Anhydrite
Type
Non-clastic chemical sedimentary rock
It is considered an evaporite mineral.
Grain Size
Fine to medium-grained crystalline
- Crystalline texture
- Often appears as a compact mass with no discernible grains
Color
White to light gray, sometimes tinged with blue, pink, or purple due to impurities
Granule Shape
Crystalline or blocky
- Crystals are usually triangular in shape, but may be interlocking.
- Cleavage surfaces are sometimes evident.
Sorting
Not classifiable by sorting because it does not contain clastic grains - rather it is the result of direct chemical precipitation
Cohesion
Well bonded
- Harder than gypsum
- Does not dissolve as easily as halite
- Can be scratched, but requires a sharper tool than fingernails
Chemical Formula
→ CaSO₄ Anhydrous calcium sulfate (like gypsum, but without water)