Lecture Notes Oxides and Hydroxides
Lecture Notes Oxides and Hydroxides
Lecture Notes Oxides and Hydroxides
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Descriptive Mineralogy<br />
<strong>Oxides</strong> <strong>and</strong><br />
<strong>Hydroxides</strong><br />
• Hemioxides<br />
– Cuprite (Cu 2O)<br />
– Ice (H 2O)<br />
• Monoxides<br />
– Periclase (MgO)<br />
– Wüstite (FeO)<br />
– Manganosite (MnO)<br />
– Lime (CaO)<br />
– Zincite (ZnO)<br />
– Bromellite (BeO)<br />
– Tenorite (CuO)<br />
Simple <strong>Oxides</strong><br />
• Sesquioxides<br />
– Corundum (Al 2O 3)<br />
– Hematite (Fe 2O 3)<br />
– Bixbyite (Mn 2O 3)<br />
• Dioxides<br />
– Rutile (TiO 2)<br />
– Anatase (TiO 2)<br />
– Brookite (TiO 2)<br />
– Cassiterite(SnO 2)<br />
– Pyrolusite(MnO 2)<br />
Hemi-<strong>Oxides</strong> (M2O)<br />
• Ice (H2O) Hexagonal<br />
• Cuprite (Cu2O)<br />
• Why not Na2O?<br />
– Na radius too large<br />
– Na has no covalent orbitals available<br />
Classification of the Minerals<br />
• Non-Silicates<br />
– Native Elements<br />
– Halides<br />
– Sulfides<br />
– <strong>Oxides</strong><br />
– <strong>Hydroxides</strong><br />
– Carbonates<br />
– Sulfates<br />
– Phosphates<br />
Simple <strong>Oxides</strong><br />
• Silicates<br />
– Orthosilicates<br />
– Sorosilicates<br />
– Cyclosilicates<br />
– Chain Silicates<br />
– Layer Silicates<br />
– Tektosilicates<br />
Hemi-<strong>Oxides</strong> (M2O)<br />
• Na 2O occurs as a mineral<br />
– A. True<br />
– B. False<br />
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Cuprite Cu 2O<br />
• Occurrence: Low Temp<br />
Hydrothermal (Supergene)<br />
• Use: Minor ore of Cu<br />
Ice H 2O<br />
Crystal System Hexagonal<br />
Point Group 6/mmm<br />
Space Group P63/mmc Optical Uniaxial<br />
Color Colorless<br />
Luster Vitreous<br />
Hardness 1.5<br />
Density 0.95<br />
Ice H 2O snow morphology<br />
Cuprite Cu 2O<br />
Ice H 2O<br />
• Occurrence: Low<br />
Temp Hydrothermal<br />
(Supergene)<br />
• Strongly covalent<br />
• O SP 3<br />
• Cu SP<br />
• Use: Minor ore of Cu<br />
Ice H 2O<br />
High<br />
Pressure<br />
Phase<br />
Diagram<br />
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Ice H 2O What’s Wrong Here?<br />
Monoxides (MO)<br />
• Rocksalt oxides<br />
– Periclase MgO - Wüstite FeO<br />
– Manganosite MnO<br />
– Lime CaO<br />
– Bunsenite NiO<br />
• Zincite oxides:<br />
– Zincite ZnO,<br />
– Bromellite BeO<br />
• Other monoxides:<br />
– TenoriteCuO, Montroydite HgO<br />
Periclase - Wüstite<br />
MgO - FeO<br />
Lower mantle phase<br />
Mg2SiO4 = MgSiO3 + MgO<br />
Ringwoodite = Perovskite + periclase<br />
Rocksalt <strong>Oxides</strong><br />
MgO -FeO -MnO -CaO<br />
Crystal System Cubic<br />
Point Group 4/m-32/m<br />
Space Group Fm3m<br />
Optical Isotropic<br />
Periclase<br />
MgO<br />
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Zincite Group<br />
ZnO – Zincite,<br />
BeO Bromellite<br />
Crystal System Hexagonal Point Group 6mm<br />
Space Group P63mc Optical Uniaxial<br />
Extreme Piezoelectric<br />
Uses: Transducers<br />
Sesquioxides (M2O3)<br />
• Corundum Group<br />
– Corundum Al2O3<br />
– Hematite Fe2O3<br />
– Karelianite V2O3 <strong>and</strong> Eskolaite Cr2O3<br />
• Other Sesquioxides<br />
– Bixbyite Mn2O3<br />
Corundum Al 2O 3<br />
Other Monoxides<br />
CuO – Tenorite<br />
HgO Montroydite<br />
Oxidized hydrothermal deposits<br />
Covalent Bonding<br />
Irregular coordination<br />
Corundum Al 2O 3<br />
Crystal System Trigonal<br />
Point Group -32/m<br />
Space Group R-3c<br />
Optical Uniaxial<br />
Color Colorless<br />
Luster Vitreous<br />
Hardness 9<br />
Density 4.02<br />
Corundum Al 2O 3<br />
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Hematite Fe 2O 3<br />
Crystal System Trigonal<br />
Point Group -32/m<br />
Space Group R-3c<br />
Optical Nearly opaque<br />
Color Red/Metallic<br />
Luster Earthy/metallic<br />
