Xonotlite: Gemstones Information
Xonotlite is Ca6Si6O17(OH)2 and forms needle-like translucent chalky white to bluish grey crystals or fibrous masses in the monoclinic or triclinic system with one direction of perfect cleavage, hardness 6– 6.5 and SG 2.71–2.72. The RI for the alpha, beta and gamma rays is 1.581–1.583, 1.581–1.583 and 1.591–1.593, biaxial positive. The birefringence is 0.010. Xonotlite occurs in contact metamorphic deposits within limestones and serpentines. Specimens are found at Tetela de Xonotla,Puebla, Mexico.