Search Documents

By J. B. Hedrick

Rare earths were not mined in the United States in 2008. However, processing of intermediate rare-earth concentrates continued throughout the year at the Mountain Pass Mine in California. Consumption of refined rare-earth products increased. U.S. rare earth imports were primarily from China, with lesser amounts, in decreasing order, from France, Hong Kong, Japan, Austria and Russia. The United States imported 100 percent of its supply of yttrium metal and compounds primarily from China. United States In 2008, lanthanide concentrates were processed by Chevron Mining Inc. (previously Molycorp Inc.) at its mine site at Mountain Pass, CA. Chevron Mining sold its entire holdings in the rare earths mine to Molycorp Minerals LLC in September and operations continued at the site through-out 2008. Major uses for these mineral commodities were in automotive catalytic converters, petroleum fl uid-cracking catalysts, permanent magnets, glass-polishing compounds, ceramics, metal-alloying additives, phosphors and recharge-able batteries. Three domestic companies produced and sold lanthanide intermediate concentrates and refined products. Chevron Mining sold its interests in the Mountain Pass Mine to Molycorp Minerals LLC on Sept. 30, 2008. Molycorp Minerals LLC is an investment company owned by Resource Capital Fund IV L.P., Pegasus Partners IV, LP, The Goldman Sachs Group Inc., Traxys North America LLC, Carint Group LLC and Mark Smith. The Molycorp operation previously mined the rare earth fluocarbonate mineral bastnäsite by hard-rock surface methods, and the mine remained on care and maintenance in 2008. Molycorp maintained significant stocks of bastnäsite concentrates, intermediate concentrates and high-purity rare earth compounds at its operations at Mountain Pass. In October 2007, Chevron Minerals completed phase one of its three-stage plan and restarted the rare earth separation plant at Mountain Pass. The company also processed intermediate rare earth concentrates from existing stocks during the first three quarters of 2008. Molycorp Minerals LLC maintained production in the last quarter of the year. The mine at Mountain Pass has been closed since 1998. Future plans are to restart processing of stockpiled bastnäsite concentrates followed by reopening of the mine.

Jan 1, 2009

By E. Bloomstein

The Lone Tree gold mine is located about 4S kilometers east from Winnemucca on the west flank of Lone Tree Hill in Humboldt County, Nevada. The deposit occurs at the north end of the low, rolling Havallah Hills and is about 1 kilometer south of Interstate Highway 80, in sections 11 and 14, Township 34 North, Range 42 East, Mount Diablo Base and Meridian (Fig. 1). The Lone Tree deposit is outside of any previously established mining district and all lands are owned or controlled by Santa Fe Pacific Gold or affiliated companies.

Jan 1, 1993

By P. Hadzeriga

Ion exchange techniques have been growing fast and spectacularly in all phases of Science for the last two decades, but still its acceptance as a unit operation in Metallurgy is resisted. Mainly this is because ion exchange procedures are thought of as glamorous techniques by which only relatively expensive metals are to be recovered. Perhaps this concept comes from the early and basic marriage of uranium and other high price metals and ion exchange procedures. The general trend is that ion exchange technique requires equipment and materials which are too expensive to economically perform a chemical step whenever "cheap" commodities are produced. However, we are here presenting a means of utilization of waste hydrochloric acid by an ion exchange technique. We have studied this from the engineering and economic standpoint in a number of variations of the main procedure discussed here and we-conclude that under proper economic circumstances, the cost of the ion exchange material as well as the equipment and labor involved in the ion exchange section, is by no means unreasonable.

Jan 1, 1964

By O. R. Bell

In Australia's remote North West are located the operations of Cliffs Robe River, one of the world's largest iron ore projects. Initial project cost was $US300 million and required the construction of a deepwater port, two toms for 3000 people, a 105 Mw power station and 170 km of railroad, all in harsh, arid country over 1300 km from the nearest industrial centre. The ore occurs as goethite cappings on scattered mesas and averages 57 percent iron. All aspects of the project are reviewed from pre-operational research, through project construction to current operation.

