Tenacity
Solubility
Durability
Specific Gravity
Fracture
Cleavage
Mohs Hardness
Chemical Composition
Perfect on [001] imperfect on [100]
(K,Na) 3(Fe2+ ,Mn) 7Ti 2Si 8O 24(O,OH) 7Anthony et al , Handbook of mineralogy (2001)
Subconchoidal, Uneven, Conchoidal
(Mg,Fe2+ ) 9(SiO 4) 4(F,OH)) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references