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By N. B. Aughenbaugh

Subsidence due to abandoned coal mines has received copious attention recently. This is a result of many factors such as the enactment of new mining laws and the effect subsidence has on land use over the mines. Prediction of subsidence features and the time aspects over supercritical extraction (i.e., longwall and high extraction ratio pillaring) is relatively accurate. However, predicting when subsidence will occur and the surface features' size and shape above subcritical extraction of room and pillar mining is not yet possible. This paper will discuss the factors that influence the time aspects of subsidence in room and pillar mining.

Jan 1, 1983

By P. Somasundaran, F. F. Aplan

The Formative Years Douglas Winston Fuerstenau was born December 6, 1928 in Hazel, SD to Edwin Arnold and Hazel Pauline (Karterud) Fuerstenau. His father, of German extraction, was a farmer and, later, a cabinet maker, while his mother, of Norwegian lineage, was a school teacher. His parents are still alive today at ages 91 and 88, respectively. Two younger brothers, Richard and Maurice and a sister, Jean, completed the family. The family first lived near Watertown and later in Lemmon and Mobridge, SD. The 1930's were a difficult period for any family in South Dakota. A decade-long drought made this a part of the dust bowl, which together with a serious infestation of grasshoppers (the locust plague described in The Bible), and the world-wide depression, made living difficult for all. In spite of these privations, Doug has many happy memories of his childhood which can be attributed to the resilience of youth and a strong family structure. He has fond memories of summers spent with his cousins on family farms where the children were introduced to farm chores at an early age. When he was old enough, he worked in a grocery store after school. At the age of 14 he spent the summer hearding 2,000 sheep near Lemmon, SD as his contribution to the war effort in that labor-short period. He remembers well the dust storms of the 1930ts, the destruction at his grandmother's farm by tornado, pulling weeds on the farm, threshing grain with a monstrous steam-driven machine and such pleasant childhood activi- ties as fishing for bullheads, hunting for rabbits, searching for arrowheads in newly plowed fields, and ice skating in the winter. Early in life his parents instilled in him a strong work ethic, a love of learning and the need for a good education. In 1943, the family moved to Rapid City, SD. With a population of 13,000, it was

Jan 1, 1989

By P. Rusin

Many oxide silver and molybdenum deposits remain undeveloped because chemical extraction yields poor recoveries or is environ-mentally unacceptable. Bio-reductive leaching of such ore samples at MBX resulted in high recoveries of silver and molybdenum. When baseline 3-day cyanide bottle roll tests were conducted on manganiferous oxide silver ore, 13.7% of the silver was extracted. In contrast, 86% of the silver was microbially solubilized into the organic growth medium by bio-reduction with 99.8% dissolution of manganese. A follow-up cyanide bottle roll test yielded an additional 8.5% silver recovery for a total recovery of 94.5%. Baseline 3-day acid bottle roll tests of the iron oxide molybdenum ore yielded 1.8% moly. However, bio-reduction solubilized 93.3% of the moly into the growth medium. An additional 0.3% moly was recovered during the follow-up acid bottle roll test. Microbial treatment of refractory oxide ores with bio-reductive bacteria resulted in higher recoveries of silver and molybdenum than conventional chemical leaching. The bioleaching process occurred at a near-neutral pH at ambient temperatures. The bacterial solubilization of silver and moly was achieved without the use of cyanide or sulfuric acid.

Jan 1, 1992

By Stephen L. Chryssoulis

The detection and quantification of invisible gold by microbeam techniques is discussed. Ion probe microanalysis is used to quantify the gold content of individual sulphide, sulpharsenide and oxide particles with a detection limit of 0.2 ppmw (g/t). The proton microprobe is used to determine the gold concentration of gangue minerals with a detection limit of 2 - 4 ppm. Using these techniques complete mineralogical balances for gold are obtained to assist in the process selection and optimization. A total of twenty gold and gold-bearing ores have been examined. Selected examples are presented.

