ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
UnevenArthur Thomas, Gemstones (2009) Tough, UnevenArthur Thomas, Gemstones (2009) Tough, Brittle, Uneven
MgAlBO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Mn 8Si 6O 15(OH,Cl) 10Ulrich Henn and Claudio C.