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By Nancy L. Jackson, Leslie C. Thompson

Acid rock drainage is one of the most complex issues facing regulators and mining companies for management and remediation of mining wastes. All mining waste units, including open pits, underground workings, tailings, waste rock and leached spent ore have the potential to generate acidic leachate based on the acid generation or neutralization potential of the material. This paper uses a case study of the Walker Mine in northern California to give an overview of the available control and mitigation methods. Wetland design is emphasized as a low-cost alternative treatment option for wastewater remediation. The Walker Mine is located on the eastern flank of the Sierra Nevada, 20 miles north of Portola in Plumas County, California. The Walker Mine was an active copper mine between 1915 and 1941. During active mining, tailings were discharged into an area 1 mile west of the site at the confluence of Dolly Creek and Grizzly Creek. In addition, there were two main sources of metal-rich, acid waters impacting Dolly Creek: discharge from the mine tunnel portal, and seepage and surface runoff from waters contacting mine waste downslope from the portal area. A mine portal seal was installed in 1987 which prevented the majority of mine water drainage from further contaminating the area. Minor drainage from the portal and seeps discharge into a holding pond which overflows into Dolly Creek when elevation exceeds 6,200 feet. A site characterization study was performed to evaluate the potential water quality threat to Dolly Creek from mine tunnel discharge and waste rock seeps. Based on the results of this study several remedial options were investigated, both on a design and cost basis, to determine which abatement alternatives could be realistically implemented. The remedial options considered include both in situ containment (landfill, waste pile) or removal (backfilling into underground workings and/or sinkholes) of solid wastes. Waste water remedial options include long-term, seasonal treatment of the portal mine water, or long-term, passive treatment of portal discharge and waste pile leachate.

Jan 1, 1993

By Michael Davis

In the fairly recent past, with a history of cheap and abundant energy, it has been possible to predict with reasonable confidence that world energy demand would continue to double about every 15 years. Those who attempted to forecast the role of nuclear energy in future electricity generation could also start with the fairly safe assumption that electricity demand would increase even faster : with a doubling in demand about every 10 years. To estimate the likely future world demand for uranium it was then necessary to introduce a number of other assumptions including the rate of penetration of nuclear energy, the timing and the specific fuel requirements. This series of assumptions naturally compounded the uncertainty, but, remarkably, usually led to future uranium demands being overestimated. Such a bias which has almost always been observed in predictions made over the past 20 years has increasingly made uranium producers sceptical when expected to match the forecast demand with increased production capacity and supporting reserves. This scepticism has, of course, been reinforced by the persistence so far of a buyers' market in uranium throughout the entire period of emergence of commercial nuclear electricity generation.

Jan 1, 1974

By Darryl J. Butcher

The Akjoujt Project is operated by MORAK SA, a company incorporated in the Islamic Republic of Mauritania. MORAK is jointly owned by General Gold International SA (A wholly owned subsidiary of General Gold Resources NL.), SAMIN, and the International Finance Corporation. The project was devel­oped to treat approximately 2.1 million tonnes of TORCO (Treatment of Refractory Copper Ores) tailings containing an average 3.2gAu/t, and 0.75%Cu/t. The process involves the use of ammoniacal cyanidation for gold extraction, and conventional carbon adsorption, and eventual desorption, of gold values. This is believed to be only the second commercial application of this leach chemistry in the world. The other being a small vat leach operation on the Paris Mine Dumps. (This operation was described by Mr M Ruane in a paper to a previous Randol Forum.) Initial work on the process, and the Akjoujt process design assumed that the reaction involved was anaerobic. This paper describes the operating experience, plant trial, and eventual installation which has lead MORAK to the conclusion that the process is not anaerobic, but requires oxygen, or an oxidant to proceed.

