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By A. Singh, C. Da Corte

"South Africa possess the biggest fluorspar reserves in the world followed closely by China. In light of the current commodity downturn this paper explores the use of Dense Media Separation (DMS) as a coarse pre-concentration method for two fluorspar deposits located in South Africa in which the dominant gangue is carbonate present in the form of dolomite and calcite. Heavy Liquid Separation indicated that conventional pre-concentration of the drill core samples from both deposits would result in unacceptably high fluorite CaF2 losses. At a maximum CaF2 loss to floats of 5% the benefit of DMS would be economically marginal and difficult to justify as a conventional pre-concentrator. In light of cashflow constraints, a twin flowsheet was proposed for the sole purposes of upfront cash generation in which the majority (67-77%) of the CaF2 would report to a high grade flotation plant in 38-41% of the mass whilst the rejects would be stockpiled for flotation at a later stage. Considering the proposed twin flowsheet approach the high grade product split was achieved using DMS and this paper documents the challenges encountered and results achieved. INTRODUCTION Fluorspar is the commercial term for the mineral fluorite (calcium fluoride, CaF2). Worldwide production of fluorspar is dominated by four countries namely China, Mexico, Mongolia and South Africa. Although South Africa is the fourth largest producer, it has the largest fluorspar reserves closely followed by China (U.S. Geological Survey, 2017a). Fluorspar is broadly categorized into two grades namely acid grade also referred to as acidspar (>97% CaF2); and sub-acid grade (ceramic and metallurgical grade) commonly referred to as metspar (=97% CaF2). Acid grade fluorspar is used for the production of hydrofluoric acid (HF) which in turn is used for the manufacture of fluorocarbons and semi-conductors in the electronics industry; metal processing; the production of insecticides, herbicides and cleaning detergents, and the manufacture of uranium tetrafluoride used to concentrate the uranium isotope 235 for use as a nuclear fuel (British Geological Survey 2010; Miller 2001). Ceramic grade fluorspar (85-95% CaF2) is used in the ceramic industry as a flux and opacifier in the production of glass and enamels. Ceramic grade fluorspar is also used to make coatings for welding rods and as a flux in the steel industry. Metallurgical grade fluorspar (60-85% CaF2) is primarily used in the steel industry as flux to reduce the melting temperature and remove impurities in steel making. Similarly metallurgical grade fluorspar is also used as flux in cement production to reduce energy consumption (British Geological Survey 2010; Miller 2001)."

Jan 1, 2018

By S. R. Clark

"INTRODUCTION Of all the natural resources being taxed by the needs of the modern world, perhaps the most important is the continually expanding demand for water resources. As water becomes scarcer, and increasingly important, new technologies are needed to find innovative ways to preserve this precious resource. In Chile, for example, the mining industry is investing billions of dollars to build desalination plants and pipelines; bringing ocean water as far as 200 kilometers inland to meet their demand and maintain operations. It is a full-blown crisis for that nation and a top priority for their government and economy. It has been reported that world water consumption will increase by 40 percent in the next 10 years, representing nearly exponential growth. In the U.S., as more and more communities continue to be built, more drain on the current water infrastructure is created. For 25 percent of people and operations that rely on water from aquifers, this source is being consumed at a rate that will create significant problems meeting the demand in as few as two generations.1 A PROACTIVE APPROACH When it comes to controlling dust at your operation, whether a landfill, a transfer station, a haul road or another ancillary area, what are the options? We know watering is not the answer, but at the same time, we need to prevent dust from flying to ensure a safe environment and keep our skies clear of pollution, for both regulatory requirements and neighbors. Creating a Dust Mitigation Program instead of looking to buy the first dust control product off the shelf is a first step to conserve water and, at the same time, maintain the operational demands and environmental standards for a given site. The program concept is straightforward enough. However, the process of effectively constructing and executing a program is quite involved. When undertaking a program, each manager needs to work with their team and their partners/vendors in analyzing the following elements: 1. Site Expectations—It is important to understand how to balance your internal standards with your regulatory requirements, as well as how to keep your neighbors satisfied. 2. Site Aggregate—Variations in native soil, such as clay content or gravel levels, greatly affect the approach that will yield the highest results. 3. Climate—Relative humidity and seasonal variations are critical to achieving predictable results through product choice, application frequency and timing. 4. Daily Traffic—The type and frequency of traffic is an essential variable for site management. 5. Environmental Responsibilities—If you have additional, specifically defined responsibilities, the approach to your site may vary. 6. Budget—While efficiency is the goal of any program, some sites will have more stringent restrictions than others. 7. Current Usage Rates—Document and understand where you’re starting from, both with water, supporting products, and maintenance so that effective measurement of results is possible."

