page_title: Phosphorite
section_title: Production and use
hierarchical_section_title: Phosphorite / Production and use
context_page_description: Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock that contains high amounts of phosphate minerals. The phosphate content of phosphorite varies greatly, from 4% to 20% phosphorus pentoxide. Marketed phosphate rock is enriched to at least 28%, often more than 30% P₂O₅. This occurs through washing, screening, de-liming, magnetic separation or flotation. By comparison, the average phosphorus content of sedimentary rocks is less than 0.2%. The phosphate is present as fluorapatite Ca₅(PO₄)₃F typically in cryptocrystalline masses referred to as collophane-sedimentary apatite deposits of uncertain origin. It is also present as hydroxyapatite Ca₅(PO₄)₃OH or Ca₁₀(PO₄)₆(OH)₂, which is often dissolved from vertebrate bones and teeth, whereas fluorapatite can originate from hydrothermal veins. Other sources also include chemically dissolved phosphate minerals from igneous and metamorphic rocks. Phosphorite deposits often occur in extensive layers, which cumulatively cover tens of thousands of square kilometres of the Earth's crust.
  Limestones and mudstones are common phosphate-bearing rocks.
caption: Guano phosphorite mining in the Chincha Islands of Peru, c. 1860
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