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By Offler R, Lau J, Lea J. F

The stratiform and vein-type pyritic silver-Iead-zinc-copper sulphide deposits of Sunny Corner, NSW are hosted by acid volcanic and clastic sedimentary rocks of Middle Silurian to Early Devonian age. The rocks have been subjected to low-grade regional metamorphism (prehnite-pumpellyite facies) and three phases of folding and four faulting events are recognised. Pyrite is intensely fractured, indicating brittle deformation. Chalcopyrite and galena exhibit deformation twins and slip planes indicating ductile deformation; sphalerite and chalcopyrite show straight and curved grain boundaries and dihedral angles of 120° as evidence of annealing recryslallisation. Sulphur isotope ratios for 22 samples from five deposits range from 1.7 to 10.7 per mil and average 7.4 per mil. Sulphur isotope data are similar to those from other stratiform sulphide deposits in acid volcanic rocks of Late Silurian age in the eastern Lachlan Fold Belt, especially Woodlawn and Captains Flat and together with other features of the mineralisation, suggest a volcanic exhalative origin for the Sunny Corner deposits.

Jan 1, 1984

By Peter J. Szabo

In 1980, a caravan of representatives of Japanese trading companies debarked on the shores of the United States bearing gifts of watches, electronic games, and radios. In early 1983, we find in a parking lot of a major U.S. coal company, a haggard general manager of marketing returning to the Orient with a box under his arm of trinkets of his own; cross pens with company logos, alarm clocks, etc. The tables have turned, but our fellow sitting in a jet plane over the Pacific Ocean had only to heed the warning of the famous 19th Century poet well familiar with the ways of the Far East. Kipling said; "And the End of the Fight is a tombstone white and with the name of the late deceased, And the epitaph drear, a fool lies here who tried to hustle the East."

Jan 1, 1984

By G. Langlands

"R. Tenbergen Is this flotation machine suitable in the flotation ofInco ball mill discharges where we have a coarse feed at 60% solids?Reply Experience has shown that there is not a significant increase in the wear life of these machines when handling coarse material (8 mesh) at 60% solids. A common practice in Europe is shut down on the week-ends.The material is allowed to settle and on start-up an injectic of air for 15 seconds is sufficient prior to start-up. At,mining we put our unit in the middle of a bank of 44 cells and in order to ensure severe sanding we shut the aker cell down while the remaining cells kept running. After 20-25 seconds of air the cell started without trouble.P. Mahant Is there a build-up inside the impellor shaft housing? Falconbrige Ltd.Reply There is no sand build-up but rather a scale build-up which due to a flexing action frees itself periodically. Part of the design of the machine permits a water injection into the shaft housing to free any build-up. This is done in Europe during the week-end shut down."

Jan 1, 1984

By Kendall Y. Keuhey

The Mercur Mine, developed and operated by Getty Mining Company, is designed to process 3,000 tons/day of gold ore from the historic Mercur Hill mining district. The mill process involves crushing, grinding, and cyanide carbon-in-leach for recovery of gold from ores ranging from 0.08 to 0.10 oz/ton. During the mining of normal grade ore, a substantial tonnage of material containing 0.02 to 0.05 oz/ton is mined and would be available for heap leaching. Also, Getty Mining is developing methods to test and prepare lower grade material for heap leaching by rejecting a coarse rock fraction from the grinding SAG mill circuit. This lower grade fraction is suitable for heap leaching, and its removal will upgrade the regular mill feed. Other test methods are directed toward leaching techniques on some 4.0 million tons of tailings that resulted from roasting and/or cyanide leaching Mercur ores in the early 1900's. The natural carbons associated with the Mercur deposits require special treatment to reduce their gold adsorption effects when leached with cyanide.

Jan 1, 1984

By Donald E. Scheck

Blasting practices based on sound engineering principles are well established but the successful application of these practices requires accurate information about the overburden geology and close supervision of the drilling and blasting operations. Good design alone is not sufficient to insure good results, but the process may be difficult to control unless steps are taken to measure the variables and to provide management and the operators with the information they need to establish and maintain control. Satisfactory blasting can be defined as loosening and fragmenting the rock so that it can be handled by the excavating equipment, while at the same time, governmental regulations on air blast and ground vibrations are not violated. Optimum practices achieve these objectives at the lowest combined cost of the drilling and loading operations and the blasting materials. Total system optimization, that is, taking into consideration the effect of fragmentation on the cost of operating and maintaining excavating equipment as well as drilling and blasting costs, probably is not a reasonable goal at the present time.

