Lecture 18 (11/29/2006) Systematic Description of Minerals Part 2: Oxides, Hydroxides Halides,...
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Transcript of Lecture 18 (11/29/2006) Systematic Description of Minerals Part 2: Oxides, Hydroxides Halides,...
Lecture 18 (11/29/2006)Lecture 18 (11/29/2006)
Systematic Description of MineralsSystematic Description of Minerals
Part 2:Part 2: Oxides, Hydroxides Halides, Oxides, Hydroxides Halides, Carbonates, Sulfates, and Carbonates, Sulfates, and
PhosphatesPhosphates
OxidesOxidesThree main groups based on metal cation/oxygen ratiosThree main groups based on metal cation/oxygen ratios
Hematite GroupHematite Group (X (X22OO33) ) Corundum X=AlCorundum X=Al+3+3
most phases hexagonal most phases hexagonal Hematite X=FeHematite X=Fe+3+3
Ilmenite X=1FeIlmenite X=1Fe+2+2+1Ti+1Ti+4+4
Rutile GroupRutile Group (XO (XO22)) Rutile X=TiRutile X=Tix- +4 cationx- +4 cation Pyrolusite X=MnPyrolusite X=Mn
most phases tetragonalmost phases tetragonal Cassiterite X=SnCassiterite X=Sn
Uraninite X=UUraninite X=U
Spinel GroupSpinel Group (XY (XY22OO44)) Spinel X=Mg, Y=AlSpinel X=Mg, Y=Al
X- +2X- +2 ; Y- +3 cation; Y- +3 cation Magnetite X=FeMagnetite X=Fe+2+2, Y=Fe, Y=Fe+3+3
most phases isometricmost phases isometric Chromite X=FeChromite X=Fe+2+2, Y=Cr, Y=Cr
or orthorhombicor orthorhombic Chrysoberyl X=Be, Y=AlChrysoberyl X=Be, Y=Al
Ulvospinel X=TiUlvospinel X=Ti+4+4, Y=Fe, Y=Fe+2+2
Fe-Ti oxidesFe-Ti oxides
FeFe+2+2FeFe+3+3
Spinel Group Spinel Group (XY(XY22OO44))
Gem-quality Gem-quality SpinelsSpinels
Other Common OxidesOther Common Oxides
Rutile (TiORutile (TiO22))
Rutile needles in Rutile needles in QuartzQuartz
Pyrolusite dendritesPyrolusite dendriteson fracture faceson fracture faces
Pyrolusite (MnOPyrolusite (MnO22))
Mass of botryoidal Mass of botryoidal PyrolusitePyrolusite
Corundum (AlCorundum (Al22OO33))
Hardness=9Hardness=9
Red = RubyRed = RubyBlue = SapphireBlue = Sapphire
Chrysoberyl (BeAlChrysoberyl (BeAl22OO44))
Cyclic twinningCyclic twinningin Chrysoberylin Chrysoberyl
HydroxidesHydroxides(OH)(OH)- - main anionic group forming octahedrally main anionic group forming octahedrally
coordinated sheets with weak bonds betweencoordinated sheets with weak bonds between
Two structural types: Two structural types:
Brucite-typeBrucite-type – trioctahedral – trioctahedral sheets (all octahedral cation sheets (all octahedral cation sites are filled)sites are filled)
Gibbsite-typeGibbsite-type – dioctahedral – dioctahedral sheets (only two of three sheets (only two of three octahedral sites are filled)octahedral sites are filled)
Common Types of HydroxidesCommon Types of HydroxidesBrucite Brucite Mg(OH)Mg(OH)22 Gibbsite Gibbsite Al(OH)Al(OH)33
Manganite Manganite MnO(OH)MnO(OH) DiasporeDiaspore AlO(OH)AlO(OH)
GoethiteGoethite FeO(OH)FeO(OH) Bauxite Bauxite Al-hydroxide* Al-hydroxide*
*hybrid mix of diaspore, gibbsite, and boehmite (*hybrid mix of diaspore, gibbsite, and boehmite (AlO(OH))AlO(OH))
HalidesHalides
