Mineral Structure Data
The gypsum group is composed of minerals of the general formula
The crystal structure of gypsum.
End-Member Gypsum Anhydrite Formula CaSO4.2H2O CaSO4 Form.Wt. 172.173 136.142 Density 2.313 2.953 Mol Volume 74.440 46.103 Z 4 4 Cryst.Sys. Monoclinic Orthorhombic Cryst.Class 2/m mmm Space Group I2/a Amma Cell Parameters a 5.670 7.006 b 15.201 6.998 c 6.533 6.245 beta 118.60 90. Vol. 494.37 306.18 Thermal expansion alpha a0 a1 a2 Elastic Properties Ks(GPa) G(Gpa) Ref. Cole & Kirfel & Lancucki(1974) Will(1980) |
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End-Member Gypsum Anhydrite C.N. 8 8 Occupant Ca Ca Point Sym. 2 m2m Wyckoff Not. 4e 4c Frac.Coord. x 1/2 3/4 y .0797 0 z 1/4 .34765 Distances O1(2) 2.528 2.563 O1(2) 2.464 O2(2) 2.545 2.347 O2(2) 2.378 2.510 O(w)(2) 2.380 Mean 2.458 2.471 sigma .084 .085 Poly.Vol. 25.983 26.433 Site Energy -978. -1014. |
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End-Member Gypsum Anhydrite C.N. 4 4 Occupant S S Point Sym. 2 m2m Wyckoff Not. 4e 4c Frac.Coord. x 0 1/4 y 0.0772 0 z 3/4 0.15577 Distances O1(2) 1.457 1.473 O2(2) 1.461 1.472 Mean 1.459 1.472 sigma .002 .000 Poly.Vol. 1.589 1.635 Q.E. 1.0023 1.0012 Ang.Var. 9.7 4.8 Site Energy -9404. -9651. |
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