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By J. A. Meech

An analysis of screen design options on the operating efficiency of secondary crushing plants has been conducted using a dynamic computer model. The model allows for the simulation of a wide variety of crushing circuits and can be run on either a microcomputer (IBM PC/XT) or a large time-sharing mainframe computer. Size reduction and separation characteristics of crushers and screens are based on standard manufacturer design and performance data. Input/output routines are available in tabular, alarm or strip chart recorder modes to facilitate operation of the program. A number of alternate circuit designs are compared to show the influence of surge capacity, screen size and area, screen deck location, and closed side crusher settings on the operation of a 10,000 ton per day plant. The program is currently in use at Queen's University to teach plant operations and control. It has potential to be a valuable tool for operator training.

Jan 1, 1985

By B. T. Darnton

Gravity concentration at the Pegasus Gold Montana Tunnels Mine was initiated in late June, 1991 with the commissioning of a coarse gold scalping circuit that processes a small portion of the ball mill circulating load. The primary objective for the circuit was to reduce the risk of gold particles advancing to flotation that are too coarse to float. The secondary objective was to enhance overall gold recovery and payable gold ounces in a cost effective manner. The gravity circuit has proven itself to be a major success. The above mentioned goals have been achieved, and they have been maintained at record throughput rates that are 30% higher than when the circuit was commissioned. A number of modifications and improvements were made over the last three years which allowed the gravity circuit to keep pace with the higher tonnage, these are discussed in detail in the body of this paper. The overall approach to gravity concentration at Montana Tunnels has always been to optimize production rather than maximize the gold ounces produced. This philosophy has now yielded a circuit expansion and relocation project which will allow for an estimated 50% increase in gravity gold production, while reducing the overall unit costs of production significantly. This paper will review historical gravity circuit performance, improvements, and the current relocation and expansion project.

Jan 1, 1995

By Emily Sing, Ashim Gajurel, Thomas Pennington, William Brown

The Pardee Chemical Feed Shaft Project involves construction of two new chemical feed shafts to improve raw water treatment capabilities at the East Bay Municipal Utility District’s (EBMUD) Pardee Reservoir in Valley Springs, California. The project includes construction of two 250-foot deep, 16-inch diameter stainless steel chemical feed shafts that penetrate an existing 8-foot diameter concrete lined conveyance tunnel. The design approach required the shafts be installed using top-down drilling methods and within a strict verticality tolerance (0.1%). Innovative precision drilling techniques ensured that the shafts penetrated the tunnel in their planned locations and the installed chemical feed lines would function as designed. Challenges included extremely limited access to the tunnel because of a requirement to maintain the tunnel in service during construction. This paper discusses the overall project’s design and construction approach, including unanticipated conditions that the project team faced and how these conditions were managed and overcome through collaboration between the contractor, designer, and owner.

Dec 1, 2022

By M. J. Raffaldi, L. A. Sandbak, K. K. Dehn, S. N. Warren, J. B. Seymour

"Confidence in the design and stability of an undercut cemented rockfill (CRF) span requires a thorough understanding of its emplaced material properties. The unconfined compressive strength (UCS) of cast 6×12-inch QA/QC cylinders is typically used as an index test to track the performance of a backfill plant. However, these strengths need to be adjusted for oversize aggregate removal and sample size effects if used to estimate the emplaced UCS. UCS testing of 6×12, 12×24, and 18×36-inch cast CRF cylinders was used to quantify the relationship between readily available 6×12-inch QA/QC strength data and the emplaced UCS. Test results indicate that the UCS of 18×36-inch cylinders is roughly 40% of the 6×12-inch UCS for similarly compacted samples. Mine QA/QC data indicate that the UCS of CRF is highly dependent on the degree of compaction as measured by bulk density. Based on these results, knowledge of the emplaced CRF density compared to 6×12-inch QA/QC density is also necessary to estimate the emplaced UCS. The scale effect reported in this study is more pronounced, compared to current understanding of backfill properties discussed in the literature, and underscores the need for further site-specific testing. INTRODUCTION The National Institute for Occupational Safety and Health (NIOSH) Spokane Mining Research Division (SRMD), in cooperation with Barrick Gold Corporation, is conducting research with the goal of determining a relationship between 6-inch QA/QC cylinder strengths and the in-place strength of cemented rockfill (CRF). CRF cylinders with dimensions (diameter × length) of 6×12, 12×24, and 18×36 inches were cast onsite at the Turquoise Ridge Joint Venture (TRJV) and Cortez Hills Underground (CHUG) mines using CRF mixed at the mines’ respective batch plants. UCS tests were performed after 28 days of curing to estimate the size correction factor for each mine’s CRF. This paper presents an overview of the mix designs, sample collections, testing methods, test results, and an estimate of the UCS size correction factor for CRF at these mines. BACKGROUND Underhand cut and fill mining methods utilizing cemented backfill are common in underground metal mines in the United States. These methods are advantageous for controlling weak or highly stressed rock mass conditions by creating an engineered material that can be placed in openings, forming a beam that provides a safe, stable back for the next undercut. Increased use of underhand methods in the last 30 years has greatly improved safety in many cut-and-fill mines. However, with the continual push for more efficient and cost effective mining, there is a need to thoroughly understand the geotechnical properties of cemented backfill to assist in designing safe, stable openings while optimizing costs and production schedules."

