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Optical Mineralogy > Identification of Minerals > Flashcards

Identification of Minerals Flashcards

(84 cards)

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1
Q

The following properties can be observed at what light?

Opacity, Relief, Habit, form, Mode of Aggregation, Relative Index of Refraction, Color, Pleochroism, Habit, Form, Cleavage

A

Plane polarized Light (PPL)

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2
Q

The following properties can be observed at what light?

Isotropic vs Anisotropic, Habit, Form, Mode of Aggregation, Cleavage, Interference Color, Sign of Elongation, Extinction and Extinction Angles, Twinning, Zoning

A

Cross Polarized Light (XPL)

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3
Q

The function of the wavelength transmitted by the mineral.

A

Color

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4
Q

The _______ of a mineral in hand specimen
and in thin section have the same hue although
the _______ in thin section is typically not as intense

A

Color

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5
Q

The ability of a mineral to absorb different wavelengths of transmitted light depending upon its crystallographic orientation

A

Pleochroism

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6
Q

Pleochroism is used to describe the color variation for __________ __________ with the polarization direction of the light, which depends on the orientation of the material in the light path

A

Destructive Interference

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7
Q

Colored _________ and _________ are usually pleochroic.

A

Uniaxial, Biaxial

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8
Q

Term for pleochroic hexagonal, trigonal, and tetragonal minerals.

A

Twofold Pleochroism

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9
Q

Other term for twofold pleochroism.

A

Dichroism

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10
Q

Term for pleochroic orthorhombic, monoclinic and triclinic
minerals

A

Trichroic

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11
Q

Light vibrating at Optic Axis = color 1; light at perpendicular to Optic Axis = color 2

A

Uniaxial Minerals

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12
Q

Minerals that exhibit varying degrees of absorption

A

Biaxial Minerals

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13
Q

Pleochroism described as darkest at long axis oriented perpendicular to polarizer

A

Normal Pleochroism

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14
Q

Type of pleochroism described as darkest at long axis oriented parallel to polarizer

A

Reverse Pleochroism

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15
Q

The degree to which mineral grains stand out from the mounting medium.

Have sharp grain boundaries, show fractures and cleavages well.

A

Relief

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16
Q

Property of a mineral that describes its shape/appearance.

A

Habit / Form

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17
Q

Without regular crystal faces.

A

Anhedral

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18
Q

Has well-formed crystal faces.

A

Euhedral

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19
Q

Has crystal faces but they are poorly formed or irregular.

A

Subhedral

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20
Q

Elongated, needle-like grains.

A

Acicular

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21
Q

Elongated and Slender.

A

Bladed

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22
Q

Shaped like a column; moderately elongated grains with equidimensional cross section.

A

Columnar

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23
Q

Equidimensional Grains.

A

Equant

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24
Q

Individual grains are long slender fibers.

