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By Fred V. Carrillo

California was the leading state in industrial mineral production value with an estimated value of nearly $2 billion. In total value of U.S. non-fuel mineral production estimated for 1992 by the U.S; Bureau of Mines, California ranked second; 81 % of California's total production value was derived from industrial minerals. California led all other states in the production of boron minerals, portland cement, diatomite, calcined gypsum and construction sand and gravel, and ranked second in potash and soda ash production. California's five leading industrial minerals in terms of value were portland cement, construction sand and gravel, boron, crushed stone, and soda ash. California had 13 additional industrial minerals production with reported sales of over $1 million including; industrial sand and gravel, magnesium compounds, lime, salt, potash, natural sodium sulfate, clay, feldspar, crude gypsum, pumice, dimension stone, calcium chloride and perlite.

Jan 1, 1995

By T. Rudolph, M. Pawlik, J. Benndorf, X. Yin, J. F. Brune, P. Goerke-Mallet

The long and often undefined period in the post-mining phase challenges geo-monitoring with its various responsibilities, like the detection of environmental changes, ground movements and water management. Modern methods of geo- and environmental monitoring observe numerous aspects using active and passive sensors with multispectral, hyperspectral and microwave sensors, with diverse spatial dimensions and spatiotemporal resolutions from satellites, Unmanned Aerial Vehicles (UAVs), in-situ sensors. Data integration, together with on-site knowledge and experience, provides the basis for comprehensive modeling, which improves the understanding of the environmental changes and their related causes, which is an essential step for public acceptance. In this paper, we aim to give a brief overview of various geo- and environmental monitoring methods.

Mar 2, 2022

By Arthur W. Ruff

The iron-ore beneficiation and shiploading facilities of the Marcona Mining Company are at San Nicolas Bay which is on the Peruvian coastal desert about two hundred and seventy miles south of Lima. The mines are at elevation of 2,500 ft. Crude ore is transported from the Mine primary crushers to the beneficiation plants by ten miles of overland belt conveyors. After the predominantly magnetic ore is reduced to minus 3/4 in. in the secondary crushing plant, the ore is ground by rod and ball mills and concentrated with magnetic separators. The concentrate slurry is pumped to a thickening and filtering installation for desliming and dewatering. Pelletizing is accomplished with a Lurgi and also a Dravo-Lurgi machine. Deep-water shiploading facilities are available close to the beneficiation plants. Figure 1 shows a flowsheet of the general operation. Pelletizing operations are scheduled 24 hours a day and 365 days per year. A maximum tonnage rate with a high percentage of operating time is necessary to produce the three and one half million tons per year required from the two pellet lines. Process control is a major responsibility and of primary concern to all Operating personnel. The particle size, moisture, and chemical composition of the filter cake must be closely controlled to get uniform high-grade pellets. Key points are sampled routinely and analyzed on a two-hour basis to provide the necessary structure and chemical data to maintain a superior final product. The iron content of the pellets is held between 65.3 and 65.8 percent with 4.0 percent Si02. Sulfur is below 0.04 percent and copper is below 0.02 percent in the finished pellet.

Jan 1, 1968

By H. D. Freeman

The Pacific Northwest Laboratory (PNL) is developing cover technology for uranium mill tailings that will inhibit the diffusion of radon to the atmosphere. As part of this cover program, an improved radon flux measurement system has been developed. The radon measurement system is a recirculating, pressure-balanced, flow-through system that uses activated carbon at ambient temperatures to collect the radon. With the system, an area of 0.93 m2 is sampled for periods ranging from 1 to 12 h. The activated carbon is removed from the radon trap and the collected radon is determined by counting the 214Bi daughter product. Development of the system included studies to determine the efficiency of activated carbon, relative calibration measurements and field measurements made during 1980 at the inactive tailings pile in Grand Junction, Colorado. Results of these studies are presented.

