Epidote-Zoisite Structure PDF

10-EPIDOTE Epidote-Zoisite Structure  Crystal system = Monoclinic (Epidote/Clinozoisite) Zoisite (Orthorhombic) Zoisite is an orthorhombic polymorph of clinozoisite Epidote-Clinozoisite Structure  Chemical Formula- X2Y3Z3(O,OH,F)13  X=Ca  Y=Al, Fe+3  Z=Si Epidote Ca2(Al,Fe3+...

10-EPIDOTE Epidote-Zoisite Structure  Crystal system = Monoclinic (Epidote/Clinozoisite) Zoisite (Orthorhombic) Zoisite is an orthorhombic polymorph of clinozoisite Epidote-Clinozoisite Structure  Chemical Formula- X2Y3Z3(O,OH,F)13  X=Ca  Y=Al, Fe+3  Z=Si Epidote Ca2(Al,Fe3+)Al2O(SiO4)(Si2O7)(OH) Clinozoisite Ca2Al3O(SiO4)(Si2O7)(OH) CaO:(Al2O3+Fe2O3):SiO2:H2O=2:1.5:3:0.5 Substitutions: Al→Fe+3, CaFe+3 →Fe+2REE+3 Epidote-Clinozoisite Structure The monoclinic structure contains chains of edge sharing octahedra. Bridging the chains of octahedra is by single (SiO4) and double tetrahedral (Si2O7) groups, who shares oxygens from octahedra. The framework formed contains large cavities which is occupied by Ca in 9 or 10 fold coordination  CaO: (Al2O3+Fe2O3) :SiO2:H2O=2:1.5:3:0.5 Chemical Ca2(Fe+++,Al)3(SiO4)3(OH) = Formula: Ca2(Fe,Al)Al2(SiO4)(Si2O7)O(OH) Composition: Molecular Weight = 519.30 gm Calcium 15.44 % Ca 21.60 % CaO Aluminum 3.90 % Al 7.36 % Al2O3 Iron 24.20 % Fe 34.60 % Fe2O3 Silicon 16.22 % Si 34.71 % SiO2 Hydrogen 0.19 % H 1.73 % H2O Chemical Ca2Al3(SiO4)3(OH) = Formula: Ca2AlAl2(SiO4)(Si2O7)O(OH) Composition: Molecular Weight = 454.36 gm Calcium 17.64 % Ca 24.68 % CaO Aluminum 17.82 % Al 33.66 % Al2O3 Silicon 18.54 % Si 39.67 % SiO2 Hydrogen 0.22 % H 1.98 % H2O Oxygen 45.78 % O  Rock types Protolith Elements Rocks Ultramafic rocks Very high Mg, Fe, Ni, and Cr. Mantle rocks, komatiites, and cumulates. Mafic rocks High Fe, Mg, and Ca. Basalts, gabbros, and some gray- wackes. Shales (or pelitic rocks)- High Al, K, and Si. most common sedi rock. Carbonates (or High Ca, Mg, and CO2. Mostly sedimentary calcareous rocks) limestones and dolostones. Impure carbonates Shale+carbonate components may contain sand or shale (marls) components. Iron Rocks Rich in Fe BIF, Iron stone Quartz rocks Nearly pure SiO2. Cherts, sands Quartzo-feldspathic High Si, Na, K, and Al. Arkose or granitoid and rocks rhyolitic rocks Epidote-Zoisite Occurrences  Metamorphic-Essential component in greenschist with Chlorite, Actinolite and Albite Hydrothermal alteration of Plagioclase in Calc silicate  Zoisite is found in impure calc silicate and at higher grade converts tio plagioclase  Epidote in Hand Specimen  Crystal System-Monoclinic  Cleavage: 1 set  Color:Yellowish green, Brownish green, Black, Yellow, Gray  Density: 3.45  Habit:Prismatic  Hardness:7  Luster:Vitreous (Glassy)  Streak:grayish white Epidote in Hand Specimen  Imp. Optical Property Refractive Index high In thin section, Epidote has yellow-Yellow Distinguishing green pleochroism and higher order Features interference colour (in comparison to Hbl) Epidote under microscope