Quiz 8 results1: 1: Wulfenite (79%Wulfenite (79%))2:2:PurpuritePurpurite(79%(79%))3.3.VarasciteVarascite(79%(79%))4:4:WolframiteWolframite(74%(74%))5:5:Barite (53%Barite (53%))6: 6: Celestine (68%Celestine (68%))Bonus:Bonus:GibsiteGibsite(32%(32%))Average: 82.6% Highest grade: 108%A: 7B: 5C: 3D: 2F: 2GY 302: Crystallography & MineralogyGY 302: Crystallography & MineralogyUNIVERSITY OF SOUTH ALABAMALecture 21: Inosilicates 1Pyroxenes and PyroxenoidsLecture 21: Inosilicates 1Pyroxenes and PyroxenoidsClass VIII Minerals1. Sorosilicates2. Cyclosilicates (3, 4 and 6 fold coordination)Last TimeSorosilicatesMineral Formula SystemZoisite Ca2Al3O(SiO4)(Si2O7)(OH) Orthorhombic Clinozoisite Ca2Al3O(SiO4)(Si2O7)(OH) Monoclinic Epidote Ca2(Al,Fe)Al2O(SiO4)(Si2O7)(OH) Monoclinic Allanite (Ca,Ce) 2(Fe,Fe)Al2O(SiO4)(Si2O7)(OH) MonoclinicLawsonite CaAl2SiO7(OH)2·H2O OrthorhombicPumpellyite Ca2MgAl2(SiO4)(Si2O7)(OH)2·H2O MonoclinicVesuvianite (Idocrase) Ca10Mg2Al4(SiO4)5(Si2O7)2(OH)4TetragonalHemimorphite Zn4Si2O7(OH)2·(H2O) OrthorhombicHemimorphite[Zn4Si2O7(OH)2·H2O]Crystal: OrthorhombicPt. Group: 2mmHabit: massive to mammillarySG: 3.45; H: 5L: vitreous; Str: whiteCol: colorless, brown, to greyClev: perfect [001]Optics: Biaxial (+); bir=0.020 nα=1.61; nβ=1.62, nγ=1.736Sorosilicate Mineralshttp://webmineral.com/data/Hemimorphite.shtmlNamed after the hemimorphic nature of the crystals.CyclosilicatesMineral Formula SystemBeryl Be3Al2Si6O18Hexagonal “Tourmaline” (Na,Ca)(Li,Mg,Al)(Al,Fe,Mn) 6(BO3)3(Si6O18)(OH)4Hexagonal (Trigonal)Cordierite Al3(Mg, Fe)2(AlSi5O18) Orthorhombic Axinite (Ca, Mn, Fe)3Al2(BO3)Si4O12(OH) TriclinicDioptase CuSiO2(OH)2Hexagonal (Trigonal)Silicate rings come in 3, 4 and 6 fold structures. 8-fold structures also occur in nature (e.g., sulfur)Cyclosilicate Minerals 6 fold ring structureBeryl [Be3Al2Si6O18]Crystal: HexagonalPt. Group: 6/m 2/m 2/mHabit: euhedral, columnarSG: 2.76; H: 7.5-8L: vitreous; Str: whiteCol: blue, yellow, red, greenClev: imperfectOptics: Uniaxial (-); bir=0.004-0.007ne=1.564; nw=1.568Cyclosilicate Minerals (6-fold rings)http://webmineral.com/specimens/picshow.php?id=123From the ancient Greek, beryllos, signifying a "precious blue-green color of sea water" stone.Today’s AgendaClass VIII Minerals: Inosilicates (part 1)1. General Introduction to Inosilicates2. Pyroxenes3. PyroxenoidsInosilicatesThe “chain” silicates come in 2 main “flavors”Single chains (Si:O = 1:3)(Pyroxene Group)(Pyroxenoid Group)Double chains (Si:O = 1:2.5)(Amphibole Group)Inosilicates (single chain)Two major sub groups of pyroxenes are distinguished on the basis of crystal structure:1) Orthopyroxenes (orthorhombic)2) Clinopyroxenes (monoclinic)http://www.uwgb.edu/dutchs/GRAPHIC0/ROCKMIN/ATOM-STRUCT/PyroxChain.gifInosilicates (single chain: pyroxenes)General formula: XYSiO3or XY(Si,Al)2O6X[larger ions] = Ca2+, Na+, Fe2+and/or Mg2+; rarely Zn2+, Mn2+, Li+Y[smaller ions] = Cr3+, Al3+, Fe3+, Mn3+Si:O ratio is 1:3(octahedrally coordinated cations between SiO3 chains)http://www.tulane.edu/~sanelson/images/opx-cpxphasediag.gifInosilicates (single chain: pyroxenes)General formula: XYSiO3or XY(Si,Al)2O6X[larger ions] = Ca2+, Na+, Fe2+and/or Mg2+; rarely Zn2+, Mn2+, Li+Y[smaller