Mineralogy Midterm

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True or False?

Most minerals have a single cation or cationic group, while they often have more than one anion.

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Variety of vocab words from the slides

Geology

43 Terms

1

True or False?

Most minerals have a single cation or cationic group, while they often have more than one anion.

False.

Most minerals have a single anion or anionic group, while they often have more than one cation.

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2

Crystal Chemistry

relationship of chemical composition to atomic structure

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3

Mineral

A mineral is a naturally occurring solid with a highly ordered atomic arrangement and a definite (but not fixed) chemical composition. It is usually formed by inorganic processes

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4

Steno’s Law

"In crystals of the same species (different specimens), under equal conditions of pressure and temperature, the corresponding dihedral angles are always the same, the number, shape and size of the faces being variable"

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5

The 5 chemical bonds

ionic

covalent

metallic

van der waals

hydrogen

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6

Compounds ending in–ide…

are simple binary compounds containing 2 elements even if there is no metal

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7

Compounds ending in–ate…

means oxygen is present

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8

Ending in –ite…

have less oxygen present than in –ate compounds

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9

4 Crystal Bonding Types

  1. Molecular Crystal

  2. Covalent Crystal

  3. Metallic Crystal

  4. Ionic Crystal

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10

radius ratio

is the ratio of the cation radius to the anion radius

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11

symmetry

Property that makes an object (motif) coincide with another identical one through a movement called the symmetry operation

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12

4 Basic Symmetry Operations

Translation

Rotation

Reflection

Inversion

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13

6 Crystal Systems

Triclinic

Monoclinic

Orthorhombic

Tetragonal

Hexagonal

Isometric

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14

Crystal shape is determined by _______

Atomic arrangement

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15

THE BECKE LINE WILL ALWAYS MOVE ONTO THE MATERIAL WITH THE________ AS THE STAGE IS LOWERED

HIGHER REFRACTIVE INDEX

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16

When the RI of the mineral and the RI of the mounting material are equal, the Becke line…

splits into two lines, a blue line and an orange line.

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17

Anisotropic minerals extinct _____ times

4

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18

Isotropic minerals extinct ___ times

Isotropic minerals are always extinct. This is because they cannot reorient light

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19

What causes extinction?

The direction of vibration of light in the mineral is parallel to the direction of polarization

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20

Uniaxic crystal systems

Hexagonal

tetragonal

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21

biaxic crystal systems

rhombic, monoclinic, triclinic

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22

C axis refers to the…

Optic axis

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23

All uniaxial minerals show ____ extinction

parallel

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24
<p>What type of interference figure is this + label the elements</p>

What type of interference figure is this + label the elements

Centered Uniaxial Interference Figure

Isochrome: pattern of interference colours that are identical to those on the colour chart, increase in order from the melatope

Isogeres: Two arms of the cross

Melatope: The point where the optic axis emerges in the interference figure; it corresponds to 0 retardation

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25

The 3 Uniaxial Interference Figures

Optic Axis Figure-OA vertical

Off Centred Optic Axis Figure- OA inclined

Flash Figure- OA horizontal

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26

Which quadrant helps you determine the sign?

The NE quadrant

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27
<p>Label 1-5</p>

Label 1-5

  1. Optic Axis

  2. Z axis

  3. Optic Axis

  4. Y

  5. X

<ol><li><p>Optic Axis</p></li><li><p>Z axis</p></li><li><p>Optic Axis</p></li><li><p>Y</p></li><li><p>X</p></li></ol>
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<p>direction X = ?</p><p>direction Y =  ?</p><p>direction Z =  ?</p>

direction X = ?

direction Y = ?

direction Z = ?

  1. direction Z = nγ (highest)

  2. direction X = nα(lowest)

  3. direction Y = nβ (intermediate; ray of circular section)

<ol><li><p>direction Z =  <strong>nγ (highest)</strong></p></li><li><p>direction X = <strong>nα(lowest)</strong></p></li><li><p> direction Y =  <strong>nβ (intermediate; ray of circular section)</strong></p></li></ol>
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29

How is 2V measured?

Using the interference figures

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30

Bxa stands for…

Acute Bisectrix

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31

OA stands for…

Biaxial Optic Axis

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32

Bxo stands for…

Obtuse Bisectricx

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33

ON stands for…

Biaxial Optic Normal or Flash Figure

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34

The appearance of the interference figure is dependent on the ____ of the mineral grain and its corresponding______

orientation ; indicatrix

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35

Isotropic

speed of light is the same in any direction.

Vibration direction will always be perpendicular to the propagation direction

only ONE index of refraction

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36

Anisotropic

speed of light varies depending on the direction the light is traveling in

more than one index of refraction

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37

“Cross Nichols” refers to…

adding the analyzer (XPL)

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38

Pleochrism

minerals ability to change its color when its position is changed on the stage

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39

The slow ray in an anisotropic mineral will have a _____ than the fast ray

higher index of refraction

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40

The fast ray is the ______ and is _______ when going through the mineral

extraordinary ray ; not deviated

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41

The slow ray is the ______ and is _______ when going through the mineral

ordinary ray ; slowed down + deviated

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42

the sign of elongation is POSITIVE if the ____ beam vibrates ____ to the maximum length of the crystal

slow ; parallel

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43

the sign of elongation is NEGATIVE if the ____ beam vibrates ____ to the maximum length of the crystal

fast ; parallel

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