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Volume 9, Number 2 C OLORADO G EOLOGICAL S URVEY Fall 2006

Uranium—It’s Hot!! And Back by Popular Demand

Pure elemental is a slightly parent element. This decay is radioactive metal, silvery white in color a natural constant in that half and dense (almost as dense as gold). Ele- of a given amount of uranium- mental uranium metal does not occur 238 (238U—the 238 superscript in nature because it readily combines refers to the atomic weight of with to form several uranium the atom) will decay to lead in and compounds. The about 4.5 billion years. It does most significant property of uranium is not decay directly to lead but that it is the “parent” element in a passes through several daugh- series that eventually ter elements including tho- leads to formation of a particular iso- rium, , radon (a gas), tope of lead. Radioactive decay means and bismuth on its path to a that certain elements, such as uranium, stable isotope of lead. See Fig- will over a specific period of time, give ure 1 for a much-simplified off atomic particles—electrons, protons, chart of the uranium-lead and neutrons—leading to changes in radioactive decay series. the atomic weight and Uranium is found in nature number of the in three main isotopes. 238U is the most common constitut- ing about 99.3 percent of all ; 235U consti-

tutes about 0.7 percent of all Burro No. 7 Mine, Slick Rock, . (Photograph by Jim uranium; and other isotopes Cappa, 2005) such as 234U form trace amounts. 235U is important because it is stantial energy. 235U is more radioactive readily split as part of the fission process than 238U because of its shorter half-life, (Fig. 2) and in the process releases sub- about 700 million years, and as such, the ratio of 238U to 235U has changed Figure 1. Simplified uranium-lead radioactive decay series. over geological time. In the earth’s past, Abbreviations and explanation: Elements: U = uranium, there was a higher percentage of 235U Th = thorium, Ra = radium, Rn = radon, Po = polonium, than today. Scientists believe that this Pb = lead, Bi = bismuth. Half-lives: By = billion years, higher percentage of 235U (about 3 per- y = years, d = days, min = minutes. Subatomic particles; α = alpha particle, essentially y a nucleus consist- cent) led to a natural nuclear fission ing of two protons and two neutrons. β = beta particle a event that occurred about 1.7 billion high-energy electron or positron. years ago in present-day western Africa.

Inside this issue: The Discovery of Uranium, its Uses and Future, the History of Uranium in Colorado, Geology of Uranium Deposits in Colorado, Cleanup of Contaminated Mill Sites, and other useful information about Uranium

CGS ROCKTALK Vol. 9, No. 2 1 From the Division Director— The boom is back! Colorado, A Natural Nuclear Reaction in which has supplied uranium Africa 1.7 Billion Years Ago to the world for more than a In the early 1970s, scientists noted that something century, is seeing the return of was strange about the uranium being mined at interest in this important the Oklo deposit in Gabon, West Africa. The ore energy resource. Prospectors was depleted in the fissionable isotope of uranium, are dusting off their scintil- 235U, and resembled the percentage found in spent lometers and heading for the -about 0.25–0.30 percent (it should hills. Their apparent success is have been 0.7 percent). At the time, this uranium indicated by the filing of 3,000 deposit was formed (about 2,000 million years ago) new mining claims in the state the percentage of 235U was close to 3 percent, about last year. the same as what is used in a modern nuclear reac- Why the boom? Currently, tor. Scientists think that water seeped into the the 435 nuclear reactors in the world need 180 million deposit at about 1.7 billion years ago and allowed pounds of uranium per year, but the world only pro- the neutrons emitted from uranium to slow enough duces 110 million pounds. The shortfall has been made to initiate a chain reaction, which then over time up by depleting stockpiles from the last boom cycle and heated the water into steam causing the chain reac- by conversion of nuclear weapons. Both are diminish- tion to cease. This process may have happened ing in supply and consequently the price of uranium numerous times until the amount of 235U was increased from $10 per pound in 2003 to more than depleted enough to cause the cessation of the chain $55 per pound today. reaction. China and India’s increase in the use of nuclear energy The products of the nuclear reaction remained increases the demand for uranium. However, the United within the Oklo deposit and were never dissolved States also needs a lot of uranium because we are the or spread by ground water for 1.7 billion years. This world’s leading producer of nuclear energy. Indeed, we fact gives scientists hope that nuclear waste stored produce more nuclear energy than , Spain, Ger- in geological formations may be immobile for, at many, Sweden, and the United Kingdom combined. least, millions of years. One of the best kept secrets in our country is that U.S. production of electricity from nuclear plants has increased over the decade since the last plant came on line in 1996 (it was ordered in the early 1970s). This was achieved by increasing the operating Discovery of Uranium and Radioactivity efficiency of the plants. Today we produce nearly twice In 1789, was first recognized as the as much nuclear power as any other country in the pitchblende (now considered as a variety of ). The world, an amount equal to 30 percent of the world’s mineral was recovered from a mine in Joachimsthal, nuclear energy. Bohemia, now a part of the Czech Republic, by an amateur The increase in interest in uranium is but an indica- chemist, Martin Klaproth. Klaproth named the compound tor of growing interest in all of Colorado’s rich natural uranium in a tribute to his friend, William Herschel, a famous resources. China and India’s appetite for natural resources composer and astronomer, who had discovered the planet creates worldwide shortages and drives up prices of Uranus (Uranus is the Greek god of the Heavens). However, nearly every energy and mineral commodity. Colorado it was not until 1841 that the true metal, uranium, was iso- communities are already suffering from China-caused lated from its oxide form by a French chemist, Eugene Peligot. shortages of steel and cement. Prices for such diverse In 1896, another French scientist, Henri Bequerel, left some commodities as gold, copper, aluminum, molybdenum, uranium in a drawer with a photographic plate for a few days chromium, titanium, selenium, and antimony have sky- and to his surprise found the photographic plate to be rocketed in the 21st century with percentage price exposed. This lucky “experiment” was the beginning of atomic increases ranging from a low of 48 percent to more than research and the understanding of radioactivity. 1,700 percent! As shortages grow and prices increase, Marie Curie and her husband Pierre conducted various Colorado can expect to see increasing pressure to develop experiments on , some of which came from Colo- our rich array of energy and mineral resources. rado, from 1898 through the 1920s in their lab in Paris. They recognized the process of radioactivity and discovered two Vince Matthews of uranium’s daughter products, polonium and radium. In the 1930s and early 1940s, scientists discovered that one