ions] = Cr3+, Al3+, Fe3+, Mn3+Si:O ratio is 1:3(octahedrally coordinated cations between SiO3 chains produce orthorhombic or monoclinic symmetries)http://ruby.colorado.eduMonoclinic OrthorhombicInosilicates (single chain; pyroxenoids)General formula: X2SiO3X[larger ions] = Ca2+, Na+, Fe2+and/or Mg2+Si:O ratio is 1:3(larger cations force triclinicsymmetry)http://ruby.colorado.eduInosilicates (single chain)Orthopyroxene: orthorhombic minerals (5)Hypersthene, Enstatite, Ferrosilite, Donpeacorite, NchwaningiteClinopyroxene: monoclinic minerals (18)Clinoenstitite, clinoferrosilite, pigeonite, diopside, hedenbergite, spudomenePyroxenoid: Triclinic minerals (lots)wollanstonite, pectolite, rhodoniteInosilicates (single chain)Enstitite [Mg2Si2O6]Crystal: OrthorhombicPt. Group: 2/m 2/m 2/mHabit: laminar, massive, fibrousSG: 3.2; H: 5.5L: vitreous to pearly; Str: grey Col: white, yellow, brown, grayClev: [110]; [010] goodOptics: Biaxial (+); bir=0.009nα=1.65; nβ=1.65, nγ=1.66Occurrence:mafic intrusive rocksInosilicate Minerals (orthopyroxene)From the Greek enstates - "opponent."Enstitite is actually one member of a continuous series suite of “orthopyroxene” (Enstitite-Ferrosilite).http://ruby.colorado.edu/~smyth/min/images/enstatite.gifInosilicate Minerals (orthopyroxene)http://upload.wikimedia.org/wikipedia/en/4/42/Pyrox_names.png2009 textbook’s “mineral” (p265)hypersteneOrthopyroxenesEnstitite (En) can also be related to many other silicate minerals through this phase diagramInosilicate Minerals (orthopyroxene)http://web.pdx.edu/~ruzickaa/meteorites/McSween/Fo-Qz.gifThere is complete Mg-Fe solid solution between the pyroxenes, and as with most Mg-Fe solid solutions, the Mg-rich end members crystallize at higher temperatures than the Fe-rich end members. http://www.geo2all.com/vb/Inosilicate Minerals (clinopyroxenes)ClinopyroxenesThere are more options for ternary plots as there is more variability in cation composition… and you are going to ♥ the phase diagram possibilitiesAugite(Ca,Na)(Mg,Fe,Al)(Si,Al)2O6Crystal: MonoclinicPt. Group: 2/mHabit: columnar, massive, fibrousSG: 3.4; H: 5 to 6.5 L: vitreous; Str: green-greyCol: green-greyClev: perfect [110], poor [010]Optics: Biaxial (+); bir = 0.0260nα=1.68; nβ=1.684, nγ=1.706Inosilicate Minerals(clinopyroxene)From the Greek auge -"luster."http://webmineral.com/data/Augite.shtmlOccurrence: basic igneous & metamorphic rocksInosilicate Minerals(clinopyroxene)http://www.mii.org/Minerals/photoaugite.htmlFrom the Greek auge -"luster."Occurrence: basic igneous & metamorphic rocksAugite(Ca,Na)(Mg,Fe,Al)(Si,Al)2O6Crystal: MonoclinicPt. Group: 2/mHabit: columnar, massive, fibrousSG: 3.4; H: 5 to 6.5 L: vitreous; Str: green-greyCol: green-greyClev: perfect [110], poor [010]Optics: Biaxial (+); bir = 0.0260nα=1.68; nβ=1.684, nγ=1.706Inosilicate Minerals(clinopyroxene)Spodumene [LiAlSi2O6]Crystal: MonoclinicPt. Group: 2/mHabit: bladedSG: 3.15; H: 6.5-7L: vitreous; Str: whiteCol: grey-white, yellow, pinkClev: [110] perfect; [100] goodOptics: Biaxial (+); bir = 0.014-0.018nα=1.648; nβ=1.655, nγ=1.662Occurrence:Li-bearing pegmatitesFrom from the Greek, spodoumenos, "burnt to ash," alluding to its
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