Jan 1, 1981

By Thomas R. Kuesel

Just south of the L'Enfant Station in Seventh Street, the WMATA system splits into two branches, each comprising twin single-track soft ground tunnels. Immediately at the beginning of the section, Interstate Route 95 crosses transversely over the alignment in open cut, removing most of the cover over the tunnels. Seventh Street spans I-95 on a bridge whose abutments and pier also cross transversely over the four tunnels, with their footings as little as 7 feet above the tunnel crown (Figure 1). Soil investigations revealed that the tunnels would have to be driven through mixed face, with a clay invert and a waterlogged sand crown. Thus, there was a good chance that the roof would fall in, leaving 1-95 and the Seventh Street Bridge in a crater. Since there was no roof that could be counted on, these were figuratively (and potentially truly) Washington Metro's Topless Tunnels (Figures 2 and 3). DESIGN ALTERNATIVES Faced with this situation, the designers considered several options, including temporary detours that would permit demolition of the bridge and building tunnels under the 1-95 Freeway by cut-and-cover methods. They also investigated structural underpinning of the bridge and freeway pavement, and strengthening the bridge abutments and center pier by post-tensioning to enable them to span over any subsidence trough.

Jan 1, 1976

By R. McCulloch

Exploration activity in metallic minerals continued to decline in Montana in 1992 as companies either reduced budgets or left the state. The number of active projects dropped another 50% from 1991. Expenditures were 3% to 6% of 1989's 28.6 million. Many of the major mining companies closed offices in Montana. Although depressed commodity prices have hurried the exodus, continuous changes in environmental regulations, as well as the Mining Law of 1872, without regard to economic effect have had the most serious impact. Many companies indicate that Third World countries present a more stable business environment than the United States. Grassroots projects are nearly non-existent, while late-stage programs continue cautiously. Exploration activity continued at the following projects: Garnet, Pegasus Gold; Southern Cross, Asarco; Elkhorn, Goldfields; 7-Up-Pete, Phelps Dodge and Canyon Resources; Miller Mountain, Pegasus Gold; Sheep Creek, Cominco American Resources; Checkerboard, Kennecott and BHP Utah International; Emigrant Creek, Pegasus Gold; and Crevise, American Copper and Nickel. All mineral activity, whether on private, state or federal land, is regulated by the Montana Department of State Lands under three classes of permits - Small Miner Exclusion Statements (SMES), Exploration Licenses and Operating Permits. A total of 230 Exploration Licenses are active in the state with 26 of those being new. However, there are only 433 projects current in Montana, with many of those in the reclaiming stage. The majority of exploration projects consist of individuals expending time rather than money on properties. The number of mines functioning under operating plans declined by one when W.R. Grace closed its Zonolite operation.

Jan 1, 1993

By F. Dehghani, B. Rezaie, T. Ghosh, A. Sachan

Comminution is an integral part of the mineral extraction process. However, the influence of the comminution method (ball and rod mills) on silica and magnetite particle shapes has not been substantially investigated. Shape parameters for fractions of -250+212, -150+125, and -106+75 μm sizes were examined utilizing a scanning electron microscope and a Clemex vision PE image analysis system. The silica particles displayed higher elongation and flatness parameter values for rod mill products, but roundness and relative width parameter values of rod mill products are less than that of the ball mill products. Magnetite particle elongation and flatness parameter values of ball mill products in fraction sizes of -250+212 and -106+75 μm are larger than rod mill products, but roundness and relative width parameter values of ball mill products are smaller than rod-mill products, but for the -150+125 μm size range the result is converse. Furthermore, particle elongation and flatness increased with decreasing particle sizes of silica, whereas, roundness and relative width decreased for both Ball and Rod Mills. In case of magnetite, ball mill products displayed an increase of flatness and particle elongations with decreasing particle sizes but flatness increased and roundness and relative width decreased. Similarly for rod mills, magnetite fractions of -150+125 μm were found to have the largest values of elongation and flatness. INTRODUCTION Comminution alters the size and shape, causes lattice distortion, changes chemical composition, surface area, surface-free energy, and polymorphic transformation of all materials. The quantity and quality of such changes depend on specifications of the material feedstock, the type of mill being utilized, the specific energy input, ambient temperature, and environmental pressure [1]. The shape difference between the milled products depends on different grinding mechanisms and the respective breakage principles that these mechanisms depend on [2, 3]. With decreasing particle sizes, the nature of the particle surface become crucial [1]. The influence of the breakage technique has been found to be non-trivial and heavily dependent on the type of grinding mill used for particle size reduction [4]. Shape is an important industrial parameter for predicting particle behavior in downstream processes. The shape parameter affects the way particles burn, compact, are recovered, flow in fluids, sinter, float, agglomerate, fluidize, interact with pulmonary tissue, cut, abrade, react with chemicals, form structural materials, and retain and permit fluids to flow [5, 6]. The distribution of particle sizes and shapes are important for mining, civil and chemical, pharmaceutical, and various other industries with interest in the population modeling of atmospheric dusts, smoke, and grit [1, 3, 6]. The shape parameter not only affects the chemical, physical, surface properties of particles but is also important for downstream processes [5, 6]. Image analysis has been found to provide detailed information about size and shape of the particles and can be used for the control of product quality [4].

