Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Ca 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)
(Zn,Mn2+ )OMichael OâDonoghue , Gems, Sixth Edition (2006)