Uneven, Brittle, Metallic, Brittle, Metallic, Brittle, Metallic
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
(Na,Fe,Ca)Si 2O 6Ulrich Henn and Claudio C.
ThCa 2Si 8O 20Walter Schumann , Gemstones of the world (2001) More from other references