Phosphorite mining

The phosphates of lime are the most valuable natural fertilisers and raw material of the fertiliser and phosphorus industry, which uses also to a less extent phosphates of aluminium and the apatites. Over 80 per cent, of the easily decomposible phosphorites mined are used in the preparation of superphosphate or other fertilisers (1980). 

The ultimate sources of nitrogen and phosphorus causing cultural eutrophication are industrial N2 fixation, fossil-fuel burning, and the mining of phosphorite. The nitrogen and phosphorus used as fertilizer have three possible 6tes they either enter the food chain, become part of the soil, or are washed off the land by stormwater runoff The nutrients that enter the food chain eventually end up as either animal wastes or dead biomass. Animal wastes include human sewage, livestock manure, and pet feces. Sanitary... 

It is an interesting fact that the two elements most necessary in the maintenance of soil fertility are the related elements nitrogen and phosphorus, which occupy adjacent positions in Group V of the periodic table. Phosphorus occurs in nature only in the combined form, chiefly as the mineral phosphorite [Ca3P04)2]. Impure calcium phosphate, known as phosphate rock, is mined extensively in Tennessee, Florida, Montana, and Idaho. Large deposits of this mineral are also found in Morocco and Tunisia in North Africa. 

Significant commercial deposits of sedimentary phosphate ore occur in the United States, the Former Soviet Union, Morocco, China, Jordan, and Tunisia, and lesser deposits are mined in many other countries. Although phosphorite ores generally are classified as having siliceous or carbonate gangue minerals, soluble salts and organic material are also of concern. The phosphate content of the ores,... 

Poorly crystalline or amorphous Phosphorite sediments made from the hard remains of marine organisms are the principal commercial source of phosphates, although Apatites are also mined. Treatment of phosphate minerals with sulfuric acid yields superphosphate fertilizer, a mixture of Ca(H2P04)2, H3PO4 and CaS04. Phosphoric acid treatment gives triple superphosphate , rich in Ca(H2P04)2. Other soluble fertilizers such as ammonium phosphates are obtained from these products. 

The mining of phosphate rock (mostly from terrestrially emplaced marine phosphorite deposits) for use as agricultural fertilizer has increased dramatically in the latter half of this century (F72). In addition to fertilizer use, deforestation, increased cultivation, urban and industrial waste disposal all have enhanced phosphorus transport from terrestrial to aquatic systems, often with deleterious results. For example, elevated phosphorus concentrations in rivers resulting from these activities have resulted in eutrophication in some lakes and coastal areas, stimulating nuisance algal blooms and promoting hypoxic or anoxic conditions harmful or lethal to natural populations (e.g., Caraco, 1995 Fisher et al., 1995 Melack, 1995). 

In Florida, fluoride and phosphate are chemically and industrially associated. Phosphate deposits in Florida occur as sedimentary phosphorite of Miocene age (10-15 million years old). The principal mineral is apatite, Ca5(P04)3F, containing about 4% fluorine. The deposits are centered in a 500-sq mile area around Bartow. Mining was initiated in 1890, and in 1972, Florida produced more than 30 million tons of phosphate valued at about 170 million. Florida supplies over three-fourths of United States needs and roughly one-third of the world needs (7). 

Dietz, R.S. and Emery, K.O., 1950. Submarine phosphorite deposits off California and Mexico. Calif. J. Mines Geol., 46 7—15. 

The most important manifestation of hyperfluoric status is dental and skeletal fluorosis. In regions of volcanic activity, and in some arid zones and areas where phosphorites and apatites are mined and processed, agricultural animals and population often suffer from endemic and civilization-related fluorosis that mostly affects the teeth and skeleton. There arises the problem of reproduction and maintenance of dairy cattle (Ermakov etal. 1998, Ermakov 2001). In toxic quantities, fluorides impair the metabolism of calcium and synthesis of bone collagen by stimulating bone accretion, and speed up bone resorption and total calcium turnover in the body (Susheela and Mukher-jee 1981). 

The unique settings in which phosphorites form, those areas where phosphate is concentrated millions of times above normal and sedimentation rates are drastically slowed, are not fully understood, and have been the subject of sometimes intense scientific debate over the last century and a half Furthermore, the mineralogy of these deposits is unique, difficult to study, and contentious. Because of our dependence on phosphate for use in fertilizers and other agricultural and chemical uses, these deposits are interesting not only from a scientific viewpoint but from an economic standpoint as well. However, like many mining operations, phosphate mining has environmental problems that must be addressed. 

This chapter provides an overview of the salient points in phosphorite formation, mineralogy, and mining and puts into context the current work being undertaken on the Phosphoria Formation in southeastern Idaho. This chapter does not provide a full description of all the sedimentalogical, mineralogical, and industrial work that has been done on sedimentary phosphates indeed numerous full volumes have been published on phosphorites and more will undoubtedly follow. 

Phosphorous is one of the essential nutrients for both plant and animal life. As the human population grows, humankind has become increasingly dependent on the use of manufactured fertilizers, and thus on phosphorous. Sedimentary phosphates account for over 90% of the total mined phosphorous. Like any ore body, economic phosphorites must be highly concentrated and relatively easy to extract. These extra demands make ore-producing phosphorites an important subgroup of phosphorites. 

Apatite also occurs (less abundantly) as igneous phosphate rock which is highly crystalline and much purer than sedimentary phosphorite. Commercially important igneous rock formations of crystalline fluorapatite are found in the Kola peninsula (Khibiny) of Russia, South Africa (Palabora), Brazil (Jacupiranga) with smaller deposits in Uganda, Finland, South Norway and South Sweden. All these deposits, however, at present account for less than 15% of the world total of mined apatite. 

Certain rare phosphate minerals such as Monazite, (Ce,Li,Th)P04 and Xenotime, YPO4, are important sources of rare earth elements which they frequently contain as impurities. Monazite, which is mined in Brazil, Travancore and Australia, is the most important commercial source of thorium (Chapter 3.5). One commercial source of lithium is Nalipoite, NaLi2P04, which is present in some natural brines. Phosphorite ore itself is a potentially valuable source of Uranium (Chapter 5). A few orthophosphate minerals are sometimes useful as gemstones (Table 5.23). 

Phosphorite was first mined in Snffolk, England, in 1847 and soon after in a few other places in Europe. Igneous apatite was first mined in Norway in 1851. Operations have long since ceased at most of these sites, however, and overall European prodnction is now very small compared to the rest of the world. 

Workable apatite deposits occur mostly near the earth s surface in sfiata varying from a few inches to over 30 ft. About 80% of the world s phosphorite is obtained by open-cast mining methods. 

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