ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Uneven, Sub-Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Al 2Be 3Si 6O 18Martin H.
ZnCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references