A

Fibrous

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25
Flat, elongated grains.
Lathlike
26
The dominant faces are those of a prism.
Prismatic
27
Shaped like a book.
Tabular
28
Refers to how the individual mineral grains are grouped together to form a larger structure or assemblage.
Mode of Aggregation
29
Parallel arrangement of columnar grains.
Columnar
30
More or less parallel, tabular, or platy grains; flaky.
Foliated
31
Equant grains, all about the same size.
Granular
32
Elongated grains in a random pattern.
Matted
33
Elongated grains that radiate out from a center.
Radiating
34
The way a mineral splits in preferred directions. Represents the planes of weak bonding in the mineral’s atomic structure.
Cleavage
35
A mineral’s cleavage should be repetitive and subparallel. If this circumstaces are not met, the mineral has a ________ instead of a cleavage.
Fracture
36
Characterizations of mineral cleavages.
Perfect, Good, and Weak/Poor
37
Light rays are parallel to the wave normal. Shows the same velocity of light in all directions. Bonds are the same in all directions.
Isotropic Materials
38
Example of isotropic materials.
Isometric Minerals and Mineraloids
39
Light rays are not parallel to the wave normal. Shows difference velocities of light in all directions. Bonds are not the same in all directions.
Anisotropic Materials
40
Example of Anisotropic Materials
Tetragonal, Trigonal, Hexagonal, Orthorhombic, Monoclinic, and Triclinic Minerals
41
The wavelength (color) exhibited by a mineral when viewed under XPL.
Interference Color
42
Resultant of two superimposed polarized light emerging from analyzer.
Interference Colors
43
Maximum interference colors can be observed ______ degrees from the extinction position.
45
44
Chart used to assign interference colors.
Michel-Levy Color Chart
45
Observed under XPL, dependent on orientation of mineral, or presence of cleavages of mineral grain.
Extinction
46
Types of Extinxtions on Minerals
Parallel, Symmetrical, Inclined, Undulose
47
All uniaxial minerals exhibit ______ extinction. — the crystal axes and indicatrix axes coincide.
Parallel
48
Orthorhombic minerals show ________ extinction.
Parallel
49
Monoclinic and triclinic minerals have ________ extinctions. — indicatrix axes do not coincide with crystallographic axes. — extinction angle helps to further identify them.
Inclined
50
No cleavage to base extinction from.
No Extinction Angle
51
Different parts of a grain become extinct at different angles. — consequence of stress, deformation
Undulose / Undulatory Extinction
52
The distance that one wave lags behind the other (measured in nm).
Retardation
53
Where i is an integer, then the two waves are said to be in phase.
Constructive Interference
54
Two waves are said to be out of phase.
Destructive Interference
55
True or False Light rays travelling along the same path will the same direction will not interfere with each other.
False, they will interfere with each other.
56
A property used to determine which of the two rays coming through the mineral is the slow ray and which is the fast ray. When these two rays leave the top of the mineral grain, the slow ray is behind the fast ray by a distance equal to the retardation Δ1.
Sign of Elongation
57
What is produced when a material with known retardation ΔA is superimposed over the mineral so that the slow ray vibration directions are parallel, the resulting slow ray and is further retarded.
Higher Interference Colors
58
What is produced when a mineral’s fast ray is parallel to the slow ray of the material with known retardation ΔA, slow ray of mineral becomes fast ray in material with known retardation ΔA; mineral’s fast ray is retarded.
Lower Interference Colors
59
When looking for signs of elongation, when the interference color of a mineral increases, it can be characterized as _________.
Length-slow
60
When looking for signs of elongation, when the interference color of a mineral decreases, it can be characterized as _________.
Length-fast
61
Three types of compensators/accesory plates/retardation plates.
Muscovite/Mica, Gypsum, and Quartz Plates
62
The compensator marked with 137 nanometers.
Muscovite / Mica Plate
63
The compensator marked with 500 nanometers.
Gypsum Plate
64
Fast ray direction.
NW-SE
65
Slow ray direction.
NE-SW
66
Other term for length-slow sign of elongation.
Positive Elongation
67
Other term for length-fast sign of elongation.
Negative Elongation
68
When looking for signs od elongation, if the mineral has 1 degree white-gray interference color, ______ plate should be used.
Mica
69
When looking for signs of elongation, color blind users shall use the _______ ________.
Quartz Wedge
70
The intergrowth of two or more crystals in a symmetrical fashion by the sharing of lattice points in adjacent crystals. — best observed in plagioclase, but other minerals such as quartz, pyrite, fluorite, etc.
Twinning
71
Type of twinning observed in Albites, where in hand samples it can be observed as striations, and in thin sections can be observed as inter-layering of colors.
Albite Twinning
72
The most common type of twinning observed in orthoclase.
Carlsbad Twinning
73
_________ twinning only occurs in Triclinic feldspars.
Albite
74
_________ twinning occurs in monoclinic and triclinic fledspars.
Carlsbad
75
__________ twinning is a characteristic feature of the mineral Microcline, defined as the combination of albite and pericline twinning laws.
Tartan
76
Variation in the extinction angle from one zone to another. Albite-Anorthite Series Common, particularly in volcanic and hypabyssal intrusive rocks.
Zoning
77
Changes smoothly from a more calcic core to a more sodic rim. Core has a larger extinction angle.
Normal Zoning
78
Changes smoothly from a more sodic core to a more calcic rim. Core has a smaller extinction angle.
Reverse Zoning
79
Alternation between calcic and sodic zones. Usually from a more calcic core to a more sodic rim.
Oscillatory Zoning
80
A _______ zoned plagioclase has a calcic core and sodic rim.
Normal
81
The higher the Calcium content, the _________ the extinction angle of plagioclase.
Higher
82
1λ of the compensator corresponds to ________ nanometers.
500
83
Biaxial minerals exhibit ________ pleochroic colors.
Varying
84
True or False: A euhedral mineral has no regular crystal faces.
False, euhedral minerals has well-developed crystal faces.

Optical Mineralogy (7 decks)

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