Uranium ore minerals

The geological term, uranium occurrence, implies a naturally occurring anomalous concentration of uranium. The term, uranium deposit, implies a mass of naturally occurring mineral material from which uranium could be exploited at present or in the future. An often-encountered term in uranium mineralogy is uranium ore mineral. It is a mineral having such physical and chemical properties and occurring in a deposit in such concentra-... 

Table 1.20 Some types of uranium ore minerals deposits.

Kyser, T.K., Chipley, D., Vuletich, A., Alexandre, P. 2008. Variations in 238U/235U ratios in natural uranium ore minerals from sedimentary basins Abstracts of the 18th annual V. M. Goldschmidt conference. Geochimica et Cosmochimica Acta, 72(12), A508. 

Uranous ion (U ) and its aqueous complexes predominate in groundwaters of low Eh. U(IV) is the major oxidation state in the most common uranium ore minerals uraninite [U02(c)]—pitchblende is roughly U02(am)—and coffinite (USi04). The U(IV) concentrations in groundwater at low... 

Apart from zircon, other common accessory minerals that can be used for U/Th-Pb dating are monazite, rutile, titanite, apatite and allanite results on rarer minerals such as columbite-tantalite, perovskite, baddeleyite and the uranium ore minerals uraninite and davidite have also been reported. 

Radiometric ore sorting has been used successfully for some uranium ores because uranium minerals emit gamma rays which may be detected by a scintillation counter (2). In this appHcation, the distribution of uranium is such that a large fraction of the ore containing less than some specified cut-off grade can be discarded with tittle loss of uranium values. Radioactivity can also be induced in certain minerals, eg, boron and beryllium ores, by bombarding with neutrons or gamma rays. 

Plutonium occurs in natural ores in such small amounts that separation is impractical. The atomic ratio of plutonium to uranium in uranium ores is less than 1 10 however, traces of primordial plutonium-244 have been isolated from the mineral bastnasite (16). One sample contained 1 x 10 g/g ore, corresponding to a plutonium-244 [14119-34-7] Pu, terrestrial abundance of 7 x 10 to 2.8 x 10 g/g of mineral and to <10g of primordial Pu on earth. The content of plutonium-239 [15117 8-3], Pu, in uranium minerals is given in Table 2. 

Nonferrous Metal Production. Nonferrous metal production, which includes the leaching of copper and uranium ores with sulfuric acid, accounts for about 6% of U.S. sulfur consumption and probably about the same in other developed countries. In the case of copper, sulfuric acid is used for the extraction of the metal from deposits, mine dumps, and wastes, in which the copper contents are too low to justify concentration by conventional flotation techniques or the recovery of copper from ores containing copper carbonate and siUcate minerals that caimot be readily treated by flotation (qv) processes. The sulfuric acid required for copper leaching is usually the by-product acid produced by copper smelters (see Metallurgy, extractive Minerals RECOVERY AND PROCESSING). 

With the exception of actinium, which is found naturally only in traces in uranium ores, these elements are by no means rare though they were once thought to be so Sc 25, Y 31, La 35 ppm of the earth s crustal rocks, (cf. Co 29ppm). This was, no doubt, at least partly because of the considerable difficulty experienced in separating them from other constituent rare earths. As might be expected for class-a metals, in most of their minerals they are associated with oxoanions such as phosphate, silicate and to a lesser extent carbonate. 

Uranium is a metal that is found naturally as a constituent of chemical compounds m minerals such as pitchblende. Uranium ore is mined much like coal Open pits are used to mine shallow deposits, deeper deposits require shaft mining. Commercial ores yield 3 to 5 lb of nranitim compounds per ton of ore. A material called yellow-cake is produced that is... 

Polonium, completing the elements of Group 16, is radioactive and one of the rarest naturally occurring elements (about 3 x 10 " % of the Earth s crust). The main natural source of polonium is uranium ores, which contain about lO g of Po per ton. The isotope 210-Po, occurring in uranium (and also thorium) minerals as an intermediate in the radioactive decay series, was discovered by M. S. Curie in 1898. 

Langmuir D (1978) Uranium-solution-mineral equilibria at low temperatures with applications to sedimentaiy ore deposits. Geochim Cosmochim Acta 42 547-569. 

Langmuir D (1978) Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits. Geochim Cosmochim Acta 42 547-569 Langmuir D, Herman JS (1980) The mobility of thorium in natural waters at low temperatures. Geochim Cosmochim Acta 44 1753-1766... 

Vigier N, Bourdon B, Turner S, Allegre CJ (2001) Erosion timescales derived from U-decay series measurements in rivers. Earth Planet Sci Lett 193 549-563 von Gunten HR, Roessler E, Lowson RT, Reid PD, Short SA (1999) Distribution of uranium- and thorium series radionuclides in mineral phases of a weathered lateritic transect of a uranium ore body. Chem Geol 160 225-240... 

As a specific illustration reference may be drawn to molybdenum reserve scenario in the United States. The reserves are mainly grouped under five categories (i) primary, (ii) byproduct of copper ores, (iii) co-product of copper-molybdenum ores, (iv) by-product of tungsten ores, and (v) by-product of uranium ores. These have been presented and briefly elaborated in Table 1.14. It may finally be recorded by way of summary that the present day molybdenum sources in the world today seem to be principally of two main kinds first, the large-tonnage, low-grade, disseminated type of deposit in which molybdenite is the principal economic mineral second, the deposits in which molybdenite occurs as a by-product in... 

In most uranium ores the element is present in several, usually many diverse minerals. Some of these dissolve in sulfuric acid solutions under mild conditions, while others may require more aggressive conditions. Thus, while it may be comfortable to recover 90-95% of the uranium present, it may be tough or impractical to win the balance amount of a few percent economically. Some of the most difficult uranium minerals to leach are those of the multiple oxide variety, most commonly brannerite and davidite. These usually have U(IV) as well as U(VI), together with a number of other elements such as titanium, iron, vanadium, thorium, and rare earths. To extract uranium from these sources is not as easy as other relatively simpler commonly occurring sources. 

The element exists as an intermediate in uranium and thorium minerals through their decay. There is no stable isotope. The longest-living isotope has a half-life of 8.3 hours. In the crust of the Earth, the total steady-state mass is estimated at a few tens of grams. Thus astatine is the rarest element (record ). A few atoms of this relative of iodine can be found in all uranium ore. It exhibits certain metallic properties. 

Uranium minerals, 25 396-397 Uranium mononitride, 25 427 Uranium nitrides, 25 426-427 Uranium ore concentrates, 25 407... 

Occurrence. Important minerals are carnotite K(U02)V04 3/2 H20, more important as a uranium ore, vanadinite Pb5(V04)3Cl and some complex sulphides. It occurs also in certain crude oils and may be recovered from dusts after combustion. 

This element has not been found in any naturally occurring mineral but Seaborg believes it may exist in minute amounts as the result of neutron bombardment in uranium ores (63). Neptunium is not absorbed from the digestive tract of animals, but when it is injected it tends to accumulate in the bones. Subsequent loss from this site is very slow (64, 65). 

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