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Jan 1, 2008

The Bureau of Mines conducted large-scale laboratory copper ore leaching tests to enable improving copper recovery from large dump-leaching operations. This was done by comparing leaching progress when copper was recovered from recycled leach liquor either by cementation or by solvent extraction. Copper was leached from 7-ton ore samples at room temperature using pH 2 ferric sulfate solutions. With are samples containing 11 percent minus 0.5-inch fines, no marked advantage in using either of the copper recovery methods was evident after 416 days of leaching. With ore containing 32 percent minus 0.5-inch fines, solvent extraction of copper was advantageous in that 60 percent of the copper was extracted after 568 days, whereas only 48 percent of the copper was extracted when cementation was used. Less acid was consumed during leaching when solvent extraction, rather than cementation, was used for copper recovery. Iron, contributed by cementation with scrap iron, plugged the ore bed containing 32 percent fines.

Jan 1, 1981

Demand for primary aluminum ingot increased during February, and several producers temporarily suspended new bookings for ingot. Alcoa announced that it would restart a potline at its Warrick, IN aluminum smelter by April 1, 1979, increasing the operations of that plant to its full capacity of 290,000 tons per year. At the end of February, it was reported that Alcoa would reactivate two of the seven units at its idle Point Comfort, TX smelter in May 1979, increasing the company's annual capacity by about 60,000 tons.

Jan 1, 1979

By John E. Wiegand

This study will discuss the AMAX Coal Co., Penndiana Pipeline Project, which was conducted in conjunction with the following parties: AMAX Coal Industries, (U.S.B.O.M.) United States Bureau of Mines, (I.D.O.R.) Indiana Division of Reclamation, Ohio Valley Pipeline, Inc., New Mexico Tech, and ourselves, VIBRONICS, INC., Evansville, Indiana. The purpose of this study was to find a safe vibration level for active gas transmission pipelines near surface coal operations.

Jan 1, 1994

Mining is both a high risk and a long term business. This is dramatically illustrated by the fact that, on average, the explorer will expend over $30 million in a ten year period for each significant economic discovery. The time required to complete the exploration process is one of the most substantial commitments made by any mining company. For example the time lag between the implementation of an exploration programme and an economic discovery is variously estimated to take two to ten years. The ore definition phase following discovery currently takes between two and five years while subsequent mine development may take one to two years in easy situations and up to 8 in difficult environments. In most countries the critical path through the early stages is determined largely by technical considerations but in almost all countries the path through the later phases is dictated by the plethora of permits, licences and community involvement steps.

Jan 1, 1982

By James D. Eklund

Towards the goal of improving safety, economy and efficiency of scaling in underground metal/nonmetal mines, Battelle developed a combination prying/hammering scaling tool. A prototype was subjected to limited testing 1) to verify its operational functions and 2) to assess its potential capability in future underground testing.

Jan 1, 1983

WHEN making comparisons of the efficiencies of different grinding and crushing machines it is desirable to be able to estimate the work actually done in crushing the ore from a given size of feed to a given size of product, the screen analysis of both feed and product being determined. Messrs. Klug and Taylor, in a paper on this subject, published in the monthly journal of the Chamber of Mines of WA, 31st January, 1906, have described a method adopted by them in calculations made in connection with a series of trials of grinding pans. Their methOd is based upon the assumption that if a quantity Q of material consisting of particles of average diameter x be crushed down until the average diameter of the particles is y, then the work done in grinding is proportional to Q x. There is no theoretical basis for this assumption that the writer is aware of, and it does not appear to satisfy the fundamental conditions necessary. If the material be further crushed until the diameter 2 becomes Z, the additional work done is measured. The work done in crushing from diameter x to diameter Z in one operation is proportional to Q x:, and therefore we ought to have zx2 y2 x2 Q-+Q-=Q-. y2 Z2 Z2But these expressions are not in general equal to one another. In other words, according to the theory underlying this method, if we crush from diameter x to diameter y, and then from diameter...