Hardness 6<br />
Density 5.26<br />
Bixbyite Mn 2O 3<br />
Crystal System Cubic<br />
Point Group 4/m-32/m<br />
Space Group Ia3<br />
Optical Nearly opaque<br />
Color Red/Metallic<br />
Luster Earthy/metallic<br />
Hardness 6<br />
Density 4.95<br />
Rutile TiO 2<br />
Pyrolusite MnO 2<br />
Cassiterite SnO 2<br />
Stishovite SiO 2<br />
Hematite Fe 2O 3<br />
Dioxides<br />
• Rutile Group<br />
– Rutile TiO2; Anatase; Brookite<br />
– Cassiterite SnO2<br />
– Pyrolusite MnO2<br />
– Stishovite SiO2<br />
• Uraninite (UO2) <strong>and</strong> Thorianite<br />
(ThO2)<br />
• Baddeleyite ZrO2<br />
Rutile TiO 2<br />
Crystal System Tetragonal<br />
Point Group 4/mmm<br />
Space Group P42/mnm Optical Nearly opaque<br />
Color Red<br />
Luster Adamantine<br />
Hardness 6<br />
Density 4.23<br />
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Anatase <strong>and</strong> Brookite TiO 2 Cassiterite SnO2<br />
Uraninite UO2 Crystal System Cubic<br />
Point Group 4/m-32/m<br />
Space Group Fm-3m<br />
Optical Nearly opaque<br />
Color Black<br />
Luster Submetallic<br />
Hardness 5.5<br />
Density 7-9<br />
Occurrence Lo T Hyd<br />
Roll-front<br />
Use: Major Ore of U<br />
Simple <strong>Oxides</strong><br />
Uraninite UO 2<br />
The Major ore of U<br />
U4+ or U6+?<br />
Same structure as fluorite<br />
U6+ is soluble U4+ is insoluble<br />
U is mobilized by oxidation; immobilized by reduction<br />
Roll-front deposits.<br />
Natural reactors<br />
Complex <strong>Oxides</strong><br />
• Two or more different cations<br />
– Spinel Group: M2TO4<br />
– Ilmenite Group : FeTiO3<br />
– Pseudobrookite Group : A2BO5<br />
– Perovskite Group : CaTiO3<br />
• High Pressure silicate analogues<br />
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Spinel Group<br />
• Spinel MgAl2O4<br />
• Hercynite FeAl2O4<br />
• Chromite FeCr2O4<br />
• Magnesiochromite MgCr2O4<br />
• Magnetite Fe 2+ Fe 3+ 2O4<br />
• Magnesioferrite MgFe2O4<br />
• Gahnite ZnAl2O4<br />
• Ulvospinel TiFe2O4<br />
• Ringwoodite Mg2SiO4<br />
Ringwoodite<br />
(spinel) γ-(MgFe) 2SiO 4<br />
• Dark blue<br />
color<br />
• 525 –<br />
660km<br />
• ~5%<br />
Earth<br />
Ilmenite Structure FeTiO 3<br />
• Corundum<br />
Structure<br />
• Space Group R-3<br />
• Alternating<br />
layers of Fe <strong>and</strong><br />
Ti Octahedra<br />
• Face-sharing<br />
Octahedra<br />
• Dense<br />
Space Group Fd3m<br />
Edge sharing<br />
octahedra<br />
Cell edge ~8.5Å<br />
Two octahedra per<br />
Tetrahedron<br />
MgAl2O4 (Normal)<br />
or<br />
Al (MgAl) O4 (Inverse)<br />
Spinel Structure<br />
Ilmenite Group<br />
• Ilmenite FeTiO3 • Geikielite MgTiO3 • Akimotoite MgSiO3 Pseudobrookite Group<br />
• Pseudobrookite Fe 2+ Ti2O5<br />
• Ferro-pseudobrookite TiFe 3+ 2O5<br />
• Armalcolite (Mg,Fe 2+ )Ti2O5<br />
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Pseudobrookite Structure<br />
• Space<br />
Group<br />
Bbmm<br />
• M1 dark<br />
• M2 lighter<br />
• Open<br />
Structure<br />
Accessory <strong>Oxides</strong><br />
Perovskite Structure<br />
• Pseudo-cubic<br />
• Orthorhombic<br />
• Space Group<br />
Pbnm<br />
Accessory <strong>Oxides</strong><br />
Perovskite<br />
• Perovskite CaTiO 3<br />
• MgSiO 3 (Lower mantle phase)<br />
<strong>Hydroxides</strong><br />
• Brucite Mg(OH) 2<br />
• Gibbsite Al(OH) 3<br />
• Boehmite <strong>and</strong> Diaspore AlO(OH)<br />
• Bauxite (Mixed Al hydroxides)<br />
• Goethite FeO(OH)<br />
(+Lepidochrosite)<br />
• Limonite Fe(OH) 3<br />
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• Two out of<br />
three<br />
possible<br />
octahedral<br />
sites<br />
occupied<br />
• Tri-valent<br />
cations<br />
Gibbsite Al(OH) 3<br />
Di-octahedral<br />
• All three<br />
possible<br />
octahedral<br />
sites<br />
occupied<br />
• Divalent<br />
cations<br />
Brucite Mg(OH) 2<br />
Tri-octahedral<br />
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