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By Patrick Scott, Germán Schmeda, Morgan Mullins, Liam Knudsen, Bradley S. Van Gosen, Carma A. San Juan, Nicholas A. Karl, Jeffrey L. Mauk, Clayton Forbush

The objective of the US Geological Survey’s mineral deposit database project (USMIN) is to develop a comprehensive twentyfirst century geospatial database that is the authoritative source of the most important mines, mineral deposits, and mineral districts of the US. Since May 2017, the project has focused on critical minerals. Data for critical minerals that are produced as products are relatively robust, whereas data for critical minerals that may be recovered as byproducts are commonly of much poorer quality. Similarly, more is known about critical minerals that occur in conventional deposits than where those critical minerals occur in unconventional deposits. For example, rare earth elements occur principally in deposits hosted by alkaline igneous rocks, but there is potential for their production from phosphate rock mining, which is less documented. Lithium (Li) has been recovered from pegmatites and brines, but other Li-bearing deposit types have been delineated that may go into production. Cobalt may be produced as a byproduct or coproduct from a wide range ofmineral deposit types, whereas rheniumis a byproduct of copper ore. Significant opportunities for research exist that could help identify new sources of critical minerals, and may also help increase production and recovery from existing sources.

Feb 8, 2021

By R. H. Lesernann

Copper has held up extremely well as we have moved through the trough of the economic cycle. In the aluminum, lead and zinc industries at least half of the Western World production was unable to cover its operating costs at the prices prevailing throughout most of 1991. In copper, less than 10 percent of production ran in the red last year. Most of that was in Peru where the government has not allowed its currency to devalue at the same pace as inflation. Thus, mining company revenues in local currency terms have risen very modestly while costs have escalated tremendously. Excluding such governmentally imposed distortions, virtually every mine in the Western World ran at a profit last year. While copper producers have to be extremely happy about staying in the black through the trough of the consumption cycle, consumers have to be worried. They must be asking themselves, "If copper held at over $1.00 in a year when consumption declined, how high will prices go when demand picks up?" Consumers are accustomed to paying high prices at the peak of the cycle, but they are also accustomed to paying low prices at the trough of the cycle. What went wrong this time?

Jan 1, 1992

By B. C. Lewis

The mining industry has experienced a general trend toward an increasing number of longwall operations, an increasing percentage of underground coal being mined by longwalls, and increasing productivity from the longwalls. Longwall operators have not yet reached a state of mining euphoria. Competitiveness both within the industry and from alternate fuel sources is forcing continued pursuit of higher productivities and lower costs. The following graphics present trends in the industry. Longwall mines, as defined for this presentation, are those reportedly having longwall installations in each of the respective years. Production from both the continuous miner and longwall units is included in the longwall mines. Non-Longwall mines are all other underground mines. Productivity calculations are based on total employee-hours associated with the operation.

Jan 1, 1990

By F. G. Miller

To improve coal flotation Bethlehem Steel Corporation's Research Department has been working on a number of related problems based on both physical and chemical factors. The ideal is of course full understanding of the interrelated effects of both sets of factors. However, detailed studies5 of each physical factor have produced immediately usable results in commercial coal flotation and are providing the bas is for our current work on the effect of chemical factors. Since these detailed studies provided the basis for the present investigation of froth sprinkling, their key results are highlighted here. For example, for a highly floatable bituminous coal, particle floatability was shown to be directly related to the percentage of coal surface available for bubble attachment and inversely related to particle mass. The data also underscored that in a given size range the addition of mineral matter to a particle makes flotation more difficult both by adding to the mass of the particle and by decreasing the amount of coal surface available for bubble attachment. Size also affects particle floatability in that as the size of particles of a given specific gravity increases, mass increases and the ratio between coal surface area and mass of the particle decreases. Flotation tests showed that any recovery of the coarsest particles in a coal feed is accompanied by progressively higher recovery of finer and finer particles. Consequently, fine high-specific-gravity particles are recovered with the coarse good coal. As a result, when the entire 14M x 0 size range is processed by froth flotation, the good coarse coal is contaminated with high-specific-gravity fines. It is the small quantities of these fines that must be rejected from the froth product if flotation efficiency is to be increased above its present level.