Jan 1, 1995

By William K. Burriss

Computer technology was applied to solve three problems in the selling of certain industrial minerals to the glass and foundry industries. The computer solutions provide for better service to customers and have helped increase sales. II. Summary Electronic data processing techniques were applied: 1. To automatically and continuously "trace" rail car shipments of bentonite. 2. To aid our sales people in recommending to glass plant purchasing agents which of several possible feldspathic materials is the best value at any of about 100 glass plants and to give guidance on the amount of value difference. 3. To help in locating plant sites for three blending or pre-mixing stations to serve the foundry industry at minimum cost and with maximum tonnage and maximum profitability.

Jan 1, 1968

By Alexander N. Winchell

"The iron ores of the Lake Superior region are found almost exclusively in rocks of Huronian age, the only exception of importance being in the Vermilion district. It may be estimated that about 95 per cent of the ores thus far mined have been obtained from Huronian rocks. Although these ores come from rocks of varying age and slightly varying type, they have many features in common, and therefore may readily be described together.The iron formations of the Lake Superior region consist essentially of interbanded layers of mixtures in widely varying proportions of silica and iron oxide, and are called taconite, ferruginous chert, or jaspilite. They vary considerably in hard¬ness and color, depending upon the tenor of silica and the history of the rock. Local phases of the iron bearing formation consist of cherty iron carbonates, greenalite or ferrous silicate, rocks, amphibole-magnetite masses, cherts and slates, and pyritic quartz rocks. The average iron content of all the original phases of the iron bearing formations, excluding interbedded slates, is about 25 per cent, while the average iron content for all portions of the formation, whether in the original condition or not, is about 38 per cent. It is believed that this difference is due essen¬tially to the removal of silica in solution from the. primary phases, and, of course, such removal of silica has in many cases produced material now used as iron ore, since it contains con¬siderably more than 38 per cent of iron."

Jan 1, 1920

By Douglas F. Crickmer

Pocahontas Land Corporation, a wholly-owned subsidiary of Norfolk and western Railway Company, owns a 100,000-acre block of coal lands in Martin, Johnson, Pike, Floyd and Lawrence Counties, Kentucky. These holdings were largely acquired in three major purchases between the years 1942 and 1959. The area is undeveloped and constitutes a part of the coal reserve for future mining. This block, which is principally in Martin County, lies in a triangle formed by the Levisa and Tug Forks of Big Sandy River on the sides with Dewey Dam at its base and the Town of Louisa at the apex. The topography'is typical of eastern Kentucky and consists of steep hills rising from 500 to 800 feet above creek level. There is little level ground in the area. As a matter of fact, some roads are on the creek bottoms with what little bottom land is available in the hollows being utilized for small-scale farming. The steep hills are marked by three separate massive sandstone formations which form cliffs ranging from 40 to 100 feet in height.

Jan 1, 1964

By Rodolfo V. de la Cruz

Abstract. The Hoskold mineral valuation method was critically examined. The original derivation was presented and found to contain a number cf erroneous assumptions as follows: the sinking fund must be available for reinvestment in another property; the series of reinvestment of the sinking fund results in a perpetual annuity to the investor, and; evaluation of the present value of the net cash flows at the speculative rate of interest. The proper procedure of deriving the Hoskhold mineral valuation formula was discussed and illustrated with a cumulative cash position diagram, a useful tool in economic evaluation and investment decision methods.

