Gemstones of the world (2001), Difficult, Splintery
ConchoidalWalter Schumann, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2 Jadeite: NaAlSi2O6
Be 2BO 3(OH)Ulrich Henn and Claudio C.