2 CGS ROCKTALK Vol. 9, No. 2 isotope of uranium, 235U, was fission- able—that is when an atom of 235U is bombarded by neutrons its nucleus splits into two equal parts, usually an atom of and krypton, at the same time releasing substantial energy in the form of heat and two or several more neu- trons (Fig. 2). The released neutrons then collide with other atoms of 235U, releas- ing more energy and neutrons, a process known as a chain reaction. The chain reaction released such large amounts of energy that it led to the development of nuclear weapons, ending World War II. After the end of the war scientists put the energy released by fission to work to heat water, create steam, turn a tur- bine to generate electricity—the major use of uranium today.

Figure 2. Atomic fission of uranium. Explanation: Solid blue circles = protons, White circles = neutrons; circles = electrons.

Uses of Uranium The very first uses of uranium, mostly radium; again, the manufacturers court case in which five “Radium Girls” in the form of complex uranium , espoused their curative effects. Radium sued U.S. Radium Corporation was set- were as an agent in glass manufacture. was also being used to paint luminous tled in 1928 and exposed the deadly A small amount of uranium was added dials on clocks, watches, altimeters, and effects of radium. Its use declined dras- to the glass giving yellow and green col- other instruments. Young girls were tically after that. ors to the finished product. The glass is hired to paint the radium on the dial In the 1930s, scientists came to under- called Vaseline glass because it resem- faces and they were instructed to point stand the nature of radioactivity and the bles the color of Vaseline (Fig. 3). Ura- their paintbrushes with their lips. Many atomic nuclear fission process as hav- nium oxide minerals, because of their of the young women contracted radia- ing the potential of releasing large bright yellow colors, were probably used tion poisoning and a number of them amounts of energy. After World War II as ornamentation paints by aboriginal died in the 1920s and 1930s. A famous began in late 1941, the tribes in North America and other local- government began a research project at ities. The uranium colored glass fell out Los Alamos, New Mexico to develop an of favor in the 1920s; however, one atomic weapon, which resulted in the American manufacturer used uranium production of three atomic bombs, one oxide to color its popular “Fiestaware” that was tested in southern New Mex- dinner plates a brilliant orange-red color ico and two that were dropped on the as late as 1940. cities of Hiroshima and Nagasaki, Japan The work of Pierre and Madam Curie in August 1945, effectively ending World demonstrated that radium was a daugh- War II. Uranium production continued ter product of uranium and that small in the United States, Canada, and other amounts of radium could be recovered places during the Cold War years follow- from uranium mineral deposits. In the ing the end of the World War II. Almost early 1900s, it was thought that radium all of this uranium went into the pro- was a cure for cancer and other ailments. duction of nuclear weapons. Hot springs and spas advertised them- Uses of uranium changed in the selves as “radium springs,” whether they Figure 3. Erich and Ida Martin piece from Sixth 1950s with the 1954 launch of the USS had radium in them or not. Various Annual Vaseline Glass Collectors Inc. 2004 Nautilus, the first ship to be powered by drinks and ointments were made from Convention. (http://www.vaselineglass.org/) See Uses on page 4