Jan 1, 1980

By Ireneusz Tomza, Jolanta Lebecka

INTRODUCTION Radioactive deposits were observed in 1972 in some of the Upper Silesian coal mines. They were located mainly in the drains in galeries and on the inside surfaces of water pipes. They also caused some problems by accumulating in water pumps. It has been postulated that the deposits are produced by natural radioactive waters seeping from the rocks. Investigations were initiated to answer the following questions: - What is the composition and the amount of radioactivity in the deposits? - What radioisotopes are present in the water? - How are the radioactive deposits formed? - Do the radioactive waters also occur in other mines? - How does the radioactivity of the water depend on chemical composition? - What is the origin of the radioactive water? - Does the water and the deposits cause radiation hazards for miners? -How can the radiation hazard be reduced? METHODS OF MEASUREMENT Determination of Radium Isotopes in Water The commonly used methods of radium determination in water are either based on measurements of the radioactivity of 222Rn which is in equilibrium with 226Ra, or on the detection of alpha particles of the radium radioisotopes after chemical separation of radium from the water sample. The method based on radon activity measurements is very sensitive and does not require any chemical Separation, but it can be used for determination of 226Ra from the uranium series only, because the thorium daughter 220Rn has too short a half-life (55s to yield the required accuracy. The method developed by Goldin, 1961 [2] involved alpha-particle measurements in thin layers of RaS04 and BaS04 separated from the water. This method is not convenient for saline water and water with high barium concentration because the amount of barium carrier in this case is too large to obtain a thin layer of precipitate with sufficient activity. The Upper Silesian carboniferous waters are often saline with high barium content, so the method described by Goldin was not convenient for this case and it was necessary to change the detection system and modify the chemical preparation. The procedure developed by the authors for the determination of radium isotopes in water was as follows: - Depending on the Ba2+ content and the required sensitivity of measurement, a water sample of 200 cm3 to 3 dm3 was taken. - 10 cm3 of 0.25 M citric acid and 5 cm3 15M ammonia was added to form complex Ba2+ ions and avoid the immediate precipitation of BaSO4. (This was repeated as long as the addition of BaC12 did not form a precipitate.) - 1 cm3 of 1N solution of Pb(N03)2 as a carrier for radioactive isotopes of lead and 10 cm3 of 0.1 N BaC12 as a carrier for radium were added. - The sample was heated to the boiling point and the precipitation of RaS04, BaSO4 and PbS04 with 50% H2SO4 was carried out. - After several hours the sample was centrifuged and the precipitate was purified by washing with nitric acid and distilled water. - The precipitate was then redisolved in 20 cm3 0.125 M Na2EDTA and 3 cm3 6M ammonia and reprecipitated from the solution by dropwise addition of acetic acid to d pH of 4.5. At this value of pH, precipitation occurs only for the barium and radium sulfates, while lead and all other radioactive elements remain in the solution. The date and time of deposit precipitation was recorded. - The final barium-radium sulfate mixture was washed with distilled water and transferred to standard measurement vials. - Each vial containing a deposit had 6 cm3 of distilled water added and was then shaken vigorously. 12 cm3 of liquid gelling scintillator (INSTA-GEL UNISOLV-1 type) was then added and the vi 1 was shaken again. After a while the scintillator turns into a milky gel in which the deposit is uniformly distributed. - The standard sample of 226Ra was prepared in the same way. - The activity of the samples was measured using a liquid scintillation spectrometer. (In this case the TRICARB 3320 produced by Packard Instruments, was used). Tests run on standard radium solutions provided by Amersham Radiochemical Centre indicated that this method of measurement enables one to achieve an efficiency of almost 100% (within measurement error). For alpha particles no quenching effect was observed for the BaS04 concentration in the range up to 80 mg of BaS04 per 1 cm3 of liquid scintillator coctail (Fig. 1). This provides a sensitive determination of radium in water with high barium content and also in saline water. In saline water the solubility of barium sulfate is much higher than in

Jan 1, 1981

By James L. Patton

Automation of mining increases the productivity of labor, thereby reducing the unit cost of labor. Such cost constitutes the largest portion of the direct or variable costs of producing coal. Therefore, any increase in productivity directly reduces variable cost. The large investment in mechanical equipment carries with it the burden of increased fixed charges. As the proportion of fixed cost to the total cost increases, the effects on the cost of production changes are amplified. Therefore, equipment must be fully utilized at all times. Averaged fixed costs rise with any decline in production. Such a situation forces coal companies to seek every means of main¬taining full production. Figure I will reflect the story on the relationship of production to cost.