Jan 1, 2018

By R. J. Kolada

The ventilation systems of coal storage silos are normally capable of rapidly dispersing any accumulations of methane in the atmosphere above the coal pile surface. However, the results of an investigation which is presented in this report show that hazardous concentrations of methane can accumulate within the coal pile. Methane trapped within the coal pile is released into the atmosphere of the loading gallery when coal is discharged from a silo. If the methane released is of a flammable concentration it is necessary to ventilate the gallery to reduce the risk of an ignition. This report proposes a simple test, which, after further investigations may prove to be an effective method to calculate gallery ventilation requirements.

Jan 1, 1985

By S. Kelebek, G. W. Smith

Four samples of galena, each prepared differently, dry ground chalcopvrite and real gar have shown various quantities of liberated sulfur corresponding up to nine equivalent monolavers on their surfaces as determined by the solvent extraction/UV analysis of sulfur using ethanol. The pretreatment of a dry ground galena sample with acidified ammonium chloride or neutral, saturated sodium chloride solutions rendered the mineral readily floatable. The collectorless floatabilities of galena pretreated with the former solution and of drv ground chalcopvrite have been evaluated in reference to the natural floatability of sulfur using the critical surface tension of floatability approach with aqueous methanol solutions. It is shown that the amount of sulfur- on these samples can be correlated with their flotation rate, which was found to he first order within the critical surface tension range. The larger the concentration of surface sulfur, the faster the sulfide mineral floats, thus, the greater its flotation rate constant.

Jan 1, 1990

By P. D. Nora, M. G. Ranade

A statistically designed pot grate-kiln test program was conducted to determine the agglomeration process variables necessary for increasing the low temperature disintegration resistance (LTD) and reducibility (R40) of magnetite-based Empire acid pellets. The ASTM tumble index and compression strength were to be maintained at an acceptable level. Six process variables - bentonite addition level, preheat time and temperature, firing time and temperature, and cooling rate - were investigated within the constraints of the Empire plant. The bentonite addition level and firing temperature had the largest effect on pellet properties. The results of this program were verified during a plant trial. The target firing temperature at the Empire plant has been decreased for increasing the LTD and R40 of commercially produced Empire pellets.

Jan 1, 1987

By Richard W. Cannon

INTRODUCTION The authors, by means of this paper, will attempt to show the role of Induced Polarization and Resistivity surveys in the discovery of the orebodies of Gibraltar Mines Limited (N.P.L.). In this paper, we will also attempt to show the importance of conducting large enough surveys in order to properly evaluate the results obtained from these surveys. LOCATION The orebodies of Gibraltar Mines Limited (N.P.L.) are located on the western slope of Granite Mountain, central British Columbia (52°30' north, 122°16' west) (See Fig. 1). The property lies approximately 28 miles north of Williams Lake, B.C. and can be reached by way of 10 miles of newly improved road from McLeese Lake, on the Cariboo Highway. The area in and around Gibraltar Mines has a moderate topographic relief with elevations between 3,500 and 4,100 feet. {EARLY HISTORY AND GEOLOGY The present Gibraltar Mines property before amalgamation consisted of the Pollyanna property (Duval-Canex) and the Gibraltar property (original Gibraltar Mines) as well as some Coast Silver and McLeese Lake Copper claims (See Fig. 2). The Pollyanna property was first described in the 1917 B.C. Minister of Mines Report which referred to it as the "Rainbow Group". The development at that time consisted of several open-cuts on copper bearing quartz veins.

