Uneven, UnevenArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Uneven, Splintery, Conchoidal, Uneven, Splintery, Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001)
(Na,Ca) 8Al 6Si 6O 24(SO 4,S,Cl) 2Ulrich Henn and Claudio C.
SiO 2Arthur Thomas , Gemstones (2009)