Uneven, Conchoidal, Brittle
Uneven, Sub-Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
(Na,Ca)4-8Al6Si6(O,S)24(SO4,Cl)1-2
ZnCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references