Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Uneven, Subconchoidal, Uneven, Subconchoidal, Splintery, UnevenArthur Thomas, Gemstones (2009)
SiCArthur Thomas , Gemstones (2009)
Al 2SiO 5Michael OâDonoghue , Gems, Sixth edition (2006) More from other references