ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Uneven, Brittle, Metallic, Gemstones (2009)
Be 3Al 2Si 6O 18Ulrich Henn and Claudio C.
Na 2[Al 2Si 3O 10] · 2H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references