Jan 1, 1990

By George A. Komadina

The Pima Mining Company lies 20 miles southwest of Tucson, Arizona, and some 45 miles north of the Mexican border. The mill is situated on a hillside overlooking Tucson and the Santa Cruz Valley, the ground generally sloping northeast at a 2.5 percent grade. The hillside location allows for gravity flow generally through the plant as well as for: tailing disposal.

Jan 1, 1965

By D. H. Stonehouse

There is no such thing as an industrial minerals industry. There are, however, many industries operating in the general field of industrial minerals. And although we use the phrase "industrial minerals industry" out of sheer convenience, the only common denominator among, say, the potash mining and processing industry, the sulphur-sulphuric acid industry and the granite industry is, in fact, that they each are exploiting an industrial mineral resource. May I quote the person whom I consider to be the reigning Mr. Industrial Minerals, Robert L. Bates, who in the 4th edition, 1975, of Industrial Minerals and Rocks states: "An industry is considered to belong to the industrial minerals field if its operations consist of extraction and processing, but not manufacturing. Thus the mining and beneficiation of feldspar is a mineral industry, but the manufacture of ceramic products is not. In the cement and lime industries, processing merges into manufacture, and the line is less distinct. It disappears altogether in a plant that extracts salt as artificial brines, and makes sodium and chlorine chemicals, all under the same roof."

Jan 1, 1981

By Paul K. Sims

The Central City district is one of several adjacent mining areas in the Front Range, Colorado, that contain precious metal-bearing sulfide veins of Laramide (Late Cretaceous and early Tertiary) age. The districts are in the Front Range segment of the Colorado mineral belt, and are characterized by porphyritic igneous rocks of intermediate composition that have intruded Precambrian crystalline rocks in the core of the Front Range. The veins and minor stockworks that constitute the ore deposits in the district were formed largely as fracture fillings. The veins range from simple fissures to complex, branching lodes, and commonly range from less than 0.5 to about 1 m in width. The principal values are in gold and silver. The common metallic minerals are pyrite, sphalerite, chalcopyrite, tennantite, and galena; minor minerals are enargite, pitchblende, and gold tellurides. Quartz, cryptocrystalline silica, carbonates, fluorite, and barite compose the gangue. The ore deposits have a well-defined concentric zonal arrangement. A core of pyrite veins (central zone) is surrounded by a peripheral zone of galena-sphalerite vein with gold and silver. An intermediate zone contains transitional veins that have minerals characteristic of both the central and peripheral zones. The minerals were deposited in three stages during a single period of mineralization: uranium; pyrite; base metals, gold and silver. The wall rocks were altered primarily during pyrite-stage mineralization. Sericite envelopes developed adjacent to fractures, and were succeeded outward by zones of argillized rock. The valuable ore minerals were deposited in ore shoots localized by several types of structural controls, principally vein intersections, the physical nature and structure of the wall rocks, and irregularities along the fractures themselves. During supergene alteration, gold was concentrated in the upper, oxidized parts of the veins, commonly to depths of 50 m. The precious metal-bearing sulfide ore deposits are closely associated in space and time with the Laramide porphyritic igneous rocks and are believed to have been derived from hydrothermal fluids related to the magmatic activity. The ore deposits have mesothermal aspects and apparently formed in the temperature range 200°-320°C.

Jan 1, 2013

By Enrique Llewellyn

North River Energy Company a previous subsidiary of Republic Steel Corporation commenced development of the Number One Mine in mid-1972. The mine is located in West Alabama and presently employs a total of 632 people. Production capabilities have increased to 1.4 million clean tons of steam coal per year with the newly purchased Longwall System. Washer recovery averages 57 percent. The seam being mined is the Pratt or Corona with an average height of 52 inches and an average cover of 540 feet. The immediate roof is laminated sandstone and the floor is composed of a hard fireclay. Total production out of the mine is provided to Alabama Power Company under a longtime contract.