CGS ROCKTALK Vol. 9, No. 2 3 Uses from page 3 amount of the next largest generator, emissions. However, technical and polit- Japan. France, which has the highest ical issues on nuclear waste disposal and a . The Nautilus is a sub- percentage of electricity generated by nuclear plant decommissioning are marine and it made headlines because nuclear power—78 percent, boasts only ongoing concerns. of its ability to remain submerged for 59 nuclear power plants. No new nuclear long periods powered by its nuclear reac- power reactors have tor. The first nuclear reactors designed been built in the United for the generation of electricity went States since construc- into production in the 1950s. As the tion commenced on the 1960s ended and the 1970s began, the Riverbend reactor in use of uranium as fuel for reactors to cre- Louisiana in 1977. In ate electricity grew. Today, the primary spite of this, nuclear use of uranium is to provide fuel for power production has nuclear reactors that produce electric- been steadily increas- ity; although it is still used for weapons ing, mostly because manufacture. reactors have increased Today, there are 103 operating nuclear their efficiency (Fig. 4). power plant reactors in the United Nuclear power plants States, which generate about 20 percent provide low cost elec- Figure 4. Nuclear energy consumption in the United States. of the United States’ electrical power tricity and have essen- (From Energy Information Administration—U.S. Department demand. This is more than double the tially no greenhouse gas of Energy)

What is enriched History of Uranium Prospecting and Mining in Colorado— uranium, and depleted a Story of Boom and Bust uranium? Uraninite, the black oxide mineral of 4. Uranium energy boom of the In order to make a nuclear reaction uranium (UO2) was first discovered in 1950–70s, decline from the late 70s occur there has to be a greater per- the United States in 1871 within gold to 90s, and the uranium resurgence centage of the more fissionable 235U and quartz veins at the Wood Mine near starting in 2003. in the fuel than occurs in nature. Central City, Gilpin County, Colorado. The enrichment process converts Minor production of uranium occurred Radium Boom U3O8 into a gas, uranium hexaflu- through the late 19th Century from Uranium in Colorado were not oride (UF6), which enables the ura- these mines. developed until the early 20th Century nium to be enriched from a 235U In 1881, a yellow uranium oxide min- after the Curies announced the supposed content of 0.7 percent to about eral was discovered in southwestern beneficial uses of radium. Prospectors three to four percent. The enriched Colorado on Roc Creek in Montrose realized that the carnotite ores of south- UF6 is converted back into UO2 and Country. This was the first discovery in western Colorado were easily mineable formed into fuel pellets. So-called what would become the highly produc- and contained radium. The amount of weapons grade uranium is enriched tive Uravan mining district. It was not radium in the typical carnotite ores of to much higher levels of 235U, gen- until 1898, that this new mineral was the Uravan district is very small. It took erally greater than 90 percent. named carnotite after the French min- about 200–300 tons of high grade (about is created by eralogist Adolphe Carnot. Some of the 2 percent U3O8) carnotite ore to produce the process of making enriched ura- ore from Roc Creek was sent to Madam one gram of radium. However, during nium and contains 0.25 to 0.30 per- and Pierre Curie in Paris for their early this period radium was selling for cent 235U. Every ton of natural investigations into the properties of ura- $160,000 to $120,000 per gram (31 uranium enriched for nuclear nium and radioactivity. grams = one ounce) making the mining energy purposes contains about 260 Colorado experienced four periods of of these ores a very profitable operation. pounds of and uranium and associated minerals boom The radium boom got underway in 1910 the remaining 1,740 pounds is and bust cycles. when the Standard Chemical Company depleted uranium. Depleted ura- 1. Radium boom of the 1910s started producing radium and nium is very dense (about 1.7 times 2. Vanadium boom of the 1930s–40s at the Joe Dandy property in Paradox lead) and is used as counterweights (the uranium ores of southwestern Valley south of Uravan. Other mining in aircraft, keels of boats, and as Colorado are very rich in vanadium). and processing operations supported by military projectiles. 3. Uranium boom of the 1940s—related the U.S. Bureau of Mines and the to weapons manufacture National Radium Institute commenced

4 CGS ROCKTALK Vol. 9, No. 2 Uranium Minerals

O Uraninite (pitchblende): UO2, often containing thorium, lead, and other metals of the lanthanum and yttrium group. Uraninite is very dense, black to brown, has a greasy luster, and is radioactive. It commonly occurs with coffinite in the Uravan district.

O Coffinite: U(SiO4)1-x(OH)4x, a black hydrated aluminum silicate is named after R.C. Coffin, a Colorado Geolog- ical Survey geologist who wrote the one of the first monographs on the Uravan district (Coffin, 1921).

O Carnotite: K2(UO2)2(VO4)2·3H20, a secondary mineral of uranium with a bright yellow color.

O Autunite: Ca(UO2)2(PO4)2·10–12H20, a common secondary mineral after uraninite. It has a yellow to yellow- green color and a prominent yellow-green fluorescence.

