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By L. W. Scott, T. H. Dubaniewicz, F. T. Duda, P. G. Kovalchik

Recent research conducted by NIOSH, Pittsburgh Research Laboratory showed that electrical current levels permitted under parent regulations may not limit cable temperatures to less than 90 °C in reeled trailing cables. Reeled cables, tightly wrapped with many turns, ell carrying current in an enclosed space, can become overheated due to poor heat transfer. This overheating can cause the cable insulation to soften and become easily damaged. The damaged insulation reduces the life of the cable and can lead to shock, electrocution, and mine foes. This paper describes a method of measuring the conductor temperature of untie trailing cables during no anal operation. The temperature is measured using a 50/175 micrometer Graded Index Multimode Optical Fiber located in the center of the metallic conductors. Distributed temperature measurements arc made using an Optical Time Domain Reflectometer (OTDR). This system is capable of measuring temperature with an accuracy of plus or minus one degree centigrade over a length of 4 km at 1-m intervals. With this unique way of measuring temperature, tests can be conducted simulating actual mine conditions and provide important data to allow MSHA's Approval and Certification Center to develop approval criteria for cyclically rated reeled machines.

The first steps in the process of mine evacuation are the recognition of a problem and an attempt to communicate the problem to miners who may be affected. This chapter will focus on the way that a problem, fire, came to the attention of mine personnel and the messages that were sent to miners in the affected areas. The concept of information uncertainty, which was introduced in chapter 4, will be discussed as it influences problem perception and diagnosis. Sociotechnical and interpersonal communications will be explored and suggestions for improving these systems will be offered. It might seem that the first indication of a dangerous fire would motivate individuals to take self-protective action, to evacuate the affected area or structure, and to provide clear warning to others who are in danger. Research has actually shown that in most situations this does not occur. Instead, time is taken to gather more information, confirm information that is provided, and consider possible alternative explanations that could account for the given circumstances [Canter 1990; Scanlon 1979; Bickman et al. 1977]. This process of confirmation can lead to the loss of critical time. Canter [1990] summarizes the problem in his book, which reports studies of a number of fire events: "As discussed throughout this book, ambiguity and confusion, incoherent instructions and time-wasting actions, lack of appropriate instructions and misunderstanding of the nature of the event that is unfolding, are all hallmarks of fires and emergencies that kill people." In this chapter, the detection of each mine fire and the communication of warning to endangered miners will be reviewed with an emphasis on how those processes were affected by the availability and use of information. Information can become available through a variety of mechanisms during an emergency situation. First, cues may be taken directly from the environment. Smoke is an obvious example. Secondly, mechanical devices, such as smoke detectors, may provide warning messages. A third source of information is interpersonal communications. These can occur face-to-face or through some mechanical device such as a telephone. With all three methods there is a possibility of miscommunication, misunderstanding, and misinterpretation. All of these means of communication were used with varying degrees of success in the three mine fires analyzed here. A fire, like any nonroutine situation, engenders uncertainty about a diagnosis and understanding of the problem [Mead 1938]. This uncertainty leads to delays in realization of the seriousness of the situation and therefore in the proper response to it. Delay in action is an important concern in any fire setting, but is even more at issue in underground coal mine fires. Mine fires are qualitatively different from structural blazes: workers' escapeways may be miles long; the seam height at many operations is so low that it is impossible to walk upright; access to underground workings is always limited to a few (sometimes only two)

Jan 1, 2000

By W. E. Young

Iron ore occurs in abundance in Iron and Washington Counties in southwestern Utah. Outcrops are encountered over a wide area extending from Paragonah on the northeast to Bull Valley on the southwest. Outcrops also occur on the Wah Wah Range and on Blue Mountain on the north edge of Iron County. The greater concentration of known deposits occurs in and around the margins of three mountainous uplifts - Iron Mountain, Granite Mountain, and Three Peaks - comprising a belt about 3 miles wide and 23 miles long (fig. 1). This area was partly explored by the Bureau of Mines in cooperation with the Geophysical Division of the Bureau of Mines and the Geological Survey under the strategic minerals program during 1942 to 1945. The exploratory work comprised geological and topographic mapping, geophysical prospecting with a magnetometer, diamond drilling, trenching and test pitting, sampling ore exposures and old workings, and constructing and repairing roads. The Pinto-Iron Springs district is the most important known source of iron ore for the steel plants of the West. The future economic status of the Intermountain and Pacific coast regions will depend largely upon the successful development and exploitation of substantial iron-ore bodies in this district.

