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By I. AITKENS

Turquoise is prized solely for its attractive color ; it is dull and opaque , wholly lacking the brilliant luster that is the chief attraction of transparent gems . The best quality of turquoise is blue , of a soft and pleasing tone , like the color of clear sky but distinctive , as indicated by use of the term " turquoise blue . " Often its value is lessened by a greenish cast ; in many stones the green predominates . A large proportion of the turquoise that is mined is utterly worthless , so inferior and unattractive is its color . The finest grade of turquoise comes from Persia , notable from Nishapur . Large quantities have been mined in the Southwestern States of the United States , and less important deposits have been found in a number of the other States .

Sep 1, 1931

By Lloyd A. Morley, Alan M. Christman

Mine One General. The first summer field trip for the purpose of collecting data on open-pit metal mine grounding systems was marred by the fact that the group's ground test instrument was damaged in transit and proved to be inoperative. Fortunately, the mine personnel had a similar instrument which was then used for all tests. System Description. Power is purchased from the utility at either 69 or 100 kV. This is transformed to 4160 V at the pit substations and distributed around the periphery of the pit via a "ring bus." The three phase wires and the safety-ground conductor are carried on a conventional wooden pole and cross-arm support structure. At key loca¬tions, overhead feeders carry power from the ring bus down over the benches and into the pit. Each overhead feeder is terminated at a switchhouse, from which an SHD-GC trailing cable supplies power to the electric loading shovels. Each pit substation has a main or system-ground mat, installed by the utility, and a separate safety-ground mat, which is constructed by mine personnel. Three of the safety-ground mats are quite old, and personnel at the mine could not recall what type of construction was used. However, records are available on the fourth mat and construc¬tion details are shown in Figure 64. Protective circuitry includes a donut or window-type current transformer through which the three phase wires are run. Additional

Jan 1, 1976

By Robert P. Vinson, Kissell. Fred N., Edward D. Thimons

"The Bureau of Mines investigated the presence and extent of methane accumulations in mine roof cavities using a full-scale mine model. Methane was released at a constant rate into the roof of a cavity built onto a 700-ft wind tunnel. Two box-shaped roof cavities were used in the study: one had a volume of 114.7 cu ft; and the other had a volume of 57.3 cu ft. Methane concentration was measured at 28 sampling points in the cavities using 21 different combinations of gas emission rates and air velocities. Brattice hung in the cavity helped reduce methane concentrations without auxiliary ventilation. It was also found that the effective ventilation rate increased by a factor of 40 in the large cavity and by a factor of 20 in the small cavity when air velocity was increased from 100 to 600 fpm.INTRODUCTIONAny location in a coal mine where 5 pct or more of methane is present constitutes a potential site for an explosion and roof cavities are likely locations. Unfortunately, little is known about the buildup of methane in roof cavities. Some research has been done using scale models where no air flows past the cavity so that methane disperses only by diffusion (5) 4 a rare situation in mines.No known cavity-model investigations have been made that simulate air and methane flow conditions normally encountered underground. These Bureau of Mines studies were undertaken to determine the extent and manner of methane buildups in coal mine roof cavities with air velocities in the range normally found in coal mines and with various methane emission rates."

Jan 1, 1978

By A. C. Rice

Aminopolyacetic acid chelating agents were added to separatory-funnel-scale solvent-extraction systems to determine the effect on separating rare-earth elements. Average values for separation factors between adjacent elements obtained with Primene JM-T2 increase 36 percent when EDTA is added to the aqueous phase. Adding HEDTA or DCTA also improves separation factors for certain rare-earth elements. Percentage of extraction and the separation factors exhibit marked sensitivity to concentrations of amine, chelating agent, and hydrogen ion. The chelating agents improved separation in Primene JM-T, BHDA, and Primene 81-R extraction systems.

Jan 1, 1963

By Henry E. Blake

Defluorination studies on refractory fluoride - bearing compounds and minerals , particularly on partly defluorinated residues from high - temperature pyrohydrolysis , required a dependable and reasonably accurate analyticalcontrol method for the analysis of fluorine . The difficulty in liberating fluorine from the fluorides of metallic elements such as aluminum, zirconium , and rare earths by steam- distillation can be largely overcome if the distillation is made from a sulfuric - phosphoric acid solution of a sodium carbonate fusion of the sample material and if the distillation temperature is maintained at about 155 ° C. The data presented in this paper show that liberation of fluorine by this method is more complete and proceeds more rapidly than by usual distillations from perchloric or sulfuric acid alone or a mixture of phosphoric and perchloric acids . Fluorine in amounts ranging up to about 140 mg can be recovered by collecting only about 300 ml of distillate . Determination of fluoride in the distillate is made by the usual thorium nitrate titration .