Jan 1, 1984

By R. A. Pimentel

Many longwall operators experience difficulty complying with the federal regulation limiting average dust exposure. Others are currently in compliance, but the dust exposure limit keeps then from increasing their production. Spray water is a major means of dust control. Excess water can cause problems in the transportation system and the cleaning plant, and reduces the Btu value of the run of mine coal. Thus, the dust exposure reduction per unit of water sprayed must be maximized. This paper discusses underground tests recently completed as part of a Bureau of Mines research program to determine the effects of variations in spray water flow rate, pressure, proportioning and spray orientation on longwall shearers.

Jan 1, 1984

By Jay Parrish

Appalachian kimberlites appear to be spatially distributed along two structure parallel trends running from Tennessee to New York. It is hypothesized that the kimberlites were emplaced at the intersection of structure parallel basement faults and cross- structural lineaments. The latter are expressed in potential field and remotely sensed data. The western trend follows the Rome Trough from eastern Kentucky to south central New York. The eastern trend parallels the edge of the Ridge and Valley in Virginia and Maryland.

Jan 1, 1984

By Senanayake G

A sample of crude copper powder produced by the CLEAR Process was refined by dissolution and recovery in sulfate media using the Parker Process. The Parker Process offers an alternative method of copper recovery to electrorefining and allows a range of Eh and pH conditions to be used to provide further discrimination of impurities. High purity copper powder was recovered by the Parker Process even in the presence of added impurities when the Eh and pH was maintained near constant throughout the refining step.

Jan 1, 1984

By A. S. Atkins

The interest in the use of micro- organisms in the leaching of sulphide minerals has been traditionally exploited as a scavenger process for the recovery of valuable metal by- products from waste ore dumps. Environmental concern on sulphur emission from conventional pyrometallurgical plants together with the cost of stack cleaning systems to comply with legislative control also indicate baccerial leaching to offer a low cost treatment for the processing of sulphide minerals. The paper describes the effect and limits of relatively coarse particles on the complete leaching of pyrite and its importance to the practical application in dump leaching operations of sulphide minerals. It has also been demonstrated that static leaching techniques have encouraging economic potential for process plant operations compared with agitated leaching systems.

Jan 1, 1984

By F. B. Brost

In 1976, a decision was made by Anamax Mining Company to install an unusual conveying system to transport ore 10.3 km (6.4 mi) from the new Eisenhower Mine to the Twin Buttes concentrator. The system, supplied by Cable Belt Limited of the United Kingdom, represents a radical departure from conventional belt conveyors. The driving tension is applied through two endless wire ropes driven by a single 2 240 kw (3 000 HP) drive while the belt acts only as the ore carrying medium. Full production was begun in January, 1979. Start-up problems hampered production for several months but were resolved by a joint Anamax-Cable Belt effort. The system has been operating at design capacity for 4-1/2 years, and has proven itself as a reliable, low cost ore transportation system.

Jan 1, 1984

By Robert B. Parsons

"New Brunswick Finance Minister John Baxter pulled something out of a hat for the mining industry in April, but there is a general concensus in the industry that he should put II back where it came from.The industry has never been in the mood f or progressive rate structures, but that is exactly what New Brunswick 's 1984 budget offers to this depressed sector of the economy.IntroductionThe Province of New Brunswick stunned the Canadian mining community in April with the announcement that the province' s 16% mining tax rate would be replaced with a progressive rate structure effective January 1, 1984 (Table I). The proposed change, contained in the bud get papers tabled by Finance Minister John Baxter on April 17, caught the industry totally by surprise. The move to a progressive rate structure was completely unexpected for a variety of reasons:• Generally speaking, relations between the province and the industry have been relatively good, yet the industry was apparently not consulted with respect to the proposed measure and had no indication that a change of th is nature was coming. This is in stark contrast to the mood which prevailed during the major revamping of the province' s mining tax regime in 1977: at that time, the industry was invited to contribute in advance to the province's plan for a new tax structure.• The new structure would appear to make th e province less competitive in terms of mining tax rates with Ontario , Quebec, and other provinces, despite indications in the past that New Brunswick is very cognizant of this competitive factor in formulating mineral policy.• A joint report in November 1978 by federal and provincial officials to federal and provincial finance and resource ministers, which was careful not to directly criticize Ontario and Quebec's progressive mining tax rate structures, recommended that provincial "" tax regimes be examined to ensure the inclusion of appropriate mechanisms to avoid the excessive taxation of cyclical type profit "" , and that ""the federal and provincial governments consider the concern over progressive tax regimes expressed by the industry and examine mining and royalty tax regimes and the income tax regime with a view to alleviating the effect of such regime on the aggregate marginal tax rate"". In this context, any move to a progressive rate structure would be viewed by many observers as retrograde."

