Search Documents

By Michael G. Pojar, Peter G. Chamberlain

Solution mining, primarily by heap leaching, has emerged as an important method for mining gold and silver in the United States. Heap leaching offers many economic and environmental advantages over conventional production techniques, in particular for lean ores and old mine waste rock. In order to more effectively pursue research on heap, dump, and in situ solution mining of gold and silver, the Federal Bureau of Mines conducted an extensive survey of leaching practices and problems. This presentation summarizes trends and statistics. Leaching is projected to provide 20 pct of primary mine produced gold and 10 pct of primary silver by the end of 1982. Current leaching practices in the United States are reviewed; operational problems and research programs to alleviate those problems are discussed.

Jan 1, 1981

By Douglas B. Silver

Super Cycle future The final topic is mining?s future. The most important questions are ?How much longer is the Super Cycle going to last? What should we expect to see going forward? How will the Super Cycle end?? Three possible scenarios follow. Scenario one: Super Cycle has peaked Kathy Casey-Kirschling is officially the first Baby Boomer. She was born Jan. 1st, 1946. If you google ?first baby boomer,? she?s the one that shows up. A Baby Boomer is anybody born between 1946 and 1964. In the United States, it represents about a quarter of the population ? approximately 76 million people. The Baby Boomer generation is going to change the economics of the world because there are so many in the generation. A review of spending patterns indicates that the largest amount of discretionary spending occurs between the ages of 49 and 52. Retired people tend to live on fixed incomes so they have less discretionary income. They also tend to downsize their house, which may contribute to the housing glut and the need for a lot less metal. Therefore, the upcoming retirement of the Baby Boomer generation could result in a massive shift in economic spending resulting in the peaking of the Super Cycle. Figure 1 is an index graph from the Toronto Stock Exchange (TSX). The index has recently peaked. A lot of people see that as a sign that bad things coming our way. A careful review of different commodity prices also suggest that the peak has occurred and it does not seem to matter which commodity prices are considered. Copper prices have seen a peak as have nickel prices. Nickel and molybdenum displayed the same trend with a peak in 2005 as did zinc. Uranium, which has single-handedly tried to behave like the dot com craze, has also peaked.

Jan 1, 2008

By R. G. Benson, P. R. Wotruba, K. W. Schmidt

Introduction The Fortitude deposit is located in Nevada's Battle Mountain mining district in the central Great Basin region of the Basin and Range province of the western US. The deposit is at Copper Canyon in the southernmost portion of the district, about 19 km (12 miles) southwest of Battle Mountain (Fig. 1). Mining activity in the district began in 1866 (Roberts and Arnold, 1965). Base and precious metals were mined by underground methods intermittently until 1955. Placer gold was first discovered at Copper Canyon in 1912. Moderate scale dredging of alluvial gravel at the mouth of Copper Canyon was conducted by the Natomas Co. from 1944 to 1955 (Johnson, 1973). In 1967, Duval Corp. began large scale open-pit copper mining. (Sayers, Tippett, and Fields, 1968). Copper prices decreased and precious metals prices increased in the mid-1970s so Duval's exploration efforts at Copper Canyon shifted to precious metals. These exploration efforts resulted in the discovery of the Tomboy-Minnie deposits and shortly afterward, the Northeast Extension deposit at Copper Canyon (Blake, Wotruba, and Theodore, 1984; Fig. 2). The Fortitude deposit was discovered in late 1980, after Duval had proceeded with precious metals production at Copper Canyon. Converting the existing plant facilities at Copper Canyon to a precious metals recovery system was completed in 1978 (Jackson, 1982). Production from the Tomboy-Minnie deposits began in early 1979. Precious metals production moved to the Northeast Extension deposit in 1982. In late 1984, after three years of preproduction stripping and mining of the Upper Fortitude ore zone, production from the higher grade Lower Fortitude ore zone began. Currently, Battle Mountain Gold Co. operates the Fortitude deposit. Production from the Battle Mountain mining district before 1967 included 4.6 t (150,000 oz) of gold, 65.3 t (2.1 million oz) of silver, 13.6 kt (15,000 st) of copper, 4.5 kt (5,000 st) of lead, and 13.6 kt (15,000 st) of zinc (Roberts and Arnold, 1965). At the time of Duval's 1967 start-up, ore reserves at Copper Canyon included 12.6 Mt (14 million st) in the East ore body and another 3.6 Mt (4 million st) in the West ore body. Both had average grades of 0.79% copper, 16.1 g/t (0.47 oz per st) silver and 0.86 g/t (0.025 oz per st) gold (Blake et al., 1984). The Tomboy-Minnie deposits collectively contained 3.5 Mt (3.9 million st) of ore grading 3.09 g/t (0.09 oz per st) gold and 9.6 g/t (0.28 oz per st) silver. The Northeast Extension reserves were identified as 1.4 Mt (1.5 million st) of ore with an average grade of 2.9 g/t (0.085 oz per st) gold and 5.1 g/t (0.15 oz per st) silver. Initial total reserve estimates for the Fortitude deposit were 14.5 Mt (16 million st) grading 5.14 g/t (0.15 oz per st) gold and 29.8 g/t (0.87 oz per st) silver (Jackson, 1982). Therefore, before large scale mining, the Copper Canyon area contained a minimum of 102.6 t (3.3 million oz) of gold and 541 t (17.4 million oz) of silver as mineable reserves. The Fortitude deposit reserves as of Jan. 1, 1985 were 10.6 Mt (11 million st) grading at 5.28 g/t (0.154 oz per st) gold and 28.5 g/t (0.83 oz per st) silver. Currently, the company is producing 6.8 t (220,000 oz) of gold and significant amounts of

