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By Steven G. Vick

Effects of the August 1995 failure of the Omai tailings dam in Guyana continue to be felt throughout the mining industry. This article is taken from the final report of the independent body of experts commissioned by the government of Guyana to establish the cause of the failure. It explains what happened, why and how to avoid it in the future. Despite environmental, health and safety effects that were negligible by any objective measure, the failure has received wide international attention. Coming on the heels of the shift in exploration targets and development opportunities to developing countries, it has intensified interest in tailings dam safety and environmental management issues. An informed understanding of the nature of the failure and its effects is key to responding to these concerns.

Jan 1, 1996

Instabilities occurred as a result of climate changes caused to investigate the rock behavior dependency to temperature changes, in this paper. In the natural earth condition, the phase transition of pore water has known to be the most effective factor causing different rocks mechanical properties due to temperature changes. So, the temperature range of [-30, 30]°C is selected in laboratory tests of this study. P-wave velocity, unconfined compressive strength (UCS) and elasticity modulus of rocks at different temperatures are studied by developing a temperature adjusting apparatus. The tests were performed on three rock types. The results show that firstly, the temperature reduction and pore fluid freezing improves these rock?s mechanical properties. Secondly, the dependency of rock properties to climate changes depends on the type and shape of its porosity as well as porosity percent. The improvement of rock mechanical properties in jointed rocks exceeds rocks with spherical pores. Finally, maximum changes in rock?s properties occur at [-10, 0]°C, which includes the phase transition of pore fluid. Keywords: Temperature; Rock Mechanical Properties; Pore Fluid; Porosity.

Feb 27, 2013

By M. Wiber, P. Nicoll

Rio Algom has embarked on a major programme of expansion with the goal of becoming one of the world’s top-performing base-metal mining and metals distribution companies. To assist the company and its operations in achieving its business objectives, we are implementing an environment, health and safety (EHS) management system, built to be compatible with the 14001 model. We recognize that a sustainable development approach for Rio Algom includes outstanding performance in EHS and community responsibility and is essential to earn acceptance within the communities where we operate or wish to locate; raise capital; obtain permits, and operate efficiently. We are committed to triple bottom line accountability, i.e. full consideration of environmental, social and economic concerns in our business decision making.

Jan 1, 2000

By J. D. Bliss

The discovery that triggered the current gold rush in southeastern Peru was made in about 1975 along the Rio Madre de Dios in Madre de Dios Department (Fig. 1). About 5000 to 10,000 miners (called chichiqueros) were working in the area as of 1990. Placer mining is the principal source of revenue for people living along the Rio Inambari and west of Puerto Maldonado. As in past gold rushes, working and living condition are harsh. Supplies are expensive, and the area has poor access compared with other areas in Peru. Food, fuel and all mining supplies are trucked over dirt roads from Cuzco, a three-to-five-day trip (Fig. 1). Some material also comes from Brazil. Many placers have a similar life cycle, beginning with small-volume mining (surface or underground). At the end of this small-scale mining, the placer is exhausted or it has a sufficient volume of gravel high enough in gold grade to be worked by large-volume methods, which lead to exhaustion of the resource. The level of maturity of a placer can be determined from its gold grade. The amount of gold production from large-volume mining can be predicted, given detailed, cumulative gold-production data on placer deposits during small-scale mining (Bliss et al., 1987). Using this general model, the authors analyzed the placers in the Rio Madre de Dios area. Small-volume mining Most placer mining in the Rio Madre de Dios area is in alluvial deposits either in or bordering the major rivers. Locally, some placer mining is in terrace deposits above the rivers. All minerals (including the subsoil) in Peru belong to the state. However, a mining claim (denuncia) is easily obtained for mineral exploitation. It is separate from property ownership.

