In 2015, 27.6 million metric tons of marketable phosphate rock, or phosphorite, was mined in the United States, making the US the world's third-largest producer, after China and Morocco. The phosphate mining industry employed 2,200 people. The value of phosphate rock mined was US$2.2 billion.
As of 2015, there are 10 active phosphate mines in four states: Florida, North Carolina, Idaho, and Utah. The eastern phosphate deposits are mined from open pits. The western deposits are mined from both surface and underground mines.
The exact phosphate content of the phosphate rock mined in 2015 is not available, but in the latest five-year period for which ore grades are available, 2009-2013, the grade of US phosphate rock varied from 28.5 to 29.0 percent P2O5.
As of 2016, remaining reserves of phosphate rock in the United States totaled 1.1 billion metric tons.[1]
Industry structure
As of 2017, there were 11 active phosphate mines in the US, operated by 5 companies. In addition, one mine in Idaho was in permitting and development status.
Many phosphate processing plants are located at the mines. In addition, some processing plants are located remote from the mines. Some process imported phosphate rock.
Use
Phosphorus is an essential component of fertilizer. In 2013, about 90 percent of phosphate rock was used in fertilizer manufacture. Other uses included animal feed and detergents.[4]
Geography
The states mining phosphate rock as of early 2016 were, in descending order of tonnage mined: Florida, North Carolina, Idaho, and Utah. In 2016, 65 percent of US phosphate was mined in Florida.
Central Florida / Bone Valley / Florida Land-Pebble
The Bone Valley mining district, also known as the Central Florida district, or the Florida Land-Pebble district, is centered in Polk County, Florida, and extends into Hardee, Hillsborough, and Manatee counties. As of 2013, phosphate was being extracted from five mines in the district, all operated by Mosaic.[5]
Florida Hard Rock
The Florida Hard Rock district mines phosphate from a belt up to 30 miles (48km) wide and 150 miles (240km) long, extending from Tallahassee on the west to Pasco County on the east. Phosphate deposits occur in Bradford County, Hamilton, and Union counties.
One mine is currently operating in the Hard Rock district: The Swift Creek mine, operated by Nutrien Ltd, in Hamilton County, Florida.
Beaufort County, North Carolina
The North Carolina phosphate deposit was discovered in 1955.[6] Phosphate is currently being extracted at the Aurora mine, operated by Nutrien Ltd.
Mining started in the central Tennessee phosphate district in 1896. Counties where mining took place included Giles, Hickman, Maury, and Williamson. The district has been inactive since 1991.[8] It is regarded as largely exhausted.
Parts of the Phosphoria Formation of the western United States carry economic grades of phosphorus. The Phosphoria has been mined in a wide area stretching north-south from southwest Montana, through western Wyoming and southeast Idaho, and into northeast Utah.[9]
Phosphate rock from the JR Simplot mine near Vernal, Utah, is crushed at the mine, then transferred in a slurry pipeline to the company's processing plant at Rock Springs, Wyoming.[10][11]
Although some igneous rocks have economic grades of phosphate, no igneous phosphate rock is mined in the US. Small amounts of phosphate were mined from igneous apatite deposits in Virginia, New Jersey, and New York. But since 1948, all phosphate deposits mined in the US have been sedimentary deposits. However, a small amount of phosphate was produced in the 1970s, as a byproduct of iron mining in Missouri.[12]
Most phosphate mining is of sedimentary phosphorite, a phosphorus-rich deposit formed under shallow marine conditions. However, a number of US phosphate deposits occur where the original marine-deposited phosphate minerals have been concentrated by weathering and redeposition, often under nonmarine conditions.
The Florida Hard Rock district mines phosphate from the Alachua Formation of Pliocene age. The Alachua Formation is nonmarine and consists of sediments rich in phosphate that was weathered from the Hawthorne Formation of Miocene age.[13]
North Carolina
The North Carolina phosphate deposit occurs in the Pungo River Formation of Miocene age.[14] The phosphate was deposited under shallow marine conditions.[15]
South Carolina
The South Carolina river-pebble deposits formed along modern rivers which reworked and concentrated lower-grade phosphate deposits.
Tennessee
Three classes of phosphate deposits have been mined in central Tennessee; in order of decreasing importance: brown phosphate rock, blue phosphate rock, and white phosphate rock.[16]
The most important phosphate deposits were the so-called brown phosphate rock, mined from Ordovicianlimestones, some parts of which are rich in phosphate. The highest-grade deposits were found where weathering or shallow groundwater had preferentially dissolved away the calcium carbonate. The last mine in Tennessee, which produced phosphate rock from the Bigby-Cannon formation, closed in 1991.
Minor phosphate production was mined from white phosphate rock, which formed in karstedSilurian limestones.
Western US, Phosphoria
The western deposits, in Utah, Wyoming, Idaho, and Montana, are in the Phosphoria Formation of Permian age. The phosphate deposits occur in two members of the Phosphoria: the Retort phosphatic shale member in the upper part of the formation, and the Meade Peak phosphatic shale member in the lower part of the formation.
