Brittle, UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
(Mg,Fe)Al 3(BO 4)(SiO 4)OUlrich Henn and Claudio C.
Na 8Al 6Si 6O 24Cl 2Michael OâDonoghue , Gems, Sixth Edition (2006)