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Classification of Minerals by
Anionic Species
(Anions are negative ions)
How would you organize
some 5000 species of
minerals?
Color?
Hardness?
Occurrence environment?
Chemistry?
Positive ions? (cations)
Negative ions? (anions)
Chemical Classification of
Minerals
Learning goals:
How are minerals classified by
chemistry?
Why is this useful?
Chemical Classification of
Minerals
Learning goals:
How are minerals classified by
chemistry?
By anionic species.
Chemical Classification of
Minerals
Learning goals:
Why is this useful?
Because there is very little substitution
at anion sites
Anions are Negative Ions
• May be single species
– O2-, F-, Cl-, S2-
• May be anionic group (polyanion):
– CO3
2-, SO4
2-, PO43-
• Silicates are classified by
polymerization of the silicate
polyanion.
– Isolated tetrahedra
– Chains
– Sheets
– Frameworks
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Chemical Classification
• Native Elements (no anions)
• Halides (F, Cl, Br, I) (monovalent halogen)
• Sulfides & arsenides (S, Ar)
• Oxides (O)
• Hydroxides (OH)
• Sulfates & phosphates (SO4, PO4)
• Carbonates (CO3)
• Silicates:
– orthosilicates, sorosilicates, chain
silicates, layer silicates, framework
silicates
Periodic Table
Native Elements
(no anions)
• Pure elements that occur as
minerals
– Graphite, diamond (C)
– Sulfur (S)
– Gold (Au), Silver (Ag), Copper (Cu)
– Iron (kamacite)
– Nickel (taenite)
– As, Te, Se, Pt, Ir, Os, Pd, Ru, Rh
Native Elements
Halides:
anion is F, Cl, Br, or I
• Halogens are the elements F, Cl, Br, I
• Halogens are monovalent anions
• Halite (NaCl), Sylvite (KCl)
• Fluorite (CaF2)
• Cryolite Na3AlF6
Periodic Table
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Sulfides: anion is S
• Sulfur is ��anion��, but is more covalent than
ionic (stoichiometry is less strict)
– Pyrite, marcasite (FeS2), chalcopyrite (CuFeS2)
– Sphalerite ZnS, galena (PbS)
– Chalcocite Cu2S, covellite (CuS), bornite
(Cu5FeS4)
– Realgar (AsS), orpiment (As2S3), cinnabar (HgS)
– Stibnite (Sb2S3), molybdenite (MoS2)
• Sulfide minerals typically have
metallic luster, covalent bonding,
and occur in hydrothermal veins.
• Only rarely do they occur at the
surface.
Elements in Sulfide Minerals
Oxides (Single):
anion is O (no polyanion)
• Hemi-oxide Cuprite (Cu2O), Ice (H2O)
• Monoxides
– Periclase group MgO, FeO, CaO, MnO
– Zincite ZnO, Bromellite BeO
• Sesquioxides
– Corundum Al2O3, Hematite Fe2O3
• Dioxides
– Rutile TiO2, Cassiterite SnO2, Pyrolusite
MnO2
Oxides (Complex):
anion is O
• Ilmenite FeTiO3
• Spinel Group
– Spinel MgAl2O4, Magnetite Fe3O4
• Perovskite CaTiO3
Hydroxides:
anion is (OH)-
Hydroxides:
anion is OH
• Brucite Mg(OH)2
• Gibbsite Al(OH)3
• Diaspore AlOOH (Bauxite)
• Goethite FeOOH
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Carbonates
anion is (CO3)2-
Carbonates
Anion is (CO3)2-
• Calcite CaCO3, Rhodochrosite MnCO3
• Siderite FeCO3, Smithsonite ZnCO3
• Dolomite CaMg(CO3)2
• Aragonite CaCO3, Witherite BaCO3
• Strontianite SrCO3,Cerussite PbCO3
• Malachite and Azurite
Sulfates and Phosphates:
(SO4)2- and (PO4)3-
Sulfates and Phosphates:
(SO4)2- and (PO4)3-
• Sulfur is 6+
• Phosphorus is 5+
• Contrast sulfide (S2-) and sulfate (S6+).