Jan 7, 1986

By Yang Ge, Yuzhu Pan, Mansheng Chu, Jue Tang, Cong Feng, Lihua Gao, Zhenggen Liu

The low-grade nickel laterite ore used in this study was successfully upgraded through selective reduction by industrialized rotary kilns followed by magnetic separation. The results indicated that both iron metallization extent and nickel metallization extent showed obvious linear correlation. In addition, rational roasting temperature and prolonged grinding time could enhance the overall fineness level of reduced laterite nickel ore. The moderate roasting temperature at a range of 1100–1150 °C should be suitable enough to a conversion of total nickel to metallic nickel and partly inhibited the conversion of total iron. Ultimately, the obtained ferronickel alloy with a nickel content of 7.32% and an iron content of 84.15% was prepared successfully from the lowgrade nickel laterite ore containing a nickel content of 1.92%. Nickel and iron recoveries were 96.72 and 89.08% respectively, which achieved the highly efficient recovery and utilization of iron and nickel from low-grade laterite nickel ore

By Jose A. Gomez, Javad Sattarvand

Failures of tailings dams have been happening lately. Due to the lack of laws on particular design criteria and stability requirements related monitoring during construction and maintenance, they are thought to be more fragile than hydraulic dams. Monitoring the dam is therefore necessary to understand its current condition and guarantee its safety. The physical condition of the dam could be evaluated with the early identification of seepage. Additionally, due to their adaptability and capacity for high-resolution data collecting, UAVs are an excellent choice for efficiently covering the tailings dam site. UAVs may capture high-quality photos when equipped with a high-resolution RGB camera, thermal sensors, or multispectral sensors. When these sensors are paired with image processing and machine learning algorithms, the result is a reliable estimate of the dam condition.

Jun 25, 2023

By Zephaniah Varley, Dominic Parmantier, Paul Schmall, Richard Martin, Red Robinson

Sequential excavation of the Beacon Hill Station has been accomplished in highly complex and inter-layered sand, silt, and clay soils with multiple perched groundwater tables. Successful excavation has required the installation of a deep dewatering well system used to depressurize sand layers above and within the excavated tunnel faces. In addition, the presence of sand layers in the crown of the Platform Tunnels required jet grouting at depths of up to 49m (160-ft). This paper discusses the design intent, construction, and effectiveness of the dewatering system and the selective jet grouting of sand horizons and shaft break outs for the successful construction of the deepest SEM station excavation ever completed in the United States.