Jan 1, 2018

By R. J. Zagrocki

Rekindled public concern about lead toxicity has intensified the awareness of lead-bearing materials in contact with the environment and the human population. Lead's common association with other metals makes the increasingly restrictive lead standards a primary concern for a large number of metal and metal-related industries. In commercial scale demonstration tests with lead-bearing wastes, the HRD Flame Reactor process has a demonstrated ability to separate and recover over 95% of the lead as a recyclable oxide, while rendering the remainder of the material as vitrified, non-leaching, and nonhazardous co-product. Recent Flame Reactor process tests and preliminary cost data for secondary lead soda slag are highlighted.

Jan 1, 1992

By G. T. Austin

Every year the United States consumes millions of dollars worth of abrasive materials as blasting media. Entrained in either a gas or liquid stream or propelled by paddles or wheels, they are directed onto the surface of another material to modify that surface. The modifications to impacted surfaces include cleaning, cutting, deburring, etching, finishing, and peening. Blasting media can be either organic or mineral abrasive materials. Information and data presented are for only a portion of the mineral abrasives, they are; fused aluminum oxide, coal slag, copper slag, garnet, metallic shot and grit, nickel slag, olivine, silica sand, silicon carbide, and staurolite.

Jan 1, 1994

By John L. Shafer

Often an in situ leach is the only practical economic method for copper recovery from small low grade oxide deposits. The decision to develop a copper property by an in-situ blast and leach is strongly dependent on ore grade, tonnage, hydrology, and the copper extraction and acid consumption rates. The inherent "leachability" of the ore will in part determine the desired amount of fracturing of the ore deposit by the blast in order to obtain a copper extraction rate that is economical. For the last several years Occidental Research Corporation (ORC), the corporate R&D for Occidental Petroleum has under-taken a modest effort to address the question of "how to best identify and determine the information necessary to predict and control the operation of an in-situ leach for the economic recovery of copper."

Jan 1, 1977

By Douglas G. Fox

Outputs from industrial activities planned in the Riley Ridge natural gas project are modeled to determine the potential locations of air pollution impacts on the Bridger and Fitzpatrick Wildernesses in Wyoming. The nature of modeling, especially with regard to its realism, is discussed. Alpine lakes which, along with their watersheds, have minimal buffering capacity are being studied because of their sensitivity to acidic deposition from proposed new air pollution sources. A hypothesis which relates a source's emissions to deposition and lake chemistry in a worst-case sense is presented. Research designed to test the hypothesis and reduce uncertainties is outlined and progress reviewed. Focus is placed on the meteorological transport and atmospheric deposition parameterization contained in the hypothesis.