O : Ca(UO2)2(VO4)2·5–8H20, similar to carnotite with Ca substituting for K. Often associated with carnotite and very similar in appearance.

in Long Valley (Fig. 5). In 1913, Stan- vanadium was beginning to be used to dard Chemical Company built the Joe harden steel, especially in cannons and Junior radium processing plant and other weaponry. The carnotite ores of town site on the San Miguel River at southwestern Colorado and the area what would later grow into Uravan. around Rifle, Colorado contain signifi- Later the Radium Company of Colorado cant amounts of vanadium. In 1916, Figure 6. Advertisement (Fig. 6) or its contractors utilized several Standard Chemical Company added a from the Radium radium processing plants in Denver. The vanadium circuit to the Joe Junior plant Company of Colorado Environmental Protection Agency rec- See History on page 6 ognized the hazard posed by these old radium processing sites, and in the 1980s began an ongoing cleanup of the con- taminated sites. The Colorado radium business received a shock in 1921 when very high-grade uranium ores (up to 60 per- cent U3O8) were found and developed at the Shinkolobwe deposit in the Bel- gian Congo (present day Democratic Republic of the Congo). The Belgians lowered the price of radium to $70,000 per gram and the Colorado radium mines could not compete and were shut down. From 1898 to 1923, the mines of southwestern Colorado and Rifle pro- duced an estimated 67,000 tons of carnotite ore, which resulted in the pro- duction of 202 grams of radium (454 grams/ pound) at an average price of $120,000 per gram resulting in a value of $24.2 million—$265 million in 2005 dollars (Amundsen, 2002). Vanadium Boom In the mid 1910s, the world was gradu- Figure 5. Long Park 16 Mine, near the site of the Radium Institute processing plant. (Photograph by ally moving towards World War I and Jim Cappa, 2005)

CGS ROCKTALK Vol. 9, No. 2 5 Figure 7. United States Vanadium Company plant, Uravan, in the late 1930s or early 1940s. Photograph courtesy of the Colorado Historical Society, CHSX 6203. (Photograph by Bob Zellars)

History from page 5 piles. Unites States Vanadium Company this war they needed a superior weapon. installed a uranium recovery circuit in The nuclear fission process was barely and began producing vanadium. After their mill in 1937 and used the uranium, understood when the government ini- the radium bust of 1921, the mines of just like the vanadium, as a steel hard- tiated the , the goal southwestern Colorado continued to ener. Vanadium was a strategic mineral of which was to develop an atomic produce vanadium for steel hardening. and a government-buying program bomb. The Manhattan Engineers Dis- Vanadium Corporation of America encouraged continued exploration and trict, part of the project focused on gained control of the radium mines and development. acquiring uranium, purchased all the plants and United States Vanadium Pre-1946 production of vanadium uranium-rich waste piles from the Ura- Company expanded the Joe Junior site from Uravan and the surrounding dis- van mineral belt mines and mills and and named it Uravan after the combi- tricts was 636,166 tons at a weighted contracted with United States Vanadium nation of uranium and vanadium min- average grade of 1.9 percent V2O5 result- Company to process the ores for ura- erals. Throughout the 1930s and 1940s, ing in the production of 24,138, 822 nium. Uravan became a bustling, busy production of vanadium brought some pounds of V2O5 (Chenoweth, 1981). place with many new workers, homes, prosperity to Uravan and all of south- schools and all the amenities of a regu- western Colorado (Fig. 7). Uranium in Weapons Boom lar community. Prior to 1937 the uranium in the United States entry into World War II in Most of the uranium that was carnotite ores of southwest Colorado December 1941 changed the picture in acquired by the Manhattan Project came was considered a contaminant and the Uravan district dramatically. The from the Shinkolobwe Mine in the ended up in the mine and mill waste government realized that in order to win Congo (approximately 4,150 tons), and