Jan 1, 2007

By William C. Cooley

SUMMARY A review is presented of the state of development of high pressure water jet equipment and of large impact hammers for rock tunneling. Information from the U.S.S.R. is based on published literature and three personal visits. Applicable papers which were presented at the International Symposium on Jet Cutting Technology in Coventry, England in April 1972 are reviewed. Data are presented on continuous jet systems, pulsed water cannons, and hydraulic-powered impact hammers with respect to the specific energy of rock breakage and potential application in tunneling machines. INTRODUCTION It has been estimated that the cost of underground excavation during the period 1970-1979 in 15 countries of the Organization for Economic Cooperation and Development will be over $54 billion, an increase of 104% over the period 1960-1969. It is expected that 55% of the tunneling construction will occur in hard rock (Ref. 1). Present tunneling machines are generally limited to soft and medium-hard rock. When used in hard rock, the cost of replacing mechanical cutter bits is high. Therefore there is a need for improved rock fracture methods which can be applied economically in tunneling machines for hard rock. Water jets and mechanical hammers are two

Jan 1, 1997

By A. Mayton, W. Porter, A. O’Brien

In 2004, management at Unimin’s Gleason, TN operation began implementing ergonomic interventions specifically targeted to reduce risk of musculoskeletal injuries (MSIs). Together with corporate and site management, Unimin identified work site hazards and began to modify work practices/equipment. Some interventions were relatively simple and were implemented immediately. Others, like improvements to a mobile shredder, were more complex but were eventually resolved through a participatory approach with employees, management, manufacturers and NIOSH. This paper discusses ergonomic interventions that were successfully implemented using a bottom-up approach to reducing the risk of injury.

Jan 1, 2007

By A. Thatcher, C. Day, C. Meyer

The purpose of this paper is to provide general information about the bioaccessibility of metals and specific information about the use of bioaccessibility in risk assessments (human health risk assessments [HHRA] or ecological risk assessments [ERA]) and a list of sites where regulatory agencies have approved the use of bioaccessibility data in risk assessment. The memorandum also cites current U.S. Environmental Protection Agency (USEPA) guidance as well as state specific guidance where applicable. BRIEF HISTORY OF METAL BIOACCESSIBILITY TESTING AND METHODS The bioaccessible fraction of a constituent is that fraction that dissolves or desorbs from its matrix (e.g., soil) in the gastrointestinal tract and is available for absorption (USEPA 2007a; ITRC 2011; ITRC 2017). This is different from the bioavailable fraction, which is the percentage of the amount of an element that an organism is exposed to that is absorbed by that organism during a given time under defined conditions (USEPA 2007a). The bioaccessibility factor is the percentage of a metal that is potentially available for absorption and, therefore, is a conservative estimate of the bioavailable fraction since all that is available for absorption may not ultimately be absorbed into the organism’s system. Currently, there are two main techniques for estimating bioavailability of metals within a medium: in vivo animal studies (time-consuming and often cost-prohibitive), and in vitro tests that simulate human, or animal digestion in a laboratory setting. In vitro and in vivo test methods and protocols have been extensively evaluated by numerous researchers (Ruby et al. 1996; Rodriguez and Basta 1999; Sips et al. 1998; Sips et al. 2001; Molly et al 1993; Oomen et al 2002; Kelley et al. 2002; Oomen et al. 2003; Furman et al. 2006; Drexler and Brattin 2007; Basta et al. 2007; Wragg et al. 2009; Wragg et al. 2011; Chaney et al. 2011; Bradham et al. 2015; Bradham et al. 2018). The most recent scientific literature demonstrates that protocols used to estimate the bioavailability of metals to mammals also predict bioavailability of metals to birds as well (Beyer et al., 2016).

Jan 1, 2019

By K. Short

Today?s modern mining operations have literally dozens of applications and systems generating data whose information very often, are not crossed or centralized for operational decisions. In remote locations, the information and situation awareness is typically limited to the location itself. In addition, access to that information is limited to a small, select group of personnel that have received training on how to interpret the results. When the situation affects another area of the mine then information is relayed to the applicable areas involved. Few workers have time to analyze the situation thoroughly, to see how it affects the mines symbiotic relationship within all areas of production. If the capability to correlate and measure events and situations that affect your overall key performance indicators are not in place, the opportunity to identify process improvement becomes more difficult.

