The mineral calcite is perhaps the most amazing mineral. It has many crystalline forms and can form in many geologic settings. It is also an exceeding important mineral resource - it is used in the manufacture of cement, and is used in some manner in the process of manufacturing of thousands of compounds used in industry, including the manufacture of steel and the production of medicines and food. Calcite consists of a crystalline structure composed of molecules of calcium carbonate CaCO 3.
From a "point blank" science view, the Ca comes from the earth, and the CO 3 comes from the atmosphere, and nearly all the CaCO 3 is deposited in the oceans and by water underground. It is important to note that CaCO 3 is a chemical formula representing a single molecule.
It takes many molecules of CaCO 3 to make the unit cell of "pure" mineral calcite see Figure A pure specimen of calcite CaCO 3 would be perfectly clear form called "iceland spar" discussed more with Fig. With pure calcite the unit cells will have 28 molecules of CaCO 3 , however, there can be a variety of other elements that can be substituted for a few of the calcium and carbon atoms with a unit cell, and it will keep the general crystal pattern of calcite.
Elements including sodium, magnesium, iron, zinc, chromium, strontium, barium, and sulphur and can sneak into the structure of the unit cell and still maintain the general character of crystalline calcite. However, these differences can result in varieties calcite with some subtle differences in physical properties including color, crystal form, and special properties including fluorescence, phosphorescence, and thermoluminescence discussed below.
Calcite also doesn't fit the definition of a "true" mineral because it can also be of biological origin—a product of respiration, excretion, and skeletal structures in plankton, microbial deposits, algal and coral reefs, and incorporated tissue of plants, invertebrate shells, and the shell of eggs.
Mineral Commodity Summaries 12222
The arrangement of unit cells can produce differently shaped crystals. For example, calcite can form several variation including "dogtooth spar," "nailhead spar," and combined forms of these crystal varieties see Figure and This variation of crystal shapes is related to the physical conditions of where the mineral formed. Structure of the unit cell of the mineral calcite calcium carbonate - chemical formula: CaCO 3.
It takes 28 molecules of CaCO 3 to create the a single hexagonal shaped unit cell of calcite illustrated here on an atomic level. Calcite crystals have a hexagonal crystal structure. The alignment of unit cells can form different crystal forms, all in hexagonal arrangement. Crystal forms of calcite include dogtooth spar, nailhead spar, and combined forms. Crystal forms of calcite : dogtooth spar, nailhead spar, and combined form.
It takes many billions of unit cells combined to form visible crystals. Crystals like these form in open cavities underground where the crystals grow slowly over time. The mineral aragonite is also composed of calcium carbonate CaCO 3 , but the molecules are in a different crystalline structural arrangement than calcite. Calcite has a hexagonal crystal structure, whereas aragonite has an orthorhombic crystal structure see crystal systems below.
Calcite crystals can be split along mineral cleavage planes to form blocks with perfect rhombohedral shape. Note that this rhombohedral shape still retains its internal hexagonal crystal structure! Cleavage planes are naturally weak zones within a crystal structure. This image illustrates how molecules of calcium carbonate line up in repeating arrangement forming the rhombohedral shape. Note the hexagonal shape of the crystal block.
Calcium carbonate molecules arrange in the rhombohedral structure of the mineral calcite. When a crystal of calcite is crushed it tends to split into many small pieces that retain a rhombohedral shape. These "rhombs" can range in size from microscopic to large blocks. Another mineral, dolomite , has a chemical formula of CaMg CO 3 2.
It has a trigonal-rhombohedral crystal form. The pink color comes from traces of iron within the crystal structure. What Is Mineral Cleavage? Mineral cleavage is the tendency of crystalline materials to split along definite crystallographic structural planes or, for clarification, to break along smooth planes parallel to zones of weak bonding in crystalline substances.
For instance, as illustrated in Figures to , calcium carbonate forms crystalline forms, calcite and aragonite. However, when a mineral sample of calcite is crushed, the crystals shatter along planes of weakness in the crystal lattice. In the case of calcite, the crystals break along 3 planes of weakness within the crystal structure, forming rhombohedral blocks. These cleavage planes are always at the same angles in 3 directions, the x, y and z dimensional axes see Figures to The rhombohedral shape of the calcite crystal fragments are always the same, whether as a hand-size specimen or crystal fragments on a microscopic level.
The same is true for halite illustrated in Figure , except the salt crystals are cubes instead of rhombs. Three factors play important roles in the physical properties of mineral: 1 the crystal structure, 2 character of chemical bonds within crystalline substances, and 3 the ability of substances to split along cleavage planes. How the arrangement of atoms affect physical properties is easily illustrated with two carbon minerals, graphite and diamond. In Figures and , the lines between atoms represent chemical bonds. These factors, particularly the hardness of a mineral and its tendency to split along cleavage planes, determine if and how a mineral specimen might be cut or faceted into a gemstone.
Crystal structure of the mineral diamond. Crystal structure of the mineral graphite. Although both diamond and graphite consist of the element carbon, the two minerals have very different crystal structure arrangements. Well over 4, different minerals have been identified occurring naturally in the world. There are probably many more. Hundreds of thousand of inorganic compounds are known and patented and perhaps billions of organic compounds exist having carbon and hydrogen and other elements combined.
However, with all the chemical compounds that are known, there are only a relatively low number of naturally occurring, common or "important" mineral compounds that are gems or have "economic" significance. Figures to illustrate a classification of natural crystal forms and shapes grouped within crystal systems. Minerals have characteristic crystal shapes that can be used to help identify them. Cubic and isometric crystal system Crystal forms: include cube, octahedron, dodecahedron , and other more complex forms.
Gem minerals diamond, garnets, spinel, and gold. Tetragonal crystal system. However, two sides of the crystal axes share equal length, whereas the length of the third axis is either shorter or longer than the other two. Some examples of minerals include apophylite, cassiterite, sheelite, and vesuvianite. Gems include zircon and rutile. The Hexagonal or Trigonal System includes crystal shape that are hexagonal. Minerals with hexagonal form include calcite, dolomite, hematite, ice, quartz, and siderite.
Gem minerals include beryl including emerald , corundum including ruby and sapphires , quartz varieties crystal, citrine, amethyst , and tourmaline. Orthorhombic crystal system : prisms, pyramids, and combined forms. Minerals with orthorhombic forms include aragonite, barite, celestite, cerrussite, enstatite, olivine, stilbite and sulphur. Gem minerals include peridote olivine and topaz. Monoclinic crystal system.