• Phosphide (P3-) and phosphate (P5+).
• Sulfates and phosphates are
oxidized!
Sulfates and Phosphates:
(SO4)2- and (PO4)3-
• Barite (BaSO4), Celestine (SrSO4)
• Gypsum CaSO4.2H2O
• Anhydrite CaSO4
• Apatite Ca5(PO4)3OH
• Turquoise CuAl6(PO4)4(OH)8·4H2O
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Silicates are classified
by polymerization
• Orthosilicates (SiO4)4-: Isolated
tetrahedral O / Si = 4.0
• Sorosilicates (Si2O7)6- ��Bow-Ties�� 3.75
• Chain silicates
– (SiO3)2- : Infinite single chains 3.0
– (Si4O11)6- : Double Chains 2.75
• Sheet Silicates (Si4O10)4- sheets 2.5
• Framework Silicates (SiO2)
framework 2.0
Orthosilicates: (SiO4)4-
Si/O: <~1/4
O / Si = 4
• Isolated SiO4 tetrahedra
• Olivine Group (Mg2SiO4)
• Garnet Group (Mg3Al2Si3O12)
• Aluminosilicate Group (Al2SiO5)
• Staurolite, Zircon, Titanite
Orthosilicates:
Isolated Tetrahedra
Sorosilicates and
Cyclosilicates
Si/O: 1/3 ~ ¼
O / SI = 3 – 3.5
• Epidote Group Ca2Al2FeSi3O12(OH)
• Tourmaline NaMg3Al5B3Si6O27(OH)4
• Beryl Be3Al2Si6O18
• Cordierite (Mg,Fe)2Al(AlSi5)O18 •nH2O
Chain Silicates
• Single Chains Si/O ~ 1/3
– O / Si = 3.0
– Orthopyroxenes Mg2Si2O6
– Clinopyroxenes CaMgSi2O6
– Pyroxenoids Ca3Si3O9
• Double Chains Si/O 4:11
– O / (Si+Al) = 2.75
– Amphiboles (Mg,Fe)7Si8O22(OH)2
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Chain Silicates
Layer Silicates
O / Si = 2.5
• Antigorite
Mg3Si2O5(OH)4
• Talc
Mg3Si4O10(OH)2
• Kaolinite
Al2Si2O5(OH)4
• Pyrophyllite
Al2Si4O10(OH)2
• Biotite
K(Mg,Fe)3AlSi3O10(OH)2
• Muscovite
KAl2(AlSi3)O10(OH)2
• Chlorite
(Mg,Fe)6AlSi3O10(OH)2
Layer Silicates
Framework Silicates
(Tektosilicates)
O / Si = 2
• Silica Group SiO2
• Alkali Feldspar (Na,K)AlSi3O8
• Plagioclase NaAlSi3O8-CaAl2Si2O8
• Feldspathoids (Leucite, Kalsilite, etc)
• Zeolites (open hydrous frameworks)
O / (Al + Si)IV
• Framework Silicates = 2.0
• Sheet Silicates
= 2.5
• Amphiboles
=
2.75
• Chain Silicate
=
3.0
• Sorosilicates
=
3.5
• Orthosilicates
=
4
Tektosilicates
(Framework Silicates)
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Chemical Classification
• Native Elements (no anions)
• Halides (F, Cl, Br, I)
• Sulfides & arsenides (S, Ar)
• Oxides (O)
• Hydroxides (OH)
• Sulfates & phosphates (SO4, PO4)
• Carbonates (CO3)
• Silicates:
– orthosilicates, sorosilicates, chain
silicates, layer silicates, framework
silicates
Chemical Classification of
Minerals
Learning goals:
How (why) are minerals classified by
chemistry?
Why is this useful?
Why not by cations?
How else might you classify minerals?
Hardness? Color?
Occurrence? Abundance?
