calciques

Calciques refers to minerals and rocks that contain calcium as a dominant element in their composition. The term is used in geology and mineralogy, particularly in French-language literature, to distinguish calcium-rich materials from silicate- or aluminous-dominated rocks. Calciques encompass a range of calcium-bearing minerals, including carbonate, sulfate, and phosphate groups such as calcite (CaCO3), aragonite (CaCO3), dolomite (CaMg(CO3)2), gypsum (CaSO4·2H2O), anhydrite (CaSO4), and apatite group minerals (calcium phosphate).

The concept emphasizes calcium as a major component rather than a trace element. In sedimentary environments, calciques often form as biogenic or inorganic carbonates; reef- and shell-building organisms contribute significant calcium carbonate, while diagenetic processes can cement sediments through calcite precipitation.

Geologically, calciques are common in sedimentary rocks such as limestone and dolostone, as well as in evaporite deposits like gypsum and anhydrite. They are economically important as building materials and industrial feedstocks, with limestone and marble used in construction and lime or cement production derived from calcium minerals.

Calciques can display a range of crystal systems and physical properties, reflecting the diversity of calcium-bearing minerals from relatively soft gypsum to harder calcite and dolomite. The term is distinct from calcareous in a broader sense, which describes materials containing calcium carbonate but not necessarily exclusively calcium-based minerals.