nonsilicate

Nonsilicate minerals are minerals that do not contain the essential structural component of silicate minerals, the silicon-oxygen tetrahedron (SiO4). They form a diverse set of mineral classes, including oxides, sulfides, carbonates, sulfates, phosphates, halides, and native elements. This group contrasts with silicate minerals, which dominate Earth’s crust.

Representative examples come from several classes. Carbonates such as calcite (CaCO3) and dolomite (CaMg(CO3)2) form in marine and freshwater environments. Sulfates like gypsum (CaSO4·2H2O) and anhydrite (CaSO4) crystallize in evaporite settings. Sulfides such as pyrite (FeS2) and galena (PbS) are common ore minerals. Oxides including magnetite (Fe3O4) and corundum (Al2O3) occur widely, often in igneous and metamorphic rocks. Phosphates such as apatite (Ca5(PO4)3F) are important in biology and industry. Halides like halite (NaCl) and fluorite (CaF2) form in saline environments. Native elements, including gold (Au), copper (Cu), graphite, and diamond, occur as uncombined minerals.

Formation and occurrence: Nonsilicate minerals form through processes such as precipitation from aqueous solutions, evaporative crystallization, hydrothermal activity, and metasomatic alteration. They are common in sedimentary rocks (limestones, evaporites) and ore deposits, as well as in metamorphic and hydrothermal environments. They can appear as discrete crystals, veins, or crusts.

Economic and practical significance: Many nonsilicate minerals are important ore minerals (galena for lead, sphalerite for zinc, magnetite for iron) and industrial materials (gypsum, limestone). Some serve as gemstones (corundum varieties such as ruby and sapphire are oxides; diamonds and other native elements also have economic value).