Jan 1, 1979

By K. N. Han, Y. Guan

[The dissolution behavior of copper and gold from their pure state and from Au-Cu alloys in cyanide solutions has been investigated using a rotating disc. Oxygen was used as an oxidant. The effect of the alloy composition, stirring speed of the disc. [lixiviant] concentration, solution pH and temperature on the overall dissolution kinetics has been studied. An-Cu alloys of three compositions were used in this study. The atomic percent of gold in these alloys was 75, 50 and25, respectively. The dissolution behavior of these three alloys was compared, under the same chemical conditions, with that of pure gold and pure copper. In general, the dissolution of copper and old from alloys is controlled partially by surface chemical reaction and largely mass transfer.]

Jan 1, 1994

By D. E. Walsh

The behaviour of gold particles on a spiral was studied using radioactive gold tracers. The method allowed the effect of particle size, particle shape, pulp density, feed rate, and splitter settings to be studied. Although the method has been successfully applied to other gravity concentrators, it was found that reliable results were more difficult to obtain on the spiral. However, these preliminary results show that provided suitable precautions are taken, the technique is capable of providing valuable information that cannot be obtained by conventional studies, and could be used to better optimize spiral performance.

Jan 1, 1992

By Kerry Spickelmier

Editor's note: information for this feature was taken from the published APCOM proceedings. Computer trends, with special focus on the reasons for computer use, grabbed the lion's share of attention at the 23rd worldwide meeting on the Application of Computers and Operations Research in the Mineral Industry (APCOM 23). However, technical topics did not provide the meeting's sole focus. The last-minute inability of certain former communist countries to fund the travels of a few scheduled speakers was a reminder that science does not operate in a void. As with all technical progress, the APCOM presentations raised interesting questions regarding interrelated organizational dynamics and political and socioeconomic issues. Consider US Bureau of Mines (USBM) research to design an expert control systems to "duplicate" an experienced, "good" operator during automated underground roof bolting. In his presentation of the project, Takach, Jr. stressed the importance of preserving the ability to switch from automatic to manual drilling control. From a technical standpoint, this allows the expert system to "learn" from a good operator. As important, he said, is that this flexibility decreases the human operator's sense of being replaced by the machine. The question arises: Which will loom larger in union minds, increased operator safety through remote opera¬tion or the potential for total operator replacement? Like any new product, computer technology relies on marketing to aid its acceptance and use. Consider, too, a decision support system, by Schena and Gochin, for mineral resource management in a developing country. The authors said "the analysis permits the assessment of the overall socioeconomic consequences of mineral prospects and allows incorpo-

Jan 1, 1992

By Dennis Arthur Fenton

The hydrodynamic bearing was first described by, Reynolds in 1886, and has since been widely applied in motors, engines, compressors, hydroelectric turbines, and other machinery. For various reasons, the hydrostatic bearing currently predominates in the large, horizontal rotating machinery field (e.g. grinding mills). However, the current industry trend towards increasing size and energy efficiency has resulted in renewed interest in the advantages of hydrodynamic bearings. These advantages include structural improvements, reduced bearing friction, improved bearing life, improved transient characteristics, and reduced lubricant pump size and power requirements. In particular, the higher energy efficiency results in substantial savings on large machines. This paper describes some aspects of the design of large hydrodynamic bearings based on thirty years, of experience in the design of such bearings on grinding mills ranging in journal size from 2.1 m to 6.4 m, see Table 1.

