Brittle, Metallic
Subconchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
CaCuAlSi 2O 6(OH) 3Michael OâDonoghue , Gems, Sixth Edition (2006)
(Mg,Fe2+ ) 9(SiO 4) 4(F,OH)) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references