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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
Q

A mineral with _________ will go extinct with the cleavage at an angle to these directions as the stage is rotated.

A

inclined extinction

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26
Q

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.

A

parallel extinction

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27
Q

The color of a mineral under cross-polarized light is called its _____________

A

interference color

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28
Q

Interference colors categorized by _____________________ order colors

A

first, second, third, and fourth

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29
Q

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.

A

Michel-Levy Interference Color Chart

30
Q

______________ 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).

A

Birefringence (δn, or nγ – nα)

31
Q

____________ 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.

A

Twinning

32
Q

Due to compositional changes during crystal growth

A

Zoning

33
Q

Spatial variation in birefringence caused by a bent crystal lattice.

A

Undulatory extinction

34
Q

A process by which a solid solution phase unmixes into two separate phases in the solid state.

A

Exsolution lamellae

35
Q

An intimate intergrowth of sodic and potassic feldspar resulting from subsolidus exsolution (unmixing of two minerals).

A

Perthite

36
Q

An intergrowth arising due to exsolution where potassic feldspar is present as blebs or lamellae within a sodic feldspar.

A

Antiperthite

37
Q

When sodic and potassic feldspars are in broadly equal abundance.

A

Mesoperthite

38
Q

Perthite that can only be observed with the aid of microscope is known as __________.

A

Microperthite

39
Q

Minerals that shows complete solid solution at higher temperatures, but do not show such solid solution at lower temperatures.

A

Exsolution

40
Q

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.

A

Myrmekite

41
Q

An igneous texture in which an intergrowth of two minerals has the appearance of runic writing.

A

Graphic texture

42
Q

Rocks containing abundant graphic texture can be described as ________.

A

Granophyric

43
Q

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.

A

Exsolution lamellae in pyroxene

44
Q

The same dimensions in all directions (garnet, spinel)

A

equant

45
Q

equant with a nearly square cross sections (halite, galena)

A

blocky

46
Q

Needle like (actinolite, sillimanite)

A

acicular

47
Q

Appearing to be a plates or a thick sheet (gypsum, graphite)

A

tabular, platy

48
Q

Hairlike or threadlike (serpentine)

A

capillary or filiform

49
Q

Elongated and flattened in one direction (kyanite, wollastonite)

A

bladed

50
Q

Elongated with faces parallel to a common direction (apatite, beryl)

A

prismatic or columnar

51
Q

Easily split into sheets (muscovite, biotite)

A

foliated or micaceous

52
Q

Appearing as a solid mass with no distinguish feature

A

massive

53
Q

Composed of many individual grains

A

granular

54
Q

Containing crystals emanating from a common point

A

radiating or divergent

55
Q

Composed of fibers

A

fibrous

56
Q

Appearing stalactite shaped

A

stalactitic

57
Q

Appearing like flat plates or slabs growing together

A

lamellar or tabular

58
Q

Containing an aggregate of crystals giving starlike appearance

A

Stellated

59
Q

Having feathery appearance

A

plumose

60
Q

Appearing like a branching tree or plant

A

arborescent or dendritic

61
Q

Net-like, composed of slender crystals forming a lattice pattern

A

reticulated or latticelike

62
Q

Made of spherical/hemispherical shapes made of radiating crystals.

A

colloform or globular

63
Q

Having an appearance similar to a bunch of grapes

A

Botryidal

64
Q

Having a kidney shaped appearance

A

Reniform

65
Q

Having surface covered with fine crystals

A

Drusy

66
Q

Composed of very small or small spheres

A

Elliptic or pisolitic

67
Q

Having a planar composition surface separating 2 individual crystals {021}.

A

contact twinning

68
Q

Have an irregular composition surface separating 2 individual crystals {001}.

A

penetration twins

69
Q

Compositions surface are parallel to one another, they are called _________ {010}. Plagioclase is the common example of this type of twinning.

A

polysynthetic twins

70
Q

If the composition surface are parallel to one another, they are called ________. Occurs in chrysoberyl along a {031} plane.

A

Cyclical twins

Correlation Course (15 decks)

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