May 1, 1947

By M. Townsend, E. L. Petsonk, H. Abrons, E. Daniloff, K. Kinsley

Workers exposed to certain inhaled dusts may show increased levels of nonspecific airways responsiveness (AR). In some studies, cigarette smokers have also been reported to have increased levels of AR. As part of an ongoing study, we compared the results of preshift methacholine inhalation challenge, spirometry, and smoking and occupational histories, in 191 under-ground bituminous coal miners (M) and 215 non-mining control workers· (C) . All M and c were selected to have normal baseline% predicted FEVI (PPFEV). Mining tenure was recorded as years worked underground (YRUG) and at the coal face (YRFC). AR was assessed as the% decrease in FEVI from baseline divided by the dose of methacholine delivered. M reported similar years smoked (YRSM) but fewer pack-years* (PY) than c~ Overall, both increasing YRSM and PY were associated with more AR*. Smoking C* but not M showed increased AR with increasing PY. In smoking and nonsmoking M, baseline AR and PPFEV showed no association with YRUG. The level of AR was inversely related to YRFC*, possibly representing selection away from dustier jobs. AR was inversely correlated with PPFEV*. In this study, AR and baseline PPFEV were not significantly associated with mining tenure, but cigarette smoking was related to both baseline lung function and level of AR. * p < 0.05 (Supported in part by Grant Gll35142, us Bureau of Mines, Generic Mineral Technology Center for Respirable Dust.)

Jan 1, 1989

By D. B. Dow

In collecting and dissctinating inforr:.at'ion on ir.:,provec.. practices us0i in the pr eduction cf petroleur:1 and in the r;:;.:.1.nuf __ cture of gasoline, the Bureau of Mines ha.s aidei in creatin5 an interest i-n efficient 11:ethods in all phasas of tr.e oil ani gi:i.s iniustry. In the refinin£ ir...mstry ther.:: is a growing tend.ency for incre.:l.sea. effi. ,:;iency, ana inforr;.Eition rela:tin!s to ic:;p·roved practices should be of value not only to the larger and. core efficient plants, but particularly to srr.a.11 refineries unable to carry out a lar6e experLnental pro!§.rarn. The refi?eries of the United States required 4.3,915,029 barrels cf crude oil J.uring the year 1920*, inclu.::.in1:, 611136,210 barrels of Mexican cru::...e. This yielded. 4,8821546,599 gallons of E>asoline, a.n avara.t;,e ciaily pro;.iuct1on of 13,340,291 e,allons·, Besides the easoline obtainel fro;., cruie· oil by-fr:;.cticna.1 distillation and. from heavy oils by crackini:,, this a,-r;ount incluC1.es 3,152,924 bar­rels of natural-ga.$· gasoline blended. With asoline fro,., th otha two sourcs.

Apr 1, 1922

Develop methods of enhancing and measuring the high-temperature softening and melting properties of iron oxide pellets reduced under simulated blast furnace smelting conditions. Approach Add dolomite and Limestone flux and a low-cost organic binder, such as starch, carboxyl methylcellose (CMC), or waste papermill sludge, to the iron oxide concentrate to produce hematite (ferric oxide) pellets with superior high-temperature metallurgical properties. Simultaneous increases in softening temperature, gas permeability, and enhanced metallization rates are sought to improve blast furnace productivity and energy efficiency. Background In the past, bentonite, an inorganic binder, was the only additive (binder) used in the production of pellets made from iron ore concentrate. Research has shown that the reducibility of conventional (acid) pellets can be increased by the addition of flux or an organic binder. The increase in pellet reducibility results in less wustite in the center of the pellet at high temperatures, such as those obtained in the cohesive zone of the blast furnace.

