Uneven, Conchoidal, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle
Gemstones of the world (2001), Difficult, Splintery
FeS 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2 Jadeite: NaAlSi2O6