Jan 1, 1972

Ceremonies for the induction of four mining industry pioneers into the National Mining Hall of Fame will be held Saturday, Sept. 11, 2010 at the Charles F. Barber Pavilion of the Museum Convention Center in Leadville, CO. The 23rd Annual National Mining Hall of Fame and Museum Banquet will begin with an open house and reception at 5:30 p.m., followed by the dinner and program at 7 p.m. The four inductees are: William Wheeler Coleman who served 46 years, from 1911 to 1957, as president and chairman of the company that is now Bucyrus International of South Milwaukee, WI, a world leader in the manufacture of surface and underground mining equipment. Dr. Allen Van Heyl, Jr., an economic geologist who served with the U.S. Geological Survey for nearly 50 years beginning in 1943. He studied more of the nation?s mineral deposits than most could begin to imagine. Arthur Lakes contributed enormously to the geological and mining sciences in the western United States as a geologist, teacher, writer and artist over a period of more than four decades beginning in 1869. The Arthur Lakes Library at the Colorado School of Mines, Golden, CO, is named for him. Samuel Calvin McLanahan, through his inventive genius, changed the direction of his family?s company from that of a foundry to a leading manufacturer of minerals processing equipment to become today?s McLanahan

Jul 1, 2010

By A. I. Kalugin, A. A. Abramov, D. E. Kozlov, D. V. Magazanik

Based on theoretical and experimental researches of phosphate and carbonate minerals flotation in the presence of soluable glass at various pH values and sodium silicate concentrations, it has been established that the presence of soluble glass in solution leads to formation of silicate compounds on the surface of phosphate and carbonate minerals causing change in their floatability for the worse. The harmful influence of soluable salts is done by tying of collector as metallic soaps, forming precipitates on the surface of minerals to be floated and causing their depression of flotation, and breaching of the froth etc. Depressing action of slimes and products of interaction with collector depends on the ratio of values and signs of potentials of the mineral surfaces. The possibility of phosphate and gangue minerals separation can be evaluated by comparing the minimum-necessary concentrations of collector required for their flotation.

Jan 1, 2002

By A. J. Jeffery

Heat transfer to a fluid flowing through a rough duct has been shown by many researchers to be a function of surface roughness. The effect of roughness asperities on the duct surface is to turbulate the fluid as it flows through the duct, increasing frictional pressure losses and convective heat transfer rates, and also increasing the surface area per unit length available for heat transfer. These factors combine to increase the total costs to the mine in terms of refrigeration and fan power requirements. A measurement system designed to automate the collection of tunnel roughness information and based on an infra-red timed pulse laser has been developed at the Royal School of Mines in London. The system allows accurate, high resolution digital recordings of tunnel surfaces to be made in two or three dimensions. Software for analysing the data has been written, and the description of a complex surface via single numerical term has been explored. A relationship between the numerically measured surface roughness and the pressure loss of the ventilating air is being investigated with a view to establishing an alternative method of describing tunnel roughness. The paper describes the roughness measuring technique developed and the analytical techniques explored so far.

Jan 1, 1993

By H. Sevim

Belt network simulators developed in the last two decades are reviewed. Critical parameters in belt network design are identified, and the capabilities of belt simulators in providing values of these parameters are investigated. An alternative design model that optimizes values of the critical parameters is introduced. To illustrate the capabilities of the alternative model, a real life case is treated and the outcomes are discussed.

Jan 1, 1990

By D. K. Sengupta

Increased recycling of waste paper has been emphasized in recent years in both the USA and Canada for environmental and economic reasons. Removal of ink particles from the waste paper pulp is therefore necessary. One of the most promising methods for ink removal is froth flotation. Our study investigated the feasibility of a simplified flotation scheme which showed that about 90-92% ink removal can be achieved while 95-97% ink removal is achievable if a hydrophobic polymer is used ahead of flotation. The clean paper pulp recovery was over 90%. The effects of pulping pH, flotation pH, and concentrations of flotation and polymeric reagents are discussed in the paper.