Jan 1, 1981

By J. W. Mustard

The Macmillan Pass tungsten property (MacTung) is the largest known copper-tungsten, calcic, exoskarn deposit in the Western Hemisphere. Located on the border between the Yukon and Northwest Territories in northwestern Canada, the deposit crops out on Mt. Allen within the Selwyn Mountain Range. It was discovered in 1962 by a subsidiary of AMAX Inc. and has since been explored by 16,300 meters of surface and underground diamond drilling and by 800 meters of underground development. Geologic reserves are in excess of 30 million tons, grading slightly less than 1.0% WO3. Scheelite (CaWO3 ) is the main mineral of economic interest. Accessible by road, the property is not in production. Previously estimated reserves at MacTung have been unable to fully utilize all the geological controls on mineralization. In the past three years, however, an intensive program has been underway to improve our understanding of the deposit and to use the resulting information in a more precise way. This paper will discuss the key aspects of the geology as they specifically relate to reserve estimation and will demonstrate how these controls are being used in a geostatistical model of the deposit.

Jan 1, 1985

By Ayman A. El‑Midany, Hassan E. El‑Shall, Kerri‑Ann A. Hue

Modification of clays is necessary for the zearalenone (ZEN), as long-chain mycotoxins, removal. The organic-cations were usually used to modify the clay hydrophobicity to accommodate the large mycotoxin molecules. In this study, tri capryl methylammonium (TCMA) chloride and common corn oil were used in clay modification. Several characterization techniques such as XRD, FTIR, and TGA were used to identify the d-spacing changes after modification either by TCMA or corn oil. The results of applying the TCMA-corn oil-modified clays in ZEN removal indicated a noticeable improvement where more than 90% of ZEN could be removed in vitro at acidic and neutral pH values. The success of eliminating a high percentage of ZEN molecules is due to the expansion of intergallery spacing as a result of TCMA surfactant intercalation within the clayforming layers. The removal percentage does not depend only on pH but also on the amount of clay used. In addition, the ZEN removal in the presence of corn oil is better at acidic pH and small clay amount where the ZEN can be fully removed.

Sep 27, 2021

By Fred L. Myers

The use of finite element programs for evaluating large grinding mill shells is becoming increasingly popular. However, large scale, detailed analysis can become a burdensome task when one is required to manually prepare the necessary data to be entered into the program, while evaluating the voluminous results is even more devastating. Although available computerized finite element analyses can reduce computation time from years to months or even weeks, additional pre and post processors can reduce the time for data preparation and result evaluation to hours, while simultaneously reducing the probability of human error. Examples of the uses of these processors are presented as well as typical modeling techniques.

Jan 1, 1979

By E. C. Winegartner

In producing and selling coal, the coal company is faced with many different parameters by which the quality of its product is evaluated. One type, which we choose to call the economic parameters, includes moisture, ash, sulfur, and Btu's. These are reasonably well understood by both the coal supplier and the customer, and the dollar values can be placed on them. This is the group of parameters of primary interest to most purchasing agents buying coal. A second group of parameters governs how the coal will behave in the boiler itself and is of primary concern to the engineers designing the boiler and to the men who must operate and maintain it. Since we have not yet learned to put dollar values on these parameters, they generally show up in coal contracts simply as cutoff points, the purchaser simply saying that he will not accept coal outside of certain limits.

Jan 1, 1975

By Peter I. Brooker

The semi-variogram, the basic tool of geostatistical estimation procedures, must itself be estimated from the available data. From a numerically simulated two dimensional deposit, with known variability expressed through its semi-variogram, the standard arithmetic mean estimator is used to calculate experimental semi-variograms. These are determined on a series of data sets obtained from the deposit with various sampling grids which cover different areas of the deposit and which have a wide range of available data. The orders of discrepancies between estimated and theoretical semi-variograms are determined in this idealized situation; and this provides a basis against which to assess experimental semi- variograms made on field data.

