Gemstones of the world (2001), Difficult, Splintery
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Conchoidal, Uneven
Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2 Jadeite: NaAlSi2O6
Mn 3B 7O 13ClMichael OâDonoghue , Gems, Sixth Edition (2006)