Jan 1, 1968

By J. E. Urosek

In October, 1990, a fire started in a large underground coal mine in Western Pennsylvania. During fire-fighting activities, an explosion occurred and all personnel were evacuated. Safe re-entry into the mine was not possible and the mine was sealed. Recovery efforts began in January, 1991 and continued until March, 1991, when permanent underground seals were installed between the fire area and the mine openings. This paper describes an extensive atmospheric monitoring program conducted by the Mine Safety and Health Administration (MSHA), Pittsburgh Safety and Health Technology Center (PS&HTC) including the analysis of mine fire gases, natural ventilation, fan pressure and air quantity distribution.

Jan 1, 1993

By P. Michael

Proponents of geomorphic mine land reclamation have criticized current reclamation practices in the coal fields of steep-sloped Central Appalachia as too narrowly focused on civil engineering principles and neglectful of the functional and aesthetic benefits of reclaiming mine sites in ways that mimic natural landforms and drainage patterns. They observe that current mining and reclamation practices are radically transforming the mountain-and-valley terrain into gigantic flat plateaus and, in doing so, disrupting the beauty and ecology of the natural landscape. Instead of designing and constructing linear or planar surfaces and unvarying slope gradients during the reclamation process, they recommend ?landforming,? i.e. the adoption of curvilinear, compound slope forms that blend well with the surrounding physiography and represent the result of naturally stabilizing geomomorphic processes. The authors feel that the concept of geomorphic mine land reclamation is sound, however, its application to the Central Appalachian coal fields faces significant--albeit not insurmountable--challenges. They include: (1) existing reclamation enforcement regulations that are focused on civil engineering principles and not explicitly supportive of geomorphic methodologies; (2) regulatory agencies? current intent to limit the down-gradient reach of excess spoil fills in order to allay disruption or burial of natural streams; (3) actual or perceived increases in reclamation costs; and (4) the challenge of designing and constructing ?natural? landforms that are mature and stable in an otherwise youthful, erosional landscape.

Jan 1, 2010

By M. L. Rizzone

Since time immemorial, Mother Nature has been transporting slurries with both air and water serving as the carrier medium. Consider for example the formation of the continental shelves off our coast lines which are being formed by rivers emptying erroded land surface and depositing it into bays and gulfs. As the erosion processes take place, the fines are suspended in water which flows in streams and rivers and deposits where the velocity of the flow reduces sufficiently to allow the fines to settle out. The same process in some crude form is provided when one hoses his driveway or patio and moves dirt so as to provide a cleaning action. These examples illustrate rather crudely how the formation of slurries allows for the transport of solids. In recent years, this mechanism has become fairly well understood and slurry pipelining of many materials is now a vivid reality. The movement of liquids in pipelines necessarily occasions the use of pumps for the purpose. Those of us who have had some rub with the petroleum industry are familiar with the transport of solids through mud pumps and cementing and fracturing pumps where the movement of slurries is an everyday matter. In the drilling of an oil well the circulating fluid utilized to remove chips which are cut by a drill bit from holes drilled deep in the earth is called drilling mud. This substance contrary to what the name might imply is usually a fairly sophisticated material designed to develop certain characteristics which are desirable in the drilling process. The particles which have been cut by the drill bit are suspended in the moving column of fluid and brought to the surface and deposited. The separation of the cuttings from the drilling fluids is accomplished by the use of shaker screens and settling pits. However, it is impractical to remove the fines completely from the drilling fluid and as a result they are pumped through the mud pumps back into the circulatory stream.

Jan 1, 1969

By M. D. Scott

Lornex Mining Corporation operates an open pit porphyry copper mine in the Highland Valley southwest of Kamloops with a rated capacity of 43 500 TPD (48,000 TPD). It went into production in April 1972. Its concentrator consists of two grinding and flotation circuits in parallel each composed of a 6 000 KW (8,000 HP) 9,75 m (32 foot) diameter by 4,724 m (15'-6") semi-autogenous primary mill feeding two 3 000 KW (4,000 HP) 5,029 m (16.5 foot) diameter by 7,01 m (23 foot) secondary ball mills each feeding a bank of flotation cells. ,The original tailings system picked up the tailings from the flota¬tion circuits in a concrete collection box in the mill and carried the 36% solids density by weight slurry 488 m (1,600LF) through a 1100 mm (42 inch) diameter wood stave pipeline on a .46 percent slope to three 99,06 m (325 foot) diameter center drive thickeners. From the collection box under the thickeners the tailings line con¬sisted of three sections, carrying 50% solids density slurry. The first section consisted of 1460 m (4,800 LF) of 910 mm (36 inch) asbestos cement pipe for gravity flow from the thickener under flow elevation of 1252,4 m (4,109 feet) to the first pump station at elevation 1207,6 m (3,962 feet). Eight concrete drop boxes were used to limit the maximum slope on the pipeline to 0.5 percent.

