Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Conchoidal, Uneven
Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Mn 3B 7O 13ClMichael OâDonoghue , Gems, Sixth Edition (2006)
Fe 2O 3Arthur Thomas , Gemstones (2009)