Jan 1, 1992

By J. F. Lupo

There are numerous mines throughout the world that have open pit highwalls developed partially or wholly in soil or soil-like materials. Soil-like materials are considered to include soils (either transported or residual) and highly weathered rock, which may have soil-like behavior. These materials generally have characteristics or material properties that vary considerably from those of moderately weathered or fresh rock. Given these differences, it is important to consider the characteristics of soil-like materials to design safe open pit slopes. In the design of open pit slopes in soil-like materials, it is important to recognize the behavior of these materials is strongly dependent upon their mineralogy, degree of weathering, cementation, stress history, depositional history, and presence of water. As a result, soil-like materials may contain one or more of the following characteristics that can have a significant effect slope stability and design: - Relict structural features (joints, faults, etc), - Sensitivity to moisture (both wetting and drying), - Zones of alteration with variable strength and drainage characteristics, - Zones of low permeability creating perched ground water conditions, and - Undrained and drained strain softening or strain hardening behavior.

Jan 1, 2011

By T. H. Eyde

Worldwide production of natural zeolites during 2001 was estimated to be about 3.5 Mt (3.85million st). Construction and agriculture continued to be the major consumers. Estimated production in North America during 2001, including the United States, Canada and Mexico, was about 40 kt (44,000 st). In the United States and Canada, the zeolitic tuffs are ground, extruded or modified for use as adsorbents, desiccants, ion-exchange media and carriers. In Mexico and the rest of the world, the zeolitic tuffs are cut into dimension stone that is used in construction. Zeolitic tuffs are usually composed of the minerals clinoptilolite, mordenite or both. They occur in a variety of colors and are easy to cut and shape. And they have low thermal conductivity. This construction application is classified with dimension stone rather than with chemical and agricultural uses.

Jan 1, 2002

By VIVEK KASHYAP, Evody Tshijik Karumb, PATRICK TAYLOR

The partial reduction of zinc ferrite to zinc oxide and iron (II, III) oxide can enhance the leaching rate of zinc. Zinc ferrite has often been found as a major component of zinc residues and electric arc furnace dust. The Waelz process is an existing process for zinc ferrite processing, which requires a temperature of more than about 1200 °C to produce Waelz oxide containing ZnO. Since zinc residues have been deemed as a potential way for the extraction of zinc and other critical metals, it is important to analyze the reaction kinetics in the temperature range of interest. This manuscript discusses the chemical kinetics of zinc ferrite reduction by hydrogen gas. Several researchers studied the reduction of zinc ferrite with CO; however, unlike CO, the use of H2 gas as a reductant allows partial reduction of zinc ferrite even at low-temperature range (400–600 °C). Thermogravimetric analyses (TGA) experiments were performed in the temperature range of 300–700 °C with 10% and 30% H2, and the data obtained was analyzed using the isoconversional method of kinetic analyses. The standard models used for isoconversional kinetic analysis were chosen from literature and experimental data were fitted to determine the controlling mechanism and calculation of kinetic parameters of reduction of zinc ferrite. The rate of reaction was found to be increasing with an increase in temperature and partial pressure of H2 gas. The reaction could be divided into three stages, where reaction interface contraction was found to be the controlling mechanism at the initial stage of reaction. As the reaction proceeds, product layer thickness increases, and thus, diffusion was found to be the controlling mechanism. Roasting products obtained from TGA experiments were also characterized using a scanning electron microscope (SEM) to verify critical morphological details.

Jul 26, 2022

By Liming Yuan

To reduce fire hazards from spontaneous combustion of coal in longwall gob areas, a series of computational fluid dynamics (CFD) simulations were conducted by the National Institute for Occupational Safety and Health (NIOSH) to model the spontaneous heating of coal in longwall gob areas. The previous modeling results demonstrate that spontaneous heating of coal usually occurred behind the longwall shields and along the face with a bleeder ventilation system. Assuming a stationary longwall face, the spontaneous heating could turn to a spontaneous fire in several days for the most reactive coal under favorable conditions. When the longwall face advances, the spontaneous heating process will be significantly affected. In this study, the effect of longwall face advance on the spontaneous heating in the gob area is investigated using the CFD model developed in previous studies. One longwall panel with a bleeder ventilation system is simulated. The width of the panel is 300 m (984 ft), while the length of the panel is changed between 1,000 to 2,000 m (3,280 to 6,560 ft). The same permeability and porosity profiles are used for gobs with different lengths. The spontaneous heating first develops in the gob when the longwall face is stationary. Then, the face advances at a certain rate. The face advance is simulated as a series of discrete movements, and the effect of the face advance on the maximum temperature developed during the face stoppage is examined.

