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*Mineralogy > Mineral Groups > Flashcards

Mineral Groups Flashcards

1
Q

Oxides

A

X2O / XO / X2O3 / XY2O4 / XO2

  • strong ionic bonds
  • dense
  • hard
  • high melting point
  • accessory minerals
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2
Q

Oxide ores

A

Fe2O3 (hematite) vs Fe3O4 (magnetite)
*Fe3O4 has Fe2+ and Fe23+

FeCr2O4 (chromium) vs UO2 (uranium)

MnO2 (pyrolusite) vs SnO2 (cassiterite) vs FeTiO3 (ilmenite)
*(manganese vs tin vs titanium)

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3
Q

Hydroxides

A

*OH- or H2O —> weaker bonds!

  • soft
  • low density
  • formed by alteration / weathering
  • form some RESIDUAL ores of Al & Fe
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4
Q

Hydroxide ores

A

Al(OH)3 (bauxite) vs ZnO (zincite; hexagonal)

MgAl2O4 (spinel, isometric; XY2O4) vs Fe3O4
(magnetite, *a* spinel, isometric)

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5
Q

Sulfide

A

XmZn

  • all opaque
  • majority of metallic ores
  • brightly colored streaks (characteristic of sulfides)

Polymorphism: pyrite & marcasite (FeS2)

NOTE: Arsenopyrite (FeAsS) often contains gold

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6
Q

Copper sulfides

A

Cu2S (chalcocite)

CuFeS2 (chalcopyrite)

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7
Q

Stibnite (sulfide)

A

Sb2S3
(Sb = antimony, hence “stibnite”)
*primary ore of antimony

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8
Q

Ore zones (3)

A

Oxidized zone / oxidized enrichment
- oxidized, above water table

Supergene enrichment / enriched zone

  • secondary
  • below water table
  • reduced!

Hypogene / primary zone
- primary ore

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9
Q

Carbonates

A
  • strongly bonded ionic complexes
  • anoisodesmic bonding (bond strengths: anionic complex > cation-anion)
  • (-2/3) = residual oxygen = total cation charge - total anion charge

*O cannot be shared

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10
Q

Carbonate groups

A

Calcite (hexagonal); polymorph = aragonite
CaCO3

Aragonite (orthorhombic); polymorph = calcite
CaCO3

Dolomite (hexagonal)
CaMg(CO3)2

Copper carbonates (monoclinic)

  • malachite (Cu2CO3(OH)2)
  • azurite (Cu3(CO3)2(OH)2)
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11
Q

Phosphates

A
  • strongly bonded ionic complexes
  • anoisodesmic bonding (bond strengths: anionic complex > cation-anion)
  • Ca5(PO4)3 (apatite; hexagonal)
    *found in titaniferous magnetite bodies
    *(PO4)3 replacements:
    —> OH: hydroxyapatite
    —> F: fluorapatite
    —> Cl: chlorapatite
  • (Ce, La, Y, Th)(PO4) (monazite; monoclinic)
    *found in granites
    *up to 20% ThO2 —> radioactive
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12
Q

Halides

A

Based upon anionic element:
F-, Cl-, Br-, etc.

  • forms via precipitation, mostly in arid region that used to contain saline water (since evaporated)

*gypsum contains H2O vs anhydrite (no H2O)

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13
Q

Orthosilicates

A

[SiO4]4-
Si:O = 1:4

  • olivine (Mg, Fe)2SiO4
    — Mg —> foresterite
    — Fe —> fayalite
  • aluminosilicates Al2SiO5 (EXCEPTION TO 1:4!)
    — kyanite (high P)
    — sillimanite (high P & T)
    — andalusite (low-mid P & T)
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14
Q

Garnet

A

X3Y2(SiO4)3
X3: Ca2+, Mg2+, Fe2+
Y2: Al3+, Fe3+, Cr3+

Ca3Al2(SiO4)3 = grossular
vs
Ca3Fe2(SiO4)3 = andrudite

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15
Q

Framework silicates

A

SiO2
Si:O = 1:2

Quartz: SiO2
Crystalline: citrine, alpha-quartz
Microcrystalline: chert
Amorphous: opal
Polymorphous: tridymite, cristobalite, alpha-quartz, beta-quartz, coesite, stishovite

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16
Q

Feldspars (of framework silicates!)