Jan 1, 1976

By V. R. Degner

The minerals industry trend toward very flotation machines, exceeding 10 m3, began in the late 1960's and responds to the continuing desire to achieve better plant economics through improved plant floor-space utilization, power requirements, and operational /maintenance manpower heeds. In general, as process design tonnage increases, the benefits of the larger flotation machine becomes more evident. The development of the larger flotation machine can be distingushed from earlier, smaller, machines in demanding a rational "scale-up" procedure to guide the basic design, thereby producing a machine prototype capable of satisfactory-operational evaluation at minimum cost. Proven flotation machine "hydrodynamic" scale-up consideration, successfully applied in the development of both the WEMCO No. 164 (28.3 m3) and No. 190 (42.5 m3) machine will be reviewed, and the resulting economic benefits of large flotation machines in high tonnage applications will be summarized.

Jan 1, 1985

By James A. Kiger

We at Colowyo would like to thank you for the opportunity to share with the Society of Mining Engineers of A.I.M.E. the progress of reclamation at Colowyo Coal Company's multiple seam open pit coal mine which is a general partnership of W.R. Grace and Co., and the Hanna Mining Co. First, a brief history of Colowyo Coal Company (Colowyo). The Colowyo operation is located approximately 28 miles southwest of Craig, Colorado, which is in the northwest corner of the state. The Colowyo operation produces coal from a Federal Coal Lease, a portion of which has experienced previous coal mining by underground methods. The underground coal mines were known as the Red Wing Mine and The Streeter Mine, and supplied coal to numerous locations in the Rocky Mountain region.

Jan 1, 1984

By C. M. Liu

"The Freeport-McMoRan Sierrita Crystal Plant produces Copper (II) Sulfate Pentahydrate (CuSO4·5H2O) through a series of cooling crystallizers. In this process, high supersaturation and unwanted spontaneous nucleation promote fine crystals. Seeding through recycled crystal classification can manipulate the crystal size distribution (CSD) for larger crystals. Proper selection of the crystallizer for seeding can prevent spontaneous nucleation and promote final crystal size. This study shows when seeding temperature is closer to the crystallizer temperature, suspension densities in the crystallizers are promoted and overall CSD shifts to a larger size of crystals. INTRODUCTION Figure 1 shows an overview of the crystallization process. The in-plant feed flow, called Pregnant Mother Liquor (PML), enters the first crystallizer and is subsequently cooled through a series of four crystallizers. Specific temperatures are targeted for each crystallizer to ensure the crystallization process is operating within the metastable zone (MSZ). The discharged flow from crystallizer #5 then enters two cyclones. The overflow from the cyclones contains smaller crystals providing seed crystals for crystallizer #5. The underflow from the cyclones begins the drying process. The overflow from crystallizer #5 enters cyclone #3 for removal of fine crystals and seeding purposes. The underflow from cyclone #3 has the capability to provide seed crystals for crystallizer #1 or crystallizer #2. The overflow leaves the system as Spent Mother Liquor (SML). Undersize crystals dissolve into the PML and return back to crystallizer #1.THEORIES AND METALLURGICAL TESTS Seeding requires an understanding of the crystal size, solution temperature and amount of crystals that enter the crystallizers (1). For the seed crystal size, classified crystal seeds can prevent fine crystals returning back into the system which eventually leads to excessive agglomeration (2). Proper selection of the crystallizer can ensure seeding at an appropriate temperature. Seeding at a temperature much lower or higher than the saturation temperature promotes spontaneous nucleation. Typically, seeding between 4-5°F below the saturation temperature is acceptable (5). A general rule of thumb is to add the seed crystals at the temperature between the solubility curve and the metastable zone. An experiment conducted by Mettler-Toledo AutoChem, Inc. indicates seeding close to the solubility curve rather than the metastable zone promotes a lower supersaturation and nucleation rate but yields a higher growth rate and a greater number of larger crystals (1). The amount of seed crystals can not only change the suspension density but also narrows the width of the MSZ in the crystallizers. An experiment conducted by Jaroslav Nyvlt reports with the crystals absent, the maximum allowable undercooling is 6.3 degrees at a cooling rate, 5°C/hour. With the presence of crystals, it narrows the MSZ width to 2.2 degrees (4). Industrial crystallizers normally operate at suspension densities between 15% and 25% by mass. When suspension densities are lower than 15%, it increases the risk of primary nucleation and the probability of incrustations; on the other hand, if the suspension densities are greater than 25%, it can cause a greater attrition rate and increase the probability of deposits (6). Moreover, operating suspension densities between 15% and 25% are also sufficient to minimize supersaturation rate which promotes crystal growth over nucleation (2, 6)."

