UnevenArthur Thomas, Gemstones (2009) Tough, UnevenArthur Thomas, Gemstones (2009) Tough, Brittle, Uneven
Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Mn 8Si 6O 15(OH,Cl) 10Ulrich Henn and Claudio C.
CaB 2(SiO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references