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By James M. Barker

The borate deposits of Death Valley, first exploited in 1882, were a major world source of boron-bearing products until shortly after very large deposits near Boron, California (Kramer) came on stream in 1926. Borate mining in Death Valley then became moribund, with most extant deposits held as reserves backing Kramer. Tenneco began borate operations following acquisition of claims in 1967 and is the only active borate producer inside Death Valley National Mon¬ument. Borate ores, confined to the lower Furnace Creek Formation (early to middle Pliocene), initially precipitated in a shallow lake fed by boron-rich volcanic hot springs associated with the Basin and Range province. Later diagenesis and remobilization plus regional folding, faulting, and erosion altered and complicated originally simple borate mineralogy and distribution. Dominant ore minerals are ulexite (NaCaB509.8H20), probertite (NaCaB509.5H20), and colemanite (Ca2B6011.5H20). Tenneco currently operates two open pits near Ryan, California. Mining is by bulldozer-pushed scrapers hauling waste and front-end loader/off-highway truck combinations for ore and waste haulage. Archeological, environmental, and aesthetic considerations influence both mine plans. Boraxo Pit, opened in 1970, has deep ore (stripping ratio 10 to 13:1) which occurs along a fault and as beds in shale on the hanging wall. Problems include pit wall instability (adverse bedding), non¬ripable calcareous shale (11,000 fps), and mixed ore separation. Sigma Pit, opened in 1975, has shallow (stripping ratio 1 to 1). low dipping, bedded ore in shale. Massive ulexite and "granular" un- cohesive colemanite present problems in mining and milling. Colemanite is crushed to -6 inches, washed, dried at 350°F, then calcined at 800°F with 100 tpd capacity. Crushed (-6 inch) ulexite or probertite is Raymond milled to customer specifications with a capacity of 1000 tpd.

Jan 1, 1976

By Derek J. Barratt

The existence of a critical size buildup in an autogenous or SAG mill can be predicted from proper examination of drill core and ore samples. Methods of dealing with such critical size in a primary mill are reviewed in the context of ore properties, whether or not pilot plant-scale testwork has been conducted, and also with respect to the design of new plants or the retrofitting of existing operations. The implications of not planning for pebble crushing in situations where it is appropriate are discussed.

Jan 1, 1992

By W. J. Atkinson

Since the inception of the Ashton (formerly Kalumburu) Joint Venture in 1972 the parties have expended 524 million in exploration for diamonds in the Kimberley region. This has resulted in the discovery of the currently subeconomic Ellendale deposits in 1976/77 and the economic Argyle - Smoke Creek Deposits in 1979/80. In addition to Argyle and Ellendale some 90 kimberlitic and lamproitic bodies have been discovered grouped broadly into three provinces, on the west, east and north margins of the Kimberley block. These bodies range in size from dyke-like features less than one metre in width to pipes with a surface area of 128ha. The bodies with larger surface area are volcanic crater deposits, infilled with air-fall and water deposited tuffs and epiclastic sediments.

Jan 1, 1984

By Justin Cardwell, Alyson Cartwright

"Grade estimation is the cornerstone of longrange mine planning. Pit designs, metal recovery, mining costs, reserves calculations and reporting are all dependent upon a reliable grade model. If the geology is poorly understood or the interpolation methods and parameters have been haphazardly constructed, then massive financial losses will be the inevitable outcome. Therefore, a properly trained geologist must use all of the appropriate tools available including deposit knowledge and advances in modeling technology to construct the most geostatistically and practically sound long-range block model.Certain deposits, such as the sedimenthosted deposits at Tenke-Fungurume, require an interpolation method that best suits the style of mineralization. In 2014, Hexagon Mining developed a tool in MineSight called dynamic unfolding (MSDU) that has the potential to improve upon previous Euclidean-based interpolation methods. MSDU utilizes the nonstationarity of a folded grade trend to more accurately construct variograms and improve interpolation results based upon a modeled three-dimensional surface.Geology overview. The sediment-hosted Tenke-Fungurume mining district is located in the southeastern part of the Democratic Republic of the Congo (Fig. 1). The rocks within the district are primarily dolomites and shales from the lower half of the Roan Supergroup that were mineralized by ascending pregnant copper and cobalt rich brines within a massive sedimentary basin (Cailteux et al., 2005) (Fig. 2). These oxidized brines likely found a fluid channel in the porous RSC unit. The surrounding rock units provided a redox boundary for copper and cobalt precipitation along organic rich beds, forming a massive stratabound deposit that was later broken up by several subsequent tectonic events (Dewaele et al., 2006)."

