Uneven, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Ag 3AsS 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Al 6B 5O 15(F,OH) 3Ulrich Henn and Claudio C.