Tenacity
Solubility
Durability
Specific Gravity
Fracture
Cleavage
Mohs Hardness
Chemical Composition
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001)
Perfect on {100}, imperfect on {001}
PbCu(SO 4)(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006)