There is one two-fold axis of symmetry. Mineral examples include azurite, malachite, gypsum, epidote, amphiboles, jadeite, micas, and orthoclase. Triclinic crystal system. The Triclinic System includes crystal forms where the three axes are of unequal length, and one of the axes are perpendicular to each other.
Mineral examples include kyanite, axinite, rhodonite, and albite. How can physical and chemical properties of minerals be used for their identification? All minerals have unique properties that aide in their identification. Some minerals have "unique" characteristics that have an appearance or characteristic that make them easy to identify. However, these identifying characteristics may not be easy to determine without extensive testing more extensive testing. Fortunately, the most common minerals are fairly easy to identify by general appearance or with simple tests for hardness, crystal form, color, magnetism, and "streak" does it leave a colored line when scratched on a piece of tile?
Note that some tests can be destructive to mineral samples such as measuring hardness, streak, malleability, elasticity, and testing with acid. In addition, tasting a mineral is not recommend - some are actually poisonous! Washing your hands after handling mineral samples is always recommended. Observable Characteristics and Tests for Identifying Minerals. Properties of minerals The following physical properties of minerals can be used to identify a mineral through sensory observations or conducting simple tests.
Equipment for such tests are typically available in science education departments or are available from commercial sources. Easily observable physical characteristics simple visual observations of the form and character of some minerals. For most samples used in mineral tests, crystal form may not be apparent or easily measurable. Amazonite is a blue-green form of microcline feldspar. Samples of feldspars are fairly easy to find or purchase, and they typically have good crystal form angles for students to measure.
Some minerals have obvious color associations. The combination of color with other mineral characteristics make the easy to identify: malachite green , sulphur yellow and cinnabar blood red. Problems arise with mineral samples are white or gray - there are dozens of minerals that have those neutral tones and make them difficult to easily identify without other tests.
Mica, feldspar, calcite, and selenite gypsum have good mineral cleavage. Many minerals have cleavage planes that make them easy to identify, with micas biotite is black, muscovite is silvery-white being perhaps the most easy to recognize. Crushing irregularly shaped samples may demonstrate repeatable shapes associated with cleavage planes, such as with feldspar and calcite. Examples of minerals that may display striations include hornblende, pyrite and selenite a crystalline form of gypsum. Mineral crystals that grow in open cavities sometime display striations that are parallel to the crystal axes within the mineral's crystal structure.
This sample shows a pyrite crystal with obvious striations. Note that striations may not occur on all all examples of a mineral. For example the cube-shaped pyrite specimen shown in Figure does not display striations. There are many kinds of luster: Metallic means having the appearance of polished metal. Native copper, gold, silver, and platinum have metallic luster on polished surfaces. Metalloid minerals including galena and pyrite have high metallic luster Figure Adamantine means "having the hardness or luster of a diamond.
Other minerals with high radiance include cubic zirconium, and "Herkimer diamond" a unique variety of very clear quartz crystal. Most of the gems in Figure display an adamantine luster. Schiller is luster property best seen in labradorite feldspar that varies in color as the mineral is moved and looks like the wings of some iridescent butterflies Figure Labradorite makes an attractive building material and semiprecious stone.
Schiller is also seen in some gems such as moonstone. Pearly luster as seen in variety of gypsum called "satin spar" Figure Ulexite is sometimes called the "TV stone" because of it's optical fiber light transmission properties see Figure below. Greasy luster as in some chalcedony, a type of microcrystalline also called cryptocrystalline quartz Figure Vitreous luster as seen in broken glass.
On fresh, broken surfaces it has a conchoidal fracture pattern, like broken glass. Quartz crystals have a vitreous luster on broken surfaces. Obsidian a natural glass [rock] has a vitreous luster Figure Resinous luster as seen in amber a fossilized tree resin; not a mineral Figure Earthy means having a dull or matte like appearance, like the texture of a terra cotta flower pot.
Minerals like hematite and limonite that typically consist of very fine microscopic crystals have an "earthy" dirt-like texture see cinnabar [red], sulfur [yellow], and malachite [green] in Figure Pyrite left and galena right have a metallic luster. Tiger eye a variety of quartz displays chatoyancy luster. Labradorite a variety of feldspar displays a schiller luster.
Satin spar, a variety of the mineral gypsum displays a pearly luster. Chalcedony, a variety of the mineral quartz, has a greasy luster. Obsidian, a natural glass, has a vitreous luster. It is a rock, not a mineral! Fig, Amber has a resinous luster.
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It is actually fossil tree resin! Few common minerals are transparent. Quartz and calcite can have high transparency see Figures and below. Common milky quartz is typically translucent light passes through but is diffuse, see Figure Crystal quartz is transparent when clear.
Clear calcite can split a laser beam into two separate beams. Figure shows a piece of iceland spar causing the X pattern of the underlying paper to be doubled on itself. Figure shows the X pattern on the underlying piece of paper transmitted to the surface of the ulexite sample. Clear calcite displays double refraction. Ulexite called "TV Rock" shows fiber-optic like properties. Sulfur-bearing minerals may put off a rotten-egg like smell. Many rocks of sedimentary origin have the smell of petroleum. Note that tasting minerals and rocks is not recommended!
Minerals have a variety of physical and chemicals properties that can be evaluated using simple tests. The following tests are simple determinations using common laboratory equipment and supplies. Note that some of these are destructive to samples being tested! Depending on mineral chemistry and crystal structure, minerals have varying degrees of hardness.
Simple tests of scratching mineral samples with items or material of known hardness can give a general range of "hardness" of a specimen. Mohs Hardness Scale is a list of hardness of common minerals Figure used in mineral testing laboratory exercises. Note that testing the hardness of minerals may be destructive to samples! Figure is sample of Diablo Canyon iron meteorite that is highly magnetic. Many minerals rich in iron are partly magnetic and display measurable magnetic susceptibility that can be useful for geophysical exploration.
Large bodies of rock containing iron-rich minerals can be remotely detected below the earth surface, and may be useful for detecting hidden faults, water-filled sedimentary basins, or potentially economically valuable mineral resource deposits. Magnetic susceptibility measurement are used in regional geophysical mapping.
