Phosphorus is named from the Greek phosphoros, light bearing (ancient name for the planet Venus when appearing before the sunrise) and was isolated in 1699 from urine. Phosphorus is never found free in nature, it is widely distributed in combination with minerals. Phosphate rock, which contains the mineral apatite, an impure tri-calcium phosphate, is an important source of the element. Large deposits are found in Russia, Morocco and in Florida, Tennessee, Utah and Idaho. Ordinary phosphorus is a waxy, white solid, when pure it is colorless and transparent. It is insoluble in water, but soluble in carbon disulfide, and burns spontaneously in air. Phosphorus is important to the agriculture industry as a fertilizer, is used in the glass industry, the steel industry as well as a cleaning agent and water softener. Phosphorus is an essential ingredient of all cell protoplasm, nervous tissue and bones.