Due to its important role in biological processes, phosphorus is one of the most dispersed elements in Nature. It does not occur as a free element, but is common to find in the phosphate form in about 0,10% of earth's crust. It is the 11th more abundant element occurring in almost all volcanic and sedimentary rocks. Phosphorus occurs in almost all the volcanic rocks, having been present in the volcanic eruptions during the period of Earth formation. The erosion, by water, of the deposits of volcanic phosphates, and later assimilation by prehistoric plants, introduced the phosphorus in the biological mechanisms.
The phosphorus can be found in almost 190 different minerals, but only the apatite series has an important role as phosphorus source. This series is represented by the following formula for a unitary cell Ca10(PO4)6 (F, Cl ou OH)2.
Phosphorus is present in the bony tissues and in the teeth as hydroxyapatite, but the greatest phosphate deposits in Nature are composed mainly by fluorapatite. The deposits of rich phosphate rocks are considered to be 50 thousand million tons. These occur primarily in the Northern Africa and the remaining distributed through the territories of USA and Russia.