Magnets stick strongly to magnetite Fe 3 O 4 but also show weak attraction to other metallic and metalloid minerals including hematite, goethite, chromite, franklinite, pyrrhotite, and siderite. Shown here, a magnet sticks strongly to a meteorite composed of the metallic iron-nickel mineral crystals kamacite and taenite. Specific gravity is the ratio of the density of a substance to the density of water. Tests for specific gravity require some laboratory equipment.
Specific gravity is a measure of weight with a known volume Figure Two equal size cubes with dots representing atoms. The box on the left has fewer "atoms" in the same amount of space as the second box. The second box would therefore be denser than the first box. Hematite is red, pyrite is brown, magnetite is black, etc. Be aware that streak tests can be destructive to mineral samples. Different minerals glow brightly fluoresce under different wavelength of ultraviolet light, sometimes in different colors under different wavelengths.
The crystal structures of fluorescent minerals allow ultraviolet energy to be absorbed and the energy is released in a visible color wavelength see Figure Most rocks and minerals are not fluorescent. Some varieties of calcite, zinc minerals, and minerals rich in phosphorus sometimes display phosphorescence. Phosphorescence is only observable in a very dark setting - very shortly after energy source visible light, or better, ultraviolet light is shut off.
Some ore bodies have been very small several tons , but rich in uranium. Uraninite and pitchblende are the dominant minerals, with some accessory minerals. Phosphate Deposits Sedimentary marine phosphorite is the primary source of uranium in this category. An estimated four million tons of uranium could be extracted from U. While marketable phosphatic material obtained from phosphate deposits typically contains only ppm uranium, the large quantity approximately million MTs per year of crude ore rock produced in the United States Jasinski makes it a potentially significant source of uranium.
Disseminated Deposits Typically, these deposits are associated with granites, pegmatites, and syenites. The size, shape, and concentration of the ore bodies vary significantly. Secondary enrichment of the primary mineralization helped to form the ore grade that typically ranges between 0. Deposits near Spokane, Washington, and Bokan Mountain in Alaska, are the most prominent disseminated deposits in the United States, though their production was insignificant in comparison to that derived from other types of deposits such as sandstones.
A fifth-type of deposit is important to production in Canada: Unconformity Deposits This type of deposit is high-grade ore that occurs along and just below major Precambrian unconformities. Ore is often associated with graphite schists. In defining what is ore, assumptions are made about the concentration in the rock; the cost of mining, processing, refinement, waste management, and site restoration; and the market value of the metal.
Material too low in uranium to merit processing and refinement is often called protore, a nominal material that is currently uneconomical. Soil and rock that is otherwise essentially at background uranium and radiation levels, which is removed to gain access to underlying ore, is called overburden. Figure 1. Bureau of Mines McFaul et al. EPA b. These mines have documented production, and represent over records contained within the larger EPA database, which contains over 14, records.
Geological Survey topographic maps and one another in order to obtain an indication of accuracy and reliability. Major geologic formations noted for high uranium are the sedimentary Chinle Triassic and Morrison Jurassic Formations. The Chinle and Morrison are characterized by permeable streambed deposits of highly variable sized and sorted pebbles and sands, with associated concentrated pockets of organic matter from trees, branches, grasses, etc.
Later blankets of volcanic ash provided a source of uranium to leach into the permeable rocks of the Chinle and Morrison. The uranium-laden leachate followed the highly permeable stream channel and mudstone formations, and upon reaching the reducing environment caused by high organic matter, precipitated uranium into void spaces, typically as uraninite.
Thus, one-man mining operations could target small, rich deposits profitably. Uranium's Contribution to Natural Background Radiation Uranium is found in all rock types in varying, but usually small concentrations. Naturally occurring elemental radium and its radioactive decay products can emit radon to the Earth's atmosphere.
This section provides a basic discussion on natural background radiation. Background Gamma Radiation Numerous studies have examined the occurrence of uranium and its radioactive decay products in U. Table 1. There can be more than an order of magnitude difference in radionuclide contents among common igneous rocks. Similarly, deposits known as black shales, found in the eastern U.
This map shows mine locations plotted from McFaul et al. Readers looking for more complete information on state mine locations should refer to U. With the exception ofuranium, concentrations ofradionuclides are generally higher in sedimentary rocks. The radionuclides listed are principal NORM radionuclides. The radionuclide contents shown here should be considered average values. Individual rock deposits can have radionuclide contents that may differ significantly from the numbers shown. Source: Eisenbud and Gesell Radium a decay product of uranium primarily decays by alpha particle emission.
Its own short- lived radioactive decay products, such as polonium or bismuth, yield more gamma ray emissions over time, making radium an important contributor to overall human and environmental exposure to radiation, or radiation dose. In general, concentrations of radium in U.
Higher concentrations may also be found in locations with uraniferous igneous and sedimentary rocks, as well as phosphatic rock deposits. In addition to radium, uranium, uranium, and thorium, there are radioactive decay products that may substantially add to the radioactivity present where these radionuclides are in equilibrium to their decay products in uranium deposits, and mine or mine waste locations Primary contributors of radiation from the natural environment are soil gamma ray radiation and inhaled radon.
Atomic Energy Commission Table 1. Additional data on the distribution of radium in the U. Two additional studies of the National Council for Radiation Protection NRCP , examined the impacts of exposure to uranium and it's radon daughter decay products, and radiation protection in the mineral extraction industry, respectively.
Note: Results are based on national aerial gamma rav sun-eys. Colors'shading reflect exposure in uR per hour micro Roentgens per hour according to the map. Source: USGS Typical values for annual exposure to radiation within the United States are summarized in Table 1. Radon occurs in the environment and is listed separately in that table because of radon's significant contribution to radiation exposure: mRem two mSv of the estimated average dose from all sources. The radon is generated by rocks and soil underlying the man-made structures; it seeps into the buildings through cracks and pore spaces of the foundations.
Some radon is also generated from the building materials used in construction. NRC for ranges of variability; Fisher for radon. Cosmic radiation comes from outer space. Some of it penetrates through the atmosphere covering the Earth. The amount of cosmic radiation will vary, depending on the altitude and latitude where one lives.
