Uneven, Sub-Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Irregular, Irregular, Gemstones of the world (2001)
ZnCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
CaCO 3Ulrich Henn and Claudio C.