Jan 1, 2015

By T. B. Linde

The Morenci In-pit Crusher and Conveyor System has been designed with safe production and cost savings in mind. Large open pit mines around the world have been installing semi-mobile crushers and linking them with a pit conveyor system to lower unit cost. At Morenci two 60/89 in. gyratory crushers are incorporated into the semi-mobile crushing plants. The ore is reduced to -8 in. and transported out of the mine on a 60 in. steel cable belt. This paper includes an overview of the Morenci In-pit Crusher and Conveyor System from the drawing board to open pit installation and finally a discussion on operating and repair considerations.

Jan 1, 1990

By D. C. Shumway

Recently, the health of the cement industry has been threatened by the impact of environmental regulations, over-zealous state and federal agencies and radical environmental groups. Unfortunately, cement plant operations tend to trigger every environmental regulation and program promulgated, plus several programs designed specifically for the cement industry. These environmental burdens come at a time when the cement marketplace has been impacted by imports resulting in a situation where it has been difficult to increase prices to offset these increased environmental liabilities. The competitive world market forces the cement industry to seek creative ways to reduce costs. With additional major environmental programs coming down the pipe, like the Federal Clean Air Act Amendments of 1980 and EPA regulation of cement kiln dust, the cement industry has attempted to try innovative supplements to cement manufacturing. The cement industry has found that using waste tires, biosolids and other solid wastes in the cement manufacturing process can reduce costs and plant emissions.

Jan 1, 1996

By R. K. Clifford

The formation of elemental sulfur on the surface of sphalerite in aqueous systems was investigated. Hallimond tube flotation tests showed that unoxidized sphalerite did not float well without a collector. Flotation recoveries of greater than 95 percent were obtained without the use of a collector or frother after the sphalerite had been reacted with oxygen under pressure and water at pH 2.8 at room temperature. High flotation recoveries also resulted when sphalerite was reacted in acidic solutions in the presence of platinum sponge, titanium sponge, 316 stainless steel, copper turnings, or [10-5M++]. Conditions which produced high flotation recoveries of sphalerite yielded contact angles of 37° to 40° and also produced elemental sulfur. The increase in elemental sulfur on the surface of sphalerite was detected by elemental sulfur extraction with petroleum ether, electron spectroscopy for chemical analysis (ESCA), and the electron beam microprobe. The quantity of elemental sulfur formed was insufficient to be detected by infrared or Raman spectroscopy, or by the optical microscope or by the scanning electron microscope. An electrochemical type reaction for the production of elemental sulfur in acidic solutions was proposed. The cathodic reduction of oxygen was the slow step which needed to be catalyzed. A chemical type reaction which produced H2S rather than elemental sulfur was evident in non-oxidizing conditions.

Jan 1, 1974

By D. W. Frommer

Processing nonmagnetic taconites by selective flocculation-desliming and flotation requires large volumes of water. If impounded without treatment these off-process waters require excessively large areas for containment. To discharge the waste water into natural waterways would contribute to stream pollution and likely would not be permitted. In Bureau of Mines experiments conducted in the Twin Cities Metallurgy Research Center&apos;s 900-lb/hr pilot plant, approximately 85 percent of water requirements for the flotation-based treatment of a Michigan nonmagnetic taconite were met by reclaimed water. Water reclamation of the off-process streams from flotation was accomplished by controlled additions of lime, sodium carbonate, and a synthetic flocculant to reduce turbidities to <1,000 ppm equivalent Si02, while maintaining a Ca(II) content of 516 ppm in the finished effluent. Flotation concentrates of good quality were obtained using the reclaimed water. The cost of chemicals used in water reclamation was approximately equal to the savings in flotation reagents attributed to recycling of the water.