Jan 1, 2019

By Eugene F. Eisemann

This paper is concerned principally with the competition between fuels for industrial use in the United States. Total energy consumption in the U. S. is allocated between industrial and other uses The industrial volume is divided into two classifications (1) where-there is competition between fuels and (2) where there is no competition. The pattern of fuel consumption by electric utilities was studied because there, is competition between fuels and because it is the fastest-growing industrial market. Electric utilities fuel consumption is discussed by geographic area. The growth of each fuel in several areas is investigated. The analysis of these areas, includes the study of the relationship between prices where fuels are in, competition:- (1) on the East Coast where price competition occurs between oil and coal, and (2) in the southeastern states where competition exists between coal and gas..

Jan 1, 1961

By Ammar Henchiri

INTRODUCTION A current need of the phosphate industry is the development of process technology for treatment of high carbonate content ore. About 75 to 80 percent of the world phosphate reserves (1) are associated with carbonate gangue, which is not amenable to treatment by the existing techniques. Numerous laboratory and pilot plant studies have been devoted to carbonate-phosphate separation. Different techniques were involved (washing, sieving, attrition, flotation, calcination, and leaching). For technical and economical considerations, flotation appears to be an efficient process for this problem. Separation of carbonates (calcite and dolomite) from igneous phosphate is applied in industrial plants in Brazil, Finland, and South Africa. But, for sedimentary phosphate, no industrial realization exists at this time, with the possible exception of some plants in China. The main problems with sedimentary phosphates are: • high substitution by CO3-2 and F- for P04 -3 in the apatite lattice. • larger surface area of the phosphate particles because their surface is porous and irregular. • tendency of sedimentary minerals to produce more slimes in conditioning than the crystalline minerals, hence, larger dosages of collectors are required for sedimentary minerals. Investigations reported in the literature indicate that most processes developed for sedimentary carbonate-phosphate separation involved inverse flotation of carbonates using fatty acids as collectors (2), (3) associated with phosphoric acid (4), monosodium phosphate (5), F- (6), or SiF6 -2 (7) as phosphate depressants. Later investigations, conducted by A. Henchiri and G. Baudet (8), (9), (10), (11), (12), (13) in the BRGM technology department, of phosphoric esters revealed that these reagents are selective collectors for carbonate-phosphate separation. The above investigators developed a process which used phosphoric esters to collect carbonate minerals and sulfuric acid or sodium fluorosilicate as depressants for phosphate. Extensive comparative tests for different processes on the same phosphate sample show that the process developed at BRGM is one of the most promising methods proposed for sedimentary phosphate-carbonate separation. It should be pointed out, however, that phosphoric esters make abundant froths. The handling of these excessive froths will be a problem in an industrial-scale plant. This paper outlines test work performed in order to optimize and to improve the efficiency of the flotation process on a sedimentary phosphate ore selected from the Sra Ouertane orebody. The Sra Ouertane flotation process, illustrated on Figure 1, first removes carbonate minerals by inverse flotation and then recovers phosphate as a froth product, leaving quartz as a cell product.

Jan 1, 1993

By J. Hilgers

Metal prices are often predicted by relying on time trend projections of various economic indicators or even the trend in price itself Thus, time is the underlying explanatory variable acting through at best, a limited selection of economic variables. The price prediction method described in this paper differs from this by analyzing hundreds of economic variables to develop a few principle components that automatically capture the fundamental changes in the economy and delete duplicate or irrelevant information. This leaves a few principle variables to describe a state-space representation of the economy which can then be used for prediction. Forecasts of the price of a metal are then made based on these principle variables.

