ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Uneven, Subconchoidal, Uneven, Subconchoidal, Conchoidal, Brittle
SiO 2Ulrich Henn and Claudio C.
NaAlSi 2O 6 · H 2OMichael OâDonoghue , Gems, Sixth edition (2006) More from other references