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GLE 2024 (Day 2) > MINERALOGY BASIC CONCEPTS (CRYSTALLOGRAPHY) > Flashcards

MINERALOGY BASIC CONCEPTS (CRYSTALLOGRAPHY) Flashcards

1
Q

Long range order or crystal structure of crystalline substances

A

Crystallography

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2
Q

What is the basic unit of pattern during crystal growth?

A

Coordination Polyhedra

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3
Q

Processes which are responsible for the repetition of these basic units into long range structure

A

Symmetry operation

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4
Q

Techniques whicah can aid in examining internal crystal structures

A

XRD
AFM (Atomic Force Microscopy)

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5
Q

Smallest unit of pattern repeated to produce a long range pattern characteristic of a crystal

A

Motif

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6
Q

What s the motif in minerals?

A

Coordination Polyhedra

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7
Q

A point which represent a motif

A

Node

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8
Q

Single symmetry Oprations

A

Translation
Rotation
Reflection
Inversion

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9
Q

Symmetry operation repeating nodes by linear displacement

A

Translation

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10
Q

Product of 1D translation

A

Row of similar elements

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11
Q

Product of 2D translation which is an array of motif or nodes in which every node has an environment similar to every other noe in the array

A

Plane Mesh or Plane lattice

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12
Q

Result 3D Translation

A

Space Lattice

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13
Q

3d array of motifs (Coordination polyhera) and product of translation in crystalline substances

A

Crystal lattice

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14
Q

Symmetry operations which repeats a motif by rotation of a pattern about an axis in which every component of the pattern is perfectly repeated one or more times during a complete 360 rotation

A

Rotation

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15
Q

This denotes the number of repetitions

A

“n”

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16
Q

A symmetry operation in which a certain pattern is repeated by reflection across a aplane called mirrior plane (m)

A

Reflection

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17
Q

What changes during reflection

A

Handedness. (What right in the original image will be on the left of the mirrior image )

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18
Q

Symmetry operation which change the handedness of motifs

A

Enantiomorphic operations

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19
Q

A symmetry of operations which involves the repetition of a motif by inversion through a center of inversion symmetry (i)

A

Inversion

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20
Q

What’s the test for inversion?

A

All patterns are repeated along lines that pass through a common center and are repeated at equal distance from the center

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21
Q

Difference between reflection and inversion

A

Reflection is repeate across a plane while inversion is repeated across a point of symmetry (i)

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22
Q

Compound symmetry operations which combines Translation and Reflection across a mirror plane

A

Glide Reflection (g)

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23
Q

An operation that combines rotation and inversion about rotoinversion axis

A

Rotoinversion (?)

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24
Q

Ten plane point groups

A

1, 2, 3, 4, 5
1m, 2mm, 3m, 4mm, 5mm, 6mm

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25
Q

Five Unit meshes created by translation

A

square (p, a=b, ab=90
primitive rectangle p, a/=b, ab=90
Diamond or Centered Rectangle
c, a/=b, ab = cosa/2b
Hexagonal
c, a=b, ab=120
Oblique
p, a/=b, ab/=90

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26
Q

How are unit mesh classisifed

A

Length of Vetors
Angle between 2 translation verctors
Positions of Nodes (P or C)

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27
Q

If the nodes of a unit mesh are all on the corners it is

A

Primitive

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28
Q

If the a node exist at the center of a unit mesh

A

centered

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29
Q

When five unit meshs is combines with 10 point groups this much plane lattice group forms

A

17 lattice groups

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30
Q

3D equivalent of 10 plane point groups which are the products of non translational symmetry operations

A

Space Point groups

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31
Q

3D equivalent of plane nets

A

Splace Lattices

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32
Q

Fundamental units of space lattices

A

Unit cells

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33
Q

Consist of 3D set of one or more crystal faces that possess similar relationships to the crystallographic axees

A

Crystal Forms

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34
Q

have the potential to completely enclose a mineral specimen and therefore to exist alone in perfectly formed euhedral crystals

