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By L. G. Closs

Gold continued to be the primary focus of minerals exploration worldwide during 1995. Other targets, though, included primary diamonds and base metals, especially copper deposits amenable to solvent-extraction/electrowinning (SX/EW) processing. The discovery of nickel, copper and cobalt at Voisey Bay in Labrador, Canada was an unusual surprise. Meanwhile, exploration geochemistry continues to evolve to meet new challenges. The major event in this category during 1995 was the17th International Geochemical Exploration Symposium (IGES) held in Townsville, Queensland, Australia in May. The meeting was sponsored by the Association of Exploration Geochemists, which celebrated its 25thanniversary of service to the mineral industry, and the Economic Geology Research Unit of James Cook University, Townsville.

Jan 1, 1996

By H. Y. Yang, L. L. Tong

Semicontinuous-flow, multistage biooxidation experiments of a Chinese refractory, high-sulfur gold concentrate were conducted with different pulp densities for gold recovery. The maximum iron, sulfur and arsenic oxidation rates of 90.0, 88.8 and 96.4 percent, respectively, were obtained in the experiments with 5 percent pulp density. The highest gold and silver recoveries of 96.1 and 68.9 percent, respectively, were achieved by cyanidation. The negative effect of high pulp density on biooxidation was related to the decrease of free and adsorbed cell concentrations with increasing pulp density. The data of iron oxidation from the semicontinuous biooxidation experiments were best fitted by a shrinking core model in which the chemical reaction controlled the rate. The dissolution kinetics of sulfur and arsenic were therefore analyzed by a shrinking core model in which the internal diffusion controlled the bioleaching rates. For the quantitative description of biooxidation efficiency, two parameters — mass dissolution rate and volume dissolution rate — were proposed. In the first stage, the mass dissolution rates of minerals were negatively correlated while the volume dissolution rates were positively correlated with the actual pulp density. The iron and sulfur mass dissolution rates decreased with increasing actual pulp densities in the third and fourth stage, while linear increasing relationships between the volume dissolution rates of minerals and the actual pulp density were observed from the second to fourth stage. The highest mass dissolution rates of minerals were obtained in the first stage with 5 percent pulp density. The highest volume dissolution rates of minerals were obtained in the first stage with 15 percent pulp density. Compared to the volume dissolution rate, the mass dissolution rate was more intuitive to reflect the negative effect of high pulp density on biooxidation efficiency.

By Edward H. Eisenbrey

This paper is primarily concerned with the exploration for massive sulphide orebodies. In a discussion of this type, it seems appropriate to establish a few definitions so that all parties may consider the same beast and its habitat. First, the term "massive sulphides", as used here, not only denotes a body of mineralized rock containing in excess of 50% sulphides by volume, but a mass of sulphides that respond as a conductor to the electromagnetic (EM) systems currently in use in exploration. "Disseminated sulphides" refer to all of those sulphide occurrences that respond to the Induced Polarization (IP) geophysical methods most commonly in use in porphyry copper exploration. This latter definition may also include the disseminated sulphide halos so frequently found associated with massive mineralization as well as banded and stringer sulphide mineralization. It is plain to see that these two end members of our definitions can easily blend into each other. The term "volcanogenic" refers here to any and all geologic processes that have their origin in volcanic activity. Thus we are concerned here with the exploration for massive sulphide ore deposits derived from and affected by contemporaneous and post mineral volcanic activity. Furthermore, most massive sulphide deposits are apparently formed in a submarine environment, deposited with extrusive rocks and sediments and/or chemical hot spring accumulations, then enclosed and protected by the addition of more volcanic and sedimentary material then, probably folded and deformed into one of their myriad of shapes.