Jan 1, 1995

By N. Chow

The recovery of manganese from lower-grade resources has been studied for a number of years. Of key importance in prior work was the discovery that higher-valent manganese can be readily leached with sulfurous acid. This eliminates the need for high-temperature reduction roasting that is conventionally used in processing high-grade material. High-temperature roasting is energy intensive, emits a large amount of carbon dioxide and would not be economical for processing lower grade material. While the prior work provides important information for extracting manganese from lower-grade resources, the production of unwanted byproducts and high water and energy usage has limited its commercial use. This paper describes the results from laboratory work that demonstrate solutions to problems that to this point have precluded commercial development. Preliminary mass and energy balances show that a significant opportunity exists in producing manganese with this hydrometallurgical scheme in a low-cost, environmentally friendly manner. The emphasis of the work is on low water use, low overall energy use and economic destruction of unwanted byproducts.

Feb 1, 2012

By W. R. Reed, G. J. Joy, B. Kendall, A. Bailey

"Testing of the NIOSH-designed roof bolter canopy air curtain (CAC) has gone through many iterations demonstrating successful dust control performance under controlled conditions. J.H. Fletcher & Co. (Fletcher), an original equipment manufacturer of mining equipment, has further developed the CAC concept by incorporating it into the design of its roof bolting machines. A new CAC design has been developed incorporating the results of testing of the NIOSH design and the recent Fletcher design. Observations from smoke testing conducted on this new CAC design in a laboratory setting show promise for improved performance. INTRODUCTION Exposure to respirable coal mine dust can cause coal workers’ pneumoconiosis (CWP) otherwise known as black lung. If silica is present in the dust, the miner may develop silicosis in addition to CWP. CWP and silicosis are occupational respiratory diseases that are ultimately fatal and have no cure. The only method of prevention is through elimination of exposure to respirable coal mine dust and crystalline silica (quartz). The current occupational exposure limit (on an MRE basis) for respirable coal mine dust is 2.0 mg/m3 during each shift that a miner is exposed in the active workings of the mine or in mine facilities [30 CFR 70.100 2015]. Recently enacted legislation changes this standard beginning in August 2016 to 1.5 mg/m3 for a full working shift [Federal Register, 2014]. If the respirable coal mine dust contains more than 5% silica, the applicable respirable dust standard is reduced; calculated as 10 divided by the percent quartz present [30 CFR 70.101] so that the effective exposure limit for respirable quartz is 0.1 mg/m3 for a full working shift. Sources of exposure to respirable coal mine dust for the roof bolting occupations include infrequent maintenance and cleaning of the vacuum dust collection system and operating the bolter downwind (in the return air) of the continuous miner [Goodman and Organiscak, 2003]. Recent studies have demonstrated that vacuum dust collection systems are effective in capturing bolter-generated dust, if maintained and operated correctly and if proper face ventilation techniques are used. However, most exposure to respirable coal mine dust for the roof bolter occurs when the roof bolter machine is operated downwind of the continuous miner [Potts et al., 2011; Colinet et al., 2013]. Because of this higher exposure downwind of the continuous miner, the roof bolter is generally limited to working downwind of the miner only once during a production shift"

Jan 1, 2016

The roasting process of copper concentrates containing variable quantities of arsenic in a fluidized bed regime was analyzed, considering the technical literature published on the topic in the last quarter century. Although emphasis has been given to the analysis in the fluidized bed regime, other processes have also been considered, under a reducing, neutral or oxidizing atmosphere. The kinetic mechanisms of roasting, as well as the models that have been applied or those likely to be used to explain the kinetics of arsenic removal, are analyzed. Regarding the kinetic mechanisms, those that have been applied to copper concentrates with both high and low arsenic content are included. The roasting kinetic model includes the kinetic data analysis techniques, general models, equations and an estimation of the conversion degree through dynamic, differential and integral methods, as well as particular models for mineralogical components, such as smelter dust and copper concentrates with low and high arsenic content.

