Super Mineralogy Midterm (copy)

Old deck plus some new stuff

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.

Crystal Chemistry

relationship of chemical composition to atomic structure

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

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"

The 5 chemical bonds

ionic

covalent

metallic

van der waals

hydrogen

Compounds ending in–ide…

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

Compounds ending in–ate…

means oxygen is present

Ending in –ite…

have less oxygen present than in –ate compounds

4 Crystal Bonding Types

1. Molecular Crystal

2. Covalent Crystal

3. Metallic Crystal

4. Ionic Crystal

radius ratio

is the ratio of the cation radius to the anion radius

symmetry

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

4 Basic Symmetry Operations

Translation

Rotation

Reflection

Inversion

6 Crystal Systems

Triclinic

Monoclinic

Orthorhombic

Tetragonal

Hexagonal

Isometric

Crystal shape is determined by _______

Atomic arrangement

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

HIGHER REFRACTIVE INDEX

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.

Anisotropic minerals extinct _____ times

4

Isotropic minerals extinct ___ times

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

What causes extinction?

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

Uniaxic crystal systems

Hexagonal

tetragonal

biaxic crystal systems

rhombic, monoclinic, triclinic

C axis refers to the…

Optic axis

All uniaxial minerals show ____ extinction

parallel

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

The 3 Uniaxial Interference Figures

Optic Axis Figure-OA vertical

Off Centred Optic Axis Figure- OA inclined

Flash Figure- OA horizontal

Which quadrant helps you determine the sign?

The NE quadrant

Label 1-5

1. Optic Axis

2. Z axis

3. Optic Axis

4. Y

5. X

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)

How is 2V measured?

Using the interference figures

Bxa stands for…

Acute Bisectrix

OA stands for…

Biaxial Optic Axis

Bxo stands for…

Obtuse Bisectricx

ON stands for…

Biaxial Optic Normal or Flash Figure

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

orientation ; indicatrix

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

Anisotropic

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

more than one index of refraction

“Cross Nichols” refers to…

adding the analyzer (XPL)

Pleochrism

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

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

higher index of refraction

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

extraordinary ray ; not deviated

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

ordinary ray ; slowed down + deviated

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

slow ; parallel

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

fast ; parallel

Isometric Crystal System Angles?

a=b=c α=β=γ=90

Tetragonal Crystal System Angles?

Orthohombic Crystal System Angles?

Monoclinic System Angles?

Hexagonal System Angles?

Rhombohedral System Angles?

Triclinic System Angles?

When the NE Quadrant is Blue, what is the sign?

Positive

When the NE Quadrant is Yellow, what is the sign?

Negative

How much symmetry does the isometric/cubic system have?

High

How much symmetry does the Hexagonal system have?

Medium

How much symmetry does the Tetragonal system have?

Medium

How much symmetry does the Trigonal system have?

Medium

How much symmetry does the Rhombic system have?

Low

How much symmetry does the Monoclinic system have?

Low

How much symmetry does the Triclinic system have?

How much symmetry does the isometric system have?

Name the four basic symmetry operations

Translation, Rotation, Reflection, Inversion

Name the three composite symmetry operations

Rotation+Inversion (Rotoinversion), Rotation+Translation (Screw Axis), Reflection+Translation (Slip Plane)

Define Motif

fundamental part of a symmetrical design, which when repeated, creates the entire pattern

Define Operation

some act that reproduces the motif to create a pattern

Define Symmetry Element

an operation located at a particular point in space

Define Symmetry Plane

"Imaginary plane that divides the body into two identical parts"

Define Axis of symmetry

Imaginary line that crosses a body, around which, when the body is rotated, it presents the same appearance multiple times in a complete rotation

Define Center of Symmetry

“A part of a perfect body is diametrically opposite to another similar face located on the opposite side of the body ”

When a mineral shows nearly black interference colors, what type of indicatrix section is in the plane of the mineral?

CIRCULAR SECTION

The interference colors shown by a mineral under cross-polars depends on the thickness of the mineral and what else?

BIREFRINGENCE OR DIFFERENCE IN 2 INDICES OF REFRACTION IN SECTION

In a positive uniaxial indicatrix with light vibrating in the omega direction would it be the fast or slow ray?

FAST RAY (LOWEST N)

What is an indicatrix?

The indicatrix is a 3-dimensional visualization of the indices of refraction of a mineral.

What’s another name for the C axis in uniaxial indicatrix?

 OPTIC AXIS

Define Uniaxial Positive

Uniaxial birefringence is classified as positive when the extraordinary index of refraction n_e is greater than the ordinary index n_o

Define Uniaxial Negative

For uniaxial minerals these two extreme values of refractive index are defined as ω (or N_o) and ε (or N_e). Values between ω and e are referred to as ε'. Uniaxial minerals can be further divided into two classes. If ω > ε the mineral is said have a negative optic sign or is uniaxial negative.

A mineral in which the index of refraction (n) is the same in all vibration directions is said to portray what kind of optical properties? 

ISOTROPY/ISOTROPIC 

Define Relief

The degree to which the mineral grain stands out from the surrounding material in thin section.

How much relief is shown?

Strong relief

How much relief is shown?

Moderate to strong

How much relief is shown?

Low

Define positive relief

Relief is said to be positive when the refractive index of the mineral is higher than the refractive index of the medium,

Define negative relief

Relief is said to be negative when the refractive index of the mineral is lower than the refractive index of the medium

When the angle of incidence exceeds the critical angle of refraction, what will happen?

THE LIGHT WILL REFLECT or Total Internal Reflection

Index of refraction is a measure of?

HOW MUCH LIGHT IS SLOWED DOWN

What property of light does amplitude control?

INTENSITY or BRIGHTNESS

What type of energy is light?

 ELECTROMAGNETIC RADIATION

What property light does wavelength control?

Color

What property of light does the index of refraction control?

Speed

define Birefringence

 when light is refracted and split into 2 different rays (slow and fast) and it depends on the difference in the index of refraction

Define Diffraction

the random scattering of light waves

Define Dispersion

Dispersion of light is the process of separating white light into its individual colors

Define Pleochroism

Pleochroism is an optical phenomenon in which a substance has different colors when observed at different angles, especially with polarized light.

Define Refraction

the bending of light, or changing the path angle of light

What is Snell’s Law?

Snell's law is a formula used to describe the relationship between the angles of incidence and refraction

What is the atomic number defined by?

The number of protons in an atom

Define Iridescence

Iridescence is a optical phenomenon that causes a mineral to display a play of colors. It is caused by interference of light waves reflected from thin layers within the mineral.

T/F, Dispersion forces are only experienced in molecules with permanent dipoles?

True , dispersion forces (also known as London dispersion forces) are experienced by all molecules, regardless of whether they have permanent dipoles or not, as they arise from temporary fluctuations in electron distribution within the molecule

T/F, Ionic, covalent and metallic bonds are examples of intermolecular bonds.

False. They are interatomic bonds

T/F, Ionic radii increase with increasing coordination number.

True. An atom's coordination number is the number of other atoms that it bonds to

T/F, Minerals whose bonds are at least partially metallic are transparent in thin sections

False. metallic bonds are not transparent even in a thin section because the free electrons within the metal readily absorb visible light, making metals inherently opaque

T/F, The most common type of phase diagram for binary systems is a temperature-composition diagram

True