Jan 3, 2010

By A. Redman

Aquatic organisms are sensitive to free cyanide (HCN) though the presence of certain metals that can form stable complexes and thereby reducing both the amount of bioavailable cyanide. Recent work has suggested that consideration of HCN rather than total cyanide can provide the basis for water quality criteria. Cyanide is often present in complex effluents that affect speciation and bioavailability. We have developed a model to predict the speciation of cyanide in complex effluents and have shown that this model can predict the toxicity of metal-cyanide complexes in terms of HCN. This study evaluated available cyanide toxicity exposures with this model to assess the role of water chemistry (e.g., metal-cyanide interactions) on the observed. Toxicity endpoints based on total cyanide ranged over several orders of magnitude for a variety of metal-cyanide mixtures. However, predicted HCN concentrations among these same tests described the observed toxicity data to within a factor of 2. Aquatic toxicity can be well described using HCN though in certain metal-cyanide mixtures toxicity was jointly described by HCN and elevated levels of bioavailable metals. This work was performed in support of an industry-sponsored reassessment (Gensemer et al 2006) of the U.S. EPA water quality criteria for cyanide (EPA 1985) using free cyanide as the basis for the re-calculation. The work presented in this manuscript presents technical support for using free cyanide as the preferred basis for this recalculation.

Jan 1, 2011

By E. M. Hill, H. K. Lin, J. L. Oleson

When activated carbon is used for recovering gold in gold industry, carbon fine materials are generated in stripping, acid-washing and kiln regeneration circuits. The carbon fines at the Fort Knox mine, Fairbanks Gold Mining, Inc., contain up to 0.68 kg/t (20 oz/st) of gold. In laboratory tests, gold in the carbon fines was effectively transferred to coarse virgin carbon when the carbon fines were mixed with virgin carbon in cyanide solution at a cyanide concentration higher than 0.10%. A plant-scale test conducted at the Fort Knox mine also shows effective gold transfer from the carbon fines to virgin carbon with a 95% gold recovery in a two-stage gold transfer process.

Jan 1, 2002

The National Institute for Occupational Safety and Health (NIOSH) has continued study of the Personal Dust Monitor (PDM) developed by Rupprecht & Patashnick Co. Inc. through a CDC contract and currently being commercialized by Thermo Fisher Scientific. This report examines the effect of oversize particles, cyclone inversion, and cleaning procedures. Clean and exposed filters were examined using light microscopy and particulates counted before and after various instrument manipulations. The data presented show that the dry cleaning procedures do not cause significant (greater than limit of detection) sample contamination by respirable or oversize particulates and that the cyclone is resistant to particulate carry over during inversion.

Jan 1, 2009

By Graham Davis

The future of the world's minerals industries is often painted as bleak. Peter Drucker has repeatedly proposed that the demand for minerals has become "uncoupled" from world economic growth.' This implies that, while mineral demand was in the past linked to the growing demand for and consumption of goods and services, further world development will not require substantial mineral inputs. Lester Thurow noted that for these reasons the US minerals industry is diminishing in scale and economic importance.2 There is some documented evidence of such uncoupling, and the demand for minerals may indeed diminish in the future. But such announcements are, to this point, no more than speculation. For instance, is it not just as likely that renewed environmental concerns will cause increased demand for the relatively innocuous environmental properties of metals, replacing plastics? And even if the prophesied demand decreases do occur, a sufficient fall in metal prices due to technological advances could increase the quantity of minerals demanded above current levels, in spite of leftward shifting demand curves. Thus, worldwide mineral production activity may increase or decrease in the future and no one can say whether more or fewer of the earth's citizens will become involved in the extraction and processing of minerals.

