Calcium Sulfate
Ca(SO4)*2H2O
Chemical name
Calcium Sulfate
Mineral name
Gypsum
Chemical formula
Ca(SO4)*2H2O
Crystal system
monoclinic
Crystal Class
monoclinic-prismatic (2/m)
Space Group
A2/a
Unit cell
a [Å]:6.52
b [Å]:15.18
c [Å]:6.29
Formula units
Z=4
Frequent crystal surfaces
{010}
Twinning
very common on {001}, contact twins
Mohs hardness
2
Density [g/cm3]
2.3 - 2.4
Cleavage
perfect on {010}, distinct on {100}
Fracture / Tenacity
flexible, inelastic, conchoidal on {100}, splintery parallel to [100]
Color
colorless to white, yellow, tan, blue, pink, brown, reddish brown, gray
Streak
white
Transparency
transparent to translucent
Optical character
biaxial (+)
Refractive Index
nα=1.519-1.521; nβ=1.522-1.523; nΥ=1.529-1.530
Birefringence δ
0.010
Pleochroism δ
none