Uneven, Sub-Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
ZnCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
(Fe,Mn) 7Si 7O 21Ulrich Henn and Claudio C.