Jan 1, 1993

By V. K. Srivastava, T. Gupta, T. Ghosh

"In recent years, the demand for rare earth elements (REEs) has grown due to increasing demand and global supply shortage. The supply deficit of these critical elements has encouraged the search for new sources, with coal and coal byproducts as possibilities. Coals from certain parts of the world can be rich in REEs and can approach a total concentration of 1,000 ppm. Two Alaskan coal samples, from Healy and Wishbone Hill, were investigated for the effects of density and particle size on REE concentrations for three selected size fractions, and flotation tests were conducted on finer fractions. Additionally, bottom ash and fly ash samples from a power plant were examined for their REE concentrations. The results show that the upgrade potential for REEs on an ash basis from a whole-coal basis ranges from 2:1 for the Wishbone Hill samples to 4:1 for the Healy coal samples. Flotations of the finer fractions of the two coal samples, conducted under similar conditions, revealed higher concentrations of REEs in the tailings. Both coal samples had comparatively higher contents of light-group rare earth elements (LREEs) than heavy-group rare earth elements (HREEs). REE content trends for the power-plant products on an ash basis indicate that fly ash has slightly higher concentrations of both LREEs and HREEs than bottom ash. IntroductionRare earth elements (REEs), also known as rare earth metals, and their compounds are vital components in industrial, automotive, petrochemical, defense and medical applications. Dysprosium in combination with other elements is used in laser materials and nuclear control applications. Neodymium is present in magnets that are used in the manufacture of wind turbines and hybrid cars. Europium, terbium and yttrium are used in devices that have visual displays such as computer screens and laptops (Haxel, Hedrick and Greta, 2002; Bunzli, 2013). REEs pose fewer environmental problems of disposal and recycling than their conventional heavy metal counterparts (Haxel, Hedrick and Greta, 2002). They are key materials for radar systems, avionics, modern national defense and satellites (Cammarata and Sieradzki, 1994; Hedrick, 2010; Martin, 2010; Szumigala and Werdon, 2011; Cordier, 2011; Bunzli, 2013). REEs are often classified into light-group rare earth elements (LREEs) and heavy-group rare earth elements (HREEs). This classification is primarily based on the electronic configuration in the outermost shell. LREEs, ranging from lanthanum to gadolinium, have a single or no spinning electron in the outermost 4f shell while HREEs, ranging from terbium to lutetium, have paired electrons in the 4f shell. This difference in electronic configuration is responsible for the differences in physical and chemical properties of REEs."

Jan 1, 2017

By X. Xie

The dissolution behavior of palladium powder in thiourea solutions has been studied. The variables studied included temperature, stirring speed, and concentrations of thiourea, acid and ferric ion. Palladium was found to be soluble in thiourea solutions in the presence of an oxidant such as ferric ion. The dissolution of palladium in thiourea solutions was found to be chemical reaction controlled with an apparent activation energy of about 2S.3 kJ/mol.

Jan 1, 1995

By X. Zhu, Chen. L., R. Guru, M. Peiravi, M. Mohanty, L. Ackah, B. Xu

"The overall goal of this study is to develop a suitable flow sheet to extract rare earth elements (REEs) from coal ash. A total of 14 coal samples of different ranks were examined for REE concentration, and an anthracite coal sample with the highest REE concentration of more than 700 ppm in the coal ash was selected for REE extraction tests. This paper reports on the results of the experimental program completed in the first part of the study, which included hightemperature leaching with nitric acid followed by solvent extraction tests using various organic extractants, namely, tributyl phosphate, Cyanex 572, di-(2-ethylhexyl)phosphoric acid (D2EHPA) and their combinations. A 4×2×2 experimental design was used to conduct a total of 32 high-temperature leaching tests by varying acid molarity at four levels, solids content at two levels and leaching time at two levels. The highest recovery rates of 90 percent for light rare earth elements (LREEs) and 94 percent for heavy rare earth elements (HREEs) were obtained from the optimum leaching test conditions while maintaining impurity recovery to the leachate at less than 40 percent. D2EHPA was found to be the best extractant in this solvent extraction test series, providing an REE recovery rate of nearly 99 percent.IntroductionGlobal demand for rare earth elements (REEs) and other strategic metals is increasing rapidly due to their use in a variety of advanced technological applications, with more than 100 kt of rare earth oxides used worldwide on an annual basis. The United States has less than 10 percent of the world reserves of REE mineral deposits, and in 2013 imported more than 60 percent of its rare earth oxides from other countries, mainly China (United States Geological Survey, 2017). China’s institution of export quotas has significantly reduced supply to the United States, raising the urgency of finding new ways of producing REEs and/ or substitutes. Coal combustion byproducts, which are usually discarded as waste materials, are known to contain REEs in low concentrations that could be extracted with a suitable process flow sheet. This may be a worthwhile route to pursue, considering the short supply of rare earth minerals and the abundance of coal ash in thousands of ash ponds in the United States. More than 110 Mt of coal combustion byproducts are produced annually in the process of satisfying the country’s need for electricity (American Coal Ash Association, 2016), and less than 50 percent of these byproducts are being successfully used in various applications, with the remainder dumped as waste materials in landfills and ash ponds."

