Gems, Conchoidal, Brittle
Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Ca 3Ti4+2(Fe3+2Si)O 12Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Na 3(Na,K)Al 4Si 4O 16Ulrich Henn and Claudio C.