Jan 1, 1909

By Richard Klimpel

"Over the last 15 years, there has been a number of plant scale sulfide mineral flotation tests organized by this author specifically aimed at understanding how flotation rate varies with reagent type and dosage. With regard to the Interaction of collector dosage, particle size, and frother type, the eight specific trends listed in the paper (Illustrated with data from two specific case studies) are qualitatively the same for almost all plants studied in some depth. The Interaction of flotation rate K and equilibrium (Infinite time) recovery R in the plant has been denoted as the R/K trade-off. The effect of collector dosage on the rate of flotation of specific particle size intervals is particularly interesting and once understood, is quite useful In understanding how industrial flotation plants respond to changing reagent type and dosage. The location and magnitude of the R/K trade-off can be different for various ores and various plant configurations, but the RIK trade-off is almost always present. The purpose of this paper is to clearly describe and illustrate the nature of this very Important flotation system Interaction so that operating engineers have a starting reference point for beginning successful plant Improvement studiesIntroductionIt is well recognized by industrial froth flotation plant operators that improving existing sulfide circuit performance is often difficult due to the self-compensating systems nature of the froth flotation system, e.g. Klimpel (1988, 1989, 1995). Extensive plant testing with existing and new reagents by this author throughout the world has clearly shown that one of the more important self-compensating mechanisms is the Interaction between collector dosage, frother type, and particle size. The term self-compensation in flotation simply means that as the plant operator consistently changes one parameter in the same direction, the nature of the froth flotation system Is such that the circuit will eventually begin to resist this controlled parameter change by automatic (uncontrolled) changes In other parameters and the overall circuit performance will go through a maximum or minimum (hence causing the operator to stop the parameter change)."

Jan 1, 1997

By Y. L. Su

Deterministic and stochastic simulation were combined to develop a computer model of an open pit mining system using bucket wheel excavators and related materials handling equipment. The model is closed and dynamic in the sense that information is fed back to control activities at various levels and reservoirs. The results of interaction between unit operations in one time interval determines overall system behavior for the next interval. Equipment performance curves and system profile characteristics rather than time studies are applied to determine the operation of each activity at any time period. For that part of system where performance is dictated by a random variable~ subjective probabilities are employed. Two stages of research were considered to formulate this model. Stage one involved the formulation of equipment sub-assemblies for the sequence of equipment moves along with related assignments and routines for information retrieval. The second stage of research combined all sub-assemblies into an integrated open pit mining simulator. The model is not tailored for any specific open pit operation but is readily adaptable to any system of surface mining including operations having a high degree of complexity. Questions answered by the model include: 1) system design and selection of equipment for a new mining operation; 2) analysis of existing operations for possible changes, additions or general

Jan 1, 1971

By Thomas A. Phillips

The Bureau of Mines presents an economic evaluation of its leach- electrolysis process for recovering lead from galena concentrate. In this process, galena concentrate is leached at 200° F with a ferric chloride-brine solution to extract lead while leaving sulfur in the residue, which is discarded. The solution after leaching is concentrated and cooled to 100° F by vacuum evaporation to crystallize lead chloride from which metallic lead and chlorine are produced by fused-salt electrolysis. Chlorine is used to regenerate the spent leach solution before it is recycled. A cost estimate was prepared for a plant capable of producing 300 tons per day of lead, 330 days per year. The fixed capital cost on a third-quarter 1977 basis Fs $27,500,000, and the estimated operating cost without a charge for the concentrate is 4.9 cents per pound of lead product. Assuming a selling price for corroding-grade lead of 31 cents per pound and a charge for the concentrate of $332 per ton, the interest rate of return on investment after taxes is 16 percent. The leach-electrolysis process, therefore, appears to be economically attractive under the assumed market conditions.

Jan 1, 1978

By Claude Deveau, Stephen R. Young

Introduction Tanco History Tanco is sometimes known as the Bernic Lake Mine. It is located about 180 km east-northeast of Winnipeg close to the Manitoba-Ontario boundary. Tanco operates an underground mine employing ramp access, room and pillar mining and shaft hoisting for the production of tantalum, lithium and cesium minerals. Tantalum recovery employs conventional gravity and centrifugal concentration methods along with a flotation process which recovers ultra-fine tantalum. All tantalum concentrates are shipped to Cabot Supermetals, Boyertown, Pa., for the production of tantalum chemicals and metals. Tanco also produces lithium products from spodumene ore. The lithium concentrates from Tanco are shipped worldwide for use in ceramics, specialty glass and mold powders. Cesium processing involves the dry grinding of pollucite as feed stock to the on-site chemical plant dedicated to the production of cesium formate, a high density drilling fluid. Tantalum milling operations commenced in 1969. In the early years of the operation, feed grades were three to four times as high as they are today. Coarse-grained tantalum mineralization with complete tantalum liberation at sizes of 300 µm allowed for easy recovery with conventional equipment such as spirals and shaking tables. Over the years, the process and feed material to the plant have drastically changed. Due to drastically reduced liberation sizes, efforts have been made to try to recover as much of the liberated particles as possible in order to maintain acceptable recoveries.