A

Closed Crystal Forms

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35
Q

Crystal systems of closed crystal forms

A

Isometric
Tetragonal
Hexagonal
orthorhombic rhombohedral

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36
Q

a typical closed crystal form of pyrite

A

Pyritohedron

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37
Q

Do not have the potential to completely enclose a mineral specimen and so must occur in combination with other open or closed crystal forms

A

Open Crystal Forms

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38
Q

Consist of only a singe face

A

Pedians monohedron

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39
Q

Consist of pair of parallel face

A

Penacoids parallelohedron

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40
Q

three of more faces that paralle to an axis

A

Prisms

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41
Q

Three or more faces that intesect to an axis

A

Pyramid

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42
Q

A pair of faces symmetrical about a mirror plane (changes handedness)

A

Domes

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43
Q

A pair of faces symmetrical about an axis of rotation (donot change handedness)

A

Sphenoid

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44
Q

How to calculate axial ratios?

A

a/b: b/b: c/b whre b/b is always 1

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45
Q

Unit of axial lengths

A

Angstroms (A)

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46
Q

Planar features that are characteristic of a mineral

A

1) Crystal lattice planes that reflects xray
2) Cleavage surfaces that develop during breakage
3) Crystal face that foms during growth

47
Q

Euclidean Principle

A

Planes must at least intersect one axis and be parallel to the other 2

48
Q

What does miller indices do?

A

Identify and describe crystallographic planes

49
Q

Any face or plane that intersects all three axes at distances from the center corresponding to the axial ratio of the mineral

A

Unit Face or Unit Plane

50
Q

Any face of plane that intersect all three crystallographic axes at different lengths relative to their axial ratio

A

General Face

51
Q

How to get Weiss parameter?

A

Just divide the actual length of the face or place intercept to the axial lengths or ratio

52
Q

A method for describing the relationships between sets of crystal faces or planes and the crystallographic axes using rational numbers (Fraction)

A

Weiss Parameters

53
Q

Weiss parameter of unit planes or faces

A

1:1:1

54
Q

IN weiss parameter, how are planes that intercept to the negative crytallographic axes denoted?

A

By placing a bar over their weiss parameter

55
Q

Weiss parameter of a face that intersects c and is parallel to a and b axes

A

(Infinity, Inifinity, 1)

56
Q

If a face is parallel to a crystallographic axes the weiss parameter on that specific axes for such face is

A

Infinity

57
Q

if the weiss parameter is 1 at a specific axis it denotes that

A

the plane intersect such axis at unit length

58
Q

Whats the relationship of the Miller Indices to Weiss Parameter?

A

Reciprocal (Miller tend to be a whole number)

59
Q

Thus what is the miller index of a plane parallel to an axes?

A

0

60
Q

the larger the Miller index

A

the smaller is the actual length of interception

61
Q

A miller indices of (123) are read

A

planes intersect a-axis at unity
plane intersect b-axis at 1/2 unity
plane intersect c axis at 1/3 unity

62
Q

How is an intersection between the negative crystallographic axes and the plane denoted in miller index?

A

a bar above the index

63
Q

If the faces or planes has the same general relationship to the crystallographic axes and therefore have the same miller index, what can be the shortcut?

A

Form Indices

64
Q

Whats the preference for the Form Face whenever the indices has a common form

A

1) Top Face
2) Top right
3) Top right front

65
Q

Form indices of octahedral minerals

A

{111}

66
Q

Form indices for cube

A

{001}

67
Q

Form indices for dodecahedron

A

{011}

68
Q

Chalcopyrite is has what crystal form?

A

Tetragonal Disphenoid

69
Q

Vesuvianite and wulfenite has one crystal form?

A

Basal Pinacoid, tetragonal-pyramidal

70
Q

Why is there twinning?

