Uneven, Subconchoidal, Uneven, Subconchoidal, Conchoidal, Brittle
Conchoidal, Conchoidal, Gemstones of the world (2001)
NaAlSi 2O 6 · H 2OMichael OâDonoghue , Gems, Sixth edition (2006) More from other references
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001)