white, glassy silicate mineral that commonly occurs as masses or tabular crystals with other calcium-containing silicates (e.g., diopside, tremolite, garnet, and epidote) in metamorphosed limestones. Deposits are found in Ciclova Romînă, Rom.; Monte Somma, Italy; and Pargas, Fin. Occurrences in the United States include Utah; Isle Royale, Mich.; Riverside, Calif.; and Essex county, N.Y., where it is mined. For detailed physical properties, see silicate mineral (table).

Wollastonite, the most common of the three forms of calcium silicate, CaSiO₃, is used in many ceramic products, including floor and wall tiles, electrical insulators, and porcelain fixtures. It is also used in welding rod coatings and in paints.