May 1, 2012

By S. A. Lolon, J. F. Brune

"INTRODUCTION In underground longwall coal mining, the mined-out areas or gobs frequently contain methane which can form explosive methane-air mixtures. Historically, there have been many events of mine fires and explosions recorded in the United States and other countries that have demonstrated the existence of such explosive mixtures, herein referred to as Explosive Gas Zones (EGZs), inside and around the perimeter of bleeder-ventilated longwall gobs (Loane et al., 1975; Lynn et al., 1986; Elkins, et al., 2001; McKinney et al., 2001; Dziurzynski and Wasilewski, 2012; Brune, 2013). The risk of mine explosions can increase if the EGZs migrate out from the gob into the surrounding mine entries. Several factors can induce EGZs outflowing from the gob, but the most common cause is the fluctuating barometric pressure. Atmospheric pressures change regularly every day but can fluctuate abruptly and become increasingly hazardous in adverse weather conditions. Other sudden pressure changes can result from roof falls, failing ventilation controls and fan outages. Any such fluctuation of mine ventilation pressure will disturb the pressure differential between the gob and the surrounding mine workings and may cause EGZs to outgas from the gob. The correlation between major mine explosions and abrupt barometric pressure changes has been studied and confirmed for explosions in coal mining countries including the United States, South Africa, Australia, and Poland (Hosler, 1948; Boyer, 1964; Kissell et al., 1973; Fauconnier, 1992; Hemp, 1994; Wasilewski, 2014; Belle, 2014; and Lolon, 2017). Disastrous mine explosions appear to happen more frequently during stormy weather, which, in the United States, typically occurs during the late fall and winter seasons. ROOT CAUSE AND EFFECT OF GOB BREATHING Gob breathing is the result of the pressure differential between gob internal and external pressures caused by external atmospheric pressure fluctuations that occur naturally as a result of gravitational and thermal forces in the atmosphere (Lindzen and Chapman, 1969). Other major and sudden pressure changes may be caused by fan failures, failures of ventilation controls or roof falls can also cause an unexpected gob breathing. Normal barometric fluctuations occur every day but usually do not pose an explosion risk as they occur gradually so gob pressures have sufficient time to equilibrate. More extreme fluctuations associated with cyclonic weather systems and storms often result in more rapid and larger drops or rises in barometric pressure (Hosler, 1948; Fauconnier, 1992). A study by Lolon (2017) found that the timing of historical mine explosions showed consistency with the occurrence of abrupt and intense barometric variations."

Jan 1, 2018

By Dushasan Kundu, B. N. Shivakiran Bhaktha, Khanindra Pathak, Sarbojit Mukherjee

Mine safety and quality of life of miner working in underground mines depend to a large extent on mine illumination and communication. The provisioning of reliable, safe, and cost-effective illumination is critical, particularly in underground gassy coal mines. To prevent firedamp explosion by electrical switching operation in coal mining industry requires implementing intrinsically safe illumination circuit. The luminaire design also needs to be certified and installed properly. The current illumination systems installed inside mines require a lot of energy which is obtained from nonrenewable resources. In this work, the design and implementation of solar-powered optical fiber-based illumination are studied and implemented in the Jhanjra underground coal mine, Eastern Coalfield Limited, and a Li-Fi-based communication system for underground coal mines is proposed. Silicate optical fibers of various core diameters and numerical apertures are characterized for illumination applications and their efficiencies are reported. The possibility of achieving optical fiber-based solar, laser, and hybrid illuminations in underground mines is discussed. The design and fabrication of a Fresnel lens-based solar tracker for solar illumination are also presented. The optical fiber-based illumination system is installed in an underground coal mine and the illumination of over 70 lux is achieved at the work plane. Finally, optical fiber-based illumination and simultaneous basic Li-Fi communication are demonstrated and will be beneficial to the underground coal mining industry.

Apr 14, 2023

By Fred H. Seymour

In spite of the progress made by geostatistical theory over the years, evaluation of low grade open pit gold deposits continues to be challenging. Many Carlin type deposits are modelled from exploration drilling spaced on 10C foot centers. From these drill holes, 50 by 50 by 20 foot blocks containing about 4000 tons of material are estimated. The block size is a compromise between being large enough for a good geostatistical estimation and being small enough for practical pit limit analysis and mine planning. Most of these gold deposits are highly variable and include ore and waste zones that are too small to be properly defined from exploration drilling information. Because of this, selective mining is controlled by sampling closely spaced blast holes where the density can be as high as 50 blast holes per exploration drill hole intercept. Figure 1 illustrates an example of the ore/waste contact definition before and after blast hole sampling. With exploration information only, a tentative ore/waste contact can be drawn between the exploration blocks.

