ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Uneven, Brittle, Metallic, Brittle, Metallic, Brittle, Metallic
SiO 2Ulrich Henn and Claudio C.
(Na,Fe,Ca)Si 2O 6Ulrich Henn and Claudio C.