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*Mineralogy > Mineralogy Intro > Flashcards

Mineralogy Intro Flashcards

1
Q

Minerals (definition)

A
  • One substance
  • Inorganic
  • Crystalline structure
  • Naturally occurring
  • Solid
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2
Q

Mineral formation

A
  • precipitation
  • metamorphism (scavenging)
  • crystallization via melt (igneous)
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3
Q

Metamict minerals

A

Destruction of internal order via radioactive decay

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4
Q

Mineraloids

A

Minerals lacking internal order

Ex: amber, no regular repeating crystalline structure

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5
Q

Mineral grouping/classification

A

Systematic study, identification, and grouping of minerals into a logical classification scheme.

  • Dominant anion/anionic complex
  • Arrangement of silica tetrahedra in silicate minerals (neso-, ino-, cyclo-, phyllo-, tecto-)
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6
Q

Descriptive mineralogy

A

Observation, measurement, physical properties; descriptions which identify/describe minerals (color, specific gravity, crystal form, hardness)

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7
Q

Crystallography

A

Determination of crystal structures of minerals

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8
Q

Crystal chemistry

A

Examines chemical composition & variability of individual mineral samples

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9
Q

Solid substitutions

A

Governed by the principles of chemical bonding Ex: Mg Fe; Al Si

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10
Q

Paragenesis

A

Geologic occurrence

Characteristic occurrence of minerals in geologic setting

Clues to identify minerals in equilibrium in various geologic environments & rock types

Mineral associations (e.g. peridotite: mangle, Mg-rich pyroxene & olivine, no quartz/chromite or magnetite)

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11
Q

Rocks

A

Solids composed of one or more minerals, glass, or solid organic matter

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12
Q

Crystals

A

Physical property of minerals

External form

Internal symmetry of a mineral is exhibited in its external form

Bounded by smooth planar surfaces that assume geometric forms with specific angular relationships

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13
Q

Crystal face (3 types)

A

Euhedral

Subhedral

Anhedral

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14
Q

Euhedral

A

All crystal faces are developed

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15
Q

Subhedral

A

Some crystal faces are developed

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16
Q

Anhedral

A

No crystal faces are developed

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17
Q

Twinned crystal/twinning

A

The symmetric inter growth of two or more crystals o the SAME substance

Types:
Contact twins
Penetration twins
Merohedral twins
Multiple twins (polysynthetic twins, cyclic twins)

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18
Q

Contact twinning

A

Simple type of twinning

Definite composition plane is present

Share a single composition surface, often appearing as mirror images across the boundary

Ex: plagioclase, quartz, gypsum, spinel; often exhibit contact twinning

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19
Q

Penetration twinning

A

Type of simple twinning

Occur if 2+ parts of a crystal appear to interpenetrate each other with the surface between the parts being undefinable and irregular

Appearance of passing through each other in a symmetrical manner

Ex: Orthoclase, staurolite, pyrite, fluorite often show penetration twinning

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20
Q

Merohedral twinning

A

Type of contact twinning

Lattices of the contact twins superimpose in 3 dimensions, such as by relative rotation of one twin from another

Ex: metazeunerite

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21
Q

Polysynthetic twinning

A

Type of multiple twinning

Multiple twins are aligned in parallel 3+ individuals are repeated alternately on the same twinned plane

Closely spaced polysynthetic twinning: often observed as STRIATIONS or fine parallel lines on crystal face (e.g. calcite, pyrite)

NOTE: called lamellar (e.g. plagioclase feldspar)

Ex: albite, calcite, pyrite; often exhibit polysynthetic twinning

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22
Q

Cyclic twinning

A

Type of multiple twinning

Multiple twins are not parallel

Ex: Rutile, aragonite, cerussite, chrysoberyl; often exhibit cyclic twinning, typically in RADIATING pattern

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23
Q

Simple twinning

A

Simple twins made of only 2 parts

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24
Q

Multiple twinning

A

Multiple twins have more than 2 orientations

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25
Q

Breakage (3)

A

Cleavage

Parting

Fracture

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26
Q

Cleavage (6)

A
  1. Cubic (e.g. halite)
  2. Octahedral (e.g. fluorite)
  3. Dodecahedral (e.g. sphalerite)
  4. Rhombohedral (e.g. calcite)
  5. Prismatic (e.g. amphibole)
  6. Pinacoidal/basal (e.g. biotite)
27
Q

Parting

A

Only shown under pressure

Breakage occurs parallel to:

  • twinning
  • exsolution planes
  • crystallographic planes
28
Q

Fracture

A

Types:
- Irregular (uneven breakage)
- Conchoidal (seashell-like breakage)
*No preferred direction of breakage
*Volcanic glass
*Isometric minerals

29
Q

Hardness

A

*Some minerals display directional differences in hardness

  1. Talc
  2. Gypsum [2.2 Fingernail]
  3. Calcite [3.2 Copper penny]
  4. Fluorite
  5. Apatite [5.1 Pocket knife] [5.5 Glass plate]
  6. Orthoclase [6.5 Steel file]
  7. Quartz (& ceramic plate)
  8. Topaz
  9. Corundum
  10. Diamond
30
Q

Tenacity (and its 6 types)

A

Mineral’s resistance to breakage

Types of tenacity:

  • brittle
  • malleable
  • sectile
  • ductile
  • flexible
  • elastic
31
Q

Brittle tenacity

A

Breaks/powders

32
Q

Malleable tenacity

A

Hammered into thin sheets

33
Q

Sectile tenacity

A

Cut into thin shavings

34
Q

Ductile tenacity

A

Drawn into wire

35
Q

Flexible tenacity

A

When bent, stays bent/permanently bent

36
Q

Elastic tenacity

A

When bent, returns to original shape

37
Q

Specific gravity

A

Density ratio (substance to water density)

