monoclinic
Gypsum (Swallowtail Twin)
CaSO4.2H2O
Quick Facts
Hardness
2
Specific Gravity
2.31-2.33
Refractive Index
1.520-1.530
Crystal Structure
monoclinic[2/m]:{010}@1.0 + {100}@0.95 + {001}@0.7 + {110}@0.4 | twin(gypsum_swallow) monoclinic
2/m
{010} {100} {001} {110}
Physical Properties
Crystal Systemmonoclinic
Hardness (Mohs)2
Specific Gravity2.31-2.33
CleavagePerfect {010}, good {100} and {011}
FractureConchoidal to splintery
LustreVitreous to pearly (on cleavage)
Optical Properties
Refractive Index1.520-1.530
Birefringence0.009-0.010
PleochroismNone
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Open in Playground monoclinic[2/m]:{010}@1.0 + {100}@0.95 + {001}@0.7 + {110}@0.4 | twin(gypsum_swallow) Related Minerals
Other minerals in the monoclinic system