Jan 1, 1973

The purpose of this talk is to report the answers to the-'two following questions: I. What unique services does the mining industry expect of mining and mineral processing engineers? II. What suggestions does industry offer to educators to help revamp curricula to meet the needs of a changing industry? As the result of many questionnaires filled out in person by presidents, managers, superintendents, chief engineers, metallurgists, and other responsible individuals in operations and management of large and small metal and nonmetallic mining companies in the U. S., and to some extent abroad, we now have some, specific answers to the above questions. Although answers to questionnaires continue to arrive at this writing (February 10) the volume already received is sufficient to clearly justify certain conclusions and observations. A copy of the tally of the first 117 questionnaires received accompanies this report, and I am certain that a compilation of additional questionnaire data will merely reinforce, the trends in thinking that have been' established thus far. Here are the results of the survey:

Jan 1, 1961

By John E. Tilton

Mining is one of the oldest human activities. It goes back at least to the Bronze Age and possibly even the Stone Age. The Romans mined copper in Spain and tin in England some 2,000 years ago. The writings of Agricola in the 16th century show that mining was important in the Middle Ages. Today, more mineral commodities are mined in greater tonnages than ever before. This long and fascinating history closely tied with the economic development of the human race is one of the charms of the mining industry. It also, unfortunately, gives rise to some widespread misconceptions. Old industries are generally considered stodgy with mature and stagnant technologies. Costs tend not to decline as in newer industries, and may even increase with real wages. Costs are particularly expected to rise in the case of mining as the best mineral deposits are depleted. Thus, mining is often thought of as a sunset industry, destined to decline over time as the resource base is depleted. These perceptions have several important implications. They argue against economic policies that rely too heavily on mining and mineral processing to foster growth and development. The best and the brightest young people, along with society's other valuable resources, should be encouraged to enter newer industries. There the technological opportunities and the prospects for growth are more promising. These perceptions also suggest that the ability to compete in the mining industry depends largely on the quality of a company's or country's mineral deposits. Mining will take place first in countries with the lowest-cost deposits. Once these are exhausted, mining will shift to countries with the next best deposits. From time to time, new discoveries may also produce a shift in the location of mining, [ ] and may even for a time keep the costs and prices of mineral products from rising. Over the longer term, however, rising costs and prices are inevitable, as the world is forced to exploit poorer mineral deposits.

Jan 1, 1997

By Keith G. Wallace

The effect of face resistance on ventilation air leakage through stoppings was measured in a twin development heading. Face resistance was varied by alternately tightening or loosening the face line brattice to change the line brattice leakage. Results indicated that tight brattice lines are necessary to maintain acceptable airflow at the face but result in higher leakage throughout the entire system, reduced overall ventilation efficiency, and higher operating costs. Conversely, a low face resistance which simulated an auxiliary fan/duct system gave reduced stopping leakage losses, higher quantities of air at the last open cross-cut and greater entire system efficiencies

Jan 1, 1984

By L. E. Garner

Aggregate resources should be considered primary factors in urban development. Resource planning is essential because land values, previous construction, or zoning restrictions often preempt exploitation of aggregate deposits within an urban area. Sequential land use practices allow development of areas prior to urban development. Population and aggregate consumption trends in Austin, Texas, indicate that substantial quantities of reserves will be lost to future development. Aggregate materials are present in nearby seas. However, a comparison of transportation and reclamation costs indicates that reclaiming land after mineral extraction can be significantly cheaper than transporting materials longer distances.

Jan 1, 1979

By Harold V. Fairbanks

This investigation included a study of three different methods for the acoustic drying of ultrafine coals. Ultrafine coal being defined as coal which passes through a 100 mesh sieve. The first method employed stationary drying of small coal samples in sound fields having frequencies of 12,000 cps and 20,000 cps. Sound intensities up to 150 db were used. The second method employed the use of rotary drying kilns. The effect of such variables as temperature, sound intensity, coal feed rate, air flow rate, and initial moisture content were studied. The third method employed the use of a multi-tiered, vibrating screen dryer. The effect of initial moisture content and residence time were studied.

Jan 1, 1970

By M. S. Celik

Despite its importance in various diverse industries, research on beneficiation strategies of boron minerals has not received enough attention. Boron minerals are primarily upgraded by wet processing methods. However, severe environmental constrains have accelerated the development of dry processing techniques such as calcination. Interestingly, boron minerals, colemanite, ulexite and borax undergo respectively decrepitation (fragmentation), shrinkage and expansion upon heat treatment. Each mineral then requires a different beneficiation scheme. In this study, laboratory and pilot plant studies on calcination of boron minerals conducted in our laboratories are reviewed along with their implications in commercial operations.

