Gemstones of the world (2001), Difficult, Splintery
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2 Jadeite: NaAlSi2O6
SrCO 3Walter Schumann , Gemstones of the world (2001) More from other references