Uneven, Sub-Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Conchoidal
ZnCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
(Mg,Fe,Zn)Al 6BeO 12Ulrich Henn and Claudio C.