ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Uneven, UnevenArthur Thomas, Gemstones (2009)
MgAlBO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
KCa 4Si 8O 20(F,OH) · 8H 2OUlrich Henn and Claudio C.