Jan 1, 1984

The series of events leading to the adoption of more complex flotation circuits for coal have been reviewed. In essence, it has been concluded that ac- ceptable overall flotation recovery will only be obtained when efficient distri- bution of collector over all the component feed size fractions is ensured. The achievement of this goal is most likely to be obtained by feed classification and separate flotation of appropriate size fractions. The adoption of such a phil- osophy, however, imposes a number of process problems of both a chemical and an engineering nature. Some of these problems have been identified and possible solutions discussed. A case is emerging for the development of a new generation of flotation cells designed specifically for the flotation of classified coal and for the development of a series of novel re- agents which have the propensity to float middling particles.

Jan 1, 1984

By L. Y. Sadler

This report summarizes the findings of a 9-yr research program, sponsored by the U.S. Department of Energy and conducted by the Bureau of Mines, to evaluate refractory liner materials for coal gasifier reactors. Commercially available refractories were exposed to coal gasifier reactor environments, reproduced in the laboratory with a high-temperature, high-pressure test facility, followed by extensive postexposure evaluation. Thirty-six castable or gunnable refractories and cements and 24 refractory brick were evaluated. The behavior of castable refractories reinforced with stainless steel fibers was also examined. Gas environments that were evaluated included steam, H2, CO2, CO, and typical high-and low-Btu gas mixtures. Exposure pressures ranged from 100 to 1,000 psig, temperatures from 5000 to 1,1000 C, for periods from 50 h to 2,000 h. In some exposures, sodium and/or potassium hydroxide were introduced in order to simulate a high-alkali environment. It was found that intermediate-and low-alumina refractories produced from domestically available raw materials, rather than high-alumina refractories produced from imported raw materials, gave the best service as liner materials and that alkali attack was probably not a serious problem with most refractories. Based on the results of this program, good choices of refractory liner materials for gasifier reactors can be made.

Jan 1, 1984

By R. H. Goodman

The development of techniques for separating minerals based on differences in their specific gravities is reviewed and their present applications in process technology outlined. Special emphasis is placed on the development, in Australia, of new models of the spiral concentrator. The mechanics of separation of spiral separators are stated, including the effects of operating parameters, Some of the traditional areas of spiral application are described, together with examples of new applications such as treatment of fine alluvials and tailings, separation of liberated minerals at coarse sizes and fine coal recovery.

Jan 1, 1984

By A. L. Senkayi, L. R. Hossner, J. B. Dixon, J. S. Ahlrichs

Chemical and physical properties of soils and overburden materials must be evaluated prior to strip mining activities. This information can be used to assess whether subsurface overburden can be equal in quality to the native soils, especially when these soils are classed as prime farm lands. In northeast Texas, lignite primarily occurs in the Calvert Bluff formation which is underlain by the Simboro and Hooper formations. These formations are in the Wilcox group (early Eocene). The Carrizo formation, that unconformably overlies the Calvert Bluff formation, consists of thick layers of sand with poor water and nutrient retention capabilities. These materials are least suited for placement on the surface of reclaimed land. The oxidized, medium textured overburden of the Culvert Bluff and Simboro formations possess adequate water and nutrient retention properties and are better suited for sustained plant growth when compared to the existing native soils. Non-oxidized Calvert Bluff and Hooper sediments generally have acceptable properties for reclamation although acid forming sulfides occasionally occur. Materials high in sulfides must be buried during mining or appropriately treated prior to reclamation.