Phosphate rock mined in the United States, 1900-2015 (data from US Geological Survey)
Large-scale phosphate mining in the US began in 1868 in coastal South Carolina. Access to river transport and proximity to the port of Charleston encouraged exports, and by 1885 South Carolina was producing half the world's phosphate. Phosphate mining in South Carolina declined rapidly in the 1890s, when mining of the higher-grade deposits in central Florida began. The central Florida district has provided the majority of US phosphate ever since.
US production of phosphate rock peaked in 1980 at 54.4 million metric tons. The United States was the world's largest producer of phosphate rock from at least 1900, up until 2006, when US production was exceeded by that of China. In 2015, the US produced 12 percent of the world's phosphate rock.
For each ton of phosphoric acid produced by the processing of phosphate rock, five tons of waste are generated. This waste takes the form of impure, useless, radioactive solid called phosphogypsum. Somewhere between 100,000,000 and 280,000,000 tons of phosphogypsum waste is estimated to be produced annually worldwide.[17]
Phosphorite typically contains more than 3% fluoride, in the mineral fluorapatite. Only a small amount is recovered.
In 2015, fluorosilicic acid equivalent to 114,000 tons of fluorite (fluorspar) was produced as a byproduct of phosphate rock processing. This material represented nearly all the US production of fluoride, which is subsequently converted to fluorine. The produced fluorine is used to prepare polymers, pharmaceuticals, etc.
Uranium
The phosphorite deposits of Florida and of the western states contain from 0.005 to 0.02 percent uranium. Phosphorite deposits contain sufficient uranium to be an economic source when the price of uranium is high.
Uranium was extracted at two phosphate plants in the central Florida district from 1952 to 1961, and at seven plants during the period 1976-1998. The average uranium recovery was about 0.9 pounds (0.41kg)U3O8 per metric ton of P2O5.[19] However, uranium recovery is feasible only from the process that produces double superphosphate;[why?] most phosphate is processed into normal superphosphate, a process not amenable to uranium recovery.[20]
Although no uranium has been recovered from US phosphate plants since 1998, the Central Florida phosphate deposits remain North America's largest uranium resource, containing an estimated one million tons of uranium.[21]
Vanadium
Some parts of the Phosphoria Formation, which is mined for phosphate in the western US, contain potentially economic concentrations of vanadium. In 2008, Rocky Mountain Resources announced that they had defined 6.7 million tons of ore containing 0.88 percent V2O5, at its Paris Hills prospect. The vanadium occurred in an 11-foot-thick (3.4m) bed in the Meade Peak shale member of the Phosphoria, immediately below a 15-foot (4.6m) bed of ore-grade phosphate rock.[22] The property has since been sold to Stonegate Agricom, and as of mid-2016 was still in permitting and development status.[23]
As of 2015, no vanadium was being recovered from US phosphate operations.[24]
International trade
Annual net imports (positive) and net exports (negative) into the United States of phosphate rock, 1900-2015 (data from US Geological Survey)
The US was a long-time exporter of phosphate rock, and from the 1960s into the 1990s a major exporter. The US became a net importer of phosphate rock for the first time in 1996. Since then the US has been a net importer each year. In 2015, the US imported about 12 percent of the phosphate it used.
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid, aka. phosphoric acid H3PO4.
Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock that 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. 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 (grain sizes < 1 μm) 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.
The Bone Valley is a region of central Florida, encompassing portions of present-day Hardee, Hillsborough, Manatee, and Polk counties, in which phosphate is mined for use in the production of agricultural fertilizer. Florida currently contains the largest known deposits of phosphate in the United States.
Uranium mining is the process of extraction of uranium ore from the ground. Over 50 thousand tons of uranium were produced in 2019. Kazakhstan, Canada, and Australia were the top three uranium producers, respectively, and together account for 68% of world production. Other countries producing more than 1,000 tons per year included Namibia, Niger, Russia, Uzbekistan, the United States, and China. Nearly all of the world's mined uranium is used to power nuclear power plants. Historically uranium was also used in applications such as uranium glass or ferrouranium but those applications have declined due to the radioactivity of uranium and are nowadays mostly supplied with a plentiful cheap supply of depleted uranium which is also used in uranium ammunition. In addition to being cheaper, depleted uranium is also less radioactive due to a lower content of short-lived 234 U and 235 U than natural uranium.
Uranium mining in the United States produced 173,875 pounds (78.9 tonnes) of U3O8 in 2019, 88% lower than the 2018 production of 1,447,945 pounds (656.8 tonnes) of U3O8 and the lowest US annual production since 1948. The 2019 production represents 0.3% of the anticipated uranium fuel requirements of the US's nuclear power reactors for the year.