6 CGS ROCKTALK Vol. 9, No. 2 to a lesser extent the Port Radium Mine in Canada (1,000 tons), and the Uravan district (850 tons) (Amundsen, 2002). World War II ended with the dropping of two atomic bombs produced by the Manhattan Project on Hiroshima and Nagasaki, Japan in August 1945. Produc- tion of uranium at Uravan ceased for a short while. The total production from the United States Vanadium Company mill at Uravan to late 1945 was 1,782,000 pounds of U3O8 (Goodknight and others, 2005). In 1947, the newly created Atomic Energy Commission (AEC) contracted with United States Vanadium Company, which was bought by Union Carbide Nuclear Corporation in 1955 (Fig.8) to produce uranium for the Cold War effort. The AEC ended its uranium contract in December 1970. From 1947 to 1970, the mill at Uravan Figure 8. Manhattan District uranium mill site, Uravan, 1944. (Estalee Silver Collection, downloaded produced 23.9 million pounds of U3O8 January 15, 2006 from www.uravan.com) (commonly referred to as “yellowcake”) and 9.7 million pounds of V2O5 for the In Colorado, the largest single uranium Pitch deposit in Saguache County. The AEC. An additional 123.4 million deposit in Colorado was discovered deposit was developed by two adits from pounds of V2O5 was sold on the open along Ralston Creek in Jefferson County 1959 through 1962 and produced about market to the steel industry. in the late 1940s. Fred Schwartzwalder 100,000 tons of uranium ore at an aver- Uranium Energy Boom and New had leased for the property for its cop- age grade of 0.50 percent U3O8, equiva- Discoveries per potential and had taken some sam- lent to one million pounds of U3O8. In ples to his home. Later he ran a Geiger 1972, Homestake Mining Company Prospecting for uranium deposits con- counter over the samples and found acquired the property and proceeded to tinued throughout the 1950s and 1960s, them to be radioactive. It took Fred some develop an open pit-mineable resource resulting in limited production from the time to locate the exact spot where he of 2.1 million tons at an average grade Central City district in the Front Range, had taken the sample, but he eventu- of 0.17 percent U3O8, equivalent to and other localities throughout the state. ally did. The 7,140,000 pounds of U3O8. Homestake Schwartzwalder mined the deposit from 1975 to 1985, Mine began pro- and the ore was processed at Homes- duction in 1953 take’s mill near Grants, New Mexico. and had a total The Cochetopa uranium district is production of 17 located in northwestern Saguache million pounds of County about 20 miles southeast of uranium oxide at Gunnison. The original discovery of the an average grade district was made in 1954 at the Los of 0.48 percent Ochos claim, which eventually became U3O8 before its the Thornburg Mine. As in the Uravan closure in March district the Upper Jurassic Morrison For- 2000 (Fig. 9). mation is the host rock of the uranium Uranium ore. The Thornburg Mine produced over deposits occur in 1,253,000 pounds of U3O8 at an average Upper Paleozoic grade of 0.14 percent (Nelson Moore and carbonate rocks others, 1978). along a promi- Uranium in the form of the mineral nent north-trend- autunite was discovered in the volcani- ing at the clastic rocks of the Tallahassee Creek Figure 9. Schwartzwalder Mine, 1993. (Photograph courtesy of Jim Paschis) See History on page 8

CGS ROCKTALK Vol. 9, No. 2 7 History from page 7 demand for nuclear power, the low uranium slipped from its high of $40 prices for uranium and the increasing per pound in the late 1970s to prices district, Fremont County in the 1950s. supply from Canada, Australia, and below $10 per pound for most of the Mining commenced from several small other countries spelled out the eventual 1980s and 1990s. As uranium stockpiles mines in the district and by the late decline of the long-lived town of Ura- dwindled and worldwide economies 1960s, about 440,000 pounds of U3O8 van and the surrounding mines and improved, the demand for uranium had been produced. In the 1970s, the mills of the Uravan mineral belt. In increased and, of course, the price began Hansen Creek deposit was developed by 1984, the Uravan mill was closed and to climb somewhat dramatically in 2003 Cyprus Mines Corporation; it contains the town was abandoned. Cleanup activ- (Fig.11). The worldwide demand for ura- significant uranium, over 25 million ities commenced and continued through nium is 180 million pounds per year to pounds, albeit at a low grade of 0.08 per- the spring of 2006 (Fig. 10). Approxi- feed 435 nuclear reactors; however, cent U3O8 (Dickinson, 1981). The mately 84 million pounds of uranium worldwide mine production in 2005 was deposit was never mined because ura- oxide and 220 million pounds of vana- only 110 million pounds. Demand for nium prices tumbled in the 1980s dium oxide were produced from the Ura- uranium will increase as China plans to The Uravan district began a new van district from 1936 to 1984. build 27 new reactors in the next 15 expansion to serve the growing needs Because of the end of the Cold War years and India plans to build 17 in the of the nuclear power industry. In 1976, and the release of uranium from next 7 years. the mill was expanded to process 1,300 weapons stockpiles, the recession of the With rising uranium and vanadium tons per day. However, the declining 1980s, and other factors, the price of prices, Cotter Corporation reopened four

Figure 10. The Uravan site in Spring 2005; cleanup work is almost complete. Compare this photograph to Figure 7; both were taken from approximately the same point.

8 CGS ROCKTALK Vol. 9, No. 2 uranium mines in the Uravan district in 2003 and 2004. Cotter was transporting the ore from these mines to their mill in Cañon City for processing. Cotter closed the mines abruptly in November 2005 citing increased costs making these operations unprofitable at this time. The Cotter mines produced 394,236 pounds of uranium oxide and 1,746,251 pounds of vanadium oxide from 2003 through 2005. In July 2006, International Ura- nium Corp. announced that they plan on reopening four uranium mines in the Uravan district. Three of those mines will be in Colorado; the other will be in .