Jan 1, 1962

By S. Eugene Sankey, Geoffrey L. Payne

Fundamental choices in flocculant selection often come down to the lower cost of solid grade products versus the convenience of liquids. The ideal product would be a low cost solid grade flocculant which requires minimal handling and no sophisticated dissolving equipment. Recent polymer developments have lead to the commercialization of a limited range of dry polymers that can be screw fed at controlled rates directly to process streams without the need for predissolving. Other developments include dry polymers that can be directly added to mix tanks without the need for sophisticated wetting systems. The latter will make dry flocculants especially attractive for smaller users. Examples of these new products and their application in industrial and municipal waste treatment will be provided.

Jan 1, 1994

By I. Orisek

The methodology and results of a feasibility study of an Automatic Truck Dispatching (ATD) system in an actual open pit mining operation, are presented. Using mine cost data, an economic analysis confirms that capital and operating cost savings with ATD out-weigh the costs. Productivity improvement achievable with ATD is quantified with a computer simulation of truck haulage based on mine production and operational data.

Jan 1, 1986

By D. U. Gustafsson

After half a million meters drilled with Wassara we are now confident that ITH hammers powered with simple water will become an established product for production drilling. Today four drill rigs in LKAB Malmberget equipped with Wassara drill about 25 000 m per month of 4 1/2" holes. In Kidd Creek, Canada, Was sara is used for production drilling in stopes with good results. The first Wassara 6" hammer has drilled a 36 meter long, completely straight horizontal cut hole for drifting in the LKAB Malmberget Mine. Main advantages are about doubled penetration rate, very good air quality and improved hole cleaning which facilitates stabilized drilling. Disadvantages are resistance to new technology and, in some cases, the increased use of water.

Jan 1, 1995

By H. W. Rimmer

Automation in the aggregate industry is characterized by the increased use of purpose-built PLC systems put together by independent computer-control houses and/or equipment suppliers. These systems range in complexity from simple startup/shutdown sequencing systems through to complete centralized control/MIS systems that are increasingly concerned with providing timely information on overall plant and/or equipment performance. As such, they should be of considerable interest to the operator seeking low-cost solutions to the many problems associated with the effective operation of small-scale plants.

Jan 1, 1989

By M. Misra

The interaction of xanthate with SO2 in the flotation of sphalerite and chalcopy.ite is discussed. 'The SO depression of sphaledte is due to the decomposition reaction of xanthate by SO2 The decomposition reaction is dependent on the cole ratios of xanthate/SO2, oxygen concentration and pH. Xanthate adsorbs at a faster rate by chalcopyrite than sphalerite. The faster rate of xanthate adsorption by chalcopyrite and the specific action of S02 on the surface of chalcopy.ite facilitate the selective separation of chalcopyrite from sphaledte.

Jan 1, 1989

By F. P. van der Meer

Roller Press grinding has become an accepted technology in the cement industry, and finds a growing application in iron ore processing. Its introduction to the gold industry will depend on anticipated benefits such as a reduction in power requirements, the increase in throughput, and higher gold recoveries from the ground ore. The presentation highlights some of the specific features of the KHD Humboldt Wedag Roller Press and the effects of various operating parameters on the grinding result. Based on recent experiences examples are given on the use of the Roller Press in mineral applications. The anticipated reduction of grinding energy when using the Roller Press is discussed, together with the reduction in Bond Work Index.

Jan 1, 1997

By M. C. Roberts

Metal producers are now suffering through a major downturn in prices for their products even though it has only been a few years since they were enjoying high prices. From an historical perspective, the current situation is another of the cyclical downturns that often occur every five to seven years. This paper uses time-trend decomposition techniques to identify the cycles and statistical methods to find the duration of these cycles for a variety of metal prices. Given some idea of how long and severe these cycles typically are, the mining industry can better plan to weather the downturns and take advantage of the upturns. For example, timing investments in new projects to take advantage of the cyclical upturns can dramatically improve project profitability.

