Uneven, Subconchoidal, Uneven, Subconchoidal, Conchoidal, Brittle
Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
NaAlSi 2O 6 · H 2OMichael OâDonoghue , Gems, Sixth edition (2006) More from other references
SiCArthur Thomas , Gemstones (2009)