| 21. | As of 2016, remaining reserves of phosphate rock in the United States totaled 1.1 billion metric tons.
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| 22. | Phosphate rocks contain high levels of fluoride.
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| 23. | "' Phosphogypsum "'refers to the gypsum formed as a by-product of the production of fertilizer from phosphate rock.
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| 24. | The bone-ash process became obsolete when the submerged-arc furnace for phosphorus production was introduced to reduce phosphate rock.
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| 25. | Nauru is a phosphate rock island with rich deposits near the surface, which allowed easy strip mining operations.
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| 26. | Minerals including copper, lead, silver, zinc, bauxite, gold, phosphate rock, magnesite and silica sand are mined in the state.
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| 27. | In 1886, phosphate rock was discovered in the Peace River, and the dominant industry went from forestry to mining.
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| 28. | The harbour lost its last commercial cargo handling operation in 1992 when Marchon ceased their phosphate rock import operations.
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| 29. | The cobalt was mixed with crushed phosphate rock which was obtained cheaply from Nauru Island in the West Pacific.
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| 30. | Phosphate rock is mined, beneficiated, and either solubilized to produce wet-process phosphoric acid, or smelted to produce elemental phosphorus.
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