Jan 1, 1984

By H. Wesley Peirce

Arizona embraces portions of two major western-U.S. physiographic-geologic provinces and a smaller, local one. These exert fundamental control over the geologic framework and associated earth-material resources and potential. The Mogollon Rim diagonally crosses the State and separates the Colorado Plateau Province to the northeast from the Transition Zone and Basin and Range Province to the southwest. More than 90 percent of the population, production of nonfuel minerals, agricultural land, and water resources are in the Basin and Range part of the State. In 1981 Arizona was ranked number one in the Nation with respect to the value ($2.56 billion) of nonfuel-mineral production. About 8.2 percent of this amount ($212.9 million) can be attributed to nonmetallic (industrial) materials. Although a diversity of nonmetallic substances is produced and some are exported, the bulk is utilized within the State and is directly related to market growth. Since 1950 there has been a fourfold increase in Arizona's population, a concomitant twelvefold jump in sand-gravel production (tons), and a twentyfold increase in "stone" production. New industries developed during this time include cement, salt (and storage of liquid petroleum gas products in solution cavities in salt), zeolite, hydrofrac sand, vitrified clay pipe, crushed marble products (teed additive, pool sand, roofing granules, etc.), and "rock" wool. Most of these newer industries serve out-of-State as well as in-State markets. In 1981 at least 225 industrial mineral or rock deposits were being worked to produce about 10 tons of material per Arizona resident per year. In 1980 the relative values of basic industrial minerals produced in the State, by major group, were cement and lime (51.6 percent); gravel (26.5 percent); sand (11.8 percent); stone (4.6 percent); and others (5.5 percent). Detailed knowledge of the nonmetallic rock-and-mineral content of most Arizona ranges and basins is lacking. Exploration opportunities in this sun-belt growth region appear encouraging.

Jan 1, 1987

By J. E. Kulas

Red Dog is a Mississippian to Permian aged sulfide deposit located in the western Brooks Range north of Kotzebue, Alaska. It belongs in the family of black Shale hosted sedimentary exhalite deposits but lacks classic sulfide sedimentary textures. Pervasive silicification, and a significant portion of the mineralization, is replacement in nature. An extensive feeder vein system cuts the footwall and the exhalite package. A Jurassic to cretaceous age compressional event has repeated the ore section through thrust faulting and folding. The orebody contains 77,000,000 metric tons averaging 17.1% Zn, 5.0% Pb and 82 g per metric ton of Ag. Weathering has locally altered the sulfides to sulfates and formed elemental sulfur.

Jan 1, 1992

By Jordan Hoover, Erika Moonin, Chuck George

"In response to a severe regional drought and in preparation for the further decline of water levels in Southern Nevada’s Lake Mead, the Southern Nevada Water Authority (SNWA) built a new intake system to ensure water supply to Las Vegas and its surrounding communities. In 2015, design began on the Low Lake Level Pumping Station (L3PS) that will move the water from this lower intake, ensuring operability of the water delivery system despite these declining lake levels. The L3PS Project includes a 159-meter-deep shaft, a large underground chamber, and 34-each 152-meter-deep, 2.4-meter-diameter drilled well shafts to be constructed in highly faulted and fractured ground. The Construction Manager at Risk (CMAR) delivery method was chosen to facilitate early contractor involvement in the design process to address the significant challenges and risks anticipated on this US$650 million Project. This paper describes the CMAR selection process; the CMAR involvement during design and benefits resulting from that involvement; and the unique collaborative effort among the owner, engineer, program manager and CMAR used to evaluate and select the best design approach, preferred underground construction methods, and coordinated geotechnical baseline report. PROJECT BACKGROUND AND NEED Seven of the United States’ western states rely heavily on the Colorado River and its tributaries for their water supply. The primary source of water for the Colorado River is winter snow that falls in the mountains ringing the Colorado River Basin. Flows in the Colorado River vary significantly from year to year, depending on the amount of snow and rain deposited in the basin. Beginning in the year 2000 and continuing to the present, snowfall has been well below documented historical averages and Colorado River flows have diminished."

Jan 1, 2016

By D. L. Whiting

Dump leaching and ,in-situ solution mining have received considerable attention during the past few years due to their apparent economic viability and minimal environmental impact. Solution mining actually dates back to the 17th century when leaching of copper ore was first reported. However-, modern day leaching didn't begin on a wide scale until the mid-1900's. In-situ mining for copper, nickel, salts, and oil shale is currently looking more attractive as the technology advances. Presently, about 15 percent of the copper production in the United States is from leaching operations at approximately 14 active sites, the largest of which are the waste dumps near the Bingham Copper Mine, Utah. To establish a common background, the discussion is centered around state-of-the-art conditions. For dump leaching, complications inherent to the physical conditions and chemical reactions such as channeling, porosity and permeability, sorption, air flow, rock alteration and pH control are discussed. Emphasis is made on those conditions which render solution recovery rates and solution mineral concentrations unpredictable. By illustrating typical and actual field conditions, the generally accepted flow theories for both dump leaching and in-situ solution mining, including rubblization, are presented. For in-situ mining, hydrogeologic techniques such as geophysical well logging, aquifer testing and digital computer modeling are also discussed. The importance of artificial fracturing and well stimulating to solution injection and recovery is made with regard to project development. Finally, the subject of water pollution control techniques and the potential impact of the