Jan 1, 2015

By J. Klemenic

This paper presents an analysis of gold production and prices over an extended period. Production patterns are provided for the world as a whole and for the five major producing countries. Gold prices as a function of interest rates, as measured by municipal bond rates, are given for the period 1947 to the present. World gold production has had a phenomenal increase since 1980, with the exception of South Africa, all major producing nations participated in this increase, even though the price of gold generally has been decreasing since the high level attained in 1980.

Jan 1, 1993

By C. J. Lewis

Considerable amounts of the world's known reserves of elemental sulfur are found near the surface in areas of volcanic activity both active and inactive. Because such deposits cannot in general-be mined by the well-known Frasch process, and because other methods of recovery have not proven to be economically competitive except in isolated instances, at present these reserves remain relatively undeveloped. However, projections of world sulfur demand indicate that new sources of marketable sulfur will be needed in future years 2/, 19/. For this reason, recovery of elemental sulfur from these near-surface deposits is of continuing interest. Solvent extraction as an approach to recovery of elemental sulfur from open pit-mined ores of these non-Frasch deposits has received considerable attention particularly at the research and development level 3 /, 7/, l l /, 16/, 21/,23/, 29/ This method has been and continues to be attractive because it presents the potential of high sulfur recovery and purity of product coupled with a relatively simple process flowsheet in which low energy requirements and reasonable operating costs are thought to be possible. However, the physical and chemical characteristics of the native-sulfur ores, of elemental sulfur, and of the known solvents, have presented difficulties in the development of solvent extraction processes. Up to the present time, viable processes have not been realized within the framework of sulfur marketing conditions.

Jan 1, 1970

By Y. J. Wang

In the mathematical analysis of electrical networks, the electrical devices are often modeled using idealized network elements such as current sources, voltage sources, and resistors. An analogous approach is outlined here for the modeling of mine ventilation networks, which can be considered nonlinear resistive networks. The modeling technique proposed uses five basic (non-reducible) elements: the H element, the Q element, the D element, the R element, and the N element. These elements are characterized by their (a) pressure gain or loss, (b) air quantity, and (c) pressure-versus-quantity relationship, each of which may be known or unknown. In addition to the definition of the basic elements, the necessary conditions for which there exists a unique solution are discussed. This is performed using theoretical developments derived from electrical circuit theory and illustrated in example networks. The proposed procedures are useful in the solution and characterization of mine ventilation networks.

Jan 1, 1996

By F. J. Sotillo

"Scrubbing both horizontal (drum) and vertical (attrition) are considered simple unit operations in the beneficiation of phosphate ores. In general, the operating conditions are fixed at high solids content based on the experience of the engineering or equipment manufacturing company responsible of designing this beneficiation step. Nevertheless, scrubbing is a complex unit operation designed to clean the surfaces of phosphate mineral particles of slimes, break loose weak inclusions or attached particles of impurities, and break aggregates of clayish material. Therefore, it is considered that as high solids content as possible should be used to enhance particle-particle interactions (impact and rubbing) without taking into consideration the rheology of the system. However, scrubbing unit operations design requires studying the balance between the increase of particle-particle interactions with the cushion effect that may occur when slimes, clays and fines decrease the availability of free water increasing the apparent viscosity of the phosphate slurry up to that of a paste consistency. This paper presents data from laboratory tests to determine the best operating conditions for the design of these unit operations based on the highest P2O5 grade obtained with the lowest impurities for different size fractions. INTRODUCTION In the beneficiation of phosphate ores, unit operations such as horizontal scrubbing (drum) and vertical scrubbing (attrition) are considered simple unit operations. Therefore, little attention is given to the design of horizontal and vertical scrubbing during the basic engineering studies, and the detail engineering stage, the manufacturers recommending “standard” units and operating conditions based on their experience. Due diligence of several beneficiation phosphate plants at industrial scale indicates that a deficient scrubbing of the phosphate ore results in significant problems in downstream unit operations, such as classification, clarification, gravity separation, magnetic separation, flotation, dewatering, and filtration. Scrubbing is in fact a complex unit operation designed to clean the surfaces of phosphate mineral particles of slimes (clays and fines), break loose weak inclusions or attached particles of impurities, and break aggregates of clayish material. Two phenomena occur, the particle-particle interaction (impact and rubbing), and the rheological effects of releasing significant amount of fines into the slurry. Therefore, high solids contents are recommended to enhance the particle-particle interactions, which may result in a change in the rheological regime of the system due to the slimes, clays, and fines decreasing the availability of free water. This increases the apparent viscosity of the system up to that of paste consistency resulting in a cushion effect that suppresses scrubbing. Under these conditions, not all fines are release and rejected (deslimed), downstream unit operations being affected by the release of clays, resulting in P2O5 losses."