Give Chemical Classification
of
Kamacite (Fe)
A. Native Element
B. Sulfide
C. Metal
D. Extra-terrestrial
E. Oxide
Give Chemical Classification
of
Kamacite (Fe)
A. Native Element
B. Sulfide
C. Metal
D. Extra-terrestrial
E. Oxide
Give Classification of
Troilite (FeS)
A. Native Element
B. Sulfide
C. Sulfate
D. Phosphate
E. Oxide
Give Classification of
Troilite (FeS)
A. Native Element
B. Sulfide
C. Sulfate
D. Phosphate
E. Oxide
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Give Classification of
Pyrite (FeS2)
A. Native Element
B. Sulfide
C. Sulfate
D. Phosphate
E. Oxide
Give Classification of
Pyrite (FeS2)
A. Native Element
B. Sulfide
C. Sulfate
D. Phosphate
E. Oxide
Give Chemical Classification
of
Barite (BaSO4)
A. Native Element
B. Sulfide
C. Sulfate
D. Phosphate
E. Oxide
Give Chemical Classification
of
Barite (BaSO4)
A. Native Element
B. Sulfide
C. Sulfate
D. Phosphate
E. Oxide
Give Chemical Classification
of
Fluorite (CaF2)
A. Native Element
B. Sulfide
C. Sulfate
D. Phosphate
E. Halide
Give Chemical Classification
of
Fluorite (CaF2)
A. Native Element
B. Sulfide
C. Sulfate
D. Phosphate
E. Halide
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Give Chemical Classification
of
Apatite (Ca3(PO4)3F)
A. Native Element
B. Sulfide
C. Sulfate
D. Phosphate
E. Halide
Give Chemical Classification
of
Apatite (Ca3(PO4)3F)
A. Native Element
B. Sulfide
C. Sulfate
D. Phosphate
E. Halide
Homework 1
Due Tuesday
Chemical Classification of
Minerals
Learning goals:
How (why) are minerals classified by
chemistry?
Why is this useful?
Why not by cations?
How else might you classify minerals?
Hardness? Color?
Occurrence? Abundance?
Geochemical
Classification of the
Elements
Lithophile - Ionic
Siderophile - Metallic
Chalcophile - Covalent
Atmophile - Van der Waals
Geochemical Classification
of the Elements
• How do the elements partition
between coexisting fluid (melt)
phases?
– Gas Phase : Atmophile : Van der Waals
– Oxide phase: Lithophile : Ionic
– Sulfide Phase: Chalcophile: Covalent
– Metal Phase: Siderophile: Metallic
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Geochemical Classification
of the Elements
• How do the elements partition
between coexisting fluid (melt)
phases?
– Gas Phase : Atmophile : Van der Waals
– Oxide phase: Lithophile : Ionic
– Sulfide Phase: Chalcophile: Covalent
– Metal Phase: Siderophile: Metallic
Geochemical Classification
of the Elements
• How do the elements partition
between coexisting fluid (melt)
phases?
– Gas Phase : Atmophile : Van der Waals
– Oxide phase: Lithophile : Ionic
– Sulfide Phase: Chalcophile: Covalent
– Metal Phase: Siderophile: Metallic
Geochemical Classification
of the Elements
• How do the elements partition
between coexisting fluid (melt)
phases?
– Gas Phase : Atmophile : Van der Waals
– Oxide phase: Lithophile : Ionic
– Sulfide Phase: Chalcophile: Covalent
– Metal Phase: Siderophile: Metallic
Elements partition among immiscible fluids by bond type (!!)
Geochemical
Classification of the
Elements
Atmophile - Van der Waals
Lithophile - Ionic
Chalcophile - Covalent
Siderophile - Metallic
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Geochemical
Classification of the
Elements
Atmophile - Van der Waals
Lithophile - Ionic
Chalcophile - Covalent
Siderophile - Metallic
Geochemical
Classification of the
Elements
Atmophile - Van der Waals
Lithophile - Ionic
Siderophile - Metallic
Chalcophile - Covalent
