Clear gypsum

General

 

Category: Sulfate minerals

 

Chemical formula: CaSO4·2H2O

 

Strunz classification: 07.CD.40

 

Crystal symmetry: Monoclinic 2/m

 

Unit cell: a = 5.679(5) Å, b = 15.202(14) Å, c = 6.522(6) Å; β = 118.43°; Z=4

 

Identification

 

Color: Colorless to white; may be yellow, tan, blue, pink, brown, reddish brown or gray due to impurities

 

Crystal habit: Massive, flat. Elongated and generally prismatic crystals

 

Mohs scale hardness: 1.5–2 (defining mineral for 2)

 

Luster: Vitreous to silky, pearly, or waxy

 

Specific gravity: 2.31–2.33

 

Optical properties: Biaxial (+)

 

Refractive index: nα = 1.519–1.521 nβ = 1.522–1.523 nγ = 1.529–1.530

 

Birefringence: δ = 0.010

Done