Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Conchoidal, Brittle
Uneven, UnevenArthur Thomas, Gemstones (2009), Brittle
Mg 2SiO 4Michael OâDonoghue , Gems, Sixth Edition (2006)
MnPO 4Walter Schumann , Gemstones of the world (2001) More from other references