Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Mg 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)
CaCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references