Internal radiation comes primarily from ingested natural radioactive substances, such as potassium Source: U. EPA c Uranium in Water Just as uranium is found in virtually all rock and soil, it is essentially ubiquitous in groundwater. Groundwater concentrations tend to reflect overall bedrock averages and can vary widely. While surface waters, originating primarily from rain and snow melt, are typically very low in uranium and other TENORM radionuclides, to the point where they cannot be measured, groundwater can be relatively high in radionuclides of both primary and anthropogenic origin.
Water is perhaps the most significant means of dispersal of uranium and related TENORM in the environment from mines and mine wastes. Surface waters contaminated by surface erosion of mines and wastes maypercolate into groundwater, and contaminated water travels underground through mines or drill holes into the groundwater. Uranium is very soluble in acidic and alkaline waters and can be transported easily from a mine site.
Radium may be leachable as well as carried in particulate form by flowing water Eisenbud and Gesell More detail on this topic can be found in Chapter 3. Occurrence of uranium and radium in water has been detailed in case studies on the Orphan Mine, Midnite Mine. EPA has updated its standards for maximum contaminant levels for radionuclides in drinking water 40 CFR The reader should understand that the uranium standard was based on its identified toxicity to the kidney, and not its potential for causing cancer.
Under the Clean Water Act See Appendix VI for more detail , mines and mills that discharge must obtain a permit, and must monitor twice a year for specific pollutants determined by the type of ore they mine or process. EPA regulations in 40 CFR , Part C, are applicable to discharges from a mines either open-pit or underground ISL operations are excluded , from which uranium, radium and vanadium ores are produced; and b mills using the acid leach, alkaline leach, or combined acid and alkaline leach process for the extraction of uranium, radium and vanadium.
Only vanadium byproduct from uranium ores is covered under this subpart. The same numerical standards for radium apply to uranium mills, though there is no uranium discharge standard. Industrial Processes and Activities TENORM may be generated during extraction, processing, treatment, and purification of minerals, petroleum products, or other substances obtained from NORM-containing parent materials.
Several hundred million metric tons MTs of TENORM are generated each year by a wide variety of industrial processes, ranging from uranium and phosphate mining to the treatment of drinking water. Although conventional uranium mining is the central focus of this report and will be discussed in more detail in Chapter 2, the section below briefly discusses activities or processes, other than uranium mining, that produce TENORM as a result of the co-occurrence of uranium and its daughter radionuclides in the source rock, soil, or water. However, not all ores of these commodities contain uranium or radium at concentrations above natural background levels in associated rocks.
In some instances, the radioactive wastes from mineral processing other than uranium mines have been used as source rock for uranium extraction under NRC license. Uranium Associations with Other Metal Mining Quite typically, beginning in the s, uranium mines would open based on the detection of radioactivity at the site and identification of uraniferous mineralization. While some deposits were mined solely for their uranium content, others produced a variety of other minerals, which co-exist with the uranium minerals Table 1.
In some cases, exploitation of uranium minerals was secondary to producing another mineral found in greater abundance, commanding a better market price, or less expensive to produce; nevertheless, their combined economic value contributed to the success of the mining venture. Many mine sites operated prior to the s, and even after, have not been recognized for the inherent hazards potentially posed by radioactivity in the discarded waste rock or subeconomic ore piles. The geological emplacement or geothermal phenomena that formed other valuable minerals may have concentrated radioactive minerals as well, or the process of mining, beneficiation, and milling may have resulted in a concentration of the radioactive minerals in the waste.
In some instances, the mineral s being mined may have radioactive elements included in their molecular structure that impart radioactivity to the ore or even the finished product. The EPA U. EPA b Uranium Location Database provides the location of mines with uranium occurrence including those that may have been mined primarily for other minerals.
Aluminum bauxite Potassium potash Coal and coal ash Precious metals gold, silver Copper Rare earths: yttrium, lanthanum, monazite, bastanite, etc. Copper Mining Copper mines have long known to be associated with uranium occurrences internationally, as well as in the U. The Bingham Canyon copper mine in Utah produced , pounds of uranium per year from and 10, pounds per month from February through the end of Chenoweth The Orphan Mine in Arizona see Appendix III was originally claimed for its copper mineralization, but only began production in the s as a result of its rich uranium occurrence.
Other mines in the southwest, such as the Yerington Mine in Nevada and Anaconda Mine in Utah have also been reported to have uranium mineralization or production. Uranium recovery from copper leaching is described in McGinley EPA's report U. Some of the mines listed also were licensed by the Atomic Energy Commission precursor to the NRC to produce uranium in addition to copper.
Phosphate Production Uranium is known to associate with phosphatic deposits primarily because hexavalent uranium complexes well with dissolved phosphate. Phosphate rock contains phosphorite, a form of the mineral apatite, which is known to accommodate uranium. Phosphate rock is the sixth largest mining industry in the United States in terms of volume of material mined.
It is mined for the production of phosphoric acid, the great majority of which is used in agricultural fertilizer. About 80 percent of U. EPA b; Jasinski Mineral processing sometimes exposes workers to measurable doses of radioactivity. Phosphate ore is crushed and digested in sulfuric acid to produce orthophosphoric acid and phosphogypsum. In the process, various other wastes are also formed.
Between 80 and percent of the radium in phosphate rock is transported to the phosphogypsum, while about 70 percent of the uranium and thorium remains in the phosphoric acid however, the fractionation of uranium and thorium is variable and still not well characterized Guimond ; Hull and Burnett ; FIPR Though uranium concentrations in phosphate ore are low compared to typical uranium ores, the low cost of uranium recovery from secondary phosphate products sometimes makes it profitable to extract uranium as a by-product of phosphate production.
Phosphate rock and tailings containing up to ppm of uranium have been mined as a source of uranium DeVoto and Stevens Before EPA required placement of phosphogypsum in environmentally isolated waste piles, called "stacks", to control radon emissions 40 CFR 61, Subpart R , phosphogypsum and waste rock containing uranium and thorium were often used to refill and reclaim open mine pits.
Due to pressures to find available land for home building, several of these reclaimed mine pits were subsequently sold as home sites. In , EPA reported that more than 1, houses were built over these sites in one Florida county alone. While it has not been determined if this housing may pose a radiation hazard to the occupants, during its study EPA found some elevated levels of radiation and radon U.