Feb 27, 2013

By Steve Kral

More than 111,350 mining and construction industry professionals from throughout the world gathered in Las Vegas, NV, March 19-23 for ConExpo-Con/Agg 2002 and IFPE 2002. The triennial event is the Western Hemisphere’s largest equipment show for the quarrying, aggregates, construction and ready-mixed concrete industries. Despite the difficulties in the world economy, ConExpo-Con/Agg 2002 attracted more than 2,450 exhibitors from throughout the world. This was an increase from the 1,882 exhibitors that were on hand for the 1999show. And this year’s show occupied more than 180,225m2 (1.94 million sq ft) of exhibit space at the Las Vegas Convention Center. This was an increase from the160,900 m2 (1.73-million sq ft) occupied at the 1999event.

Jan 1, 2002

By Brain E. Gombos

The Allen Park Sanitary Sewer Overflow (SSO) Tunnel and relief sewer project, located in the city of Allen Park, MI, is a long-term corrective action designed to bring Sanitary District One?s sanitary system into compliance with its 2005 consent order and service contract with the Detroit Water and Sewerage Department (DWSD). The $20 million project is intended to reduce Allen Park?s wet weather discharges to DWSD, reduce bypass pumping to the Ecorse Creek and limit the future risk of basement flooding by providing storage during wet weather events and eliminating hydraulic bottlenecks in the sanitary sewer system.

Jan 1, 2013

By A. K. Majumder

Particle motion in fluids is a subject of considerable practical importance to engineers working in fields such as hydraulics, river mechanics, chemical engineering and mineral processing. Many mathematical models have been proposed to predict the terminal settling velocities of particles in a fluid medium. The selection of an appropriate mathematical model has, therefore, become a challenging task for practicing engineers. This paper reports on an attempt to identify some of the useful models found in the literature for predicting particle-settling velocities in a fluid under free- and hindered-settling conditions. From this study, it was concluded that there is no well-accepted model validated by experimental data available for predicting particle hindered-settling velocities in a suspension of polydisperse and polydens particles. Collective efforts should, therefore, be made towards developing a hindered-settling model, as this is an absolute prerequisite for many model structures in mineral processing and other engineering disciplines.

Jan 1, 2007

By J. O. Voigt

No major changes took place in the salt industry during 2004. No new uses of salt appeared and only localized supply disruptions occurred. Many salt producers reported slightly increased salt sales and profits for the year. In the United States, about half of the salt supply is produced as brine, by solution mining, and is used by the chemicals industry. One-third of U.S. salt is produced as rock salt by 14 underground mines. The remaining two production techniques, each with less than 10 percent of the total tonnage, are vacuum-pan-evaporation for refined, food-grade salt, and solar pond crystallized salt.

Jan 1, 2005

On Dec. 20, 2013, an 8-m (26.2-ft) diameter Robbins hybrid single shield/earth pressure balance tunnel boring machine (EPB TBM) was launched to bore the Grosvenor decline tunnel for Australia?s Anglo American coal mine. The machine was built using onsite first time assembly (OFTA) in order to fit within a tight project schedule. Assembly at the remote jobsite near Moranbah, Australia took about four-and-a-half months, and then the machine was walked down into a launch tunnel. Two decline tunnels, at grades of 1:6 and 1:8, will be used for mine access to new coal seams. The hybrid machine is tackling mixed ground conditions ranging from sand and clay to varying types of sedimentary hard rock up to 120 MPa UCS, as well as coal seams. Methane gas is expected to be present throughout the tunnel, so the machine has been designed as explosion-proof-compliant to ERZ-1. ?Grosvenor is the first underground coal mine in Queensland to use a TBM for drift construction,? said Glenn Tonkin, Grosvenor project director. ?We are proud to be pioneering this technology.? Only about 300 m (984 ft) of ground in each decline tunnel is expected to require EPB mode, while the rest of the tunnel will be bored in hard rock mode. Thus, the design was optimized toward hard rock excavation.

