GY 302: Crystallography & MineralogyGY 302: Crystallography & MineralogyUNIVERSITY OF SOUTH ALABAMALecture 20: Class VIII-SilicatesSoro- and CyclosilicatesLecture 20: Class VIII-SilicatesSoro- and CyclosilicatesLast TimeClass VIII Minerals: Nesosilicates1. Garnet Group2. Aluminum Silicates3. Other NesosilicatesandraditeSilicate ClassificationAlmandineGrossularNesosilicateshttp://www.geol.lsu.edu/henry/Geology3041/lectures/21MetamorphicIntro/BarrovianBuchan.jpgToday’s AgendaClass VIII Minerals1. Sorosilicates2. Cyclosilicates (3, 4 and 6 fold coordination)SorosilicatesMineral 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) OrthorhombicSorosilicatesMineral 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) OrthorhombicEpidote[Ca2(Al,Fe)Al2O(SiO4)(Si2O7)(OH)]Crystal: MonoclinicPt. Group: 2/mHabit: fibrous, prismatic, massiveSG: 3.4-3.5; H: 7L: vitreous to earthy; Str: white Col: green to yellowClev: perfect (001), poor (100)Optics: Biaxial (-); bir=0.013-0.046nα=1.723; nβ=1.73, nγ=1.736Sorosilicate Mineralshttp://www.gc.maricopa.edu/earthsci/imagearchive/pictures2.htmName Derivation: From the Greek epidosis - "addition." Zoisite[Ca2Al3O(SiO4)(Si2O7)(OH)]Crystal: OrthorhombicPt. Group: 2/m 2/m 2/mHabit: prismatic, massiveSG: 3.1-3.4: H: 6.5L: vitreous; Str: whiteCol: blue-greenClev: perfect (001)Optics: Biaxial (+); bir=0.006 nα=1.70; nβ=1.69, nγ=1.70Sorosilicate Mineralshttp://www.lynayre.com/images/r%20ruby%20in%20zoisite.jpgNamed after the Austrian natural scientist, Siegmund Zois (1747-1819).Pumpellyite[Ca2MgAl2(SiO4)(Si2O7)(OH)2·(H2O) ]Crystal: MonoclinicPt. Group: 2/mHabit: fibrousSG: 3.2; H: 5.5L: vitreous; Str: whiteCol: blue-green, brownStr: white Clev: [001], [100]; goodOptics: Biaxial (+); bir=0.014nα=1.67; nβ=1.67, nγ=1.684Sorosilicate Mineralshttp://webmineral.comNamed after the American geologist, R. Pumpelly (1837-1923).Hemimorphite[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.Chalk BoardHemimorphite[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.Chalk BoardHemimorphite[Zn4Si2O7(OH)2·H2O]Sorosilicate Mineralshttp://www.mineral-forum.comHemimorphite[Zn4Si2O7(OH)2·H2O]Sorosilicate Mineralshttp://desertscope.com/collItem.php?itemId=16http://www.mineral-forum.comHemimorphite[Zn4Si2O7(OH)2·H2O]It has unique polar or hemimorphic crystals from where it gets its name. Speciemens of hemimprhpite tend to be of two different forms. One form produces very glossy, clear or white, thin, bladed crystals, often well formed showing many crystal faces. Many times these crystals are arranged in fan shaped aggregates. The other from produces a blue to blue-green botryoidal crust that resembles smithsonite or prenite. In many cases, it is often confused with smithonite. I found this really nice method of differentiate the two: “The carbonate (smithsonite) dissolves in warm acid with some effervescence, while the silicate (hemimorphite) dissolves slowly and quietly, leaving gelatinous silica. Smithsonitehas a higher density as well a shimering luster that causes a play of light across the rounded surfaces. The two species also show differences in the way they cleave. Smithsoniteknobs break with a ready convex (rhombohedral) cleavage not characteristic of hemimorphite. Hemimorphite is slightly harder than smithsonite.”Sorosilicate Mineralshttp://desertscope.com/collItem.php?itemId=16CyclosilicatesMineral Formula SystemBeryl Be3Al2Si6O18Hexagonal Tourmaline (Na,Ca)(Li,Mg,Al)(Al,Fe,Mn) 6(BO3)3(Si6O18)(OH)4Hexagonal Cordierite Al3(Mg, Fe)2(AlSi5O18) Orthorhombic Axinite (Ca, Mn, Fe)3Al2(BO3)Si4O12(OH) TriclinicDioptase CuSiO2(OH)2Hexagonal (Trigonal)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 3 fold ring structureCyclosilicate Minerals 4 fold ring structureCyclosilicate Minerals 6 fold ring structureTourmaline Group (14) [NaMg3Al6(BO3)3Si6O18(OH)4]Crystal: Hexagonal (trigonal)Pt. Group: 3mHabit: columnar, curved sidesSG: 3.09; H: 7-7.5L: vitreous; Str: colourlessCol: black, red, green; watermelonClev: indistinctOptics: Uniaxial (-); bir=0.019-0.025ne=1.612; nw=1.63Cyclosilicate Minerals (6-fold rings)Name Derivation: Drava River, AustriaTourmaline Group (14) Tourmaline Group (14) [[NaMgNaMg33AlAl66(BO(BO33))33SiSi66OO1818(OH)(OH)44]]--DraviteDravitehttp://webmineral.comCordierite [Mg2Al4Si5O18]Crystal: OrthorhombicPt. Group: 2/m 2/m 2/mHabit: prismatic, massiveSG: 2.65; H: 7 L: vitreous; Str: whiteCol: colorless, pale blue, grayClev: poor [010]Optics: Biaxial (-); bir=0.011-0.018nα=1.52; nβ=1.53, nγ=1.54Cyclosilicate Minerals (6-fold rings)http://webmineral.com/specimens/picshow.php?id=123From the French mining engineer and geologist P. L. A. Cordier (1777-1861)DioptaseDioptase[CuSiO[CuSiO22(OH)(OH)22]]Crystal: Hexagonal (Trigonal)Pt. Group: 3Habit: massiveSG: 3.3; H: 5L: vitreous; Str: greenCol: