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Descriptive Mineralogy Oxides and Hydroxides
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Classification of the Minerals Non-Silicates –Native Elements –Halides –Sulfides –Oxides –Hydroxides –Carbonates –Sulfates –Phosphates Silicates –Orthosilicates –Sorosilicates –Cyclosilicates –Chain Silicates –Layer Silicates –Tektosilicates
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Simple Oxides Hemioxides –Cuprite (Cu 2 O) –Ice (H 2 O) Monoxides –Periclase (MgO) –Wüstite (FeO) –Manganosite (MnO) –Lime (CaO) –Zincite (ZnO) –Bromellite (BeO) –Tenorite (CuO) Sesquioxides –Corundum (Al 2 O 3 ) –Hematite (Fe 2 O 3 ) –Bixbyite (Mn 2 O 3 ) Dioxides –Rutile (TiO 2 ) –Anatase (TiO 2 ) –Brookite (TiO 2 ) –Cassiterite(SnO 2 ) –Pyrolusite(MnO 2 )
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Simple Oxides
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Hemi-Oxides (M 2 O) Ice (H 2 O) Hexagonal Cuprite (Cu 2 O) Why not Na 2 O? –(Na radius too large)
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Cuprite Cu 2 O Occurrence: Low Temp Hydrothermal (Supergene) Use: Minor ore of Cu
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Ice H 2 O Crystal SystemHexagonal Point Group6/mmm Space GroupP6 3 /mmc OpticalUniaxial Color Colorless LusterVitreous Hardness1.5 Density0.95
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Ice H 2 O
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Ice H 2 O High Pressure Phase Diagram
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Monoxides (MO) Rocksalt oxides –Periclase MgO - Wüstite FeO –Manganosite MnO –Lime CaO –Bunsenite NiO Zincite oxides: –Zincite ZnO, –Bromellite BeO Other monoxides: –TenoriteCuO, Montroydite HgO
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Rocksalt Oxides MgO - FeO - MnO - CaO Crystal SystemCubic Point Group4/m-32/m Space GroupFm3m OpticalIsotropic
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Periclase - Wüstite MgO - FeO Lower mantle phase Mg 2 SiO 4 = MgSiO 3 + MgO Ringwoodite = Perovskite + periclase
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Periclase MgO
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Sesquioxides (M 2 O 3 ) Corundum Group –Corundum Al 2 O 3 –Hematite Fe 2 O 3 –Karelianite V 2 O 3 and Eskolaite Cr 2 O 3 Other Sesquioxides –Bixbyite Mn 2 O 3
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Corundum Al 2 O 3 Crystal SystemTrigonal Point Group-32/m Space GroupR-3c OpticalUniaxial Color Colorless LusterVitreous Hardness9 Density4.02
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Corundum Al 2 O 3
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Hematite Fe 2 O 3 Crystal SystemTrigonal Point Group-32/m Space GroupR-3c OpticalNearly opaque Color Red/Metallic LusterEarthy/metallic Hardness6 Density5.26
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Hematite Fe 2 O 3
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Bixbyite Mn 2 O 3 Crystal SystemCubic Point Group4/m-32/m Space GroupIa3 OpticalNearly opaque Color Red/Metallic LusterEarthy/metallic Hardness6 Density4.95
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Dioxides Rutile Group –Rutile TiO 2 ; Anatase; Brookite –Cassiterite SnO 2 –Pyrolusite MnO 2 –Stishovite SiO 2 Uraninite (UO 2 ) and Thorianite (ThO 2 ) Baddeleyite ZrO 2
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Rutile TiO 2 Pyrolusite MnO 2 Cassiterite SnO 2 Stishovite SiO 2
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Rutile TiO 2 Crystal SystemTetragonal Point Group4/mmm Space Group P4 2 /mnm Optical Nearly opaque Color Red Luster Adamantine Hardness6 Density4.23
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Anatase and Brookite TiO 2
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Cassiterite SnO 2
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Uraninite UO 2 Crystal SystemCubic Point Group4/m-32/m Space Group Fm-3m Optical Nearly opaque Color Black Luster Submetallic Hardness5.5 Density7-9 OccurrenceLo T Hyd Roll-front Use: Major Ore of U
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Simple Oxides
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Complex Oxides Two or more different cations –Spinel Group: M 2 TO 4 –Ilmenite Group : FeTiO 3 –Pseudobrookite Group : A 2 BO 5 –Perovskite Group : CaTiO 3 High Pressure silicate analogues
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Spinel Group Spinel MgAl 2 O 4 Hercynite FeAl 2 O 4 Chromite FeCr 2 O 4 Magnesiochromite MgCr 2 O 4 Magnetite Fe 2+ Fe 3+ 2 O 4 Magnesioferrite MgFe 2 O 4 Gahnite ZnAl 2 O 4 Ulvospinel TiFe 2 O 4 Ringwoodite Mg 2 SiO 4
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Spinel Structure Space Group Fd3m Edge sharing octahedra Cell edge ~8.5Å Two octahedra per Tetrahedron MgAl 2 O 4 (Normal) or Al (MgAl) O 4 (Inverse)
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Ilmenite Group Ilmenite FeTiO 3 Geikielite MgTiO 3 Akimotoite MgSiO 3
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Ilmenite Structure FeTiO 3 Corundum Structure Space Group R-3 Alternating layers of Fe and Ti Octahedra Face-sharing Octahedra Dense
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Pseudobrookite Group Pseudobrookite Fe 2+ Ti 2 O 5 Ferro-pseudobrookite TiFe 3+ 2 O 5 Armalcolite (Mg,Fe 2+ )Ti 2 O 5
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Pseudobrookite Structure Space Group Bbmm M1 dark M2 lighter Open Structure
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Accessory Oxides
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Perovskite Perovskite CaTiO 3 MgSiO 3 (Lower mantle phase)
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Perovskite Structure Pseudo-cubic Orthorhombic Space Group Pbnm
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Hydroxides Brucite Mg(OH) 2 Gibbsite Al(OH) 3 Boehmite and Diaspore AlO(OH) Bauxite (Mixed Al hydroxides) Goethite FeO(OH) (+Lepidochrosite) Limonite Fe(OH) 3
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Gibbsite Al(OH) 3 Di-octahedral Two out of three possible octahedral sites occupied Tri-valent cations
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Brucite Mg(OH) 2 Tri-octahedral All three possible octahedral sites occupied Divalent cations
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