Jan 1, 2017

By John H. Bassarear

Large scale equipment can reduce both capital and operating costs for concentrators. Large semiautogenous mills can be effectively utilized in big mills but they must be kept fully loaded to take advantage of their great potential. With varying hardness ores, controlling throughput is difficult and careful design must take this into consideration. A variable speed drive on large primary semi- autogenous mills can overcome this problem to a considerable degree. This paper provides a base case using standard accepted technology of two wound rotor single speed 4,476 kW (6,000 hp) motors to drive the primary SAG mills of a hypothetical 36,364 mtpd (40,000 stpd) typical porphyry copper mill. One other fixed speed drive will be described and five variable speed drive configurations will be reviewed. Capital costs for the entire grinding circuit, from crusher product to flotation feed, were developed for the base case and each of the alternatives. A technical evaluation comparing the advantages and disadvantages of each drive is presented.

Jan 1, 1985

By J. Seiter

Mining has always been among the most hazardous of occupations, and with the increasing demand for coal and minerals, safety in mines assumes even greater importance. Worldwide, underground miners are being exposed to noise and respirable dust hazards associated with roof bolt drilling. These hazards are now being understood to cause irreparable damage to the health of miners. The objective of this research was to discover if a Polycrystalline Diamond Cutter (PDC) drill bit generates less respirable dust and hazardous noise than a competing Tungsten Carbide (WC) bit, in dry vacuum drilling. In order to control the drill parameters the drilling tests have been conducted in a laboratory setting. The results were met by determining the quantities of dust and noise generated using each drill bit and analyzing those levels by using monitoring devices and software to collect the data. This paper includes information on experiment setup, equipment used, drilling parameters, and data collected. The test results suggest that there are noticeable trends that the PDC bits produce less dust than WC bits but more testing is needed to substantiate these trends.

Feb 23, 2014

By Charles A. Beasley

Increased technical and legislative analysis by all parties of interest could result in more efficientand better directed regulatory legislation in the mining industry. Efforts to forestall or frustrate legislation through massive lobbying and public relations efforts are seldom effective over time and often lead to more stringent and far reaching legislation than necessary. The Federal Coal Mine Health and Safety Act of 1969 is perhaps an outstanding example of such insufficiences; a future example may well be regulatory surface mine legislation. Although a lack of extensive hard data seldom enables rapid or sophisticated analysis early in the legislative process, even preliminary analysis may be sufficient. Simple statistical analyses of available data, assessment of the legislative rationale, and subjective appraisal of other non-quantifiable constraints to improved mine safety. An average of 115 underground fatalities at an exposure frequency rate of 0.67 can be reasonably expected in the immediate future, under existing levels of technology, degree of regulation, and economic conditions. If gross unrefined estimates of 6 preparation plant, 5 surface, and 30 strip mining fatalities are assumed, the total fatality industry level could be expected to approximate 156 Serious professional, economic, and technical constraints within the the industry probably preclude any major decrease of these accident levels within the near future

Jan 1, 1972

By S. H. Seyedein, Hamed Tavakkoli, Mohammad Reza Aboutalebi, S. N. Asharafizadeh

The liquid–liquid extraction behavior of lutetium from different acidic solutions was investigated using two extractants, D2EHPA and PC88A, in kerosene. Lutetium extraction reactions with D2EHPA and PC88A from HNO3 and H2SO4 solutions were chemically and thermodynamically analyzed. It was found that each Lu cation was complexed with six monomers of the organic extractant and released three protons. Simultaneously, the Lu cation was instituted in the P–O–H group of the extractants. Thermodynamic analysis of reactions between extractants and acidic solutions showed that the D2EHPA-HNO3 system is the most favorable for extracting lutetium. It is noted that the calculated equilibrium constant of the reaction in this system was approximately six times larger than that of the D2EHPA-H2SO4 system. However, the value of the equilibrium constant for the D2EHPA-HNO3 system was evaluated to be approximately 200 times greater than that of the PC88A-HNO3 system. Therefore, one can conclude that the extraction behavior of lutetium is more influenced by the extractant type than the solutionmedium. The synergistic effect of different mixtures of extractants on the solvent extraction of lutetium was also examined, and the highest synergistic factor was obtained for a binary mixture of PC88A:D2EHPA at the ratio of 4:1 for both aqueous solutions.

