Phosphorite

[2] The phosphate is present as fluorapatite Ca5(PO4)3F typically in cryptocrystalline masses (grain sizes < 1 μm) referred to as collophane-sedimentary apatite deposits of uncertain origin.

Phosphorite deposits often occur in extensive layers, which cumulatively cover tens of thousands of square kilometres of the Earth's crust.

Phosphatic sedimentary rocks are commonly accompanied by or interbedded with shales, cherts, limestone, dolomites and sometimes sandstone.

[4] These layers contain the same textures and structures as fine-grained limestones and may represent diagenetic replacements of carbonate minerals by phosphates.

[2] Commercially mined phosphorites occur in France, Belgium, Spain, Morocco, Tunisia, Saudi Arabia[5] and Algeria.

In the United States phosphorites have been mined in Florida, Tennessee, Wyoming, Utah, Idaho and Kansas.

[9] Depending on the pH and salinity levels of the ocean water, organic matter will decay, releasing phosphorus from sediment in shallow basins.

Bacteria and enzymes dissolve organic matter on the water–bottom interface, thus returning phosphorus to the beginning of its biogenic cycle.

Tidal flat systems are created along open coasts and relatively low wave energy environments.

Since they are in the seaward section of the drowned valley system they receive sediment from both marine and fluvial sources.

Upwelling is caused by deep water currents that are brought up to coastal surfaces where a large deposition of phosphorites may occur.

This is because coastal estuaries contain a high productivity of phosphorus from marsh grass and benthic algae which allow an equilibrium exchange between living and dead organisms.

[13] As of December 2018[update], the world's total economic demonstrated resource of rock phosphate is 70 gigatonnes,[14] which occurs principally as sedimentary marine phosphorites.

[citation needed] Approximately 90% of rock phosphate production is used for fertilizer and animal feed supplements and the balance for industrial chemicals.

[1] In addition, phosphorus from rock phosphate is also used in food preservatives, baking flour, pharmaceuticals, anticorrosion agents, cosmetics, fungicides, insecticides, detergents, ceramics, water treatment and metallurgy.

According to a report for the FAO, it can be more sustainable to apply rock phosphate as a fertilizer in certain soil types and countries, although it has many drawbacks.

According to the report it may have higher sustainability compared to more concentrated fertilizers because of reduced manufacturing costs and the possibility of local procurement of the refined ore.[1] Rare earth elements are being found within phosphorites.

With yields greater than those from deposits in China, phosphorites offer a new resource located within the U.S. that would likely lead to independence from influence of countries outside of the U.S.[18]