Uneven, Conchoidal to uneven, Brittle, Metallic, Uneven, ConchoidalWalter Schumann, Brittle, Metallic
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
BeAl 2 O 4
Ca 2(Mg,Al) 6(Si,Al,B) 6O 20Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references