Mar 15, 2021

By Jerome E. Grader

Special-purpose analog computers are being profitably applied in the process industries to perform miscellaneoas online computing functions in situations where conventional measurement and/or control hardware cannot perform a required task satisfactorily. This paper will discuss the application of such equipment in the mining industry. It is divided into two parts, beginning with a description of operation of the hardware, followed by a discussion of several applications of the computers to mining industry control problems.

Jan 1, 1969

By H. E. Wyslouzil

The highly competitive nature of the international iron ore market has forced producers to improve the quality of their pellets. The demand for low acid pellets suitable for direct reduction has resulted in an increase in the number of plants utilizing reverse froth flotation for silica reduction. Column flotation is being favoured for this service due to the low capital and operating cost of the equipment, as well as improved metallurgical performance when compared to conventional flotation cells. This paper describes the benefits of column flotation and discusses some important aspects of circuit design.

Jan 1, 1993

By G. J. Karabin

The Boundary Element Method of Numerical Modeling has become an increasingly popular rock mechanics -mine design tool. It has been used by the Roof Control Division, Pittsburgh Safety and Health Technology Center, MSHA, to aid in the resolution of complex ground control problems since 1985. This paper will present an overview of an evolving simulation process and details of methods utilized to generate necessary coal, rock and gob input properties. Also included is a description of a Deterioration Index System that is used to link model output to observed mine conditions and two case studies to illustrate that process.

Jan 1, 1995

By A. Jolly, A. R. Kumar, T. Novak

"Coal dust in an underground mining environment has always been a health and safety issue, especially with longwall faces. Efforts to integrate a flooded bed scrubber within a longwall shearer are underway at the University of Kentucky (UK) in order to reduce worker exposure. Small scale physical modeling, along with numerical modeling and full-scale experimentation, are engineering tools being used by the authors for simulating operating conditions underground. Recent advances in affordable 3D printers offer a means for fabricating accurate, scale models for obtaining timely insights prior to building large, expensive test setups. Comparing scale-model results with those of numerical modeling, such as computational fluid dynamics (CFD), lends guidance and confidence in a proposed design. This paper discusses the small scale physical modeling of a longwall shearer with an incorporated flooded-bed dust scrubber in its operating environment. A tracer gas was used in the model in lieu of dust to measure dust-capture efficiency. Results obtained from the physical model are presented and compared with those of CFD model. The small scale model and the CFD results demonstrate good agreement. Dust capture results show the usefulness of the approach in advance of actual design implementation. INTRODUCTION Dust generation is an undesirable, but innate, byproduct of all mining processes. It is particularly problematic in underground coal mining, where coal dust poses potential hazards from two fronts – health and safety. Coal workers’ pneumoconiosis (CWP), commonly referred to as black lung, is a chronic lung disease that results from the long-term overexposure to respirable coal dust. Although the prevalence of CWP has steadily and significantly declined over the three decades following the Federal Coal Mine Health and Safety Act of 1969, a study by the National Institute for Occupational Safety and Health (NIOSH, 2008) indicates that significant health hazards associated with respirable dust still exist within the coal mining industry. In addition to being a health hazard, coal dust can also create a potentially catastrophic safety hazard. Dust that is not captured or removed at its source is suspended and transported throughout a mine by the ventilation airstream. This float dust is subsequently deposited on all mine surfaces along its travel path. Without adequate application of rock dust to these surfaces, forces from a localized methane ignition can reintroduce settled coal dust into the airstream creating an explosive mixture. Therefore, capturing and removing coal dust at its source mitigates the probability of two major hazards that continue to plague the mining industry."

