Uneven, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Conchoidal, ConchoidalWalter Schumann, Gemstones of the world (2001)
Ag 3AsS 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
SiO 2Ulrich Henn and Claudio C.