EPA Elemental phosphorus is produced by the thermal process. It is a raw material used primarily in chemical and food production, primarily from ore deposits in Idaho. Uranium TENORM emerges from coal- burning plant furnaces predominantly in fly ash, which is fused and chemically stable. Coal fly ash is derived from inorganic materials that were co-deposited with the organic detritus that produced the coal beds. Uranium in coal may be a combination of detrital mineral matter and uranium deposited later through adsorption by, or oxidation of, organic matter in the lignite or coal.
Pollution control devices in modern power plants usually capture about 99 percent of fly ash, and devices in some older plants capture about 90 percent. The amount of ash generated is proportional to the amount of coal consumed and the coal ash content. The ash content of coal, will vary according to the depositional environment.
The average ash content of coal burned by the U. For coal with a 10 percent ash content, a 1, megawatt plant may produce over 1, tons of ash during a hour period.
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However, the actual quantity of ash produced also depends on the plant's design and efficiency and the coal's energy content. For example, in , U. If that amount of coal is burned with 1. Other coals are quoted as ranging from up to 25 ppm of uranium and 80 ppm of thorium. Based on analyses of nearly 7, samples, of all coal provinces and coal ranks, an EPA study found that the range of uranium in U.
Most fly ash is buried, but increasingly fly ash is being used for commercial applications. A significant quantity of fly ash Class C is considered cementitious having the properties of cement, the principal binding agent in concrete which makes it a very useful material. Heavy Mineral Sands Many of the minerals which make up this commodity contain significant percentages of uranium and thorium.
As a result of their inherent hardness, weight specific gravity , and other physical properties, certain minerals are naturally resistant to erosion and to physical and chemical breakdown over geologic time. Accumulations of these minerals results in sedimentary sand deposits commonly called "heavy mineral sands," or sometimes "black sands," because they are dominated by black minerals. These deposits, if they occur in easily accessible locations and in sufficient size, may be mined to concentrate and extract valuable industrial metals U.
Typical minerals that may be found in these deposits include garnet; titanium-rich rutile, ilmenite, and leucoxene; thorium-rich monazite; and uranium-rich zircon. All of these minerals, and several others typically occurring in the deposits, are radioactive due to: the presence of uranium, thorium, and radium in their molecular matrix; radioactive coatings washed into the deposits from elsewhere; or the chemical and physical weathering of radioactive mineral grains in the sand deposit. The wastes from extracting these minerals, and often the finished products resulting from mineral processing, may retain some or all of their natural radioactivity CRCPD The uranium oxide content of monazite sands in the Southeast was measured at 0.
Monazite from the Green Cove Springs deposit in Florida, which produced monazite prior to , averaged 4. The major U. However, most titanium ore separated sands mostly, rather than finished titanium dioxide powder is imported. Although as a metal, titanium is well known for its corrosion resistance and for its high strength-to-weight ratio, approximately 95 percent of titanium is consumed in the form of titanium dioxide pigment in paints, paper, and plastics.
Other end uses of titanium include ceramics, chemicals, welding rod coatings, heavy aggregate, and steel furnace flux USGS There has been no study on disposal of any residual radioactive wastes from these industries in the U. Zirconium is a silvery-white metal obtained from zircon sands Brady et al. Most zirconium minerals contain 1 -5 percent hafnium CRG Zircon production is usually a byproduct of mining and extracting titanium minerals from ilmenite and rutile ores.
Zircon has been produced from dredging operations in Florida, and now Virginia. Major end-use categories for zircon include abrasives, ceramics, refractories, and foundry applications. Zircon is consumed directly for abrasives and welding and as welding flux. Zircon sands and finely ground zircon termed zircon "flour" are consumed in foundry molds, refractories, and ceramics.
Residual radioactive wastes from these industries have been reported to be disposed in industrial landfills, and there have been instances where abandoned barrels of zircon flour, and sites contaminated with zircon wastes have been the subject of Superfund cleanup and removal actions. The AEA also set fixed prices for uranium ore and provided production incentives e. Since then, the industry has gone through two boom-to-bust cycles U. The first of these cycles, in the s, was prompted by the demand generated by the U.
The second, in the s to early s, was fueled by expectations for increasing demand from commercial nuclear power production and the "energy crisis". Since the s, the NRC succeeded the AEC in the role of licensing uranium extraction operations, but the demand and price of uranium has been determined by external market forces. Rising demand, beginning in for uranium has begun to increase production in the domestic industry.
The importance of the uranium market and price of uranium is their role in mining industry decisions. Some of these decisions are: how to extract ore from a mineral deposit, how many and which mineral deposits should be mined, and when they should be mined. Those decisions ultimately affect the volumes of waste produced and how it is managed. This chapter examines the location and geology of uranium deposits in the United States, the methods used to mine uranium, and the methods used to extract it from ore.
Many of the geological and mining terms used in the text that follows are defined in the chapter and are also in included in the glossary in Appendix I. Prospectors locating areas with mining potential would file claims for the discovery site and nearby areas. The ownership claims were regulated according to the Mining Law of and were enforced by the U.
Department of Interior. To maintain ownership of these claims, prospectors needed to perform a variety of activities every year, including digging small pits, adits1, and trenches. If they found ore grade material higher than 0. AEC offered bonuses for shipments meeting minimum criteria. In many parts of the Colorado Plateau, the characteristic geologic forms of uranium ore bodies were small to moderate-sized isolated pods or linear sinuous channels of ore, as opposed to large lithologic2 beds typical of coal or iron. As a result, thousands of diminutive mines were developed in the Plateau region on ore bodies sometimes as small as a single uraniferous petrified log weighing a few metric tons.
In many cases, these ore bodies were clustered into districts Table 2. These small mines produced small quantities of waste rock typically discarded within several to over yards several to about meters of the mine opening or pit. Mine maps typically show extensive underground mining following ore zones with only small piles of 1 Adits are horizontal or nearly horizontal passages driven from the surface for the working or dewatering of a mine.
If driven through a hill or mountain to the surface on the other side it would be a tunnel. Lithology is the basis of correlation in coal and other types of mines and commonly is reliable over a distance of a few to several miles. Mines of this type, now abandoned, are scattered over wide areas of southeastern Utah, southwestern Colorado, northwestern New Mexico, and northeastern Arizona, as can be seen in Figure 2. As described further in Chapter 3 of this report, the mines which were abandoned or left unrestored prior to the early s left residual wastes that are a main focus of this study.
