Phosphorous is a chemical element that exists on Earth as phosphate-containing minerals, typically bound to oxygen. Phosphorous does not exist on Earth as a free element.
Phosphorous is a non-metallic element that comes from certain types of minerals, and exists in four main forms: white, red, violet and black. White phosphorous is the most toxic and least stable of the forms of phosphorous. White phosphorous burns in air and causes burns upon skin contact. Heating white phosphorous or exposing it to light converts it to red phosphorous. Red phosphorous is more stable than its white counterpart and is a major component of matches, pyrotechnics and pesticides. Black phosphorous forms under high pressure, is structurally similar to graphite, and is the most stable of the forms. Violet phosphorous results from the super-heating of red phosphorous.
Phosphorous is an important element on Earth due to its presence in DNA and in adenosine triphosphate, the molecule of energy for cells. It is an important nutrient to plants, but excess phosphorous is a pollutant of waterways when it causes excessive algal blooms that alter stream balance.
The former use of white phosphorous, instead of red, in match production was a major health risk to match factory workers. Exposure to white phosphorous vapors causes wounds in the mouth and eventual degradation of the jaw.