monoclinic Sulfates
Gypsum (Tabular)
CaSO4.2H2O
Quick Facts
Hardness
2.0
Specific Gravity
2.31
Refractive Index
1.52
Optical Character
Biaxial +
Crystal Structure
monoclinic[2/m]:{010}@1.0 + {100}@0.7 + {001}@0.8 + {111}@0.5 monoclinic
2/m
{010} {100} {001} {111}
Physical Properties
Crystal Systemmonoclinic
Hardness (Mohs)2.0
Specific Gravity2.31
CleavagePerfect {010}, good {100} and {011}
FractureConchoidal to splintery
LustreVitreous to pearly (on cleavage surfaces)
Optical Properties
Refractive Index1.52
Birefringence0.009-0.010
Optical CharacterBiaxial +
Dispersion0.033
PleochroismNone
Colours
Colorless (selenite)WhiteGrayYellowBrownPinkOrange
Localities
Mexico (Naica - giant crystals)MoroccoUSA (Oklahoma, Utah)SpainEnglandAustralia
Crystal Forms
pinacoidprismtabular crystals
Notes
Can be scratched with fingernail; slightly soluble in water; dehydrates to anhydrite when heated
Interactive Preview
Open this crystal in the CDL Playground to rotate, export, and explore in 3D.
Open in Playground monoclinic[2/m]:{010}@1.0 + {100}@0.7 + {001}@0.8 + {111}@0.5 Related Minerals
Other minerals in the monoclinic system