A

Because there are shared lattice points between two crystals

71
Q

The mirror plane that caused reflection of twins

A

Twin Plane

72
Q

Axis of rotation in twin crystals

A

Twin Axis

73
Q

Twins that formed by inversion through a point have

A

Twin Center

74
Q

The symmetry operation that relates twin in twinned crystals

A

Twin Law

75
Q

Surfaces along which twins are joined

A

Composition Surfaces/Planes

76
Q

Twins joined along composition planes

A

Contact twins

77
Q

A contact twin in orthoclase with {021} as twin plane

A

Braveno Law

78
Q

Twins joined along irregular composition surfaces defined either by twin center or twin axis

A

Penetration twins

79
Q

Twin axis of Carlsbad Law a type of penetration twin

A

[001]

80
Q

Irregular composition surfaces that are repeated but are not Parallel

A

Cyclical Twins

81
Q

Mineral with cyclical Twins

A

Chyrosberyl

82
Q

Crystals that contain only two twins

A

Simple twins

83
Q

More than two twins

A

Multiple Twins

84
Q

Multiple twins repeated across multiple parallel composition

A

Polysynthetic Twins

85
Q

Polysynthetic twinning with {010} Twin Plane

A

Albite Twin Law

86
Q

Twins that form durig crystal growth

A

Growth Twins

87
Q

Twining occurs when a preexisting crystal undergoes a transformation due to acchange in pressure or temperature producing symmetry

A

Transforamtion twins

88
Q

Example of Transformation twins

A

Tartan Twinning in Microcline
Brazil and Dauphine Twinning in Qtz

89
Q

A mechanical twinning that forms during deformation when atoms are pushed out of place and produce a symmetrical arrangement

A

Deformation Twins/Mechanical Twins

90
Q

Mineral that exhibit Deformation Twins

A

Calcite (102)

91
Q

Twinning in Gypsum

A

Swallow tail

92
Q

Twinning in Plagioclase

A

Polysynthetic Albite

93
Q

Twinning in Galena, Pyrite and Staurolite

A

Penetration twins

94
Q

Twinning in Orthoclase

A

Carlsbad

95
Q

Small scale impurities or imperfection or local scale inhomogenities that cause mienral composition and/or structure to vary from the ideal

A

Crystal Defects

96
Q

Formed when ions in question move to an interstitial site leaving unoccopied structural sites or vacanies behind. Does not cause charge imbalance but only lattice distortions

A

Frenkel Defect (VACANCY)

97
Q

A point defect wherein ions migrate oustide the lattice or were never there at all thus creating charge imbalance which can be balanced by creating a second vacancy or inducing ions that will balance the charge

A

Schottky Defect (CHARGE IMBALANCE)

98
Q

Example of Mineral that normally exhibits Schottky Defect

A

Pyrrhotite

99
Q

Defects on atomic scale and thus don’t have longer range extent and is considered to be ZERO DIMENSIONal

A

Point Defects

100
Q

Point Defects

A

1) Substitution
2) Interstitial
3) Omission (Vacancy)

101
Q

Line defects which commonly result from SHEARING STRESSES produced in crystals during deformation causing atomic planes to shift position thus producing distortion in the lattice

Permits rocks to deform withut fracturing

A

Dislocations

102
Q

Dislocation in which the slip plane is normal to the dislocation
Addition of half a plane

A

Edge

103
Q

Dislocation in which the slip plane is parallel to the dislocation (Rotated)

A

Screw

104
Q

2D Crystals defects and where crystal srtucture changes across a distinct planar boundary

A

Planar Defects

105
Q

Diffusion wherein vacancies and ions move towards the region of low stress which tends to lengthen the crystal in that direction which is the grain boundaries

A

Coble Creep

106
Q

Diffusion wherein vacaneis and ions move towards the region of highest stress which tend to shorten the crystal

A

Herring-Nabarro Creep

107
Q

Low Temp, Low Strain

A

Dissolution Creep (Pressure solution) and Mechanical Twinning

108
Q

Low Temp, High Strain

A

Cataclasis

109
Q

Mod Temp, Low Strain

A

Cobble Creep

110
Q

High Temp Low strain

A

Herring-Nabarro Creep

111
Q

High Temp, High Strain

A

Dislocation Creep

112
Q

Grains tend to migrate to the region of

A

Minimum Stress

113
Q

Vacancies tend to migrate to the region of

A

Max Stress

GLE 2024 (Day 2) (41 decks)

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