The migration of radionuclides and other hazardous substances from those mines and their waste piles have resulted from biologic, hydrologic, wind, and human actions, and are discussed in more detail in Chapter 3 and Volume II of this report U. EPA b , does show the location of the Northwest Nebraska uranium district. Table 2. Major U. Uranium Mining Districts Several major uranium districts produced uranium ore in the past and contain potential for future exploitation.
Thousands of uranium mine sites are scattered over wide areas of the western United States. Many mining properties proved to have much larger ore bodies than originally thought, both on the Colorado Plateau and in other states. Extensive mining operations were developed at these sites.
Since the early s, most uranium has been mined on a larger scale than early mining efforts and conventional mining techniques were established to recover the ores. Although the AEC incentives ceased in , the agency continued to purchase ore from properties with reserves discovered before November 24, , at guaranteed prices through the end of Several ore processing mills closed from late through the end of the s. In , for the first time since , uranium production declined in the United States. By the end of the buying program in , several hundred small to intermediate-sized underground and open-pit mines were either mined out or had become uneconomical and were abandoned.
The industry was revitalized shortly thereafter by the prospect of supplying fuel to the developing commercial nuclear power industry. The production and market prices of uranium grew rapidly through the mid- and late s and early s, as commercial markets began to emerge.
However, production and prices peaked in the early s, when domestic demand for uranium ore fell far short of its expected growth, and low-cost, high-grade Canadian and Australian deposits began to dominate world markets. As planning and construction of new U. Throughout the high uranium production years, trends in the industry changed, leading to new mining methodologies and subsequent changes in the nature of their resulting waste generation and hazards. Environmental concerns and regulatory requirements, as well as discovery of high uranium content deposits with low extraction costs, resulted in increased uranium mining overseas.
Traditional mining techniques can have high associated costs for heavy metal and TENORM waste management, acid mine runoff, and mine site restoration. These issues made many uranium mines unprofitable when market prices were low. Increasing world demand raised the price of uranium starting in AAPG and although most mines that were inactive at the time employed the less disruptive ISL technique, described in the following section , conventional mine sites have begun to reopen as a result Teluride Watch Conventional Uranium Mining Methods The following discussion describes physical methods of mining.
These methods are referred to in this report as conventional mining methods, as opposed to the solution chemical extraction processes of ISL and heap leaching.
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Ore is a mineral source from which a valuable commodity e. The term ore implies economic viability, given the concentration of metal in the host rock, the costs of extraction, processing and refinement, waste management, site restoration, and the market value of the metal. Protore is conventionally mined uranium ore that is not rich enough to meet the market demand and price. Waste materials that are, or could be classified as, technologically enhanced, include overburden, unreclaimed protore, waste rock, drill and core cuttings, liquid wastes and pit water for more detailed discussion, see Chapter 3.
The size, grade, depth, and geology of an ore body or deposit are used in combination to determine which extraction method is most efficient and economical. Open-pit mining is employed for ore deposits that are located at or near the surface, while underground mining is used to extract ore from deeper deposits or where the size, shape, and orientation of the ore body may permit more cost-effective underground mining. Since the early s, most uranium has been mined on a larger scale than earlier mining efforts, and, until recently, by using conventional mining techniques.
Those operations have generally replaced conventional mining because of their minimal surface disturbance and avoidance of associated costs See Appendix VI for discussion on statutory and regulatory authorities. Open-Pit Surface Mining Open-pit mining is the surface removal of soil and rock overburden and extraction of ore. Open-pit mines are broad, open excavations that narrow toward the bottom, and are generally used for shallow ore deposits.
The maximum depth of open-pit mining in the United States is usually about feet meters. Lower-grade ore can be recovered in open-pit mining, since costs are generally lower compared to underground mining. There are deeper surface mines for copper and other minerals Berkeley pit in Butte, Montana, reportedly at the north end is approximately feet, or meters deep. Figure 2.
Delineation of the ore deposit by drilling and computer modeling is followed by development of a plan for removing and disposing of overburden. This planning is important, since the handling of waste material comprises one of the largest shares of overall mining costs Grey EPA In open-pit mining, topsoil is the natural soil overlying the pit outline, while overburden includes material lying between the topsoil and the uranium ore deposit.
In more recent open-pit operations, soil is removed and stockpiled for later site reclamation i. Overburden is removed using scrapers, mechanical shovels, trucks, and loaders. In some cases, the overburden may be ripped or blasted free for removal. Overburden forms the largest volume of waste, is generally lowest in naturally radioactive elements, and is not as enriched in uranium as protore.
Protore is often stockpiled at the mine site as well.
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Once the ore body is exposed, radiometric probing is used to define the exact extent of the ore body. Ore, protore. Many times parts of an ore body delineated by drilling cannot be economically mined by open-pit methods. Where parts of the deposit lie adjacent to the bottom of the planned pit, underground mines may be developed from the pit bottom to recover these ores. Often waste material, including overburden, is returned to mined-out areas during mining to reduce hauling costs. In this type of open-pit mining, the ore body occurred at or near the surface along the edge or rim of a canyon.
Miners would strip the shallow overburden from the deposit and generally drop the waste material down the adjacent canyon wall. In practice, this mining resembles strip mining for coal in the eastern United States. Rim stripping was generally limited to the edge of the canyon because the overburden grew thicker farther away from the rim.
Larger, deeper deposits may require one or more vertical concrete-lined shafts or declines large enough for motorized vehicles to reach the ore. Slopes an underground excavation from which ore has been removed in a series of steps reaching out from the main shaft provide access to the ore. Ore and waste rock generated during mining are usually removed through shafts via elevators, or carried to the surface in trucks along declines.
Because of the high costs of removing such materials, some waste rock may be used underground as backfill material in mined-out areas. The extracted ore is stockpiled at the surface or trucked directly to a processing mill, which may be on site or at some centralized location. Diagram of Room and Pillar Underground Mining This figure shows a simplified diagram of a room and pillar underground mining operation.
Main vertical shafts connect with underground "rooms " that have been excavated using unmined rock columns as support pillars. Rail cars move ore and waste through the mine. The reliance on chemical or other means to extract uranium are referred to as unconventional mining methods, even though they may have been used as extraction processes for decades.
