Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
CaB 2(SiO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)