Jan 1, 1989

By J. M. Wempen, R. D. WEYHER, M. K. McCarter

Beam theory is a proxy for the behavior of intact, deforming roof strata above underground openings. Strong, stiff, intact strata have the ability to store significant strain energy when underground openings have large spans, as is typical of longwall operations. When strata fail, they may release some or all of this strain energy. Released energy is partitioned between fracture, thermal, and seismic energy. The tensile failure surface in simply supported beams is predicted to be free of shear stress. This prediction and the kinematic inability of crack slip during fracture make significant dissipation of energy by friction unlikely. In this study, the failure energy partitioning of Nugget Sandstone specimens is examined. Tensile fractures in specimens were induced using three-point loading tests. Elastic waves emanating from fracture events were recorded using an array of accelerometers. Accelerometers were placed within two crack lengths of the fracture surface, and the acceleration records are similar to strong motion seismic records. Spectral analysis was performed and used to develop synthetic, well-behaved, acceleration signals. Synthetic velocity signals were used to estimate radiated seismic energy generated by fracture. These estimates of radiated seismic energy demonstrate a potential means to constrain the minimum seismic partition. Fracture testing was performed on additional samples to estimate the fracture toughness of the sandstone. Synthesis of this data demonstrate a potential means to constrain a maximum seismic partition. Bounding the seismic partition for this type of fracture event could aid the detection and evaluation of seismicity emanating from longwall operations. Having better information about the location and magnitude of mining-induced seismicity within longwall overburdens could lead to better understanding of extraction sequencing and rock behavior in general. These energy estimates also support the hypothesis that dissipation of thermal energy by friction is small in bending tensile failure.

Jul 1, 2020

By John M. Karpinski

A method and equipment have been developed Tor measuring the impact strength of grains of brittle materials. It is shown that brittle materials develop a characteristic particle size distribution when fractured by impact. A simple mathematical model has been found to describe this distribution, and one of the parameters of the model has been designated the r value. The r value is directly proportional .to impact energy and, for fixed impact energy, it becomes a useful criterion of grain strength. Data are presented on the variation of the r value as a function of sample history, initial size, energy input and number of impacts, The results are interpreted in terms of the flaw theory of brittle fracture.

Jan 1, 1964

By William X. Chavez

The Mantos Blancos copper-silver district is located in northern Chile about 45 kilometers northeast of Antofagasta, as shown in Figure 1. Disseminated and veinlet copper and copper-iron sulfides containing economically significant silver values are hosted by andesitic to rhyolitic volcanic rocks of probable Jurassic age (Chavez, 1983). Field, mineralogical, textural and lithochemical evidence show that three major alteration types may be recognized within the district: (1) district-wide sodium metasomatism, manifested as albitization of feldspars and development of albite veinlets and pore-fillings, (2) local to widespread, incipient to intense addition (chloritization) or removal (bleaching) of magnesium and iron and (3) local to widespread, moderate to intense hematitization, usually spatially associated with bornite-digenite-covellite (as specularite) or digenite-covellite-chalcocite (as red hematite staining with or without specularite) mineralization. Carbonatization, occurring as veins, veinlets, vesicle fillings and irregular patches of calcite, varies in magnitude of development but is widespread. Sericitization of feldspars and groundmass is only locally intense yet is generally present as incipient alteration throughout the district. The district-wide albitization of the Mantos Blancos volcanic sequence has altered what were originally more potassic and calcic, less sodic, rocks to what are now more properly referred to as keratophyres (Battey, 1955; Gilluly, 1935, Hughes, 1975). The petrographic and lithochemical characteristics of the three major alteration types noted above are summarized below.

Jan 1, 1984

By M. N. Chandraprabha

This paper discusses the role of the mineral-adapted acidiphilic microorganism Acidithiobacillus ferrooxidans in the beneficiation of arsenopyrite-containing multisulfides (pyrite and chalcopyrite) and the bioremediation of the resulting arsenical waste water. It was found that adaptation to minerals alters the surface properties of the microorganism. Bacterial adaptation to arsenopyrite and controlled bacterial adhesion to mineral surfaces lead to selectivity in arsenopyrite separation. Bioremoval of arsenic ions (both arsenite and arsenate ions) by Acidithiobacillus ferrooxidans is also discussed. Key words: Acidithiobacillus ferrooxidans, Bioremediation, Arsenopyrite beneficiation

Jan 1, 2009