Uneven, Conchoidal, Brittle, Metallic, ConchoidalArthur Thomas, Gemstones (2009)
UnevenWalter Schumann, Gemstones of the world (2001) More from other references, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Uneven
Ca 3Cr 2(SiO 4) 3Ulrich Henn and Claudio C.
(Zn,Fe)SMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references