Jan 1, 1990

By W. J. Pena, C. W. Owings

"Generally, the hazard of cool-dust explosions in tipples and cleaning plants is not given the consideration that is given it underground. This lack of consideration is probably due to failure to appreciate the potential hazard. An explosion in a tipple or cleaning plant is basically little or no different from an explosion underground. If bituminous-coal dust is raised into a cloud in the air and comes in contact with arcs from motor brushes, switches, or open flame, the dust is very likely to ignite, and flame will very probably propagate or extend through it if the quantity of dust per unit of air space is sufficient. The open space in a tipple or cleaning plant may reduce the violence of the explosion, but it is not likely to prevent ignition or propagation of flame.The movement of coal through a tipple or cleaning plant naturally puts into suspension a large amount of dust, which finally settles on exposed surfaces. Any disturbance that will put this dust into suspension in a sense enough cloud can result in the dust being ignited by an arc or open flame if one should be present. An explosion of bituminous-coal dust in a tipple or cleaning plant generally can be prevented either by keeping it thoroughly clean or by removing all sources of ignition, or both.The tests at the U.S. Bureau of Mines Experimental mine have shown that the explosibility of coal dust is proportional (other things being equal) to the ratio of the volatile matter to the volatile matter plus the fixed carbon, indicated thus:The volatile ratio for the Pittsburgh coal bed is calculated as follows:Therefore, as the volatile matter decreases the liklihood of ignition decreases; however, coal-dust explosibility depends on other factors also, such as fineness, dryness, and cloud density; and under some conditions other factors also intervene.Proof of the explosibility of coal dust in the absence of explosive gas has been shown in numerous cases in mines and mine plants and also by a series of tests. In these tests a dense cloud of dust is blown onto an open flame or an electric arc, almost invariably with resultant exploding of the dust. The Safety Division of the United States Bureau of Mines has made a number of demonstrations of the explosibility of Pittsburgh coal-bed dust, using a small gallery or box in which a cloud of coal dust is blown onto a lighted match; larger-scale tests have been made with an electric arc as the igniting agent. Bituminous-coal dust is readily ignited with a medium arc, but with low-volatile coals a larger arc is required. For test purposes, a 100-ampere arc has been used. Ignition has occurred readily under these conditions with Pocahontas No. 5 coal dust with ratios of volatile to total combustible of 0.232 to 0.253, and with Pocahontas No. 3 coal dust with a combustible ratio of 0.242. Lower Kittanning coal dust, with a ratio of 0.187, did not give definite ignitions, and Pocahontas No. 4 dust did not explode, although part of the coal-dust cloud ignited. It is probable that even the low-volatile coal dust will be found to be explosive with a higher-amperage electric arc as the initiating agent."

Jul 1, 1936

Reduce the noise radiated by the auger miner cutting head (typically 105 dBA at the face) by 10 dBA without compromising the durability or productivity of the tool. Approach Research was conducted by the Bureau of Mines to identify the noise sources of auger miners with emphasis on the cutting head and coal cutting process. The overall noise level generated by the coal cutting process was found to depend greatly upon the structural characteristics of the auger cutting head. Based on this information, a quieter cutting head was

Jan 1, 1982

By N. A. Caspero, W. E. Eckard, W. T. Wertman

A thermal oil-recovery experiment was conducted in the Venango First sand, Goodwill Hill oilfield, Warren County, Pa., about 10 miles northeast of Titusville. The Quaker State Oil Refining Corp., Bradford, Pa., performed the experiment with assistance from Sinclair Research, Inc., Tulsa, Okla., and the Federal Bureau of Mines. The Goodwill Hill field was discovered in 1885. Primary-production oper- ations continued until 1930 when an air-gas injection project, which is still in operation, was started. At the location of the combustion experiment, the reservoir is 400 feet deep and 30 feet thick, with wide permeability and porosity variations. The crude oil is typical Pennsylvania Grade paraffin- base oil with a gravity of 43.9° API and a viscosity of 4.55 cp at 60° F. The well pattern for the experiment consisted of 5 producing wells, enclosing an area of 1.28 acres, and a central ignition-injection well. An air-natural gas mixture was ignited in the ignition well on July 29, 1961. Ignition was followed by injection of air and natural gas at various rates. The experiment was suspended January 5, 1962, when it became evident that economic oil production could not be achieved. There was no conclusive evidence that self-sustained combustion was achieved or that combustion increased oil and water production. A slight increase in liquid production was attributed to stripping action caused by the air-injection rates, which were higher than those normally used during air-gas injection.

Dec 1, 1963

By Lloyd A. Morley, Alan M. Christman

General An important part of any mine power distribution system is its con¬nection to earth or ground. The grounding network serves to protect men and machinery from the hazards associated with electrical equipment which is operating improperly. Since the mine site is determined by the location of the rock or mineral to be extracted, the conditions required for the installation of an adequate grounding system are not always easily met. If annual rainfall is low or soil resistivity is high, an extensive array of buried metallic conductors may be necessary to assure a low-resistance connec¬tion to earth. Measurement of soil parameters can be made before the construction of a grounding grid is begun, and the configuration of a metallic network, which will yield the desired values of earth resistance and potential gradient, thereby ascertained. Proper design at the time the ground bed is installed will save much time and expense in later years. Ground conductors extend from the buried grid to each piece of mo¬bile and portable equipment via overhead lines or multi-conductor cables. In this fashion all machine frames are referenced to the same potential as the grounding medium. Protective circuitry must be installed to monitor\current flow in the ground conductors or the potential drop across the neutral grounding resistor, which is placed between the grounding grid and the neutral point on the distribution transformer secondary. When properly co-ordinated and used in conjunction with a low-resistance

