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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
Breakage (3)
Cleavage Parting Fracture
26
Cleavage (6)
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
Parting
Only shown under pressure Breakage occurs parallel to: - twinning - exsolution planes - crystallographic planes
28
Fracture
Types: - Irregular (uneven breakage) - Conchoidal (seashell-like breakage) \*No preferred direction of breakage \*Volcanic glass \*Isometric minerals
29
Hardness
\*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
Tenacity (and its 6 types)
Mineral’s resistance to breakage Types of tenacity: - brittle - malleable - sectile - ductile - flexible - elastic
31
Brittle tenacity
Breaks/powders
32
Malleable tenacity
Hammered into thin sheets
33
Sectile tenacity
Cut into thin shavings
34
Ductile tenacity
Drawn into wire
35
Flexible tenacity
When bent, stays bent/permanently bent
36
Elastic tenacity
When bent, returns to original shape
37
Specific gravity
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
Magnetism (3 types)
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
Radioactivity
Radioactivity is due to radio isotopes in structure of minerals (alpha, beta, and gamma decays) Elements: uranium (U), thorium (Th), potassium (K)
40
Solubility in acid
Carbonate minerals w/HCl contact
41
Element abundance
Most to least: O Si Al Fe Ca Na K Mg
42
Most common mineral in crust?
Plagioclase feldspar
43
With inoic radius increasing, hardness & melting point...
Increasing ionic radius: Increasing melting point Decreasing hardness
44
Electrostatic valence bond (evb strength)
S = evb strength = (cation strength)/CN (coordination #; ie # of anions) evb strength is simply ratio of cation charge to number of anions
45
Coordination number (CN)
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
Anisodesmic
Anisodesmic = evb \> 1/2 anion charge
47
Mesodesmic
Mesodesmic = evb = 1/2 anion charge
48
Polymorphism types (3)
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
Solid solution
Element substitution; if charge & ionic radii are similar e.g. olivine (Mg2SiO4) & fayalite (Fe2SiO4)
50
Coupled/paired solid solution / coupled substitution
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
Lattice
Lattice = smallest unit to create reproducable symmetry Five possible plane lattices (the crystal systems)
52
Atomic proportion
atomic proportion = weight % / atomic weight
53
Bowen's reaction series
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
Ultramafic / mafic / intermediate / felsic
Ultramafic: peridotite/komatite Mafic: gabbro/basalt Intermediate: diorite/andesite Felsic: granite/rhyolite
55
Electroforces & bond strength affect (5 properties)
Hardness Cleavage Conductivity Melting point Optical properties
56
Covalent bonds
High melting point High hardness High strength Lmited thermal expansion
57
Ionic bonds
Moderate hardness Moderate specific gravity Soluble in polar solvents High melting point Nondirectional bonds / high symmetry
58
Metallic bonds
Conductive Soft Ductile Malleable Allows electron discharge
59
Van der Waals bonds
Polar attraction Weak Low hardness Low melting point
60
Isodesmic
Uniform bond length All ionic bonds have same strength Isometric, tetragonal, haxagonal
61
Pauling's rules
Adjacent polyhedrals will share single/pairs of anions so CATIONS are farthest apart Different cations with HIGH charge tend NOT to share anions
62
Isomorphism vs polymorphism vs solid solution
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
XPL vs. PPL
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
[stopped at p 22 of notes, 9/27/17]

*Mineralogy (5 decks)

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