Jan 1, 2003

By Victor C. Storhok, Batric Pesic, Marlyn D. Ballain

No1ihwest Alloys produces magnesium from dolomite by reduction with ferrosilicon and aluminum. This process produces alkaline by-products in quantities that allow their consideration for use as commercial products. Two such products are dicalci­um silicate, termed as Di-Cal, and magnesium oxide, termed simply MgO. The alkaline properties of these materials offer acid neutralizing power, comparable to traditionally used lime. Thus, the materials warrant study for their use in various appli­cations where neutralization of acidic waters or process solutions are required. One such application is the treatment of acid mine waters with the objective of removing heavy metals. The chem­ical stabilities of the produced metal precipitates are critically important, from an environmental point of view, for their safe disposal in tailing ponds. The EPA regulates waste material dis­posal according to the results from TCLP testing. In this ongoing study, three mine waters were selected for treatment with Di-Cal and MgO. Lime was used as the control for these experiments. The waters were collected from the Bunker Hill mine, Berkeley Pit, and the Blackbird Mine. In addi­tion to testing the chemical stability of produced metal precipi­tates by the TCLP procedure, two other parameters were studied as well. They are: 1. the effect of water pH on stability, and 2. the effect of pH on the stability of resulting precipitates. In the first three months of study, it was found that neutral­ization with Di-Cal results in precipitates that range from equiv­alent to superior in performance as compared to those produced using lime for the waters from all three mines. An additional beneficial characteristic of precipitation with Di-Cal is the fast filtering characteristics of produced precipitates, when compared to the precipitates produced by lime. This property may be of significance when considering the improvement in drainage of tailing ponds and the volume of solids produced. This paper will discuss in detail the stability of metal precipitates with respect to various pe1iinent metals found in mine waters of Berkeley Pit (Cu, Zn, Mn, etc.), Bunker Hill (Zn, Mn, Ni and Co), and Blackbird Mine (Cu, Co).

Jan 1, 1998

By Gail L. Achterman

Most mining companies today perform site assessments and operational or compliance audits regularly. The purpose of these audits is to review company facilities and operations to determine whether they comply with applicable federal, state and local environmental laws and regulations. Why Audit? Companies adopt assessment and audit programs for legal and business reasons. The business reasons include: (1) ensuring efficient and cost-effective compliance through early problem identification and resolution; (2) planning and implementing business transactions such as real estate conveyances, loans, mergers and acquisitions, and waste disposal service contracts; and (3) employee training and relations. Legal reasons for audits include: (1) avoiding enforcement actions and penalties; (2) meeting environmental permit certification requirements; (3) avoiding corporate officer liability; and (4) meeting Security and Exchange Commission disclosure requirements. The Environmental Protection Agency ("EPA") encourages environmental auditing by regulated entities. The EPA Environmental Auditing Policy Statement was published in the Federal Register on July 9, 1986 (51 Fed Reg 25,004). Although the existence of an auditing program does not create a defense to or otherwise limit a company's regulatory responsibilities, EPA considers compliance programs in setting inspection and enforcement priorities. If a company makes an honest effort to identify and correct its own problems, EPA's enforcement approach is influenced, especially if violations are promptly reported. Perhaps more significant to many executives, the U.S. Department of Justice issued guidelines last year on when it will pursue criminal prosecution for environmental violations. See Department of Justice, "Factors and Decisions on Criminal Prosecutions for Environmental Violations in the Context of Significant Voluntary Compliance or Disclosure Efforts by the Violator," (July 1, 1991). It is now commonplace to read about major companies pleading guilty to criminal violations and paying millions of dollars in penalties. For example ALCOA recently agreed to pay criminal fines and civil penalties totaling $7.5 million for unauthorized excavation of PCB-contaminated soil and improper dumping of spent caustic solution. No executive wants to explain to the Board of Directors or shareholders why the company was criminally indicted. The Department of Justice considers factors such as voluntary disclosure, preventive measures and compliance programs, such as a regular compliance auditing program, the effectiveness of the disciplinary system for employees who violate the company's environmental policies, and subsequent compliance efforts by companies to remedy ongoing noncompliance. The Department of Justice looks closely at whether audit recommendations were implemented in a timely way and whether environmental compliance was a standard by which employees were judged. The Lawyer's Role. The role of the lawyer in an audit team deserves special attention. When enforcement action or litigation has begun or is contemplated or a government agency has asked for information, attorneys always should be directly involved in environmental audits. In most situations, however, environmental audits are management tools, and the attorney's role should be to advise the team. The attorney can help make sure the team understands the laws and regulations the facility must