Jan 1, 1976

By K. Rubow, Z. Zhlqun, V. Marple

A theoretical technique has been developed and verified experimentally for determining the aerodynamic diameter of irregular shaped particles. The aerodynamic diameter of a particle is a very important property in determining where that particle deposits in the respiratory tract. Many instruments, such as impactors and cyclones, will determine the aerodynamic size distributions of aerosol particles but few analyze the particles individually. The theoretical approach of our technique is to solve, by use of high speed computers, the three dimensional Navier-Stokes equations to obtain the flow field around an irregular shaped particle of any contour. The computer program will then determine the drag on the particle, and thus the aerodynamic diameter of the particle can be calculated. The experimental approach has been to pass the particles through a centrifuge and collect the particles upon a collection foil. The position of a particle on the foil is an indication of its aerodynamic diameter. These particles were then shadowed in two orthogonal directions and inspected under an SEM. The top view of the particle in the SEM plus the views of the two orthogonal shadows allows one to determine the three dimensional shape of the particle. Studies have been performed on silica, coal and talc particles with aerodynamic diameters in the 1 to 4 um size range. The three dimensional shape, as is determined from SEM analysis was used in the theoretical computer program and the results compared. It was found that in most 'cases the agreement between the experimentally and theoretically determined aerodynamic diameters was within 5%.

Jan 1, 1988

By C. L. Wright

In 1904 the Government began a series of fuel-testing investiga- tions at its fuel-testing plant at St. Louis, Mo. These investigations, which were placed under the supervision of the United States Geo- logical Survey, included chemical analyses, steaming tests, gas- producer tests, briquetting tests, coking tests, and washing tests of samples collected from the various coal fields of the country. The specific purpose of the investigations was to analyze and test the coals and lignites in the United States, in order to deternime their fuel values and the most efficient methods of utilizing them for different purposes. Part of the fuel-testing plant, including the briquetting equipment, was moved to Norfolk, Va., in 1907, and the fuel-testing investiga- tions were made one of the divisions of the technologic branch of the Geological Survey. In 1908, after the close of the Jamestown Exposition, most of the fuel-testing equipment was removed to its present location at the Pittsburgh experiment station, Fortieth and Butler Streets, Pittsburgh, Pa. In 1910, an act of Congress, effective July 1, established the Bureau of Mines in the Department of the Interior and authorized the transfer to this bureau of the fuel-testing investigations that had been carried on by the technologic branch. Bulletins presenting the results of various inquiries and investiga- tions relating to briquetting have been published by the Geological Survey and the Bureau of Mines. As the supply of some of these bulletins is exhausted, the Bureau of Mines has decided, instead of reprinting them, to publish the more important facts they contain

Jan 1, 1913

The optimum situation in sealing the soil with latex would be to locate the sealant at the depth where natural permeability is lowest, and to narrow distribution of the latex to a film. To ascertain how closely we were achieving these objectives it was necessary to devise a method to measure the concentration of latex in soil. A number of methods were explored and two were used in actual field tests. SBR latex tagged with c14 was prepared and used to determine the distribution of polymer in the soil. The latex was made by copolymerizing a mixture of radioactive and normal styrene with butadiene in bottles by conventional methods. Average particle size was 600 Å. Diluted aliquots had 1.40 microcuries radioactivity per gram of latex. Tagged latex was mixed with soil in a range of proportions from 0.01 to 0.25% by weight to develop a calibration curve. Analyses of soil in the laboratory and from the field were determined by comparison with this master curve. Styrene-containing polymers have a characteristic peak at 700 cm-1 but crosslinked SBR is not soluble in solvents normally used in infra-red spectroscopy, e.g., carbon disulfide. We developed a method for solubilizing the crosslinked polymer by stirring overnight at room temperature a soil sample in chloroform with t-butyl hydroperoxide and osmium tetroxide. The filtered chloroform residue was dried to constant weight, thoroughly mixed and pressed into a KBr pellet, and concentration was determined by measuring the absorption at 700 cm-1. Details are given in an Appendix.