Jan 1, 2017

By K. Hanna

Early identification of adverse geologic conditions and high stress concentrations during the high-speed extraction of coal using modern mechanized long wall systems is a major challenge facing the mining industry. Often, unexpected geologic anomalies that affect rock mass quality are encountered more rapidly, leaving the mine operator with insufficient time or information to deal with the changing ground conditions. The RockVision3DTM seismic tomographic system, developed by NSA Engineering, Inc., offers substantial benefits over conventional geologic/stress-detection methods and has been used successfully in coal mines worldwide. Tomographic images, produced economically and in near-real time, are easy to interpret, allowing mine operators to deal with potential hazards on a day-to-day basis. This paper focuses on the application of RockVision3DTM technology for delineating hazards caused by stress and geologic anomalies. Case studies for two bump-prone coal mines will be discussed. For example, (1) in a German deep (>1,130 m) mine, the drilling-yield method was used to verify the effectiveness of this technology in detecting stress anomalies ahead of longwalling; (2) in a Polish mine (-500 m deep), two longwall panels 4 km apart were monitored to assess structural and stress-related factors contributing to differences in mining conditions and magnitude of structural failures.

Jan 1, 1999

By John W. Welty

Volcanic activity occurred during six periods of Arizona's geologic history. Precambrian volcanism occurred in two pulses at 1.8-1.6 billion years (b.y.) ago and at 1.2-1.1 b.y. ago. Volcanism occurred again in mid-Jurassic and Laramide (Late Cretaceousearly Tertiary) time. Volcanic rocks from these times are not used commercially in any significant quantity. Middle and late Cenozoic magmatic activity covered large areas of Arizona with voluminous volcanic rocks. During the mid-Tertiary magmatic pulse, explosive silicic magmatism, with eruption of areally extensive ash-flow tufts, covered large areas in the Basin and Range Province, while the Colorado Plateau remained largely unaffected. Basalt eruption also occurred during and immediately after silicic volcanism, leading to compositionally diverse suites of volcanic rocks. Late Cenozoic volcanism occurred throughout Arizona and was dominated by wide-spread eruption of basalt flows with local cinder-cone clusters and siliceous volcanic deposits. Perlite deposits near Picketpost Mountain in northeastern Pinal County account for the bulk of the industrial uses of mid-Cenozoic volcanic rocks. Other perlites of presumed middle Tertiary age are present in central, southeastern, and western Arizona, but to date remain unexploited. Arizona Fire Agate is a valuable gem material and is associated with volcanic rocks of middle Tertiary age. Basaltic rock of this age also is utilized in the manufacture of rock wool for insulation. Late Cenozoic volcanism produced most of the industrial-quality volcanic rocks. Basalt, cinder cones, and materials of rhyolitic composition are commercially exploited by municipal and Federal agencies and private industry for aggregates, road conditioners and maintenance materials, asphaltic concretes, cinder block construction, pozzolans, and landscaping. These deposits are generally confined to the Flagstaff and Springerville areas. A famous peridot gem locality is associated with late Tertiary basalts at Peridot Mesa on the San Carlos Indian Reservation. Important products derived from altered volcanic materials of late Cenozoic age include clay and zeolite. Arizona's volcanic-rock sequences are still incompletely known, particularly in central and western Arizona. The potential for recognition and exploitation of important new deposits of useful volcanic materials is high.

