Tenacity
Solubility
Durability
Specific Gravity
Fracture
Cleavage
Mohs Hardness
Chemical Composition
SiO2, Al2O3, FeO, MgO, CaO, K2O, Na2O
{111} Indistinct, {111} Indistinct, {111} Indistinct
(K,Cs)Al 4Be 4(B,Be) 12O 28Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references