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