Jan 1, 1985

By H. Douglas Dahl

In order to provide a reference framework for discussing the applicability of drilling technology to shaft construction in coal mining ventures, it is meaningful to review the history and nature of United States coal mines relative to shafting. Coal mining in the United States is characterized by shallow depths relative to most of the coal mining world. While the trend is toward deeper and deeper mines, many new mines have shaft depth less than 800 feet, and a large number of operating mines are drift or outcrop mines utilizing shafts for ventilation and portals. In the past, shafts of 200-300 feet have been commonly constructed. The use of conventionally sunk shafts at present and in the past is due in part to the shallow shaft length required, favoring conventionally sunk shafts. Another factor is that large shafts are required for multipurpose and production shafts. A third has been the practice of utilizing shaft construction contractors who had been until recently very competitive with raise drilled shafts at shallow to moderate depths. Recently, however, the costs of conventionally sunk shafts have skyrocketed. Too, more shafts are being required. Several factors are responsible among which are: (1) The increasing depth of shaft required for new mines and for shafts in advance of old mines. This significantly affects unit costs, e.g. $/yd3,of conventionally sunk shafts. Moreover, more gas is encountered in the shaft sinking operation.

Jan 1, 1976

By Rudy Scarabelli, John R. Wagner

At one time explosives were the only economical means of rock tunnel excavation. Except in relatively long tunnels in the right rock explosives are still the cheapest means of rock excavation where they can be used. Today the most economical means of rock tunnel excavation is increasingly not the choice of the contractor. A good part of our work is for public agencies in urban areas and the public today is increasingly less tolerant of the disruption caused by our efforts. Owners in many cases have to direct their engineers to write specifications which severely restrict noise and vibration levels during construction. Sometimes specifications allow drill-and-shoot for starter tunnels only or even eliminate powder by fiat. Recent advances in the use of explosives such as sequential firing have made blasting more palatable to the public but are not enough in all situations. Thus the roadheaders on construction projects. In recent work I have seen the Alpine Miners, a Paurant Miner and the Robbins Mobile Miners used in several rock formations and now believe this type of equipment has a place in the tunnel constructor's choice of equipment. Rudy and I have not attempted to present a formula for choosing the best alternative excavation method in any given case because, of course, of the variables involved. We have simply tried to describe our experiences on a particular project and hope our observations will be of some value to tunnel constructors.

Jan 1, 1987

By J. Stachurski, N. A. Abdel-Khalek

Flotation tests were carried out on six coal samples of different rank as well as their oxidized samples. A mixture of diesel oil and alcohols was used in these tests. Surface oxidation caused a distinct decrease during flotation recovery with some improvement in the grade. The reduction in the recovery increased with increasing concentration of the oxidizing agent. The floatability of low rank coals was affected by oxidation to a higher degree than the floatability of medium and high rank coals. The recovery-size curves of oxidized samples were similar in shape to the recovery-size curves of non-oxidized coals.

Jan 1, 1991

By S. D. Bearden

The world's barite reserve base is adequate for at least 100 years at the current consumption rate. China, India and the United States are expected to remain the leading producing countries, and the United States will continue to be the largest consumer. None of the known substitutes for barium sulfate are expected to impact existing applications. World production in 1995 was 4.41 Mt (4.86 million st), which is about 50% of capacity. Consumption is directly proportional to hydrocarbon well installation activity. Imports are expected to continue to supply more than half of the US requirements.

Jan 1, 1997

By V. I. Lakshmanan, P. D. Tackaberry

The use of activated carbon as an alternative to Merrill Crowe precipitation to recover gold from pregnant leach solutions is recognized. Recovery using activated carbon, however, suffers from the interference, due to organic fouling, clay content and increasingly from the presence of elements such as copper. Ion exchange separation technology is familiar to the mining industry (uranium) and its potential application to the gold mining industry is evaluated with considerable efforts by research workers in South Africa, Australia, and North America. The present paper reviews in detail the status of the research work that identifies potential opportunities.

Jan 1, 1990

By P. Brumit, L. Grady, R. Mitts, V. Holm

The Mesquite mine is a large, open pit, heap leach gold mine owned and operated by Gold Fields Operating Co.-Mesquite. The mine uses a fully integrated mine planning and reserve modeling software system developed at the mine. This system has recently been extended to include short-term mine planning, grade control, and daily production reporting. The grade control portion of the program uses a multiple indicator kriging (MIK) approach using the blast-hole spacing and exploration assays. The program permits ore control geologists and mine planning engineers to have immediate access to all the information.