Jan 1, 1972

To improve mining safety and efficiency by providing a practical way of detecting faults and channel sands that disturb coal seams. Approach A seismic system using a shallow blasthole has been developed and tested. How It Works A small shock is caused in a shallow hole, sending seismic waves through the ground. These waves are reflected from the top of the coal seam, acid are detected by a line of geophones on the earth&apos;s surface. Dampening of the seismic signals by channel sands and other discontinuities in the seam is detected and recorded. See Figure 1. The seismic shock wave can be produced by exploding small charges, dropping a weight, firing a gas gun, or actuating a vibrator. Depending on the soil cover, the shock is usually generated in shallow vertical holes about 10 feet deep. Hole depth depends on the soil mantle thickness because it is preferable that the seismic shock originate below that layer.

Jan 1, 1976

By Edmund S. Leaver, Jesse A. Woolf

"The Baboquivari mining district is about 60 miles southwest of Tucson, Ariz., the present railroad shipping point. The values are silver and gold. The silver is largely associated with the black oxides of manganese. The ore is highly oxidized, and careful panning shows only a very small amount of pyrite. Our sample analyzed as follows:A flotation mill has been installed in the district, but it does not concentrate the precious metals satisfactorily. Our best laboratory flotation results were obtained by grinding to pass 65-mesh and floating with Xanthate or standard flotation oils plus sodium sulphide and polysulphide. This sulphidizing method gave a concentration of 32 per cent of the silver and 80 per cent of the gold, which about equals plant practice.We do not know of an instance where the oxidized forms of manganese have been concentrated satisfactorily by flotation.Plain cyanide on the original ore extracts practically all of the gold but only one-third of the silver. A preliminary deoxidizing roast, using producer gas or powdered coal, gives a calcine from which cyanide dissolves about 90 per cent of the gold and 75 per cent of the silver. This method of treatment, known as the Clevenger-Caron process, is described in Bureau of Mines Bulletin 226.Preliminary treatment with sulphur dioxide by burning pyrite or sulphur and passing this gas into the pulp until all of the contained manganese is dissolved or changed in form best prepares the ore for cyanidation. The acid consumption will vary with the percentage of manganese and other soluble constituents. Neither gold or silver is dissolved by this acid treatment. The washed residue gives maximum cyanide dissolution of the gold and silver with minimum loss of cyanide,"

May 1, 1928

By Launa G. Mallett, Robert H. Peters, Barbara Fotta

Due to variations in the thickness of U.S. coal seams, there is great variability in the height of the roof where underground miners work. Restrictions imposed by low seam heights have important safety consequences. As the height of their workplace decreases, miners must stoop, duck walk, or crawl, and their vision, posture, and mobility become increasingly restricted. Low seam height also places important restrictions on the design of mobile equipment and other mining machinery. Using the employment and injury data reported to the Mine Safety and Health Administration (MSHA) from 1990 to 19% small underground bituminous coal mines with less than 50 employees were stratified by average coal seam height according to the following categories: low (? 42"), medium (43"60N), and high (? 61"). Injury rates for both nonfatal days lost and fatality cases were examined by seam height and leading type of injury incidents. The leading types of Incidents associated with fatalities were roof falls and powered haulage equipment. In comparison to high-seam mines, miners working in low or medium seams are at higher risk of being killed by powered haulage equipment, roof bolting machines, and falls of unsupported roof. The leading types of incidents associated with nonfatal injuries were handling materials and powered haulage. As mining height decreases, miners are at increasingly higher risk of having a nonfatal injury from incidents involving roof bolting machines, load-haul-dump equipment, personnel carriers, and powered haulage conveyors. As mining height increases, miners are at increasingly higher risk of having a nonfatal injury from slips and falls and incidents involving shuttle cars and roof and rib falls. Knee injuries are a particularly severe problem in low- seam mines. The rate of injuries to miners while crawling or kneeling is 10 times higher in low seams than in high seams

By Allen Q. Howard

An approximate solution to the electromagnetic boundary value problem consisting of a horizontal cylindrical conductor buried in a lossy half-space and excited by an arbitrarily oriented magnetic dipole is found using an iterative perturbation technique in a double Fourier transform space. This model is used to gain insight into the anomalous fields due to strong scatterers such as pipes or tracks which would be in close proximity to an EM mine rescue operation. The novel, three-dimensional aspect of the problem (i.e., the source) imposes the complexity that the current in the cylinder is not uniform. The field expressions are ideally suited to evaluation using FFT algorithm.

