calcsilicates

Calcsilicates are calcium-containing silicate minerals and mineral assemblages that form part of calc-silicate rocks. In metamorphic petrology, the term is used to describe minerals in which calcium is a dominant cation paired with silicon-oxygen networks, often with magnesium, iron, aluminum, or other elements. Calcsilicate minerals commonly occur in rocks that have undergone contact metamorphism or metasomatic alteration of carbonate rocks adjacent to silica-rich fluids.

Prominent calcsilicate minerals include wollastonite (CaSiO3), diopside (CaMgSi2O6), hedenbergite (CaFeSi2O6), vesuvianite (Ca6Al2Si9O28(OH,F)4), and garnets such as grossular (Ca3Al2Si3O12). Other minerals associated with calcsilicate assemblages can include scapolite and various calcic amphiboles. These minerals collectively contribute to rock types known as calc-silicate rocks or skarns, which form through chemical exchange between carbonate rocks and surrounding siliceous or aluminous rocks during metamorphism.

Formation and occurrence: calcsilicate rocks typically form in faulted or fault-impacted zones where heat from intruding magma and circulating fluids cause metasomatic reactions in carbonate beds. The resulting mineral assemblages reflect elevated temperatures and the availability of calcium, silicon, and often aluminum and iron. Calcsilicate rocks are commonly found in continental collision zones, near granitic intrusions, and in skarn deposits that may host valuable ore bodies.

Significance and uses: calcsilicate minerals are key indicators of metasomatic and contact metamorphic processes and help define metamorphic grade and fluid history. Industrially, certain calcsilicate minerals, notably wollastonite, are mined for use in ceramics, fillers, paints, and plastics.