Jan 1, 1997

By John Bailey

Stressmap is a program whereby the earth's stress field is charted in detail and utilized for design of mines and mine exploitation. This program is implemented by mapping the attitude (location, direction, dip, and extent) of induced rock ruptures during the process of hydrafracturing drill holes contiguous to mine interest. The program includes utilization of ancillary naturally occurring stress relief signals, They are precipitated because the earth is indeed dynamic and the strata of the crust are continually adjusting to load and/or strain differentials resulting in rock deformation and fracturing. These fracturing adjustments occur as small to tiny earthquakes comparable to Richter magnitudes of one, zero, minus one, and smaller events termed microearthquakes. Obviously, the earth's stress field changes due to continued differential loading and crustal movements; therefore it becomes conspicuously evident that resolving today's stress field as opposed to paleostresses is most important for efficient, economical, and safe mining operations.

Jan 1, 1974

By D. S. Kimbal

The McCoy/Cove mine is located 48 km (30 miles) south of Battle Mountain, Nevada, USA, in the Fish Creek Mountains at an elevation of 1548 m (5080 ft), see Figure 1. Joseph H. McCoy first discovered gold at this location in 1914. This discovery led to the Gold Dome Mine which produced the first gold from this area in 1928. After the Gold Dome era, the land remained relatively dormant until Houston oil and Minerals Corporation purchased the claims from the Summa corporation and defined an ore body at the present day McCoy pit. In 1986 Tenneco Minerals (formerly Houston oil and Minerals corporation), sold the McCoy mine and adjoining claims to Echo Bay Minerals corporation. The Cove ore body was discovered soon after the sale to Echo Bay. Echo Bay expanded the heap leach operation and built the present mill which began processing ore in the fall of 1989.

Jan 1, 1993

By Ralph L. Merklin

One of the most commonly employed set of calculations in mill design and research is the material balance, known in wet beneficiation plants, as an Ore and Water Balance. For mill designers, the balance is one of the principal requirements in determining the proper size of launders, pipelines, process equipment, etc. In process development, one of the major goals is the establishment of an optimum balance. The usual procedure for calculating a material balance involves a manual technique utilizing reference tables, pre -obtained data, and a slide rule or desk calculator. With these, the engineer must perform a series of calculations which are repetitious in nature and time consuming. Figure I is the flowsheet of the grinding and flotation circuits for a copper concentrator. The initial ore and water balance was calculated manually and required approximately 24 manhours. Later, a number of changes were made in the balance, each of which required an average of 8 manhours.

Jan 1, 1967

By Michael Markels

The United States Environmental Protection Agency (EPA) is charged under the Federal Water Pollution Control Act Amendments of 1972 with establishing effluent limitations which must be achieved by point sources of discharge into the navigable water of the United States. Section 301 (b) of the Act requires the achievement by not later than July 1, 1977, of effluent limitations for point sources, other than publicly owned treatment works, which are based on the application of the best practicable control technology currently available as defined by the Administrator pursuant to Section 304(b) of the Act. Section 301(b) also requires the achievement by not later than July 1, 1983, of effluent limitations for point sources, other than publicly owned treatment works which are based on the application of the best available technology economically achievable which will result in reasonable further progress toward the national goal of eliminating the discharge of all pollutants, as determined in accordance with regulations issued by the Administrator pursuant to Section 304(b) to the Act. Section 306 of the Act requires the achievement by new sources of a Federal standard of performance providing for the control of the discharge of pollutants which reflects the greatest degree of effluent reduction which the Administrator determines to be achievable through the application of the best available demonstrated control technology, processes, operating methods, or other alternatives, including, where practicable, a standard permitting no discharge of pollutants.

Jan 1, 1975

By D. V. Bush

There has been a great deal of evaluation and discussion on the economics of semi- autogenous grinding versus conventional grinding circuits. This paper will not discuss the merits of one system over the other, but rather will discuss the Henderson Mill's approach toward achieving the most economical milling conditions in its existing SAG mills.