Jan 1, 1963

By Kenneth E. Hjelmstad

In situ leach mining operations often encounter difficulty maintaining adequate leach solution flow into the are formation. Swelling and dis-persion of clay particles in the formation are often responsible for this permeability loss. Permeability and leaching tests were done in the laboratory on clayey ores to evaluate a clay-stabilizing polymer's effectiveness in preventing these problems. Test results indicate that treating the ores with the stabilizer could maintain permeabilities two to five times greater than the long-term permeabilities present in untreated ores. Both alkaline (pH 8.5) and acidic (pH 2.0) leaches were used in the permeability-leaching tests. Since in situ leaching throughput rate is directly related to permeability, these results also indicate a potentially beneficial effect on operating parameters such as capacity and injection pressure. To determine the reasons for the success of the clay stabilizers, an investigation was conducted to cieter-mine the effect of the stabilizer on clay swelling and dispersion. Clay-swelling tests indicated that the clay stabilizer reduced clay swelling. Zeta potential measurements made on fine clay particles treated with the stabilizer were compared to measurements made on untreated particles and indicated that the stabilizer was electropositive and, therefore, could reduce the degree of negative charge on the particles and their tendency to disperse or migrate.

Jan 1, 1984

By C. A. Herbert

Timber decay is due largely if not wholly to a fungus growth on the timber from which it derives' food; a warm, moist atmosphere is necessary for rapid growth. The decay is spread from infected timber to sound timber by countless microscopic spores or seeds given off by the fungus growth and carried by air currents or by long, cottonlike threads, which spread from timber to timber. Haulage roads in most mines in the central coal fields are also return aircourses; hence moisture and temperature conditions are ideal for the rapid decay of mine ties and mine timber. Possibly the return air, which contains a higher percentage of carbon dioxide than normal outside air, also stimulates the growth of fungi. Those familiar with coal mining have observed the more pronounced growth of fungi and decay of timber in poorly ventilated worked-out sections of mines where the air is moist and where usually the percentage of carbon dioxide in the air is considerably above normal.

Jan 1, 1934

By Christopher C. Jobes

This U.S. Bureau of Mines report describes a system to determine the position and heading of a mining machine during maneuvers in the face area of an operating mine section. The system is the first step in the development of a guidance system for automated mining machines. The position and heading algorithm is described, and a preliminary error analysis is performed. The sensors employed were linear position transducers mounted on a mining machine with their cables attached to points on a stationary reference. Four linear position transducers were used to provide a data redundancy that increased the reliability of the guidance system. The linear position information obtained from the transducers was processed mathematically via the position and heading algorithm to provide the desired position and heading information. The algorithm takes advantage of sensor redundancy to continually test the accuracy of the sensor data. The major sources of error were determined to be the linear position transducers, the analog-to-digital (A/D) converter used to interpret the data, and the sampling frequency of the measurement system. These sources of error were evaluated to determine their inaccuracies for use in calculating the overall system accuracy.

Jan 1, 1990

By Harry D. Jumper

This paper describing the methods of ruining a sand, gravel, and bowlder deposit 20 miles east of Los Angeles, and the classification and preparation of these materials for market, is one of a series being prepared for and published by the United States Bureau of Mines on methods and cost of mining sand and gravel. These papers are designed to disseminate technical information regarding, the methods used. The cost tabulations represent operating expenditures only and not total costs. It is recognized that publication of total costs might in many instances cause embarrassment to individual operators as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion anti study of the methods employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulations stall ensue. The description contained herein is typical of this industry in Southern California. ACKNOWLEDGMENT The author acknowledges tine assistance of L. L. Rogers, vice-president and manager of production and distribution for the Consolidated Rock Products Co., in the preparation of this paper.

Jan 1, 1933

By Robert C. Johnson

Single crystal whiskers of ZrO2 and TiO2 were grown by solution and crystallization of these oxides in molten baths. Mixtures of Na2B407 and LiC1 were the most suitable growth media for zirconia. Sodium borate alone and Na2CO3 plus SiO2 were best suited for titania. The solubilities of zirconia and titania in molten sodium borate were determined, Whether zirconia whiskers were dendritic or nondendritic depended on the temperature used. The best single crystal whiskers were grown below 1,100° C. Titania whiskers always grew as single crystals. The tensile strengths of zirconia and titania whiskers were about 15,000 psi and 50,000 psi, respectively. Modulus of rupture was about 49,000 psi for zirconia whiskers and 75,000 psi for titania whiskers. Chemical analyses showed the zirconia and titania whiskers to be pure. The zirconia and titania whiskers were shown by X-ray analysis to be, respectively, baddeleyite and rutile.

