Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Conchoidal, Brittle
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Fe 2SiO 4Michael OâDonoghue , Gems, Sixth Edition (2006)
Mg 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)