Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Gemstones of the world (2001), Difficult, Splintery
KNa 2Li(Fe2+ ,Mn2+ ) 2Ti 2Si 8O 24Michael OâDonoghue , Gems, Sixth Edition (2006)
Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2 Jadeite: NaAlSi2O6