Tags: Chemical Substance, Mineral.
Anhydrite is a mineral—anhydrous calcium sulfate CaSO4. It is in the orthorhombic crystal system with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the orthorhombic barium (baryte) and strontium (celestine) sulfates as might be expected from the chemical formulas. Distinctly developed crystals are somewhat rare the mineral usually presenting the form of cleavage masses. The hardness is 3.5 and the specific gravity 2.9.
