Xonotlite is a mineral 6Si )2. It crystallizes in the monoclinic with typically an acicular crystal form or habit. It can be colorless, gray, light gray, lemon white, or pink. It is transparent with a vitreous to silky luster. It leaves a white streak. Xonotlite is rated 6.5 on the Mohs scale of hardness. It was first described in 1866 and named for its occurrence in Tetela de Xonotla. It occurs as veins in serpentinite and contact metamorphism aureoles.