Jan 1, 1994

By Thomas J. Lien

Granitic Pegmatite deposits are the chief source of commercial feldspar, micas, lithium minerals, tantalum-columbium, beryl, and certain types of kaolin. The output from pegmatite mines in the United States is small compared to other mineral products in terms of bulk or value, and much of it comprises only minor metals and nonmetals. Nevertheless, pegmatite minerals play a vital part in our domestic industrial economy, particularly in the ceramic and electrical industries. Numerous special purpose uses also are important, even though they require small quantities of raw materials. In recent years, realizing the potential importance of the pegmatite minerals, the U.S. Geological Survey, the United States Bureau of Mines, several state Bureaus of Mines, and a few private companies have carried on extensive programs of pegmatite studies in the New England and southeastern states, in the Black Hills area of South Dakota, in the Rocky Mountain region of Wyoming, Colorado, and New Mexico, and in various parts of Washington, Idaho, Utah, Nevada, Arizona, and California. Currently, some of the pegmatite minerals such as micas and spodumene are selectively separated by the flotation process. To a lesser extent a few plants are selectively floating feldspar and quartz. Much of the credit for the above progress goes to the fine work done by U.S. Bureau of Mines (1), and companies such as Foote Minerals (2). Additional research efforts by the New Mexico Bureau of Mines (3) has successfully demonstrated selective separation of micas, beryl, spodumene, lepidolite, microlite, quartz and feldspar from a complex Pegmatite containing all these minerals. Since the nature of the mineralization of various valuable components of a pegmatite deposit is such that selective separation of some of these can be carried out at a coarse size using the Heavy Media Separation technique, it was felt that such a system should be investigated for selective preconcentration of their minerals. It was also felt that of all the :MS systems available, the DYNA WHIRLPOOL (DWP) device which allows a close control and adjustment of specific gravity should provide a means of achieving the above goal. Once the desired preconcentration of one or more of the pegmatite mineral assemblage is achieved, the available selective flotation techniques should provide effective recovery of various minerals into marketable products. This paper presents technical and economic aspects of selective preconcentration of some of the pegmatite minerals followed by selective flotation to produce marketable products.

Jan 1, 1978

In the last four years, 2007~2010, 9 out of 24 metal/nonmetal underground mine fatalities were caused by ground fall across United States of America (Mine Safety & Health Administration, MSHA). To reduce or eliminate incidents/accidents caused by ground fall, this paper clarified how to design and select ground support based on different ground conditions, how to use mine ground support standards, what geotechnical engineers and underground operators should do to keep mine production free of ground failures.

Jan 1, 2012

By Congcong Chen, Bo Ma

When assessing the safety of a tailings dam, the constant weight method (CWM) is one of the most commonly used methods. However, when the evaluation indicator value suggests serious defects, the evaluation value is often inconsistent with the actual situation. To address this issue, the variable weight method (VWM) is introduced to assess the safety of the tailings dam. Initially, a three-layer indicator system for dam failure safety assessment is built, and individual indicator values are divided into four grades. Then, an appropriate state variable weight function is constructed and relevant parameters are determined. Finally, a case study is illustrated to verify the effectiveness of the model. The assessment results of the VWM more closely represent the actual situation than that of the CWM, which is more helpful for decision makers and technicians to take scientific and reasonable precautionary measures, thereby improving the safety management of the tailings pond.

