Calcium metasilicate (CaSiO₃), with CAS number 10101-39-0, is an inorganic compound. It is a white or off-white powder that is insoluble in water. It is a primary component of the mineral wollastonite, which is its most common natural form. Its primary industrial application is as a functional filler and reinforcing agent in various materials. It is widely used in plastics, ceramics, paints, coatings, and construction materials (e.g., cement, wallboard) to improve mechanical properties, dimensional stability, whiteness, and weather resistance. It also serves as a flux in metallurgy and in the production of welding rod coatings. Additionally, due to its chemical stability and low moisture absorption, it finds use as an anti-caking agent and flow aid in industrial processes and some agricultural applications. It is generally considered a low-toxicity material with good environmental compatibility.