Tenacity
Solubility
Durability
Specific Gravity
Fracture
Cleavage
Mohs Hardness
Chemical Composition
ConchoidalWalter Schumann
Perfect on {010}, good on {100}
Be 2BO 3(OH)Ulrich Henn and Claudio C.
ConchoidalWalter Schumann
SiO 2Walter Schumann , Gemstones of the world (2001)