Brittle, UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
Uneven, Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Uneven, Subconchoidal, Brittle, Metallic, Brittle, Metallic
(Mg,Fe)Al 3(BO 4)(SiO 4)OUlrich Henn and Claudio C.
Zn 2(AsO 4)(OH)Michael OâDonoghue , Gems, Sixth edition (2006)