Tenacity
Solubility
Durability
Specific Gravity
Fracture
Cleavage
Mohs Hardness
Chemical Composition
Uneven, Subconchoidal, Splintery
Good on {110}, poor on {100}
Al 2SiO 5Michael OâDonoghue , Gems, Sixth edition (2006) More from other references
ConchoidalWalter Schumann
Perfect on {010}, good on {100}
Be 2BO 3(OH)Ulrich Henn and Claudio C.