Routes to reduction of phosphate by high-energy events.

Phosphate minerals such as those in the apatite group tend to be the dominant forms of phosphorus in minerals on the Earth's surface. Phosphate can be reduced to phosphides during high-energy events, such as lightning and impacts. Here we show that, in addition to formation of metal phosphides, a new compound was formed by lightning in a fulgurite from New Port Richey, Florida, USA. A calcium phosphite material, ideally CaHPO 3 , was found in spherules mainly consisting of iron silicides that formed by lightning-induced fusion of sand around a tree root. This phosphite material bears a phosphorus oxidation state intermediate of that of phosphides and phosphates in a geologic sample and implicates phosphites as being potentially relevant to other high-energy events where phosphorus may partially change its redox state, and material similar to this phosphite may also be the source of phosphite that makes up part of the phosphorus biogeochemical cycle.