Figure 11. Uranium prices. (Source: Ux Consulting Company, http://www.uxc.com/)

Geology of Uranium Deposits in Colorado Uranium is a widespread and ubiquitous widespread in the Uravan district of Formation and marine muds, silts, and element. It has a crustal abundance of southwestern Colorado. The sandstones sands of the Mancos Shale covered the 2.8 parts per million, slightly more than of the Salt Wash Member were deposited rocks of the Morrison Formation. The tin. Primary deposits of uranium tend by meandering streams and were later Salt Wash sandstones are porous, per- to concentrate in granitic or alkalic vol- covered by shales, siltstones, and vol- meable, and locally contain abundant canic rocks, hydrothermal veins, marine canic ash beds of the Brushy Basin Mem- fossil plant material. Sometime after the black shales, and early Precambrian age ber of the Morrison Formation. Later, deposition of the sandstones, uranium- placer deposits. Secondary (or epigenetic) near shore marine sands of the Dakota See Geology on page 10 deposits of uranium are formed later than the surrounding rocks that host the mineral deposit. Uranium is soluble in oxidizing aqueous solutions, espe- cially the U+6 valence state, and can be redistributed from primary source rocks into porous sedimentary rocks and struc- tures by groundwater and form second- ary (epigenetic) uranium mineral deposits. Epigenetic deposits of uranium in sed- imentary rocks form the bulk of ura- nium deposits in Colorado. These include the many mines of the Uravan, Cochetopa, Maybell, and Rifle districts, and other scattered places including the Front Range and Denver Basin. Primary uranium deposits in Colorado occur in hydrothermal veins, especially in the Front Range. Epigenetic Uranium Deposits in Colorado Epigenetic uranium deposits in the sand- stones of the Salt Wash Member of the Figure 12. A uranium roll in the Salt Wash Member, Spring Creek Mesa Mine. Hammer for scale. Jurassic-age Morrison Formation are Dark colored material is uraninite. (Photograph by Jim Cappa, 2005)

CGS ROCKTALK Vol. 9, No. 2 9 Geology from page 9 Ore mined from 1959 to 1963 was prob- located in the Ralston Buttes district of ably also from the Leadville Limestone Jefferson County. and vanadium-bearing waters, probably though the host rock was unrecognized. The hydrothermal veins of the derived from the overlying volcanic ash Uranium ore in the Tallahassee Creek Schwartzwalder Mine are hosted in Pre- beds, flowed through the sandstones. district occurs in two early Oligocene- cambrian age metamorphic rocks, The uranium- and vanadium-bearing late Eocene age formations, the Talla- schists, gneisses, and quartzite. Most of water met changing physicochemical hassee Creek Conglomerate and the the uranium-bearing veins are located conditions, such as a reducing zone Echo Park Alluvium. The Echo Park Allu- in garnet biotite gneiss and quartzite. occupied by fossil organic material or vium consists of sandstone, shale, and The veins fill north- to northwest-trend- changes in the acidity of the water, and conglomerate. The Wall Mountain Tuff, ing, mostly steeply dipping, Laramide- the uranium precipitated as the miner- a rhyolite ash flow tuff, overlies the Echo age (about 70 million years ago) fractures als uraninite or coffinite and vanadium Park Alluvium. The Tallahassee Creek in the garnet biotite gneiss, quartzite, precipitated with clay minerals. Ura- Conglomerate overlies the Wall Moun- and other rocks (Fig. 13). The ore min- nium and vanadium minerals formed tain Tuff and is mostly composed of erals in the veins consist of uraninite irregularly shaped ore deposits, com- boulders derived from the erosion of vol- (variety pitchblende), some coffinite, monly referred to as uranium rolls. Typ- canic rocks and Precambrian igneous copper sulfides, and other base metal ical roll deposits from the Spring Creek and metamorphic rocks. Uranium was sulfides. Quartz and carbonate minerals Mesa Mine near Uravan are shown in dissolved from the Wall Mountain Tuff form the gangue (non-ore) minerals. Figure 12. Ore deposits in the Uravan by groundwater leaching and district range in size from a few tons to then deposited as uraninite over a million tons. The average ura- in favorable zones in the nium grade is about 0.25 percent and Echo Park Alluvium and Tal- the average vanadium grade is about 2 lahassee Creek Conglomer- percent. ate (Dickinson, 1981). The Cochetopa uranium district also contains uranium mineralization in the Hydrothermal Upper Jurassic Morrison Formation. In deposits the Thornburg Mine, the silicified and Vein deposits containing ura- brecciated sandstone and mudstone of nium minerals are wide- the Brushy Basin Member of the Morri- spread throughout the son Formation contain black, sooty, fine- Precambrian terrain of Colo- grained uraninite in veinlets and as rado. The central Front Range finely disseminated grains. contains numerous uranium Not all epigenetic uranium deposits occurrences; most of which in Colorado are located in the much- were not very productive. favored Morrison Formation. The Juras- However, the largest and sic-age Entrada and Navajo sandstones most productive uranium in the Rifle Creek district, Garfield mine in Colorado was the County host typical vanadium-uranium hydrothermal vein deposit at minerals. The grade of these deposits the Schwartzwalder Mine ranges from 1 to 3 percent V2O5, and generally less than 0.10 percent U3O8. Figure 13. Cross section of the Epigenetic uranium deposits also Schwartzwalder Mine. (Downs and occur in carbonate rocks in the Marshall Bird, 1965) Pass district, Saguache County. In the 1970s, Homestake Mining Company geologists working on the Pitch Mine Cleanup of Contaminated Uranium Mill Sites recognized that they had discovered a previously unrecognized type of ura- Several uranium mills and processing the 1960s, the Colorado Department of nium ore deposit in brecciated facilities were built during the boom Health (now named the Colorado of the Mississippian-age Leadville Lime- years of in Colorado Department of Public Health and Envi- stone. Most of the uranium deposits and and later abandoned. All of these facil- ronment—CDPHE) and the U.S. Public prospects of the district occur along the ities had waste piles of spent uranium Health Service determined that the tail- north-trending Chester fault. Large ura- mill tailings that, in some cases, were ings in the Grand Junction area posed nium deposits were formed where the used as construction materials for resi- a significant health hazard and had fault intersected the Leadville Limestone. dences, roads, and other buildings. In to be mitigated. At this time, several

