Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Subconchoidal, Uneven, Conchoidal, Uneven
Fe 2O 3Arthur Thomas , Gemstones (2009)
Mn2+ Al(PO 4)(OH) 2H 2OMichael OâDonoghue , Gems, Sixth Edition (2006)