The sections which follow describe the heap leaching and ISL extraction processes. Ore that is removed from open-pit and underground mining operations undergoes further processing to remove and concentrate the uranium; the heap leaching may be located near the mine site. Ore is crushed in a large mill, grounded to sand consistency, and mounded above grade on a prepared pad, usually constructed of clay, coated concrete, or asphalt.
A sprinkler system, positioned over the top, continually sprays leach solution over the mound. For ores with low lime content less than 12 percent , an acid solution is used, while alkaline solutions are used when the lime content is above 12 percent. The leach solution trickles through the ore and mobilizes uranium, as well as other metals, into solution. The solution is collected at the base of the mound by a manifold and processed to extract the uranium. Heap leaching was used mostly on an experimental basis in the s and s, but is generally not in use in the U.
Illustration of Heap Leaching Process In this illustration, leaching solutions either acidic or alkaline comprising the lixiviant are sprinkled on crushed ore mounded on a liner or leaching pad. The process does not require the physical extraction of ore from the ground.
Lixiviants for uranium mining commonly consist of water containing added oxygen and carbon dioxide or sodium bicarbonate, which mobilize uranium. The lixiviant is injected, passes through the ore body, and mobilizes the uranium. The uranium-bearing solution is pumped to the surface from production wells. The pregnant leach solution is processed to extract the uranium, usually by ion exchange or by solvent extraction.
The ion exchange process employs a resin that, once fully saturated with uranium, is flushed with a highly concentrated salt e. This reverses the exchange process and releases uranium into the solution. The uranium solution is then sent to another process for concentration, precipitation and drying, as yellowcake. The solvent extraction process relies on unmixable properties between the pregnant leach solution and uranium solute. Normally, the solvents are organic compounds that can combine with either cationic or anionic solutes.
For example, anionic solutions include amine chains and ammonium compounds, and cationic solutions are phosphoric acid-based. Lixiviant is injected into the ground through a well on the left ami far right, the fluid flows underground dissolving uranium and cany ing it in solution until it reaches a production well in the center. The fluid earning dissolved uranium is relumed to the surface from the production well, then is piped off to a production facility for refinement into yellowcake.
Typically, the aquifer must be restored to background or EPA drinking water maximum contaminant limit levels where possible or practical, or to Alternate Concentration Limits ACLs in terms of the presence of metals, organics, pH level, and radioactivity, approved by the NRC and its Agreement States, with EPA concurrence. Therefore, in some cases, restoring it to the pre-operation level does not necessarily make it potable. EPA requires, however, that non-exempted groundwater sources be protected from contamination. Uranium Milling While not a central focus for this report, information is provided below primarily from U.
EPA a on the uranium milling process; for more detailed discussions on the milling process, the reader is referred to that report. Uranium mills have typically been associated with specific mines or functioned as custom mills, serving a number of mines. Most available information on milling operations was written when a dozen or more were operational, therefore the following discussions may not precisely describe milling activities being conducted at present, or in the future.
The chemical nature of the ore determines the type of leach circuit required and, in turn, the extent of grinding of ore received from a mine. Ore feeds from crushers to the grinding circuit where various mechanical mills grind the rock to further reduce the size of the ore. Water or lixiviant is added to the system in the grinding circuit to facilitate the movement of solids, for dust control, and if lixiviant is added to initiate leaching U.
DOI Screening devices are used to size the finely ground ore, returning coarse materials for additional grinding. The slurry generated in the grinding circuit contains 50 to 65 percent solids. Fugitive dust generated during crushing and grinding is usually controlled by water sprays or, if collected by air pollution control devices, recirculated into the beneficiation circuit.
Water is typically recirculated through the milling circuit to reduce consumption U. EPA d. After grinding, the slurry is pumped to a series of tanks for leaching. Two types of leaching have been employed by uranium mills, acid and alkaline. A solvent lixiviant is brought into contact with the crushed ore slurry.
The desired constituent uranyl ions is then dissolved by the lixiviant. The pregnant lixiviant is separated from the residual solids tails ; typically the solids are washed with fresh lixiviant until the desired level of recovery is attained. The uranyl ions are recovered stripped from the pregnant lixiviant. The final steps consist of precipitation to produce yellowcake, followed by drying and packaging Pehlke Ultimately, the solids may be washed with water prior to being pumped to a tailings pond; this wash serves to recover any remaining lixiviant and reduce the quantity of chemicals being placed in the tailings impoundment.
Wash water may be recycled to the lixiviant or to the crushing and grinding circuits. Operational mills currently function independently of specific conventional mines and generate materials that are, in most cases, unique from those generated at the site of extraction. Under UMTRCA, source- handling licenses place specific requirements on the disposal of radioactive wastes; the design and construction of tailings impoundments address NRC requirements for permanent storage of these wastes.
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Radionuclide-containing wastes generated by ISL operations are typically shipped to tailings impoundments at mill sites. Mills in operation and inactive are discussed below. Generalized Uranium Mill Physical Layout This figure shows how a uranium mill is physically set up to crush raw ore into particles amenuhle to chemical treatments for extracting uranium.
DOE El A. These fluctuations in price affect the numbers of operating mines and mills in the country, and the methods of extraction used. The employment structure in the uranium industry has significantly changed since the mids, when nearly 60 percent of the uranium industry labor force was devoted to uranium mining and production. This fraction steadily declined until recently, when only about 25 percent of the employment was related to mining including ISL and almost one-half of that was associated with reclamation of past production facilities.
The industry experienced the highest level of employment in with 21, workers. In employment was about 13,, and in the work force was down to workers U. Due to increased demand for uranium which resulted in higher prices, steady increases were seen in employment and production of uranium commencing in Department of Energy's EIA reports that in , 51 person-years were expended in exploration, in mining activities, in milling operations, and in processing facilities U.
By , one person-year was expended in exploration, in mining, in milling, and in processing U. It is reported in the "Domestic Uranium Report" U. Reclamation employment increased three percent. Wyoming accounted for 33 percent of the total employment, while Colorado and Texas employment almost tripled since A total of 17 uranium mines were operational in five conventional mines both underground and open-pit , four ISL and eight reported as "other" mill tails recovery operations, mine water extraction, or from low-grade stockpiles.
