Gemstones (2009), Flexible Flexible fragments.
Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Al 2Si 4O 10(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Ca 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)