ConchoidalAnthony et al, Handbook of mineralogy (2001), ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
CaBe 2(PO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006)
(Fe,Mn) 7Si 7O 21Ulrich Henn and Claudio C.