Gemstones of the world (2001), Difficult, Splintery
ConchoidalAnthony et al, Handbook of mineralogy (2001), ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2 Jadeite: NaAlSi2O6
CaBe 2(PO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006)