Oct 8, 2022

By N. A. Karl, D. R. Wilburn

"This summary of international mineral exploration activities for the year 2016 draws upon information from industry sources, published literature, SNL Metals & Mining (SNL), an offering of S&P Global Market Intelligence (New York, NY), and specialists in the U.S. Geological Survey (USGS) National Minerals Information Center. Three types of information are reported and analyzed in this annual review of international exploration: 1) budgetary statistics expressed in U.S. dollars provided by SNL; 2) regional and site-specific exploration activities that took place in 2016 as compiled by the USGS and 3) regional events and legislation that affected exploration activities including economic, social and political conditions, which were derived from published sources and discussions with USGS and industry specialists. Commodity and regional compilations are presented in this summary. Because multiple sources were used to develop commodity and regional compilations, statistics may vary depending on the source and type of data that are being reported. The SNL data summarize budget estimates for worldwide exploration activities in 2016 for 30 nonfuel mineral commodities and metal alloys, based on company surveys. Surveys focused on precious metals (gold, platinumgroup platinumgroup metals (PGMs) and silver), base metals, (cobalt, copper, lead, molybdenum, nickel, tin and zinc), bulk commodities (bauxite, chromite, iron ore, manganese, phosphate and potash) and other commodities (aluminum, antimony, diamond, graphite, heavy-mineral sands, lithium, niobium, rare-earth elements (REEs), scandium, tantalum, tungsten, uranium, vanadium and yttrium). Information on uranium exploration activities was included in SNL’s survey for the first time in 2007. Data on lithium, niobium, phosphate, potash, REE and tungsten were compiled for the first time in 2010, and scandium, vanadium and yttrium were added in 2014 because of their increased topical significance. Since 1999, companies with exploration budgets of $100,000 and greater were included in the SNL surveys. SNL budget estimates exclude coal, and oil and gas. The 2016 SNL mining company survey compilation was reported by SNL to include an estimated 95 percent of the world’s nonfuel mineral exploration budgets. The 5 percent that was not covered was accounted for by companies that chose not to participate in the SNL survey, private companies that do not publish their budget data and government-funded exploration activities."

Jan 5, 2017

By K. Oraee

Proven and probable coal reserves in Iran are estimated to be in excess of 5 Billion tons while the annual coal production is a mere 2 Million tons. Underdevelopment of the industry has proved higher production levels to be impossible, despite growing demand for energy supplies. The existences of numerous legislation are thought to have a detrimental effect on coal mining activities to the extent that some business entities have become uneconomical in many areas. This paper provides an analysis of the prevailing mining laws, policy making, legal frameworks and obstacles. It also outlines some other obstacles enshrined in the law and also highlights areas where foreign direct investment should be encouraged. The costs of lost opportunities are then estimated. The paper concludes by demonstrating that deregulations, amendments and in some cases complete abolishment of the incumbent legislations governing the coal mining industry will greatly enhance development of the industry. The analysis provided in this paper together with the results obtained, can prove useful to macro-economic policy makers both at local and national levels.

Feb 27, 2013

By Y. Nien Wang

The Devil?s Slide portion of Highway 1 between Pacifica and Montara is often closed due to the instability of the adjacent slopes. Following many years of public input and careful evaluation of alternatives, Devil?s Slide will be by-passed via two inland tunnels, providing a safe, dependable highway between Pacifica and Montara. For the twin tunnels, each 9m diameter tube will accommodate only one traffic lane. Each tunnel tube will accommodate a 3.6 meter roadway, 0.6 meter and 2.4 meter inside and outside shoulders respectively, and 1.2 meter walkways on each side. Cross passages will connect the bores at about 120 meter intervals and jet fans will provide tunnel ventilation. The twin tunnels are approximately 1,250 meter long and 9 meter wide. Excavation will progress from south to north using tunneling techniques that rely on inherent rock strength for support known as the New Austrian Tunneling Method (NATM). Both tunnels will be excavated at the same time, one tunnel face approximately 40 meters ahead of the other. Staggering the tunnels reduces the likelihood of damage from blasting in alternate tunnels. The work schedule is 24 hours a day, 7 days a week resulting in a 24-month timetable to break through to the north portal.