10 CGS ROCKTALK Vol. 9, No. 2 thousand tons of uranium mill tailings approximately 5,000 properties and the site in Mesa County, known as the from the Climax Mill in Grand Junction nine uranium mill sites, 15 million cubic Cheney disposal cell, which will not be had been used in construction materi- yards of uranium tailings were removed totally capped and closed for several als. In 1972, the U.S. Congress created to controlled disposal sites. The disposal years. Recognizing the need for long- the Grand Junction Remedial Action cells were constructed utilizing strict term management and storage of the Plan and during the 15-year program, ground water, geologic, and erosion cri- remaining uncontrolled tailings, the 594 buildings in the Grand Junction area teria. The cells are designed to last for Cheney site will remain available for underwent some type of remedial action. 200–1,000 years, are erosion resistant UMTRA-related contaminated materials The U.S. Congress soon came to realize and located primarily away from popu- until 2023, or until the cell is filled that the uranium mill tailings hazards lated areas. The structures will continue to capacity. were not restricted to the Grand Junc- to be monitored and maintained in the For further information on the tion area and passed the Uranium Mill future by the U.S. Department of Energy UMTRA program, visit the following Tailings Radiation Control Act which (DOE). CDPHE web site: http://www.cdphe. set up a protocol and funding to clean In September 1998, the CDPHE devel- state.co.us/hm/rptailng.htm up uranium mill tailings throughout oped and published a plan for manag- The Uravan mill and processing site the U.S. ing uranium mill tailings encountered began operation in 1912 and continued Cleanup of the nine uranium mill during construction activities in west- operations until 1984. The site contained sites in Colorado authorized by the Ura- ern Colorado. The Post-UMTRA Ura- nearly 10 million cubic yards of radioac- nium Mill Tailings Remedial Action pro- nium Mill Tailings Management Plan tive tailings and processing ponds that gram (UMTRA) has been completed. The provides guidance and outlines resources were leaking contaminated water into communities in Western Colorado for building contractors, private citizens, the San Miguel River. In 1986, the Envi- where uranium mill tailings were utility companies, and local govern- ronmental Protection Agency added the cleaned up are: Durango, Grand Junc- ments when faced with newly discov- Uravan site to its National Priorities List tion (including Fruita and Palisade), ered uranium mill tailings material. and cleanup remedies were imple- Gunnison, Maybell, Naturita, and Rifle. Along with the development of respon- mented which include: Final authorization for the surface sibilities and safety procedures, the O Capping and revegetating 10 million cleanup program ended in 1998. From CDPHE developed a long-term disposal cubic yards of uranium mill tailings O Disposal of radioactive crystals from processing ponds and elimination of Bulletin 40 Press Release processing ponds O Pumping and treating contaminated The Colorado Geological Survey announces the reissue of Bulletin 40, Radioac- water tive Mineral Occurrences of Colorado. Bulletin 40 was originally published O Secure 12 million cubic yards of tail- in 1978, the height of the 1970s uranium boom. It quickly sold out and, as ings along the San Miguel River uranium mining declined it was never reprinted. As uranium prices increased O Dismantling the two mills and most through 2003 and 2004, the Colorado Geological Survey decided to release of the old buildings in the town of Bulletin 40 again, this time as a CD-ROM. Bulletin 40 provides a detailed list- Uravan ing of all the known (1978) uranium occurrences in the state. Several plates O Excavation and disposal of contam- depict the radioactive mineral occurrences on 1:250,000 scale topographic inated soil base maps. More detailed maps are included for the southwest corner of the Most of the cleanup work at the Ura- state in the area around Naturita and Uravan. A 585-page bibliography related van site was completed in 2001 except to uranium and thorium deposits and mining is included as Part Two of the for final remediation of the processing bulletin. Bulletin 40 was written in 1978 by James L. Nelson-Moore, Donna ponds and some long-term ground water Bishop Collins, and A.L. Hornbaker all of the Colorado Geological Survey. The Colorado Geological Survey scanned a printed copy of Bulletin 40 in an cleanup. See Figure 10 for a photograph Adobe Acrobat PDF format in late 2004. The objective of this publication is of Uravan in 2005. to provide readily accessible information on uranium and thorium deposits in Colorado to resource developers, government planners, and interested businesses and citizens. The Future of Uranium Copies of this publication, Bulletin 40, in CD-ROM format are available for $15 plus shipping and handling, from the Colorado Geological Survey. The use of uranium in the future will To order, please contact the Publications Section, 1313 Sherman Street, Room be for the production of electricity. Elec- 715, Denver, CO 80203, e-mail address: [email protected]; Fax number: trical demand is growing sharply, espe- (303) 866-2461; Phone: (303) 866-2611. Visa and MasterCard are accepted. cially in the emerging countries of See http://geosurvey.state.co.us for a complete list of publications available China and India. Nuclear power plants through the Colorado Geological Survey. currently are and will be part of the See Future on page 12