Jan 1, 1965

By Carl N. Anderson

This paper, which is one of a group presented by the United States Bureau of Mines covering mining practice in different districts, deals in particular with the methods employed in mining the horizontal type of zinc-lead orebodies of the West Baxter area of the Tri-State zinc and lead district. These orebodies, locally termed "sheet-ground" bodies, with their relatively low working faces and low tenor of zinc and lead, require changes in the mining practice which is used in the balance of the district. In addition to the general mining methods, this paper also describes the system of hand sorting employed prior to the direct milling of the ore. The Hartley mine is situated mile west of Baxter Springs, Kans., as indicated in Figure 1. Its general outline and the location of the shafts with respect to the milling plant are shown in Figure 2.

Jan 1, 1932

By R. D. Leitch

The work of the United States Bureau of Mines on stream pollution by coal-mine drainage has included a study of seasonal variations in acidity and volume of several streams in Pennsylvania. The acidity of these streams has been determined during the two or three years prior to 1930 and the results may be considered to represent "normal" low water conditions. The summer of 1330, however, was unusually dry and represents what may be termed "extreme low water conditions on these streams. This report is a comparison of the results obtained for extreme low water of 1930 and for other years. The streams investigated were Buffalo Creek in Somerset County, Indian Creek (lower 5 miles) in Westmoreland County, Little Toby Creek in Elk and Jefferson Counties, Daguscohonda Run in Elk County and West Creek in Elk and Cameron Counties. These will be treated separately in the order given. Most of the descriptive matter and physical data pertinent to the streams and drainage basins are taken from published reports of the Pennsylvania State Water Supply Commission, 1917.

Jan 1, 1931

By Jack E. Tress

The Bureau of Mines has been involved for several years in the development of processes for the recycling of solid wastes. As part of this program, a project was initiated to determine the feasibility of producing secondary pig iron from auto scrap. During the test period, 86,000 pounds of shredded auto scrap, along with petroleum coke and fluxing agents, was charged to a submerged-arc furnace of 1-ton nominal capacity. Eighty-eight thousand pounds of pig iron, with an average carbon content of 3.90 percent and an average copper content of 0.2 percent, was produced at an electrical consumption of 512 kW-hr per net ton. A cost estimate of the process showed that the pig, iron might be produced at a cost of $57 per ton.

Jan 1, 1973

By Frank L. Hess

In the first cart of that little space of time that we have designated as the nineteenth century, chemistry had reached a wonderful stride. Viewed from the present heights attained by the efforts of innumerable chemists with perfected apparatus, mire reagents, air under pressure, water, gas, and electricity conducted to the desk, and. numberless other helps, it seems marvelous that chemists of that day obtained such results. In 1820, about half of the elements had. been discovered; of these discoveries, Swedes had made 15 or more, about once-third of the elements then known and nearly half of those discovered after 1700.

Jan 1, 1939

By W. W. Cutler

An oil-field drilling campaign is used in this paper to signify the spacing of the wells to be drilled as well as the drilling program, which is interpreted as the number of wells drilled in a unit of time, This has an important bearing upon the time of receiving income, as well as upon the amount of revenue obtained In periods of low prices for oil, such as the present, the margin of profit is at the best very small, and the correct determination of the drilling campaign may be the deciding factor between incurring financial loss or gain during the depressed period. General policy of the operator. Drilling should be planned by the field engineer to conform with the general policy of the operator. This policy may be one of conservation daring the early life of the property, but as mentioned later, this may result in a smaller ultimate recovery it often occurs that the market price of oil does not warrant rapid development, or it may be desirable to hold in reserve a supply of oil for a refinery. The policy may be to recover all of the oil as quickly as possible, or it may be to maintain a constant and sustained production. In any case, the operator should, outline as far as possible a definite policy, and should understand the principles underlying the recovery of oil, the influence of rapidity of drilling and effects of spacing, in order that he may obtain the oil as required with the least expenditure.

Jan 1, 1921

By K. J. Miller

A two-stage froth flotation technique was developed in the laboratory to separate fine-size pyrite from coal. The process consists of the initial flotation of a 15-percent solids coal slurry with a minimum of frother; the coarse, free pyrite and other refuse are removed in the tailings. The froth product from this first stage is then repulped and treated with a coal depressant, a pyrite promoter, and a frother to float the remaining fine-size pyrite or pyrite attached to coal particles. With the two-stage process, the pyritic sulfur content of a Lower Freeport bed coal sample was reduced from 1.78 percent to 0.75 percent in the first stage, and from 0.75 percent to 0.27 percent in the second stage with good clean coal recovery.

