture
42
Rocks containing abundant graphic texture can be described as ________.
Granophyric
43
A solid solution phase unmixes into two separate phases in the solid state and it occurs only in mineral whose compositions vary between two or more pure endmember compositions.
Exsolution lamellae in pyroxene
44
The same dimensions in all directions (garnet, spinel)
equant
45
equant with a nearly square cross sections (halite, galena)
blocky
46
Needle like (actinolite, sillimanite)
acicular
47
Appearing to be a plates or a thick sheet (gypsum, graphite)
tabular, platy
48
Hairlike or threadlike (serpentine)
capillary or filiform
49
Elongated and flattened in one direction (kyanite, wollastonite)
bladed
50
Elongated with faces parallel to a common direction (apatite, beryl)
prismatic or columnar
51
Easily split into sheets (muscovite, biotite)
foliated or micaceous
52
Appearing as a solid mass with no distinguish feature
massive
53
Composed of many individual grains
granular
54
Containing crystals emanating from a common point
radiating or divergent
55
Composed of fibers
fibrous
56
Appearing stalactite shaped
stalactitic
57
Appearing like flat plates or slabs growing together
lamellar or tabular
58
Containing an aggregate of crystals giving starlike appearance
Stellated
59
Having feathery appearance
plumose
60
Appearing like a branching tree or plant
arborescent or dendritic
61
Net-like, composed of slender crystals forming a lattice pattern
reticulated or latticelike
62
Made of spherical/hemispherical shapes made of radiating crystals.
colloform or globular
63
Having an appearance similar to a bunch of grapes
Botryidal
64
Having a kidney shaped appearance
Reniform
65
Having surface covered with fine crystals
Drusy
66
Composed of very small or small spheres
Elliptic or pisolitic
67
Having a planar composition surface separating 2 individual crystals {021}.
contact twinning
68
Have an irregular composition surface separating 2 individual crystals {001}.
penetration twins
69
Compositions surface are parallel to one another, they are called _________ {010}. Plagioclase is the common example of this type of twinning.
polysynthetic twins
70
If the composition surface are parallel to one another, they are called ________. Occurs in chrysoberyl along a {031} plane.
Cyclical twins

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