CGS ROCKTALK Vol. 9, No. 2 11 Future from page 11 References electrical supply equation; perhaps, even more so as concerns grow about the O Amundsen, M.A., 2002, towns: uranium mining communities emission of greenhouse gases from coal- in the American West: Boulder, Colo., University Press of Colorado, 204 p. fired powered plants and the price of natural gas. Nuclear power plants are O Chenoweth, W.L., 1981, The uranium-vanadium deposits of the Uravan expensive to build, but uranium fuel is mineral belt and adjacent areas, Colorado and Utah, in Epis, R.C. and Cal- abundant and cheap. Problems to be lender, J.F. (eds.), Western Slope Colorado, New Mexico Geological Soci- resolved include power plant security, ety thirty-second field Conference Guidebook, p. 165–170. eventual decommissioning, and spent fuel disposal. O Coffin, R.C., 1921, Radium, uranium, and vanadium deposits of south- western Colorado: Colorado Geological Survey Bulletin 16, 231 p.

O Dickinson, K.A., 1981, Geologic controls of uranium mineralization in the ROCKTALK Tallahassee Creek uranium district, Fremont County, Colorado: The Moun- is published by the tain Geologist, v. 18, no. 4, p. 88–95. Colorado Geological Survey 1313 Sherman Street, Room 715, Denver, CO 80203 O Downs, G.R. and Bird, A.G., 1965, The Schwartzwalder uranium mine, Jef- State of Colorado ferson County, Colorado: The Mountain Geologist, v. 2, no. 4, p. 183–191. Bill Owens, Governor O Goodknight, C.S., Chenoweth, W.L., Dayvault, R.D., and Cotter, E.T., 2005, Department of Natural Resources Russell George, Executive Director Geologic roadlog for Uravan mineral belt field trip, west-central Colorado: Prepared for Rocky Mountain Section Meeting of the Geological Society Colorado Geological Survey Vince Matthews, State Geologist and of America 2005 Annual Meeting. Division Director O Back issues and subscriptions Nelson-Moore, J.L., Collins, D.B., and Hornbaker, A.L., 1978, Radioactive can be obtained FREE by contacting mineral occurrences of Colorado: Colorado Geological Survey Bulletin 40 the CGS by mail, fax, phone, or e-mail (reprinted as a CD-ROM, 2005). or download them from our Web site. Phone: (303) 866-4762 O Shawe, D.R., Archbold, N.L., and Simmons, G.C., 1959, Geology and ura- Fax: (303) 866-2461 nium-vanadium deposits of the Slick Rock district, San Miguel and Dolores E-mail: [email protected] counties, Colorado: Economic Geology, vol. 54, pp. 395–415. Web site: http://geosurvey.state.co.us

THIS ISSUE O Sheridan, D.M., Maxwell, C.H., and Albee, A.L., 1967, Geology and ura- Authors: J. Cappa Editor: V. Matthews nium deposits of the Ralston Buttes district, Jefferson County, Colorado: Production: D. Eurich U.S. Geological Survey Professional Paper 520, 121 p.

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