Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
Gemstones of the world (2001), Difficult, Splintery
(Ca,Fe,Mn,Mg) 3Al 2BSi 4O 15(OH)Walter Schumann , Gemstones of the world (2001) More from other references
Nephrite: Ca2(Mg,Fe)5Si8O22(OH)2 Jadeite: NaAlSi2O6