Conchoidal, Conchoidal, Gemstones of the world (2001) More from other references
Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
SiO 2 · nH 2OGemdat.org , Management Team (2012)
(Be,Cs) 3Al 2Si 6O 18 · 0.5H 2OUlrich Henn and Claudio C.