What is "wollastonite"

Wollastonite \Wol"las*ton*ite\, n. [After Dr. W. H. Wollaston, an English chemist, who died in 1828.] (Min.) A silicate of lime of a white to gray, red, or yellow color, occurring generally in cleavable masses, rarely in tabular crystals; tabular spar.

n. (context mineralogy English) A grey inosilicate mineral, mostly calcium silicate, calciumsiliconoxygen₃, found deposited in limestone.

n. a white or grayish mineral typically found in metamorphic limestone; a silicate of calcium

Wollastonite is a calcium inosilicate mineral ( Ca Si O) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or dolostone is subjected to high temperature and pressure sometimes in the presence of silica-bearing fluids as in skarns or contact metamorphic rocks. Associated minerals include garnets, vesuvianite, diopside, tremolite, epidote, plagioclase feldspar, pyroxene and calcite. It is named after the English chemist and mineralogist William Hyde Wollaston (1766–1828).

Some of the properties that make wollastonite so useful are its high brightness and whiteness, low moisture and oil absorption, and low volatile content. Wollastonite is used primarily in ceramics, friction products (brakes and clutches), metalmaking, paint filler, and plastics.

Despite its chemical similarity to the compositional spectrum of the pyroxene group of minerals—where magnesium and iron substitution for calcium ends with diopside and hedenbergite respectively—it is structurally very different, with a third SiO tetrahedron in the linked chain (as opposed to two in the pyroxenes).