Conchoidal, Conchoidal, Gemstones of the world (2001)
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001)
ThCa 2Si 8O 20Walter Schumann , Gemstones of the world (2001) More from other references