Rock phosphate is a non-detrital sedimentary rock which contains high amounts of phosphate minerals. The phosphate content of phosphorite (or grade of phosphate rock) varies greatly, from 4% to 20% phosphorus pentoxide (P2O5). Marketed phosphate rock is enriched (“beneficiated”) to at least 28%, often more than 30% P2O5. This occurs through washing, screening, de-liming, magnetic separation or flotation.
Rock phosphate is mined from clay deposits that contain phosphorus and is used to make organic phosphate fertilizers that many gardeners utilize. In the past, rock phosphate was used alone as a fertilizer, but due to a lack in supply, as well as low concentration, most applied fertilizer is processed.
Some of the rock phosphate is processed to extract the elemental phosphorous, which serves as an important feed stock for the chemical industry. However, the most significant application of rock phosphate is in the fertilizers for the agricultural industry. The phosphate rocks used in agricultural applications typically comprise of phosphorous pentoxide (P2O5) in 30% concentration, calcium carbonate in 5% concentration, and 4% or less of aluminum and iron oxides.
Besides, fertilizers and chemicals, the other areas where rock phosphate is applied, include:
- Water Treatment
- Anti-corrosion agents
- Food preservatives
- Animal feed supplements