Jan 1, 2005

By Sam S. Taylor

In most oil fields, natural gas is the major source of energy causing flow of oil to the well. The amount of gas produced With the oil generally exceeds actual energy requirements, so that in time the gas reserve of the field becomes seriously depleted and the oil production nest be stimulated by some auxiliary means. One of these is to repressure the oil formation with natural gas; or, where a gas supply is not available, often air is used. Although air is a cheap and convenient repressuring medium, its use sometimes is attended with several disadvantages. First, the return air-gas mixture decreases rapidly in fuel value, often until it can be used no longer as a source of power. At the same time, explosive mixtures may result if recycling is used, causing hazards to life and equipment. Second, some fields experience considerable trouble with the formation of emulsions which become increasingly difficult to treat. Although there is no definite proof that air repressuring always causes these emulsions, many operators are convinced that this is the case.

Jan 1, 1934

By J. Mitchell Linne

In 1985, at the request of Bureau of Land Management, the U.S. Bureau of Mines studied a 54,480-acre portion of the 93,205-acre Dry Valley Rim Wilderness Study Area (CA-020-615), in order to evaluate its identified resources. The area studied is in Washoe County, NV, and Lassen County, CA, about 35 miles east of Susanville, CA. No metallic resources were identified. The Red Rock and Willow Springs areas contain 85 million tons of altered basalt with zeolite amygdules. This material, averaging more than 50 percent chabazite, constitutes a subeconomic zeolite resource. This zeolite-bearing material would require beneficiation to upgrade it for higher value uses. Natural zeolites have a small market in the United States, which is presently supplied by other higher grade material. There is low probability that these resources will be mined in the foreseeable future. The Capricorn claims, adjacent to the study area, are on alluvial sediments containing more than 30 percent montmorillonoid clays. The material is not usable as pozzolan and was not tested for other uses such as absorbency, oil clarification, or insecticide carrier. The term pozzolan refers to a number of siliceous materials which are combined with portland cement to enhance the physical properties of the resultant concrete. The area is remote from market and contains low value material. It is improbable that this occurrence will be mined in the foreseeable future.

Jan 1, 1987

By E. V. Lilford

The South African Minerals Development Act (?the Act?) has been promulgated and will come into full force and effect once it is gazetted. Thereafter, all Old Order mineral rights will have to be converted into New Order mineral rights within a 5-year period, probably by the end of 2008. The conversion of rights will be achieved only with the demonstrated inclusion of empowerment groups in the conversion applications. In addition to the Act, the first draft of the proposed Royalty Bill (?the Bill?) was released during the week beginning 17 March 2003. Comments on the Bill?s contents had to be submitted before 30 April 2003. The contents were to be considered in terms of applicability and acceptability to the South African minerals industry, where after proposed comments and suggested amendments were to be submitted to the relevant State Treasury office. Specifically referring to the Bill, the general response from the industry is one of concern. Since any royalty is tantamount to a tax, the general feeling is that the current mining taxation rates are already internationally competitive and to increase these effective rates, notably at differing rates depending on commodity type, will have an adverse impact on the South African mining industry. A number of these impacts can be mitigated to some degree, depending on the flexibility of the State to address the major concerns.

Jan 1, 2003

By J. Geisler

When addressing Germany’s resource supplies, we need to distinguish between those domestically available and imported ones. Resource extraction ostensibly competes with the designation of protection areas. However, the parallel existence of wildlife and plant life, and operations in the areas used for resource extractions is continually underestimated. The European Commission has compiled guidance documents facilitating the extraction of resources from protected areas. With regard to resource productivity, the market appears to be the appropriate instrument for minimising resource consumption. Policy makers are now called upon to create a legal framework leading to a consensus accepted by society.

Jan 1, 2011

By J. Geyer, B. T. Burton, H. W. Newcomen

For open pits developed in tropical climates the upper portions of the pit walls are often located in residual soils and weathered rock. Due to the presence of relict structures, and the relatively low strength of the residual soils and weathered rock, design slope angles in these materials have to be developed by blending the results of kinematic assessments of geologic structures with rock mass stability analyses and traditional soil mechanics. Background information on the engineering considerations of residual soils are discussed, and the results of geotechnical assessments for proposed pit design of the Brisas del Cuyuni Project, located in southeastern Venezuela, are presented.