Jan 1, 2016

By W. R. Reed, J. P. Rider

"The National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) has recently developed a series of models utilizing computational fluid dynamics (CFD) to study airflows and respirable dust distribution associated with a medium-sized surface blasthole drill shroud with a dry dust collector system. CFD models were constructed in ANSYS FLUENT Version 15. Previously run experiments conducted in the NIOSH full-scale drill shroud laboratory were utilized to validate the models. The setup values in CFD models were calculated using experimental data obtained from the drill shroud laboratory and measurements of test material particle size. Subsequent simulation results were compared with the experimental data for test scenarios, including 0.14 m3/s (300 cfm) bailing airflow with 2:1, 3:1, and 4:1 dust collector-to-bailing airflow ratios and 0.24 m3/s (500 cfm) bailing airflow cases with 2:1, 3:1 and 4:1 dust collector-to-bailing airflow ratios. For the 2:1 and 3:1 ratios, results showed the calculated dust concentrations from the CFD models were within the 95% confidence intervals of the lab experimental dust concentrations. This paper describes the methodology used to develop the CFD models, to calculate the model dust input, and to validate the models based on experimental data. Problem regions were identified and revealed by the simulation of a dry dust collector system. The simulation results could be used for future development of dust control methods for a surface mine blasthole drill shroud. INTRODUCTION In surface mines, production drilling is an essential process in blasting which fractures the hard rock overburden for removal. Holes with a predetermined pattern, diameter, and depth are drilled into the overburden to introduce explosives. During the drilling process, considerable amounts of respirable dust are produced. Past research conducting area sampling at blasthole drills has documented time-weighted average respirable dust concentrations ranging from 8.68 to 95.15 mg/m3 [1] and 1.04 to 52.30 mg/m3 [2]. These high dust concentrations, which may contain silica, can lead to respirable dust over-exposures for the drill operator, drill helper, and other personnel in the vicinity. These over-exposures can lead to silicosis, an occupational lung disease that has no cure and is ultimately fatal. In order to prevent the development of silicosis to mine workers, the Mine Safety and Health Administration (MSHA) regulates the exposure to respirable dust. For metal/nonmetal (M/NM) mines, MSHA has adopted the threshold limit values recommended in 1973 by the American Conference of Governmental Industrial Hygienists (ACGIH) [3]. The total airborne dust standard is 10 mg/m3. However, if the sample contains greater than 1 percent quartz (the most common form of crystalline silica), a respirable dust standard is calculated with the following equation: Respirable dust standard = (10 mg/m3) / (% respirable quartz + 2)"

Jan 1, 2016

By Shiou-Chuan Sun

The froth flotation of coal, differing greatly from that of most minerals1-5, is not improved but rather impaired by temperatures higher than room temperature6-10 This phenomenon has long taunted us for an explanation. Gayle and Associates 8,9 reported the lack of relationship between their contact angle measurements and their flotation of American coals under various temperatures. Bailey and Whelan6 stated that the viscosity of flotation reagents, offering some clue for their flotation of British coals at low temperatures, could not be put forward as an explanation either in whole or in part for the effect of temperatures on coal-flotation. In this paper, a froth hypothesis is proposed to explain the flotation behavior of coals under various pulp temperatures. Test work involved the flotation of coals and the frothing of reagents.

Jan 1, 1966

By J. P. Allen

Cobalt, nickel, and manganese can be recovered quickly, cleanly, and selectively from cobalt-rich manganese crust by leaching in dilute acid solutions in the presence of hydrogen peroxide. Common selective precipitation methods can then be used to recover these metals from the leach liquor. The leaching reaction produces only oxygen as a byproduct, and the waste residue from leaching was tested and found to be non-hazardous under existing EPA specifications. The leaching process is effective in either fresh water or seawater. This research is a part of the Bureau of Mines program to identify the mineral resources of the Exclusive Economic Zone and devise methods for recovering their valuable components.

Jan 1, 1990

By Todd Kilduff, Paul Wilkinson

Microtunneling is rarely a straight forward “business as usual” endeavor. More often than not, these projects take twists and turns that require on the fly, out of the box solutions to get the project completed. This paper is a case history of a 63-inch diameter, Permalok, microtunneling project, extending nearly 700 linear feet under a hill forming the left-hand abutment to an earth embankment tailings dam. The job had three major and unexpected challenges that required unorthodox solutions. Challenge #1— Face Configuration: The Santiago Formation, a cemented sand formation with widely varying strengths, presented a challenge to configuring the face with regards to the number and length of pics and cutters. Subtle differences in type and size of the tooling had a big impact on the performance of the machine. Challenge #2—Eccentric Loading: Issues at the launch shaft with the Permalok pipe adaptors caused eccentric loading on the casing pipe. This issue resulted in overstressing and breaking of several pipe joints that ultimately led to seizure of the tunnel. Challenge #3—Back-tunnel Excavation and MTBM Recovery: There were many detailed considerations into excavating a recovery tunnel to retrieve the MTBM, especially being under a high hazard earth embankment dam.

Jun 13, 2021