Uneven, Sub-Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
ZnCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)