Jan 1, 1982

By Francis S. Kendorski

INTRODUCTION Caving offers the lowest cost per ton of any large-scale mining method, but its successful application demands an ore body that conforms to several rigid requirements. The deposit must be of wide areal extent, massive and not spotty in ore values, and insensitive to ore dilution. It must also be a rock mass that breaks up readily. There are only three active caving operations in the US-Climax, Henderson, and San Manuel-but caving methods have recently taken on new importance as deeper lower grade mineral occurrences and ore bodies are found. These deposits are too deep for surface min¬ing methods, and too low grade to support any type of underground mining except a bulk method such as caving. Announced discoveries or indications that may be amenable to caving include: Climax's Mt. Emmons molybdenum discovery in Colorado; Molycorp's Goat Hill molybdenum prospect in New Mexico; the Phelps Dodge molybdenum deposit in Beaver County, UT; Arizona copper occurrences such as Asarco's Sacaton, Hanna's Casa Grande, Noranda's Lakeshore, and Ken¬necott's Safford; Anaconda's suspected deep copper de¬posit in Butte, MT; Anaconda's Carr Fork, UT, deposit; and perhaps others. CAVABILITY'S ROLE IN FEASIBILITY STUDIES Caving is a system of underground mining which removes support from underneath an ore body. As a result, the rock mass fractures, fails, and flows vertically downward by gravity to be collected in previously ex¬cavated funnels. Types of ore that have been mined by caving include molybdenum, copper, iron, nickel, as¬bestos, and diamonds (Julin and Tobie, 1973). It is primarily a large-scale method, with production rates of more than 45 300 t/d (50,000 stpd) having been achieved. However, the initial capital investment before return is very high, often in the hundreds of millions of dollars. The cavability of an ore body or mineral occurrence is a critical item in the feasibility study of a proposed mine, not only from the point of overall minability, but from the point of impact on other costs such as blasting, loading, hauling, crushing, and grade recovered. Aside from the often-asked question of, "Will it or will it not cave?" the real questions are, "Can we afford to make it cave, carry the rock away, and extract the mineral?" The last is not a topic of this chapter, but the first two are. The cavability of an ore deposit or mineral occur¬rence is based on many things, but clearly, if a large enough area is undermined, any rock mass will cave. The result could be a violent collapse as occurred at Urad, CO (Kendrick, 1970), or perhaps the rock mass will cave beyond the ore boundary. Another unfavor¬able result could be ore blocks that are too large for the equipment and orepasses to handle without considerable secondary blasting. Weak rock with numerous fractures may produce a very fine ore when it caves, resulting in dilution and ground control problems. DETERMINING STRUCTURAL DOMAINS It has long been recognized that the geologic nature of an ore body is important to cavability (King, 1946). Such items as weak rock material, intensity of fractur¬ing, and severity of faulting all contribute to the success of a caving operation, and information regarding these is required as a minimum for the cavability determination. In practice, the rock mass-defined as the blocks of intact rock together with the intervening fractures, joints, faults, bedding planes, and other discontinuities-that contains the ore body, as well as the surrounding and overlying rock, must be examined in a systematic and detailed fashion. Surficial geology maps must be pre¬pared, exploration holes drilled, and core logged for en¬gineering information. The fracturing of the rock mass must be studied to ascertain the three-dimensional dis¬tribution of fractures and their characteristics, and faults must be located and described. The strength and other mechanical properties of the rock material, the fracture surfaces, and the fault filling materials must be tested and reported for later use by designers and planners. With this basic information and an understanding of the geologic setting, the rock mass can be divided into one or more structural domains which tend to behave similarly in response to engineering activities (Robertson and Piteau, 1970). One must keep in mind that the determination of the structural domains goes beyond the geologic units present. Several lithologic units may be lumped together, while a single lithologic unit can be divided into multiple domains. Major faults often form their own domain, and the direction of engineering ac¬tivity-for example, cave advance to the north rather than the south-may alter rock mass behavior, resulting in different domains. As an example of the detailed rock fracture map¬ping required for such studies, the structural domain determinations at the Climax mine (Kendorski, 1973) are shown in Fig. 1. The circles are Schmidt equal area projections of the three-dimensional attitudes of frac¬tures (Ramsay, 1967) mapped in detail at various rock exposures. The attitude of fractures is important to the cavability determination since it dictates the directional behavior of the rock mass as it fails, and determines the effectiveness of arching, keying, and rock block inter¬locking. Low-angle fractures must be present to allow movement of the rock in the vertical direction during undermining (Mahtab and Dixon, 1976); if low-angle planes of weakness are absent, the rock mass may arch with a keystone effect, rather than moving vertically downward.