Amid some of the worst economic conditions that the mining industry has been faced with in more than a decade, the mood among the large crowd at the 114th Annual Northwest Mining Association?s annual meeting was surprisingly upbeat. More than 2,200 attendees showed up at John Asuaga?s Golden Nugget Casino in Reno, NV for the conference held Dec. 1-5. And more than 200 companies exhibited in 240 spaces, including SME and the Minerals Information Institute. The number of attendees and exhibitors were the most for the conference in more than 10 years. The conference was held in Reno/Sparks for just the second time in its illustrious history but began under the cloud of global financial turmoil. Prior to, and during the conference, the industry news headlines were grim, to say the least. An alarming number of mine plans and expansions had been put on hold; hundreds of miners across the United States had been or were in the process of being laid off; commodity prices were falling and some of the biggest mergers in the industry fell through while miners around the world put the brakes on to take a wait-and-see approach. It was a painful time for many, but the downsizing actions taken by many mining companies was exactly what needed to happen, according to Industry Outlook Luncheon featured speaker Frederick Sturm. He is the executive vice president and chief investment strategist and member of Mackenzie?s Investment team. He has earned a reputation as one of Canada?s leading investors in natural-based companies and he also manages the Ivy Global Natural Resource Fund in the United States Sturm said that the mining industry has fallen hard and that he expects it to bounce back quickly, before falling hard again. In these tough times, he said, the companies that have pulled back on production early are doing the right thing in the long run.

Jan 1, 2009

By Murray W. Hitzman

Two great revolutions in mining occurred during the 20th century. The first took place almost 100 years ago (1903-1905) with Daniel Jackling’s experiment in the economies of scale for large-scale mining at Bingham Canyon. Jackling’s ideas changed the focus of base metal exploration toward lower-grade, high-tonnage deposits. The second revolution was the impact of environmental and social concerns on mining. It started near the end of the 20th century and is still under way. This article speculates on the effects of this second revolution on the future of mineral exploration.

Jan 1, 2005

By S. Weiss, E. Espinoza

The El Sauzal gold-silver deposit is a high-sulfidation, epithermal precious-metals deposit hosted by an east-dipping sequence of dacitic and rhyolitic pyroclastic and debris-flow units of probable Oligocene age. Total gold production since startup in late 2004 is approximately 450,000 oz. of gold. Above the sulfide boundary gold is mainly disseminated as small grains interstitial to alunite, kaolinite and quartz. The majority of the ore is found in quartz-alunite-kaolinite altered rock that mantles tabular to irregular silicic cores of vuggy, residual quartz ±kaolinite ±dickite. Grade domains are modelled as subhorizontal to east and southeast-dipping. Higher-grade domains cut across alteration zones and also coincide with transitions from vuggy quartz to quartz-alunite-kaolinite. The highest grades are commonly found marginal to vuggy quartz in transitional, hematite-rich quartz-kaolinite and quartz-alunite-kaolinite rock.

Jan 1, 2007

By Faruk Oksuz, Cary Hirner, William A. Rochford

Grouting is a frequently utilized remedy in the planning and implementation of ground improvement and tunnel rehabilitation practice. The state-of-art grouting application used for Chicago’s McCook Reservoir project offers a unique alternative to the tunneling industry for pre-excavation grouting as well as tunnel rehabilitation, rescue and post-excavation ground improvements. The McCook Reservoir project included a computerized grouting control and data collection system for a precise and highly effective groundwater cutoff in fractured dolomites. By using balanced and stabilized grout mixes, the effective permeability of the rock mass was reduced over two orders of magnitude to less than 0.1 Lugeon by installing a double line grout curtain. The stable grout mix designs allowed high pressure and effective grouting at depths up to 125 m (410 ft).

Jan 1, 2005

By Desiree Willis

One of New York City?s largest subway projects is under way 43 m (140 ft) beneath the surface of downtown Manhattan. The East Side Access project, more than 30 years in the making, was halted after a partial excavation in the 1970s due to a lack of funding. The project, once dubbed the ?Tunnel to Nowhere,? has been revitalized into a groundbreaking subway line that includes unique tunnel boring machines (TBM), construction methods and muck removal systems. Project overview The East Side Access project involves construction of a new 6.7-km (4.2-mile) subway line needed to relieve heavy traffic congestion between the boroughs of Queens and Manhattan. The line will serve approximately 160,000 commuters daily between Grand Central and Sunnyside rail stations. Manhattan and Queens will be connected under the East River by the 63rd Street tunnel, a submersed double-decker tube. The submersed tube consists of reinforced concrete sections barged in place on the riverbed. The tube contains operational subway lines on the top deck, while the bottom deck (the ?Tunnel to Nowhere?) will become operational when the East Side Access project is completed in 2013.

Jan 1, 2008