ConchoidalWalter Schumann, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Uneven, UnevenArthur Thomas, Gemstones (2009)
Be 2BO 3(OH)Ulrich Henn and Claudio C.
KCa 4Si 8O 20(F,OH) · 8H 2OUlrich Henn and Claudio C.