Jan 1, 1973

By R. V. Ramani, P. M. T. White, D. Sutton

6.1 Summary This report deals with the investigation carried out to select, test, and implement a method of evaluating coal deposits and reserves. Cognizance is taken of the inherent characteristics of coal and the legislation covering aspects of health, safety, environment, and ecology applicable to the coal mining industry. Further, the method is computerized and provides information that is meaningful and readily available to other programs and sub¬systems within the concept of the Master Design Simulator. The Geology and Reserves Sub-system interface with the total system is provided by a geological data library which is structured to hold and make accessible all the data required by the system. The output from the program is accurate and useful to users with a wide variety of computer experience, knowledge, hardware and storage capacity. The sub-system is designed to function as a separate unit or an integral part of the total system and, there¬fore, an interface to or with the system has been established. The work carried out by the sub-system includes: (a) The analysis of raw geological data. This involves:

Jan 1, 1974

By John A. Davis, Karl L. Kithil

The principal deposits of carnotite, so far as now known, are con- fined to a well-defined area lying in the southwestern part of Colo- rado and the southeastern part of Utah (see Pl. I). Approxi- mately, this area is bounded as follows: On the east by a line ex- tending from a few miles east of the southwest corner of the State of Colorado, to a point about 6 miles west of Naturita, thence di- rectly north to the San Miguel River, thence along the course of this river and the Dolores River to Mesa Creek, thence toward the head- waters of Mesa, Blue, and Calamity Creeks on the south side of the Uncompahgre Mountains; on the north by a line extending from the last-named point westerly to the San Rafael Swell near Green River, Utah; on the west by a line extending from San Rafael Swell to the Henry Mountains, and on the south by a line extending from the Henry Mountains toward the southeast corner of the State of Utah. This area includes the main districts wherein carnotite has been found, claims have been located, and the ore produced. There are of course, extensive tracts within this area which do not contain carnotite in paying quantities. In places the carnotite beds have been entirely eroded or are not present, or lie so deep that mining is not practicable. The main deposits of carnotite within the area lie in different districts which in Colorado are as follows: Summit and Bush Canyons in Dolores and San Miguel Counties; McIntyre, Gypsum Valley, and Bull Canyon districts; the Paradox Valley, La Sal Creek, Roc Creek, Long Park, Hieroglyphic, Saucer Basin, and Hydraulic districts in Montrose County; Mesa, Blue, and Calamity Canyon districts and the Gateway area in Mesa County. The included dis- tricts in Utah are as follows: The Green River and San Rafael Swell district in Garfield County; the Thompson deposits in Grand County; the Dry Valley, Yellow Wash, and Lisbon Valley districts in San Juan County; the district around the Henry Mountains in Garfield County; and the deposits recently reported in Montezuma Canyon (south of Monticello) in San Juan County. Outside of the area described there are scattered deposits north of the Denver & Rio Grande Railroad at Coal Creek, near Meeker, Rio Blanco County; along Skull Creek and Red Wash, near Rangely, Routt County; on Horse Mountain, near Eagle, Eagle County, and in South Park, near Garos, in Park County, Colo. The claims leased from the Crucible Steel Mining & Milling Co. by the National Radium Institute are situated on the north side of East Paradox Valley, in the Long Park and Hydraulic districts. The National Radium Institute has mined no ore except from its leased claims in the Long Park district. For information regarding the general geology of the region, the probable origin of the ores, and descriptions of other carnotite deposits, the reader is referred to the literature on these subjects. The carnotite of the area described is deposited in a light-colored, cross-bedded sandstone that lies almost horizontal between the La Plata formation below and the Dakota sandstone (conglomerate) above, and is included in the McElmo formation, which is of Jurassic age. Underlying the white sandstone of the La Plata is the Dolores formation, or "Red Beds," which is plainly visible along and just below the rim rocks of the steep canyon walls in many of the carnotite districts. Along such canyons the ore crops out at different places, so that prospecting is comparatively easy. For ore on the benches and on the mesa prospecting is more difficult, especially where the ore lies at some depth and no surface indications are visible. The carnotite deposits are flat, lenticular, and irregular, varying greatly in extent and thickness. The carnotite itself forms incrustations on exposures of the white sandstone, in joints and fractures of the rock, and is deposited around and between individual sand grains, replacing the original cement. The Utah and Colorado carnotite is amorphous, and to the naked eye appears as a very fine yellow pow- der. It is often granular, and as a rule can be readily separated from the individual sand grains.

Jan 1, 1917

By Howard M. Stainer

Jan 1, 1963