UnevenArthur Thomas, Gemstones (2009) Tough, UnevenArthur Thomas, Gemstones (2009) Tough, Brittle, Uneven
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Mn 8Si 6O 15(OH,Cl) 10Ulrich Henn and Claudio C.
(K,Cs)Al 4Be 4(B,Be) 12O 28Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references