Simple compounds composed of Simple compounds composed of large halogen anions (Cl, Br, F, I)large halogen anions (Cl, Br, F, I)
Typically isometricTypically isometric Dominantly ionic bondingDominantly ionic bonding Properties – low hardness, high Properties – low hardness, high
melting points, poor conductors melting points, poor conductors (except at high temperatures)(except at high temperatures)
Common Halides Common Halides
Halite (NaCl)Halite (NaCl)
Sylvite (KCl)Sylvite (KCl)
Flourite (CaFFlourite (CaF22))
Mineral Mineral Groups Groups
formed with formed with Anionic Anionic
ComplexesComplexes
CarbonatesCarbonates
SulfatesSulfates
PhosphatesPhosphates
SilicatesSilicates
Amount of residual chargeAmount of residual chargeindicates relative strength indicates relative strength bonds with cations, which bonds with cations, which reflected in the hardness reflected in the hardness of the mineralof the mineral
CarbonatesCarbonates
AragoniteAragonite(High-P) Orthorhombic(High-P) Orthorhombic
CalciteCalcite(Low-P - Hexagonal)(Low-P - Hexagonal)
Most are Hexagonal Most are Hexagonal
Other CarbonatesOther Carbonates
Azurite - CuAzurite - Cu33(CO(CO33))22(OH)(OH)2 2 (Blue)(Blue)
Malachite – CuMalachite – Cu22COCO33(OH)(OH)22 (Green) (Green)
Rhodochrosite – MnCORhodochrosite – MnCO33
BoratesBorates
Kernite – NaKernite – Na22BB44OO66(OH)(OH)22·3H·3H22OO
Borax - NaBorax - Na22BB44OO55(OH)(OH)44·8H·8H22OO
Ulexite – NaCaBUlexite – NaCaB55OO66(OH)(OH)66·5H·5H22OO
H – 2-2.5; SG – 1.7H – 2-2.5; SG – 1.7
H – 3; SG – 1.95H – 3; SG – 1.95
H – 1-2.5; SG – 1.96H – 1-2.5; SG – 1.96
““Television Rock”Television Rock”
SulfatesSulfatesHYDROUS HYDROUS ANHYDROUSANHYDROUS
Gypsum – CaSOGypsum – CaSO44·2H·2H22OO
Alunite – KAlAlunite – KAl33(SO(SO44))22(OH)(OH)66 Barite – BaSOBarite – BaSO44
Anhydrite – CaSOAnhydrite – CaSO44
H: 3-3.5H: 3-3.5SG: 4.5SG: 4.5
H: 3-3.5H: 3-3.5SG: 2.9SG: 2.9
H: 2H: 2SG: 2.32SG: 2.32
H: 4H: 4SG: ~2.7SG: ~2.7
Tungstates & MolybdatesTungstates & Molybdates
Woframite – (Fe,Mn)WOWoframite – (Fe,Mn)WO44
Scheelite – CaWOScheelite – CaWO44
Wulfenite – PbMoOWulfenite – PbMoO44
SG: 7-7.5SG: 7-7.5
SG: ~6SG: ~6
SG: 6.8SG: 6.8
PhosphatesPhosphates
Apatite – CaApatite – Ca55(PO(PO44))33(F,Cl,OH)(F,Cl,OH)– prismatic hexagonal crystalsprismatic hexagonal crystals– common in igneous rocks and common in igneous rocks and
hydrothermal depositshydrothermal deposits
- variable colors- variable colors
Other Common PhosphatesOther Common Phosphates
Monazite – (Ce,La,Y,Th)POMonazite – (Ce,La,Y,Th)PO44
Ore mineral for Rare Earth ElementsOre mineral for Rare Earth Elements
Useful mineral in U-Pb and Th age datingUseful mineral in U-Pb and Th age dating
Wavellite – AlWavellite – Al33(PO(PO44))22(OH)(OH)33·5H·5H22OORadiating globular aggregatesRadiating globular aggregates
Turquoise – Turquoise – CuAlCuAl66(PO(PO44))44(OH)(OH)88·5H·5H22OO
Next Lecture 11/29/06Next Lecture 11/29/06
Systematic Description of MineralsSystematic Description of Minerals
Part 3: Silicates Part 3: Silicates
Read: Klein Chap. 11Read: Klein Chap. 11