Jan 1, 1984

By D. Mraz

"In certain instances, rocks around underground excavations behave as a plastic mass. This paper offers several solutions to predicting the mode of plastic flow around cavities and designing mining pillars where plastic conditions exist.IntroductionWhen stresses around underground cavities exceed yield limits of the host rock, the material often behaves as a plastic mass. The best example of this phenomenon is the behaviour of salt rocks in deep salt and potash deposits (more than 500 m deep).However, many other soft rocks exhibit similar properties. For example, Jeremic(1) described certain types of coal yielding plastically under high pressure. Alder suggested that granulated rock behaves plastically.The object of this paper is to propose a de sign procedure for mining pillars exhibiting plastic flow due to the combination of rock properties and in-situ stresses.Prandtl(3) mathematically defined a concept of a generalized, perfectly plastic substance, not possessing the property of strain hardening (Fig. I). He had in mind, a solid with a quasi quasi-isotropic , polycrystalline structure having a well defined yield point, and he postulated that its material elements start and continue to deform plastically when the maximum shearing stress ""'MAX"" reaches a sharp limit, dependent on the mean value of the sum of the major and minor principal stresses:"

Jan 1, 1984

By James F. Lemons

The potential production of cobalt from nickel sulfide deposits in Canada, from nickel laterite deposits in the Pacific Islands, and from the copper deposits of Zaire and Zambia will be a function of the cost of recovery of the primary nickel and copper products. This cost of production varies significantly for these deposits and is related to the differences in the cost of labor, energy, and supplies, to production technology, and to the grade and recovery of nickel, copper, and cobalt. This Bureau of Mines paper investigates these cost and technology differences as they relate to the cost competitiveness of the deposits in Canada, Zambia, Zaire, and the Pacific Islands.

Jan 1, 1984

By J. Weng

The equations of heat conduction are numerically solved for two kinds of artificial freezing- mechanical freezing and liquid nitrogen freezing. A two dimensional finite difference model simulating the freezing field is developed. The procedure introduces a way to simulate the effect of latent heat released when water transforms from liquid to solid. The procedure also produces a way to calculate the harmonic mean of heat conductivity used when dealing with heterogeneous material. The theoretically derived temperature distributions in frozen soil are given and compared with measured data. An analysis made on the thermal design in shaft freezing. The average temperature of frozen soil is calculated by using numerical integration. The regularity of development of frozen soil radius is revealed and given in an appropriate mathematical model.

Jan 1, 1984

By J. E. Russell

The purpose of this paper is to describe an independent study which forecasts Texas coal production, specifically for electric power generation. This study, extending to the year 2000, is justified on the following basis. Texas produces and consumes considerably more electric energy than any other state, has consistently high growth rates in the population and industrial sectors, and has large lignite reserves. Also, since recent forecasts have been criticized as overly optimistic, this study is timely when considering the long lead times required in obtaining new power sources. In the study demand for electric energy was assumed to rest on two dominant factors: 1) overall state of the Texas economy as measured by the Texas Gross State Product (TGSP) and 2) Texas population. Demand models were prepared and tested following a study of several options. A final linear regression demand model with time lags for the two variables was chosen on the basis of good correlations. On the supply side, uncertainties such as impact of nuclear sources, gas-fired cogeneration, and ratio of imported to lignite coal exist. These uncertainties were studied with high and low cases for effects on lignite. Finally a simple supply model was chosen. Results of the study indicate that lignite production in Texas will rise from the current (1984) 40 million tons per year (XTPY) to the range of 77 to 124 MTPY and more probably 100 HTPY in the year 2000.

Jan 1, 1984

By Manuel R. Lastra

Critical to successful dump and heap leaching for gold, silver, copper and uranium are factors such as permeability, solution delivery to the ore, and solution recovery. This paper deals with possible techniques for successful accomplishment of these three factors. New developments as well as older techniques are discussed, together with rationale for use of some techniques in reference to others. The authors hope to present a checklist so that the ideal application to individual mine situations can be achieved. This involves a discussion of the merits of each different method and the situations for most logical application. It is hoped that such discussion will broaden the geographic areas where dump and heap leaching can be applied to include greater winter cold and tropical regions of large amounts of rainfall.

Jan 1, 1984