Gemstones of the world (2001), Difficult, Splintery
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2 Jadeite: NaAlSi2O6
Pb 5(AsO 4) 3ClMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references