Jan 1, 1992

By R. H. Mozley

It is not my intention in this paper to review recent developments in the mineral processing industry which might fall under the above heading, but to refer to some of the research that I have done over the past 25 years or so. To begin with then, my student days at the Camborne School of Mines, the year 1952. Equipment from the last century was still in everyday use at the local tin mines. At South Crofty Ltd a steam beam engine 100 years old was pumping mine water from 2000 feet, the motive force being conveyed from surface to the pump at the bottom of the mine by a 14 inch square pitch pine rod joined with forged iron straps, steam winders were still in use, and in the mills, stamps ground the ore, and the cassiterite was recovered by equipment with exotic names like "buddies, kievs, and round frames." And to equip us students for the brave new world, we included in our practical mineral dressing a day's test programme with a Californian stamp -- experience that I am still waiting to put to good use!

Jan 1, 1984

By H. Wen, X. Zhai

"The Jurassic coal fields which lay in west China are the major energy base and contain half of coal resources in China. Due to the gather and degeneration rules, the spontaneous combustion characteristic of Jurassic coal is distinguished with permo-carboniferous coal, which needs to be studied deeply. Programmed heating experiments of five Jurassic coal samples and three permo-carboniferous coal samples from different primal coal fields in West China were conducted to identify the characteristic parameters in the low temperature stage of oxidation and spontaneous combustion. The experiments were carried out under non-isothermal heating conditions up to 180? at the heating rate of 0.33?/min in an air atmosphere. The result showed that oxygen consumption rate, CO gas production rate and heating intensity of all coal samples increased with the rising of the temperature, which of the Jurassic coal was higher than that of Permian-carboniferous coal. The C2H4 gas of Jurassic coal generated earlier, more than that of Permian-carboniferous coal in the process of oxidation and spontaneous combustion. It indicated that the Jurassic coal was easier to be oxidized and spontaneous combustion and the index parameters of spontaneous combustion were different between the Jurassic coal and permo-carboniferous coal.INTRODUCTION Coal was the foundation of industry development, and occupied 70% of primary energy production and consumption structure in China. According to the data of the 3rd coalfield prediction, 39.6% of the total coal resources were located in northwest Jurassic coal field in China [1], where the quality of coal was excellent. The study of northwest Jurassic coal already dated from the 80s of the 20th century, about coal rock composition, coal metamorphism [2], coal-derived hydrocarbons, coal structure [3], etc. The results of these studies showed that the composition and properties of Jurassic coal was obviously different from Permian-carboniferous coal, as well as the characteristic of spontaneous combustion [4]. As a result, the spontaneous combustion characteristic of Jurassic coal particularly needed to be studied. Now more and more methods could be conducted to test the characteristics of coal spontaneous combustion, for example, thermal analysis technology [5-7], programmed heating experiment [8-10] and coal spontaneous combustion experiment [11,12]. In these methods, programmed heating experiment could be conducted to determine the oxygen consumption rate, CO gas production rate and heating intensity quickly."

Jan 1, 2015