Copper mining in the United States has been a major industry since the rise of the northern Michigan copper district in the 1840s. In 2017, the United States produced 1.27 million metric tonnes of copper, worth $8 billion, making it the world's fourth largest copper producer, after Chile, China, and Peru. Copper was produced from 23 mines in the US. Top copper producing states in 2014 were Arizona, Utah, New Mexico, Nevada, and Montana. Minor production also came from Idaho, and Missouri. As of 2014, the US had 45 million tonnes of known remaining reserves of copper, the fifth largest known copper reserves in the world, after Chile, Australia, Peru, and Mexico.
Gold mining in the United States has taken place continually since the discovery of gold at the Reed farm in North Carolina in 1799. The first documented occurrence of gold was in Virginia in 1782. Some minor gold production took place in North Carolina as early as 1793, but created no excitement. The discovery on the Reed farm in 1799 which was identified as gold in 1802 and subsequently mined marked the first commercial production.
Phosphogypsum (PG) is the calcium sulfate hydrate formed as a by-product of the production of fertilizer from phosphate rock. It is mainly composed of gypsum (CaSO4·2H2O). Although gypsum is a widely used material in the construction industry, phosphogypsum is usually not used, but is stored indefinitely because of its weak radioactivity caused by the presence of naturally occurring uranium (U) and thorium (Th), and their daughter isotopes radium (Ra), radon (Rn) and polonium (Po). The long-range storage of phosphogypsum is controversial. About five tons of phosphogypsum are generated per ton of phosphoric acid production. Annually, the estimated generation of phosphogypsum worldwide is 100 to 280 million metric tons.
Uranium mining in Colorado, United States, goes back to 1872, when pitchblende ore was taken from gold mines near Central City, Colorado. The Colorado uranium industry has seen booms and busts, but continues to this day. Not counting byproduct uranium from phosphate, Colorado is considered to have the third largest uranium reserves of any US state, behind Wyoming and New Mexico.
Uranium mining in Wyoming was formerly a much larger industry than it is today. Wyoming once had many operating uranium mines, and still has the largest known uranium ore reserves of any state in the U.S. At the end of 2008, the state had estimated reserves dependent on price: 539 million pounds of uranium oxide at $50 per pound, and 1,227 million pounds at $100 per pound.
Uranium mining in Utah, a state of the United States, has a history going back more than 100 years. Uranium mining started as a byproduct of vanadium mining about 1900, became a byproduct of radium mining about 1910, then back to a byproduct of vanadium when the radium price fell in the 1920s. Utah saw a uranium boom in the late 1940s and early 1950s, but uranium mining declined in the 1980s. Since 2001 there has been a revival of interest in uranium mining, as a result of higher uranium prices.
Uranium ore deposits are economically recoverable concentrations of uranium within the Earth's crust. Uranium is one of the most common elements in the Earth's crust, being 40 times more common than silver and 500 times more common than gold. It can be found almost everywhere in rock, soil, rivers, and oceans. The challenge for commercial uranium extraction is to find those areas where the concentrations are adequate to form an economically viable deposit. The primary use for uranium obtained from mining is in fuel for nuclear reactors.
Uranium mining in Arizona has taken place since 1918. Prior to the uranium boom of the late 1940s, uranium in Arizona was a byproduct of vanadium mining of the mineral carnotite.
Uranium mining in New Mexico was a significant industry from the early 1950s until the early 1980s. Although New Mexico has the second largest identified uranium ore reserves of any state in the United States, no uranium ore has been mined in New Mexico since 1998.
The following outline is provided as an overview of and topical guide to mining:
Vincent Ellis McKelvey was an American geologist and earth scientist. Recognized as an international authority on deep-sea mineral deposits, he spent 46 years with the United States Geological Survey. From 1968 to 1982, he served as scientific adviser and senior deputy to the United States delegation to the Law of the Sea Conference of the United Nations, where fellow delegates often depended on his ability to render complex scientific issues into plain English.
The South Pass greenstone belt is located within the Wyoming craton in the US. The region was the site of Wyoming's initial gold discovery in 1842.
The Phosphoria Formation of the western United States is a geological formation of Early Permian age. It represents some 15 million years of sedimentation, reaches a thickness of 420 metres (1,380 ft) and covers an area of 350,000 square kilometres (140,000 sq mi).
The world's largest producer of uranium is Kazakhstan, which in 2019 produced 43% of the world's mining output. Canada was the next largest producer with a 13% share, followed by Australia with 12%. Uranium has been mined in every continent except Antarctica.
The geology of Niger comprises very ancient igneous and metamorphic crystalline basement rocks in the west, more than 2.2 billion years old formed in the late Archean and Proterozoic eons of the Precambrian. The Volta Basin, Air Massif and the Iullemeden Basin began to form in the Neoproterozoic and Paleozoic, along with numerous ring complexes, as the region experienced events such as glaciation and the Pan-African orogeny. Today, Niger has extensive mineral resources due to complex mineralization and laterite weathering including uranium, molybdenum, iron, coal, silver, nickel, cobalt and other resources.
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