*Thus, unitless

Metal/native elements: 5-20 sg

Ferromagnesian silicates 2.8-4.5 sg

Light-colored/felsic 1.5-2.7 sg

38
Q

Magnetism (3 types)

A

Ferromagnetic: attracted to hand magnet (e.g. magnetite, pyrrhotite)

Paramagnetic: attracted to strong electromagnet (e.g. garnet, pyroxene)

Diamagnetic: neither attracted nor repelled by magnetic field (e.g. quartz, zircon)

39
Q

Radioactivity

A

Radioactivity is due to radio isotopes in structure of minerals (alpha, beta, and gamma decays)

Elements: uranium (U), thorium (Th), potassium (K)

40
Q

Solubility in acid

A

Carbonate minerals w/HCl contact

41
Q

Element abundance

A

Most to least:

O
Si
Al
Fe
Ca
Na
K
Mg

42
Q

Most common mineral in crust?

A

Plagioclase feldspar

43
Q

With inoic radius increasing, hardness & melting point…

A

Increasing ionic radius:
Increasing melting point
Decreasing hardness

44
Q

Electrostatic valence bond (evb strength)

A

S = evb strength = (cation strength)/CN (coordination #; ie # of anions)

evb strength is simply ratio of cation charge to number of anions

45
Q

Coordination number (CN)

A

of anions a cation is in contact with

Depends on relative size of cation to anion

CN #’s and geometry:
12 = dodecahdral (e.g. K+, Na+, Ca2+)
8 = cubic (e.g. Fe2+, Ca2+, Na+, Mg+)
6 = octahedral
4 = tetrahedral (e.g. SiO4)
3 = triangular (e.g. CO3)

46
Q

Anisodesmic

A

Anisodesmic = evb > 1/2 anion charge

47
Q

Mesodesmic

A

Mesodesmic = evb = 1/2 anion charge

48
Q

Polymorphism types (3)

A

Reconstructive (e.g. graphite & diamond)

Displacive
e.g. quartz:
low PT = alpha-quartz
high PT = beta-quartz
ligher PT = coesite
highest PT = stishovite
high T/low P = crystobalite
higher T/low P = tridymite

Order-disorder (e.g. orthoclase & microcline = K-feldspars)
high T = 25% Al, 75% Si
low T = 100% Al, 100% Si

49
Q

Solid solution

A

Element substitution; if charge & ionic radii are similar

e.g. olivine (Mg2SiO4) & fayalite (Fe2SiO4)

50
Q

Coupled/paired solid solution / coupled substitution

A

Two elements simultaneously substitute into a crystal

Maintains overall electrical neutrality and charge constant

Ionic SIZE more important than ionic CHARGE

e.g. plagiclase feldspar Na+/Si4+ (albite) <–> Ca2+/Al3+ (anorthite)

51
Q

Lattice

A

Lattice = smallest unit to create reproducable symmetry

Five possible plane lattices (the crystal systems)

52
Q

Atomic proportion

A

atomic proportion = weight % / atomic weight

53
Q

Bowen’s reaction series

A

High temp to low temp:
Olivine
Pyroxene
Amphibole
Biotite mica
K-feldspar
Muscovite mica
Quartz

High temp to low temp:
Ca-rich feldspar
Na-rich feldspar

54
Q

Ultramafic / mafic / intermediate / felsic

A

Ultramafic:
peridotite/komatite

Mafic:
gabbro/basalt

Intermediate:
diorite/andesite

Felsic:
granite/rhyolite

55
Q

Electroforces & bond strength affect (5 properties)

A

Hardness
Cleavage
Conductivity
Melting point
Optical properties

56
Q

Covalent bonds

A

High melting point
High hardness
High strength
Lmited thermal expansion

57
Q

Ionic bonds

A

Moderate hardness
Moderate specific gravity
Soluble in polar solvents
High melting point
Nondirectional bonds / high symmetry

58
Q

Metallic bonds

A

Conductive
Soft
Ductile
Malleable
Allows electron discharge

59
Q

Van der Waals bonds

A

Polar attraction
Weak
Low hardness
Low melting point

60
Q

Isodesmic

A

Uniform bond length

All ionic bonds have same strength

Isometric, tetragonal, haxagonal

61
Q

Pauling’s rules

A

Adjacent polyhedrals will share single/pairs of anions so CATIONS are farthest apart

Different cations with HIGH charge tend NOT to share anions

62
Q

Isomorphism vs polymorphism vs solid solution

A

Isomorphism:
DIFFERENT chemical composition
SAME structure

Polymorphism:
SAME chemical composition
DIFFERENT structure

Solid solution:
RANGE of compositions within fixed limits
- single substitition
- coubled substitition

63
Q

XPL vs. PPL

A

XPL = cross polarized light (analyzer)

  • if inserted after the light-material interaction, the original PPL is eliminated and only the light with perpendicular orientation is transmitted
  • result is the light which underwent the polarization change

PPL = plane polarized light

  • incoming light has a plane polarization (due to a polarizer before the material)
  • after light interacts with the material the polarization of certain fraction of light might change (e.g., scattering, polarization rotation due to birefringence)
  • see the original PPL + the rotated light
64
Q

[stopped at p 22 of notes, 9/27/17]

*Mineralogy (5 decks)

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