Conchoidal, Conchoidal, Gemstones of the world (2001)
Uneven, Sub-Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001) More from other references
ZnCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references