Jan 1, 1987

By Peter Zhang, Todd Minoski, Gabriel Esterhuizen, Jack Trackemas, Berk Tulu, Morgan Sears

Roof stability in the belt entry is critical for safe and continuous production of coal during longwall mining. Previous studies of roof falls that occurred in belt entries have shown that the roof falls were largely associated with high in situ and longwall-induced horizontal stresses [1,2,3,4]. To properly support the roof in a belt entry, it is important to understand how longwall-induced horizontal stress changes can affect roof stability in the belt entry. Monitoring of horizontal stress changes was conducted in the belt entries of two Pittsburgh seam longwall panels oriented unfavorably to the major horizontal stress. Numerical models were also set up to investigate how horizontal stress concentrates and relieves in the belt-entry roof near the face as panel orientation changes. Both measurements and modeling results show that high horizontal stress concentrates in the belt entry roof within about 15 m outby the face. The study demonstrates that longwall-induced differential horizontal stress can be used to evaluate the horizontal stress concentration factors. The horizontal stress concentration factors change with panel orientation, resulting in high stress concentrations at orientations between 20 and 110° and low stress concentrations between 130 and 180°. Roof support strategies are given for the belt entries under the influence of high horizontal stress. For unfavorably oriented panels in weak roof conditions, supplementary support should be installed during development, and cable bolts should be anchored into a stable roof horizon. The bolting pattern should be designed to cover both entry corners and the entry center to prevent potential roof cutters and sagging.

Jan 1, 2023

By R. Mensah-Biney

The loading characteristics of gold-tetrabromide species onto activated carbon have been evaluated using a completely mixed batch reactor system. The overall loading of gold onto carbon was rapid for the first hour but continued slowly without cessation as a result of reduction of gold. Conventional equilibrium considerations were therefore not applicable. Although loading continued slowly after several days, abnormally high loading capacity values of 10-12 meq/g carbon (650-800 kgAu/tonne) could be attained within 72 hours. The loading of gold-bromo species by activated carbon was by the mass transfer of [AuBr4l-onto the carbon surface where reduction to metallic gold took place. Elution of gold from the loaded carbon was feasible provided the carbon had not been loaded to too high capacity values. If loading is carried to high levels, complete elution becomes impractical and the gold may be recovered by ashing the carbon. For the high loading capacities observed, this option would appear to be cost effective. The effect of several variables on the loading capacity of the activated carbon is discussed.

Jan 1, 1992

By Arthur E. Lewis

A contained nuclear explosion is proposed to produce a chimney of broken ore well below the water table. After the chimney is filled with water and reaches hydrostatic equilibrium, oxygen, under pressure, is introduced near the bottom of the mass of broken rock. The increase in solubility of oxygen at high hydrostatic pressure is sufficient to initiate the oxidation of the primary sulfides: chalcopyrite and pyrite. The oxidation and dissolution of these sulfides produces enough heat to increase the temperature of the ore and water in the chimney as much as 1000 to 150°C. The rate of dissolution of chalcopyrite becomes so rapid under these conditions that the rate of recovery is no longer limited by the rate of chalcopyrite dissolution, but by the degree of exposure and other factors. Means of solution control and distribution of oxygen in the chimney have been examined in some detail. A calculational model utilizing experimentally determined solubility rates is utilized to estimate the temperature rise in the chimney and the rate of copper recovery as a function of initial temperature, sulfide content of ore, size of sulfide particles, and fraction of sulfide exposed to solution.

Jan 1, 1972

By PDF

Previous work has shown that significant, free milling gold values exist in the Ryan Lode ore. This project used pilot scale equipment to estimate the percentage of gold recoverable by gravity methods from the circulating load of a conventional, closed-circuit, grinding mill. The pilot scale flowsheet employed three stages of gravity concentration, hydraulic classification and batch grinding to simulate a full scale milling circuit. 172 kg (379 lbs) of Ryan Lode ore were processed, having a head grade of 4.8 g/metric ton (0.14 oz/ton). Results showed that simple gravity methods are capable of recovering 45-50% of the gold values in a concentrate grading in excess of 3430 g/metric ton (100 oz/ton). Of the remaining gold values reporting to the classifier overflow solids (80% passing 70 microns, 3.1 g/metric ton (0.09 oz/ton)) 89% were recovered from 48 hour bottle roll tests.

Jan 1, 1995