Uneven, UnevenArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Uneven, Sub-Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
(Na,Ca) 8Al 6Si 6O 24(SO 4,S,Cl) 2Ulrich Henn and Claudio C.
ZnCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references