Jan 1, 1985

By James E. Palmer

Geologic constraints on mining and recoverability include the following: coal seams too thin or thick for conventional mining methods; coal seams with insufficient stratigraphic separation; unstable roof or floor strata; discontinuous or lenticular seams; coal seams that have high dips or are intensely faulted; water problems due to proximity of aquifers; and coal quality problems such as excessive sulfur, ash, chlorine, sodium, etc. The demonstrated reserve base for western coal of 220 billion tons is considered misleading as it does not adequately incorporate the above parameters in estimating procedures. Current reserve base estimating procedures involve an abstraction of data from generalized resource estimates. The authors believe the reserve base should be determined independently beginning with well-known deposits, with all mining and recoverability constraints fully incorporated.

Jan 1, 1981

By Richard L. Profio

A practical analysis of the three basic elements of a mining shovel's productive capacity. Payload Speed Reliability Improved dipper fill factor is explored referring to the latest generation of wide dippers combined with higher "bank horsepower" capabilities of modern drive systems. Cycle time improvement is reviewed including overall attachment geometry and coordination of motions. A specific case study is detailed. Basic reliability of welded structures, machinery components, and electrical systems are related to operating costs. Three basic elements determine a mining shovel's long term productive capacity: 1) Average payload per cycle. 2) Average cycle time; and 3) Reliability. This paper deals with productivity gains that are possible with existing shovels as well as new equipment.

Jan 1, 1984

By Charles W. Daugherty, Robert Nyren

The replacement of Boston’s elevated Highway I-93 running north to south through the heart of the city with 8-lane tunneled roadways, coupled with the underground extension of Highway I-90 eastward to Logan Airport, has earned the Central Artery/Tunnel (CA/T) Project the position of the largest infrastructure project in the U.S. today. The gigantic interchange featuring numerous ramps where these two main branches of the Artery intersect required the construction of three huge jacked tunnel boxes that were pushed beneath eight active Amtrak and commuter rail tracks that had to remain undisturbed in spite of poor geology and a minimum of cover between the track beds and the tunnel crowns. Ground freezing was chosen as the method of stabilizing the soil over the tunnels, and it was extended in one area to stabilize the ground at the intersection between the tunnels and an abutting deep cut-and-cover excavation. Because many standard geotechnical instruments consist basically of open standpipes filled with water, it was a major challenge to keep them de-iced and in a condition to provide data on vertical and lateral ground movements. The efforts to do so are herein described.

Jan 1, 2003

By S. Mathur

Polyacrylic acid (P AA) was evaluated as a selective flocculant for dolomite-apatite system. P AA of 4 million MW was found to flocculate both dolomite and apatite. However, their flocculation behavior was significantly different with 450,000 MW PAA which was the lowest molecular weight fraction capable of flocculation. In single mineral tests, at a dosage of 2kg/t 90% of dolomite and 35% of apatite flocculated. Selectivity was achieved in mixed mineral tests where apatite of 90% grade at 70% recovery level was obtained in the concentrate from a feed consisting of 80:20 mixture of apatite and dolomite. The dolomite rejection was about 75% which corresponds to 1% MgO in the concentrate.

Jan 1, 1995

By J. C. Heter

The P.W. Gillibrand Company has been processing and stockpiling a suite of heavy minerals at its Soledad Canyon Mine as co-products with construction aggregates since 1984. The heavy minerals are composed of ilmenite, magnetitie, apatite and zircon. The source of the heavy minerals is the Precambrian San Gabriel Anorthosite Complex of the western San Gabriel Mountains. The valuable minerals are readily amenable to standard ore dressing techniques, such as, gravity, magnetic, flotation and electrostatic separation with good recovery and product quality. More than 20,000 short tons of coarse ilmenite were sold in 1990 to the export market for titanium pigment production.

Jan 1, 1992

By D. G. Chedgy

Environmental improvement efforts are focusing with increasing intensity on pollutants resulting from combustion. The high cost of removing these pollutants at the power station is well documented. Physical coal cleaning has always been and should remain the most economic method of reducing sulfur oxide emission from coal combustion. It is critical in the selection of preparation plant circuitry to consider capital and operating costs, as well as the level of sulfur reduction. This paper describes the technical criteria which must be used for efficient process selection and summarizes the cleaning systems available or in development.

Jan 1, 1990