Jan 1, 1972

By Jim F. Lemons

The Bureau of Mines Minerals Availability System collected and analyzed data for 34 nonlaterite and 9 nickeliferous laterite domestic chromite deposits in order to assess their viability as sources of chromium under present technologic and economic conditions. These 43 deposits, none currently in production, contain approximately 6.3 and 22.3 million metric tons of Cr203 at the demonstrated and identified resource levels, respectively. Approximately 4.6 and 15.6 million metric tons of Cr203 are recoverable at the demonstrated and identified levels, respectively, for the 34 nonlaterite deposits. None of these resources are economically recoverable at January 1981 market prices. Production of metallurgical-grade chromite (market price $128 to $144) would require a minimum chromite market price of $237 per metric ton. Chemical-grade chromite production (market price $74 to $85) would require a chromite market price in excess of $188 per metric ton. From the 34 nonlaterite deposits, roughly 5.4 and 17.6 million metric tons of ferrochrome could be produced at the demonstrated and identified resource levels, respectively; however, a minimum market price of $770 per metric ton of ferrochrome would be required to stimulate production. The nine nickeliferous laterite deposits were not evaluated through production stages because of uncertainties in process technology and cost.

Jan 1, 1982

By John D. Prater

Thallium is one of the rarer metals that has come into commercial importance in recent years. Although the element was first reported by Crookes in seleniferous deposits in lead chambers of a sulfuric acid plant in the Harz Mountains of Germany, it had no commercial significance until about 190O because of the high cost of extraction. Thallium occurs widely in the earth's crust but is found in such low concentrations that it is recovered only as a byproduct from processing other elements. There are no domestic ores of thallium; the entire output in this country is supplied by the American Smelting & Refining Co. as a byproduct of its cadmium operations at Globe, Colo. Thallium also is recovered from the flue dusts of sulfuric acid works in which thallium-bearing materials are used and as a byproduct of the lithopone industry. This paper describes methods for recovery of thallium from 'white arsenic" and lead Cottrell-precipitator dust of the American Smelting & Refining Co., lead smelter, Murray, Utah. Owing to an enlarged market for thallium because of increased military requirements and expanded peacetime uses, the Salt Lake Station of the Bureau of Mines surveyed the occurrence of thallium in ores, concentrates, and smelter products from all parts of the nation and found the most promising source was certain smelter products of the American Smelting & Refining Co. plant, Murray, Utah. Much of the thallium was being lost in marketed arsenic products; therefore, this investigation was undertaken to develop methods for recovering the thallium.

Jan 1, 1952

By Constantine C. Popoff

During 1946 several limestone deposits near Fortson, Snohomish County, Wash., were examined by the Bureau of Mines. These examinations were part of a long-range investigative program of regional mineral supplies required by the anticipated industrial development of the Pacific Northwest. The .study outlined in the following paper was specifically undertaken to disclose new sources of high-purity limestone and to appraise, their economic aspects. The deposits examined -namely the Galbraith, Climax, and Hi, Hi -are somewhat similar in physical features and geologic environment. They are lenticular and belong to the same formation of metamorphosed sediments that underlies the prominent Whitehorse Ridge.

Jan 1, 1949

By Theodore Kootz

Manufacture of high-grade ferromanganese; as a rule; requires a low-phosphorus-manganese ore with 45 to 55 percent Mn, chiefly obtained in the Soviet Union, the British Dominions, and Brazil. Also, low-manganese ores have already been used for ferromanganese production, especially in North America .and Germany. During World War I, a process was developed in which a high-phosphorus ferromanganese or spiegeleisen was prepared in the blast furnace from law- or high-phosphorus manganiferous ores, then low-phosphorus manganese slag was prepared by refining under an acid slag, and this material was, worked into a low-phosphorus ferromanganese in the blast furnace.9/ Manufacture of useful manganese ores from a phosphorus-bearing spiegel with 12 to. 15 percent Mn, 4.5 percent C,, and 0.5 percent P by slagging in a refining furnace was reported by Joseph, Barrett, and Wood.10/ The spiegel was refined to 0.75 percent Mn, 3.4 percent C, and 0.45 percent P. Thereby, a slag with about 43 to 58 percent Mn and, about 10 percent Si02, was obtained. Hotter melts gave a smaller phosphorus content in the slag than cold melts. In addition, the phosphorus content of the slag varied with the manganese content of the intermediate metal.

Jan 1, 1952