Jan 1, 2000

By André C. Zingano

The coal pillars in room-and-pillar mining method are subjected to vertical stress due to overburden rock mass and horizontal stress relieve due to entries excavation around them. Some coal mining companies are applying rock bolts and steel straps to improve the pillar strength, consequently to reducing the pillar size and increasing coal recovery. This kind of approach deserves some discussion, whether it is pillar reinforcement or just rib support. The efficiency of pillar reinforcement (or rib support) is directly related to the initial load capacity of coal pillar, the type of excavation, and the width to high ratio of the pillar. The objective of this paper is to understand the mechanism of pillar reinforcement (or rib support) using rock bolts and steel straps on pillar ribs. Numerical simulation taking into account the relations listed above. The results showed that the increase of coal pillar strength is very short, and there is no influence on improvement of load capacity of pillar. However, the rib support avoids block falling, rib failure, and displacement, reducing the pillar failure propagation into the pillar center. Keywords: coal, pillar reinforcement, room and pillar.

Jan 1, 2006

By Victor R. Spironello

The Bureau of Mines has conducted studies of the slags related to ferrous technology to evaluate experimentally acceptable substitutes for the auxiliary flux, mineral fluorspar, in steelmaking operations. Comparative heats were made in a 1/4-ton, pilot-scale, basic oxygen furnace (BOF) to evaluate a waste material known as "used potlining." Used pot lining is recovered from alumina reduction cells after its useful life and contains significant levels of fluorine and sodium in various compounds. This material in both lump and pelletized form provided adequately fluid slags, based on observations made during BOF operation. No adverse effects were found on furnace performance, metal and slag chemsitry, the strength of the steel produced, or the environment. Fluorine recovery in the slag was about the same as that obtained when using fluorspar, as were the losses to the scrubber water and solids. No difference was observed in furnace-refractory attack, as determined by the level of magnesia in the slag. The sodium recovered in the slag apparently also contributed to fluidity, since the fluorine input was at about two-thirds that of the fluorspar. Used potlining was determined experimentally to be a satisfactory substitute for fluorspar in basic oxygen steelmaking.

Jan 1, 1982

Geophysical anomalies result from the passage of hydrothermal fluids through rocks. Interpretation of these anomalies, when integrated with available geological and geochemical data, assists the construction of a conceptual model of the original hydrology of the system. The original extent of a geothermal system is often indicated by the distribution of low resistivity argillic clay alteration. Quartz-adularia vein deposits, silica sinters or stockwork (often mineralised) cause local increases in resistivity. Appropriately chosen electrical techniques can therefore be used to help target such structures. Airborne magnetic surveys have also proven useful in New Zealand epithermal exploration, because hydrothermal fluids destroy magnetite causing extensive demagnetisation anomalies. Ground magnetic surveys can sometimes be useful for geological interpretation on a local scale. Positive gravity anomalies may occur as a result of mineral precipitation (silica or calcite) in high porosity host rocks, while negative gravity anomalies can result from hydrothermal fracturing and leaching of relatively dense host rocks. The relative merits of these geophysical techniques as used in the exploration of epithermal mineral prospects are discussed, with particular reference to the Hauraki Goldfield. The preferred method for defining zones of quartz veining/silicification is vector or tensor gradient resistivity. Exploration strategies and technique refinements are suggested as a means of improving the resolution of potentially mineralised target structures, in a more efficient and cost effective manner.

Jan 1, 1993

By J. I. Mathis

"The failure that was utilized for developing this model was a double bench-scale failure, approximately 20 m in height, in the Misery pit at BHP Billiton’s EKATI mine site. The bench that failed was excavated in biotite schist. Due to previous problems with bench-scale toppling failures, this bench was excavated with a 70° inclined, 30 m deep preshear. Upon exposure, the wall was very clean with half-barrels commonly observed from the pre-shear operation.In August 2003, a bench failure of about 1000 t occurred in this pre-sheared biotite schist (Fig. 1). Upon examination it was noted that the foliation that paralleled and dipped at 70° into the face when excavated was approximately horizontal at the top of the failure (Fig. 2). While the failure mode itself appears complex, the failure was apparently driven by three factors:• a low-angle, low-frictional strength fault or discontinuity at the base of the failure area;• water either contributed meteorically from precipitation and/or from permafrost melt; and• foliation planes providing a viable toppling geometry once toe block motion began to occur.The above details are illustrated in Figure 3.After considerable thought and analysis, a model was postulated for the failure.It is thought that the entire failure had been triggered by displacement of a toe block (Fig. 4). This toe block is bounded on the back by foliation, the bottom by a low-angle, lowstrength fault, and the front by the bench face. Water pressures behind the bench face developed forces on the block as can be seen in Figure 5. These forces were sufficient to induce block motion. As can be seen in the relative shear strength diagram in Figure 6, only a small amount of water is necessary in the face to initiate block displacement. Note that in this figure, a simplistic piezometric pressure distribution was assumed."

Jan 1, 2004