Uneven, Conchoidal, Brittle, Metallic, ConchoidalArthur Thomas, Gemstones (2009)
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Ca 3Cr 2(SiO 4) 3Ulrich Henn and Claudio C.
MgCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references