Jan 1, 1977

By Emily Sarver, Cigdem Keles, Jonathan Gonzalez, Nishan Pokhrel, Lizeth Jaramillo

This paper presents a case study of respirable dust characterization in a thin-seam coal mine in southern West Virginia. Samples were collected in various locations within the mine and analyzed using scanning electron microscopy with energy-dispersive X-ray (SEM-EDX), thermogravimetric analysis (TGA), and Fourier transform-infrared (FT-IR) spectroscopy. The study found high non-carbonate mineral content, particularly aluminosilicates and silica, in the dust. The results indicate that fine aluminosilicate particles may interfere with SEM-EDX analysis, leading to an underestimation of coal content. The findings highlight the importance of using multiple analytical methods to accurately characterize respirable coal mine dust.

May 5, 2022

By Mahesh C. Jha

Cyanidation has established itself as the main process for extracting gold from ores in this century. However, many ores exhibit refractoriness to the conventional cyanidation process. The main cause of the refractoriness is generally the presence of carbon, tellurium, and sulfides, particularly those of antimony, arsenic, and iron. The problem is usually solved by either modifying the cyanidation conditions or providing an oxidation pretreatment. This paper presents results from studies that help in understanding the causes of refractoriness of various gold ores. This is followed by a discussion of many processes that have been developed to solve the problem such as intensive cyanidation, pressure cyanidation, carbon-in-leach cyanidation, and pretreatment processes such as roasting, chemical oxidation, autoclave oxidation, and bacterial oxidation.

Jan 1, 1986

By L. Bloom

In 1996, lack of confidence in assaying methods and sample handling affected companies as diverse as Bre-X and Timbuktu. Both share prices and the ability to raise financing are impacted when the quality of assay data is suspect. Overseas projects are subject to enhanced scrutiny when local facilities are used that are unfamiliar to brokers, financing agencies and banks. Quality control systems can be -implemented but there are associated costs. These costs should reflect the risk to the mining company, investors and financiers and the size of the proposed investment. In this regard, assay control call is considered a form of insurance to enhance the value of an exploration or mining project.

Jan 1, 1997

By Ellen Amoako Afful, Michael Moats, Guang Xu, Ashish Kakoria

Electrowinning and solvent extraction are crucial steps in the production of high-purity copper. However, safety concerns have been raised regarding the acid mist generated from the electrowinning process. The mist generated results in health risks to workers and damage to machinery and infrastructure. Currently, chemicals and pellets are used to control acid mist. However, the effectiveness of these controls may vary depending on the type of organic solvent used in the solvent extraction process, which can influence the generation of acid mist. This study aims to evaluate the impacts of organic solvents and surfactants on acid mist suppression. In this study, an electrolyte is contacted with organic solvents to simulate the solvent extraction. The electrolyte is dosed with 20 mg/L of surfactant at each contact. Acid mist testing is performed on the electrolyte separated from the organic phase at the end of the solvent extraction step. The mist collected is analyzed to determine the level of acid mist generated. The results of this study indicate that organic solvents and surfactants showed significant acid mist suppression, but with somewhat different suppression efficiencies. After first contact, Licorice and the organic, for instance, showed a suppression efficiency of up to 69.7% but its efficiency gradually decreased as the number of contacts increased.