Jan 1, 1991

By T. Brady, J. Johnson, J. Whyatt, B. Pariseau, M. Stahl

An elastic-viscoplastic material model allows for time- dependent rock mass motion in proportion to excess stress above the elastic limit. The model produces rounded stair-step curves of displacement vs. time that are similar to those obtained from recent borehole extensometer measurements made in the central portion of the Ross Shaft pillar at the Homestake mine. The work in progress, including two- and three-dimensional finite element analyses using the UTAH2/3 codes, indicates that the model is a step towards more realistic safety and stability analysis, but that inclusion of rock mass damage may be desirable.

Jan 1, 2000

By K. N. Han, Y. Guan

The dissolution behavior of silver and copper from silver/copper alloys in ammoniacal solutions was investigated using a rotating disc. Oxygen was used as an oxidant. The effects of the alloy composition, concentration of lixiviants, stirring speed and temperature on the overall dissolution kinetics were studied. Three silver/copper alloys (containing 76.7, 46.9 and 24.1% silver) were used in this study. The rates of dissolution for these alloys were compared to that of pure silver and copper under the same testing conditions. Emphasis was given to the galvanic effect on the overall dissolution rates.

Jan 1, 1995

By T. J. Kim, S. Suh

The purpose of this paper is to evaluate overall prospects of the export market in the Pacific Rim for Illinois steam coal in terms of recent changes in global socioeconomic factors. To pursue this objective, three factors affecting the prospects of Illinois coal in the Asian market were selected for detailed analysis: quality requirements of imported coal, particularly those of the Japanese market; import controls and regulatory factors; and transportation factors affecting the export of Illinois coal. Based on these analyses, alternative long-term strategies are suggested for promoting Illinois coal export in the Asian market.

Jan 1, 1988

By Gary A. Kordosky, R. Brantley Sudderth

The solvent extraction process as it applies to the recovery of metals from solutions on a comnercial basis is described. The four types of classes of sol vent extraction reagents are explained: 1) solvation, 2) acidic, 3) ion-pair, and 4) chelation, and examples of each type of reagent system are given. The uranium and copper extraction examples, using the ion-pair and the chelate reagent types respectively, are presented in greater detail to illustrate the more subtle aspects of reagent evaluation and selection. Practical experiences in the laboratory and at some operating plants are a1 so discussed.

Jan 1, 1986

By J. Boldy

The discovery of the Delbridge massive sulphide deposit in the Noranda district of Quebec resulted from an appreciation of the significance of a mercury leakage halo as a litho-chemical pathfinder to blind ore, coupled to its location relative to a geologically inferred ore-bearing horizon within complex volcanic stratigraphy. Systematic sampling of micro-fractures present in outcrops delineated a diagnostic anomaly, drawing attention to an area considered prospective for buried ore. The massive sulphide deposit was subsequently found to be blind and topped at the 110 metre level.

Jan 1, 1984

By E. Simoncini, S. Ulgiati, M. Raugei

A thorough Life Cycle Assessment of ilmenite extraction and processing to yield synthetic rutile (ERMS/EARS process) was performed according to ISO norms 14040 and updates. The LCA includes the parallel application of selected environmental impact assessment methods (as illustrated in Ulgiati et al. [1]), the results of which are compared and discussed. A MI value of 16 kg of abiotic matter per kg of output rutile is calculated, which is largely determined by the amount of coal that is employed in the reduction and drying steps. The Gross Energy Requirement is 3.33 * 107 MJ/kg, a value which we found to be comparable with that previously calculated by us for alumina. Finally, the increase factor of the Emergy Intensity from the raw mineral to the marketed rutile is 3.19, which points to a comparatively medium-low requirement for indirect environmental support. GWP and AP were calculated to be respectively 1.89 kg(CO2eq)/kg and 12.7 g(SO2eq)/kg.

Jan 1, 2005