Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
Gemstones of the world (2001), Difficult, Splintery
(Ca,Mn2+ ,Fe2+ ) 3Al 2BSi 4O 15(OH)Anthony et al , Handbook of mineralogy (2001)
Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2 Jadeite: NaAlSi2O6