Uranium in was also produced to a limited extent as a side product of phosphoric acid production at four sites U. By , production had been reduced to three ISL operations and one underground mine U. A number of mines were closed and inactive with the possibility of reopening should the price of uranium increase in the future. In , only 2. The uranium production industry had a turnaround in An increase in all aspects of the industry was noticed for the first time since This included drilling, mining, production and employment.
In latest statistics available 2. A new underground mine and a new ISL mine started in Total U. The 4th quarter production amount was estimated by rounding to the nearest , pounds to avoid disclosure of individual company data. This also affects the annual production. Notes: Totals may not equal sum of components because of independent rounding or reporting methods mentioned previously.
Next update is approximately 45 days after the end of the fourth quarter Source: Modified from U. According to surveys of owners and operators of U. It was also estimated that foreign suppliers would provide 54 percent of the maximum projected deliveries through The decision to reopen a plant primarily depends upon the prevailing economics and market conditions. A few ISL operations are remaining open or inactive today, opening intermittently as the price of uranium continues to fluctuate. Recent power uprates3 and upgrades to U.
Since most of the demand for uranium originates from the commercial sector nuclear power plants , and that demand is increasing, it is likely it will affect uranium market demand and supplies Wyoming Mining Association The process of increasing the maximum power level at which a commercial nuclear power plant may operate.
Reserve estimates represent the quantities of uranium as U3O8 that occur in known deposits, such that portions of the mineralized deposits can be recovered at specific costs under current regulations using state-of-the-art mining and milling methods U. Underground mine reserves accounted for about one- half of the total reserves in each cost category.
The reserve decreases are based on mine production of uranium and reflect the combined effects of depletion and erosion of in-place ore quantities remaining at year-end. Uranium Reserve Areas This map shows major areas of remaining uranium reserves, all in the western U. Uranium Reserves of the United States as of December 31, An increase in the price and demand for uranium resulted in the re-opening of some conventional uranium mines and ISL operations, and decisions to re-start some sites which were undergoing closure.
Volume and Characteristics of Uranium Mine Wastes Uranium has been found and mined in a wide variety of rocks, including sandstone, carbonates1, and igneous volcanic-derived rocks see Chapter 1. This variety of source material, the type of mine and extraction operation see Chapter 2 , local climate, soil, and topography can lead to a wide range of differing physical and chemical properties in waste materials.
Waste characteristics are important because they are used to model and assess the environmental impacts and public health risks of radionuclides, heavy metals, and other chemicals associated with mine sites, and the implications for site cleanup. While this chapter discusses wastes from conventional mining, solution extraction, and milling of uranium, a principal focus of this report is TENORM from conventional mining, and in particular, wastes from abandoned mines that have not been reclaimed, or which may need future reclamation.
When uranium mining first started, most of the ores were recovered from deposits located at, or near the surface of the land. Ores were often exposed at the surface, and underground mines followed mineralized zones directly into the subsurface. Thin overburden over deeper parts of the ore body adjacent to the surface exposure would be removed to create shallow open-pits. As easily accessible ore deposits became depleted, mining had to be performed at increasing depths by either open-pit or underground methods.
To reach deeper deposits, the industry had to move larger quantities of topsoil, overburden, plus barren or waste rock. The amount. The costs of processing ore at mills also influence the overall economics of underground and surface mining. These costs have steadily. Thus, while an ore grade of 0. The NRC has established a level of 0. Waste terms that will be used in the discussions from Chapters 3 through 5, and the Appendices, are listed in Table 3. EPA b and c. The geochemistry of uranium can be extremely complicated, however, those documents provide an overview of important aqueous and solid phase parameters, as well as A sediment or sedimentary rock formed by the organic or inorganic precipitation from aqueous solution of carbonates of calcium, magnesium, or iron; e.
Some materials that are wastes within the plain meaning of the word are not "solid wastes" as defined under the Resource Conservation and Recovery Act and thus are not subject to regulation under that law. These include, for example, mine water or process wastewater that is discharged pursuant to a National Pollution Discharge Elimination System permit.
It is emphasized that any questions as to whether a particular material is a waste at a given time should be directed to the appropriate EPA Regional office. Data obtained from many older scientific studies referenced in this report may have only been originally provided in English measurement systems. Conversions are made in the text and tables of this report; however, the reader should understand that the converted numbers may be rounded.
If available in the original studies cited in this report, information on uncertainties and precision of measurements and data will be included. However, many of these studies were conducted during a time when reporting uncertainties and precision of data were not standard practice. While data quality is a vital aspect of scientific and technical endeavor, we regret that the boundaries of uncertainty and accuracy of data presented may not have been cited in many of the original studies available for this study. Table 3. Uranium Mine and Operations Wastes The following mine wastes are generated by conventional uranium mines, heap leach and ISL operations, and uranium mill operations.
They are the principal wastes discussed in Chapters 3 through 5, and the Appendices of this report. Not all wastes listed may be radioactive at all uranium mines or operations, though if they are, they may be subject to regulatory control according to the column they are listed under. EPA a,b,c; , U. Terms in Table 3. May include drill muds or other drilling fluids, sludges, or evaporation products collected in excavated pits from wastewater produced during drilling.
Insoluble materials ranging from municipal garbage to industrial wastes that contain complex and sometimes hazardous substances. Solid wastes also include sewage sludge, agricultural refuse, demolition wastes, mining equipment and mining residues. Solid waste also refers to liquids and gases in containers.
Byproduct material in accordance with the AEA. Waste Footprint of a Mine. Though all mining methods produce waste products, the volume, location, state, and environmental impacts of these wastes can be vastly different. For example, open-pit and underground mining techniques, known as conventional mining, generally produce large amounts of solid waste, while ISL methods produce only small amounts of solid waste, but result in more significant amounts of liquid waste that can spread across a very large area. In general, states, Tribes, and federal land management agencies are responsible for regulating the disposal of solid and other waste generated on their lands by mining operations.
The overall footprint of a mine area may be described as the areal extent of land physically disrupted by a mine operation. The footprint can vary significantly depending on the amount of waste left on site, and not necessarily to the amount of oxide of uranium U3O8 produced. Because the nature of mining changed over the years, waste generation also changed. This change in waste generation largely reflects changes in the scope of mining operations and the technology employed. The early small mining endeavors generated small quantities of waste, because miners found and exploited only deposits near the surface, and they had limited capacity to move large quantities of material.
These small quantities of waste typically were discarded within several to yards about several to meters of the mine opening or pit.
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