Feb 1, 2025

By W. G. Pariseau

"BACKGROUND The Crandall Canyon Mine (CCM) is located in the Wasatch coal field in central Utah. Extensive longwall mining at CCM preceded a decision to recover coal left in barrier pillars on each side of a set of main entries extending far into the mine. During mining in March, 2007, a major bump occurred that led to cessation of mining in the barrier pillar on the north side of the mains and to begin mining in the south barrier pillar. Subsequent loss of ground control in August, 2007, through coal pillar bursts had tragic consequences with loss of six miners and shortly afterwards three rescue team members. An MSHA report describes the events in detail (MSHA, 2008). An important lesson to be learned from CCM is the need to select a computer program suitable for pillar design. Computer programs are engineering tools; selecting the right tool for the job is essential. In this regard, a minimum program requirement is capability for computing stress distribution within a pillar and adjacent roof and floor strata. The reason is simple: strength of rock is stress dependent; both vary from point to point in pillars and adjacent strata. Preferably, one should follow the evolution of stress as the mining plan is executed from start to finish to assure safety or to warn of a potentially hazardous situation developing as mining progresses. The approach to the problem posed by barrier pillar mining at CCM is conventional in the sense of applying well known finite element modeling techniques to analysis of a proposed mining plan. The engineering purpose is to evaluate the mining plan with respect to ground control questions including roof, floor and pillar safety. Results of previous two dimensional finite element analysis indicated pillar safety was by no means assured (1, 2, 3). Geometry of barrier pillar mining is limited in two-dimensions, for example, crosscuts are not seen in vertical cross sections. While three dimensional analyses are preferred, even moderately sized regions often lead to very large problem sizes that exceed computer capabilities. However, a recent development in finite element modeling of tabular deposits allows for whole mine analysis in three-dimensions. This technique involves a dual node – dual mesh concept. Both have been used separately in much earlier work, but are only now are used in combination. Estimation of subsidence at a kilometer scale and details of stress, strain and displacement about barrier pillars, main entries and pillars, and so on at a meter scale are possible (4). No compromise involving empirical formulas or similar guess work is required. Indeed, all calculations are based on first principles: physical laws, kinematics, and material laws. Effects of joints and in situ variability or uncertainty in strata properties, elastic moduli and strengths, may be included for greater realism. An important objective of the present study is to assess the role of three-dimensional pillar geometry in arriving at conclusions regarding barrier pillar mining versus two-dimensional results."

Jan 1, 2015

By John B. Gustavson

Gold was first discovered in Alabama in 1830. Before a decade had passed more than 20,000 people were employed in the various gold districts scattered across east-central Alabama. By 1849 most of the presently defined gold districts were known with such towns as Arbacoochee, Chulafinnee, Goldville, Pinetucky, and Idaho being the principal mining camps. The California gold rush of 1849 signaled the end of intensive prospecting in the Alabama Piedmont for the precious metal. Reactivation of many of the old gold districts has been attempted several times since 1849. Significant activity and development took place between 1874 and 1880, 1888 and 1916, and 1929 and 1936. Locally, some of the development met with moderate succes. The last productive gold mine in Alabama ceased production in 1935. The sharp increase in gold prices since 1973 has caused renewed interest in the potential values of gold of the Alabama gold districts. Most of the gold workings have been abandoned for nearly 75 years and are for the most part inaccessible for convential property evaluation. The early gold miners and prospectors in Alabama were more intent upon finding and mining the valuable metal than in recording their activities for future generations. No matter how interesting or historically significant these records might have been the miners kept no records and left behind them few maps as clues to their activities. Inasmuch as most of the old gold districts have been extensively mined and prospected during the past 150 years, there is very little chance of finding large deposits through conventional outcrop prospecting methods. Similarly, the present geologic knowledge of the various districts is insufficient to launch successful exploration programs looking for large blind lode deposits in new locations within the general gold bearing region.

Jan 1, 1975

By M. I. Brittan

A technique has been developed that analyzes routine mill operating data to determine the key operating parameters responsible for gold losses to tails. These parameters represent the prime operating variables having a dominant effect on gold recovery. The technique quantifies these effects for the specific plant being analyzed, providing a tool to optimize recovery and costs and so enhance the mine?s cash flow. The quantitative relationships generated will be different for each ore and plant: every case is site-specific and has to be treated on its merits. Examples are provided to illustrate the considerable metallurgical and financial benefits which can be realized from optimization. The examples are taken from case studies of mills in four major gold mining districts of the world.

Jan 1, 2010

By W. H. W. Husband

Rock salt has been mined by the solution method for many years in many countries. Attempts have been made in the past in Canada and various other countries to produce potash by the' same method. However, only Kalium Chemicals Limited (1) has been successful, possibly because the conditions in Saskatchewan are the most favorable conditions to be found so far for the development of a solution mining method for potash. There are significant differences in solution mining of rock salt and solution mining of potash. First, rock salt deposits are relatively pure in respect to soluble minerals, whereas potash is never found in the pure state and contains Substantial amounts of other soluble minerals, particularly rock salt. In comparison to rock salt, much less potash is dissolved and brought to the surface for the same amount of water circulated through the orebody. The amount of water to be evaporated per unit weight of product is a major difference. Much greater amounts of water must be evaporated when producing potash and the treatment of the brine is more complicated because other dissolved salts have to be separated. Secondly, the rock salt deposits, particularly the domes, are much thicker. Bed thickness is of prime importance because it determines the yield of a well and consequently the economics of the process. Furthermore, as rock salt provides a strong roof structure, larger cavities can be developed and this prolongs the life of the rock salt well.

Jan 1, 1971