UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Brittle, UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
Ca 2(Mg,Al) 6(Si,Al,B) 6O 20Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
(Mg,Fe)Al 3(BO 4)(SiO 4)OUlrich Henn and Claudio C.