Jan 1, 2008

By Syd S. Peng

Coal mine ground control is the science of the application of rock mechanics principles to coal mining operations. More acceptance of ground control techniques by the US coal mining industry has been seen in the 1980s. It has been demonstrated many times that a proper ground control design is key to a successful coal mining operation. However, numerous in-mine applications of various ground control techniques by the author indicate that cur¬rent techniques need improvement. The biggest problem in coal mine ground control is that miners are dealing with materials of rapidly varying properties and occurrence. And only the exposed surface can be identified positively. Thus, in attempting to solve the ground control problems, many unknown factors are assumed. Some of these problems deriving from such assumptions are discussed here. Coal pillars There are two types of coal pillars - barrier and chain pillars - depending on the purpose. Barrier pillars are those located between panels or sections or mines. Their objective is to isolate the mined-out effects of one from the other. Chain pillars are characteristic of room-and-pillar mining. They are designed to support the overburden load and protect the surrounding entries and crosscuts. Pillar design is the most popular and, frequently, the only ground control technique employed by coal operators for mine design. There are many pillar design formulae available (Bieniawski, 1983; Peng, 1986). Nearly all consider both size and width/height effects. Specifically, pillar strength decreases with increases in pillar size and increases with increase in the ratio of width to height. However, the manner of those changes varies with investigators. Consequently, the pillar size determined varies considerably from investigator to investigator. And the variation grows much more pronounced as the seam depth increases (Fig. 1). The question, then, is which one should be used? One may say each formula is developed for a particular coalfield. A particular formula may have been used to design a pillar, which has not failed. Does that mean it was over designed? Not necessarily, because no one can confirm its stated "safety factor." Recent case studies (Peng, 1986; Tang and Peng, 1988) show that all pillar formulae are too conservative for chain pillar design in room-and-pillar mines due to the following two problems: • Uncertainty about in situ pillar strength. All formulae employ uniaxial compressive strength of selected samples tested in the laboratory and scaled to that for underground pillars. The scaling factors are not well proven. In situ testings by Bieniawski (1969) suggested that 1.5 m (5 ft) pillars are representative of in situ pillars that, after being tested in various US coal mines, are not universally applicable. • Uncertainty about the actual loading on the pillar. The most frequently used tributary loading theory defines the loading as total overburden weight tributary to each pillar (from roofline to surface). This is too conservative when it applies to coal measure rocks. The overburden consists of layered strata of different stiffness. Many stiffer strata will self-support over small roof spans. Depending on the location of these strata above the coal seam, it will reduce pillar loading in various proportions. It follows that total structural analysis using, for instance, finite element method is more appropriate. It can take into account the interaction of roof and floor strata with coal. This has been demonstrated by Peng et al. (1986,1988) on several case studies. However, the validity of the finite element structural analysis depends on the accuracy of in

Jan 1, 1989

By M. E. Smith

Waste rock dumps, tailings impoundments and spent leach heaps are common features at mine sites. Many of these waste disposal facilities contain sulfide-rich minerals, which generate acid mine drainage (AMD) when they oxidize. Control of AMD can be achieved by removing one or more of the three essential components in the acid-generating process (sulfides, air, or water). One AMD prevention measure is to cap the waste with an engineered cover system to minimize the infiltration of water and diffusion of air into the system. Possible cover designs include: ? Earthen ?store-and-release? covers (also known as evapotranspiration (ET) or water balance covers), including capillary barriers. These covers require climate conditions where there is both modest to little rainfall and significantly greater evapotranspiration than precipitation, both annually and seasonally. ? Low-permeability compacted clay liners (CCLs) employing fine-grained soils typically compacted at wet of optimum water content. ? Geosynthetic composite covers, comprised of a geomembrane liner placed over and in direct contact with either a CCL or a geosynthetic clay liner (GCL). These systems have been commonly used for base liners for leach pads as well as covers and base liners at municipal solid waste (MSW) landfills in the US for more than 20 years. Comparisons of these different cover systems, both in terms of performance and cost, are presented later in this paper. First, however, a review of the typical mine closure approaches, and the possible rationale behind them, is warranted.

Feb 27, 2013