UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Conchoidal, ConchoidalWalter Schumann, Gemstones of the world (2001), Brittle
Ca 2Mg 5Si 8O 22(OH) 2Ulrich Henn and Claudio C.
Be 2SiO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references