Tenacity
Solubility
Durability
Specific Gravity
Fracture
Cleavage
Mohs Hardness
Chemical Composition
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001)
Rare tabular and prismatic crystals. Usually occurs as fibrous, parallel veins that break off into cleavage fragments.
CaSO 4Michael OâDonoghue , Gems, Sixth edition (2006) More from other references