ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Uneven, Gemstones (2009), Splintery
MgAlBO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Ca 2NaHSi 3O 9Ulrich Henn and Claudio C.