Jan 1, 1982

By Paul Madsen, Bade Sozer, Thomas Hennings, Eileen Test

The Rondout Bypass Tunnel in New York has two access shafts. The upper sections of the shafts are lined with steel pipe to resist a substantial net internal water head . Initial design included a ¾-inch-thick cement mortar lining (CML) for all three components. Because of concerns with CML application on large-diameter pipes, the protective lining was redesigned for shotcrete application. This paper discusses the details of that design, mock-ups, and shotcrete application.

Jun 13, 2023

By and Heather E. Lawson, Mark K. Larson, Gabriel Walton

In this study, we evaluated the effects of different shapes and distribution densities of mineral grains in coal on failure mechanics using the numerical software 3DEC. The main aim of this study was to identify possible failure mechanisms influenced by mineral habit and frequency in coal. Exploring differences in failure mechanics associated with the mineral grains helped to determine the role of mineral character as a possible contributor to characterize burst-prone coals. To achieve the goal of this study, a series of numerical specimens were prepared in the 3DEC model as follows: first, the 3DEC modeling in conjunction with the DFNs (Discrete Fracture Networks) technique was performed to explicitly generate the discontinuities (i.e., cleats and bedding planes) in the numerical specimens based on the results of laboratory analyses. Then, the different realizations of mineral grains were embedded in the 3DEC model to simulate an unconfined compressive strength (UCS) test to assess the influence of the mineralogical characteristics on the UCS.

By P. A. Korpi

In March of 1978 the first set of Angular Spiral Liners utilized in grate discharge ball mills for wet grinding was put into service in the San Flanuel Concentrator of Flagma Copper Company. The use of these liners has decreased grinding media consumption by 19.2% and grinding energy consumption by 15.8%. In addition a 1.1% increase in grinding throughput is being realized through the use of the system. This paper describes the Angular Spiral Lining System and reviews the test program at the San Manuel Arizona Concentrator. Operating parameters are discussed in addition to the current testing program to futher optimize the system.

Jan 1, 1982

By Tracy T. Morris

The current state of the mining community has made it imperative for operations to reduce costs and increase productivity in order to remain competitive. This has been done in Colorado with the installation of an Outokumpu flash flotation machine for the production of a gold/silver/lead concentrate.

Jan 1, 1987

By William H. Pomroy

This report describes research leading to the design, prototype fabrication, and successful in-mine proof-of-concept testing of two improved stench fire warning systems for underground noncoal mines. The stench system, widely used in underground noncoal mines to warn of fire or other emergency suffers several serious shortcomings, including the toxicity of the odorant leading to debility in miners; reactivity of the odorant with iron oxide, resulting in unreliable warning because the odor may fade when transported long distances in steel pipe; lack of control over the rate at which agent is released into the air-stream, resulting in some work areas receiving unbearably high stench concentrations and other areas being missed altogether; lack of visual indication of system status, valve positions, or proper system operation; and excessively long stench transit times. In 1979, the Bureau of Mines, U.S. Department of the Interior, began research to upgrade the stench warning system. Two systems were subsequently developed which offer significant advantages over current systems.

Jan 1, 1984

By K. J. Stanaway

Environmental pressures on waste disposal are forcing pigment producers to use feedstocks with higher Ti02 content and lower levels of trace elements. Despite this, 50% of the world's Ti02 comes from ilmenite concentrates with only 37% to 54% Ti02. An industry growth rate of 25% in the next 10 years, combined with trends to diminishing resources and lower mining grades for rutile (95% P02) and leucoxenized ilmenite (55% to 90% P02), means that unless new discoveries are made soon, the industry will become even more reliant on ilmenite.

Jan 1, 1995