Fluoride is a naturally occurring element found in the Earth's crust. The primary source of fluoride in the environment, derived from minerals, is the dissolution and weathering of fluoride-bearing minerals. Fluorite (CaF₂) is the most common mineral form of calcium fluoride and is considered the principal mineral source of fluorine. While apatite (especially fluorapatite) is also a significant source, particularly in phosphate rocks (phosphorite), fluorite is the most direct fluoride mineral.