Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Uneven, Brittle, Metallic, Gemstones (2009)
Fe 2O 3Arthur Thomas , Gemstones (2009)
Na 2[Al 2Si 3O 10] · 2H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references