A

*Also part of framework silicates*

Si:O = 4:8
Si4+ <–> Al3+

K-feldspars:
KAl(Si3O8)

Plag feldspars:
NaAl(Si3O8) = albite
CaAl2(Si2O8) = anorthite

17
Q

Plagioclase feldspars

A

NaAl(Si3O8) = albite

CaAl2(Si2O8) =
anorthite - triclinic/monoclinic - albite twinning - parallel twinning

18
Q

Potassium feldspars

A

K(AlSi3O8)

\*microcline = triclinic, stable, very low T
\*orthoclase = monoclinic, stable, low T
\*sanidine = monoclinic, high T (due to rapid quenching, more sodic than lower T forms)
19
Q

Inosilicates

A

AKA chain silicates

SiO4 linked by [at least] 2 oxygen shared

Two types of chain/inosilicates:
Single Chain
Double Chain

20
Q

Single Chain Inosilicates

A

[Si2O6]4-
Si:O = 1:3 = 2:6
SiO4 linked by 2 shared oxygen

*Pyroxene group: equant (88/92 degree cleavage)
— octagonal cross section
— anhydrous
— higher specific gravity
— crystallize at higher temperature

CaMgSi<sub>2</sub>O<sub>6</sub> = diposide = a clinopyroxene
MgSiO<sub>3</sub> = enstatite = clinopyroxene or orthopyroxene?
FeSiO<sub>3</sub> = ferrosillite = orthopyroxene
CaFeSi<sub>2</sub>O<sub>6</sub> = hedenbergite (clinopyroxene?)
21
Q

Double Chain Inosilicates

A

[Si4O11]6-
Si:O = 4:11
SiO4 linked by 2 OR 3 shared oxygen

*Amphibole group = elongate (56/124 degree cleavage)
— diamond cross-section
— amphibole BREAKS DOWN into pyroxene
— contain OH-!

Ca<sub>2</sub>Mg<sub>5</sub>Si<sub>8</sub>O<sub>22</sub>(OH)<sub>2</sub> = tremolite
Mg<sub>7</sub>Si<sub>8</sub>O<sub>22</sub>(OH)<sub>2</sub> = anthophyllite
Fe<sub>7</sub>Si<sub>8</sub>O<sub>22</sub>(OH)<sub>2</sub> = grunerite
Ca<sub>2</sub>Fe<sub>5</sub>Si<sub>8</sub>O<sub>22</sub>(OH)<sub>2</sub> = ferroactinolite
22
Q

Pyroxenoid Group

A 
CaSiO<sub>3</sub> = wollastonite (twisted chain b/c of Ca size)
FeSiO<sub>3</sub> = orthopyroxene (ferrosillite?)
MnSiO<sub>3</sub> = rhodonite
23
Q

Cyclosilicates

A

[Si6O18]12-
Si:O = 6:18
SiO4 tetra-linked rings & 2 shared oxygens

Al2Be3(Si6O18) = beryl

  • rings held by Al & Be
  • in granitic & pegmitic
  • aquamarine, emerald

*tourmaline

  • circular habit b/c of ring unit cell structure
  • in cements & sandstones
  • gemstone = diagnostic
  • cross-section = striations

(Mg, Fe)2Al3(AlSi5O18)*nH2O = cordierite
*Al3 = octa
*PT conditions indicator
- partial melt/decompression mineral
- paratectic phases
- thin section: biaxial & cleavage (vs quartz w/o cleavage & not biaxial)

24
Q

Disilicates/sorosilicates

A

(SiO4)2
Si:O = 2:7
*share ONE oxygen

Ca2Al2(Al, Fe3+)OOH[Si2O7][SiO4] = epidote
*Al, Fe3+ —> complex solution series (epidote - clinozoisite)
- biaxial
- cleavage
- granular masses
- retrogression
- common association

(Ce,Ca,Y,La)2(Al,Fe3+)3(SiO4)3(OH) = allanite (aka orthite)

  • monoclinic
  • complex formula (solid solution Al3+ = Fe3+)
  • rare earth elements (e.g. O)
  • can take predicting Pb!
  • radioactive —> radiation damage
  • geochronology applications
  • igneous & ore deposits

*Mineralogy (5 decks)

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