Jan 1, 1970

By J. Y. Kim

Silver contained in zinc calcines undergoes several phase changes as it proceeds through the leaching circuit of a roast-leach-electrowin zinc plant. In the present study, the flotation response of silver from leach residues prepared under a variety of carefully controlled operating conditions in the pilot plant has been examined. Flotation of neutral leach residue is shown to be technically viable and to merit consideration for those plants without a high acid leach circuit, but having significant silver values in the feed. Residue leach conditions must be kept slightly acidic to promote the formation of Ag2S, (Ag, CU)2S and Ag2S rims on residual unroasted sphalerite, while simultaneously avoiding the hydrolysis of soluble iron which depresses silver recovery and grade. Factors to be considered during integration of a flotation process into an electrolytic zinc plant are discussed.

Jan 1, 1990

By Robert J. Garino

Around two-thirds of world silver mine production comes from mines where the majority of ex-mill revenue is obtained from other metals. In this talk I will illustrate the importance of this output of silver as a by-product of the mining of various base metals. I will also consider the impact of relative changes in base and precious metal prices on mill-head revenue, and therefore, on production decisions. During the latter half of 1982 improving silver prices encouraged re-openings at several base metal mines. Thus some production of lead, zinc and copper can be regarded as partly conditional on the prevailing silver price. Conversely, a good deal of silver production can be considered to be independent of the silver price and dependent on the production of some base metal. It is the degree to which the value of silver mined affects the revenues of nominally, base metal, producers that is the central concern of this presentation.

Jan 1, 1983

By P. J. Best

Due to its low mine production costs, competitive rail rates and low sulfur content, the Southern Powder River Basin (SPRB) now commands 30 percent of the U.S. utility coal market. In 1996, production exceeded 260 million tons, a growth of 110 million tons since 1989 and 15 million tons over 1995. Continued growth is expected as the second phase of the Clean Air Act Amendments (CAAA) looms. This growth will be the greatest in the southern part of the basin, where coal quality is higher. This article is an overview of supply and demand issues affecting markets for SPRB coal. It reviews the current markets for SPRB coal and addresses future prospects for market expansion.

Jan 1, 1998

By Jean-Marie Deschamps

In an approach to the complicated study of bauxite from Les Baux de Provence it is necessary to consider the paleogeographical context of all the bauxites in southern France. These bauxites are of Karstic type, belonging to a metallogenic area extending from the Pyrenees Mountains to the Alpine Massif. Within this area each deposit does not always correspond to the same geological period. There are differing opinions regarding the origin of Karstic-type bauxite and a discussion of these various theories is beyond the scope of this paper. Bauxite of Les Baux, in Provence, was discovered in 1821 by the chemist, Berthier, near this picturesque village located in the region of Arles. It is Les Baux from which the name of bauxite originates. For a long time this bauxite was of no interest because of high silica &apos;and mediocre alumina content. Besides, the calcium carbonate content is somewhat high and is one of the main characteristics of Les Baux bauxite. The problem of exploration of the Les Baux deposit has been to prospect minable zones according to traditional norms where silica and carbonate are low.

Jan 1, 1977

St. Peter sandstone is an arenaceous sheet that covers large area in North America. The interest for St. Peter sandstone has been increasing due to the upward trend for hydrofracturing and the consequent need for fracking sand. This material is possesses very unique mechanical properties. On the one hand, it is brittle as characterized by an unusually high friction angle, up to 69°, and steeply curved failure envelopes. On the other hand, it is friable, possessing extremely low, and in most cases zero cohesion. The underground mines that are working under this condition are lacking the ground control techniques for this particular mining environment. The geotechnical properties of the St. Peter sandstone were examined using uniaxial test, triaxial test, porosity test, flexural strength test. This paper aims to investigate the effect of microstructure on strength properties, utilizing microscopic studies, index test (porosity, size distribution).

Feb 23, 2014