Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
(Cs,Na)(AlSi 2O 6) · 0.5H 2OWalter Schumann , Gemstones of the world (2001) More from other references
Al 2SiO 5Arthur Thomas , Gemstones (2009)