Brittle, UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
(Mg,Fe)Al 3(BO 4)(SiO 4)OUlrich Henn and Claudio C.
MgCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references