Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Uneven, Uneven, Gemstones of the world (2001) More from other references
KAlSi 2O 6Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Ca 10Mg 2Al 4(SiO 4) 5(Si 2O 7) 2(OH) 4Ulrich Henn and Claudio C.