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By F. F. Peng

For a given flotation system, the rate-controlling step in fine coal flotation can be the attachment of bubble to the fine coal particles. The probability of attachment depends upon the surface characteristics and the collector adsorption on the coal particle surfaces. Thus, to further improve the flotation rate and selectivity is to alter the distribution of hydrophobicity on coal particles efficiently by applying the effective means of collector dispersion. In order to enhance the combustible recovery and selectivity of fine coal flotation, and lower the amount of collector used in the fine coal flotation processes, four modes collector dispersion/addition techniques are tested. They are direct liquid addition in pulp (mechanical agitation), ultrasonic energy dispersed collector into pulp, atomized collector into pulp and gasified collector transported by air and formation of collector-air bubbles in pulp. The effect of four collector dispersion/addition methods on the floatability of -600 µ m (-30 mesh US sieve) coal samples from four ranks of coals were studied. The ultrasonic energy dispersed collector and atomized collector flotation processes enhance flotation yield and most significantly improve the kinetics of fine coal flotation. The gasified flotation process can increase the selectivity of separation and decrease the collector consumption due to starvation flotation is achieved in this process. The flotation efficiency of gasified collector process is as high as that of conventional flotation. It is because that the effect of the decrease in the combustible recovery is offset by the increase of selectivity. In addition to flotation experiments, induction times of bubble attachment to the bed of fine coal particles for four ranks of coals are measured.

Jan 1, 1992

By Innocent John Arinze, Chidubem Okwudiri Emedo

This contribution presents the first multi-scale geophysical investigation conducted in the Abakaliki and Obubra mining districts (AOMD), southeastern Nigeria, for the exploration of shallowly emplaced (< 50 m) massive sulfide and barite mineral deposits. Raw airborne magnetic data covering the AOMD was acquired and subjected to diverse enhancement routines to facilitate the identification of areas of subtle magnetic anomalies for subsequent ground truthing. The mineralization is mainly made up of galena, sphalerite, and barite. The contrasting physical properties between these minerals and their host rocks make resistivity, induced polarization (IP), spontaneous potential (SP), and magnetic methods ideal to study and delineate the mineralization and possibly locate the ore bodies. Wenner DC resistivity and IP data acquired along the same parallel traverses are inverted using Res2dinv to produce 2D tomography models of resistivity and chargeability. The resistivity and IP models were successful in delineating zones of sulfide and barite mineralization. The ground SP data collected along the same traverses as the resistivity and IP data were interpreted as line graphs. The 1D SP models show a number of central negative anomalies that could be related to sulfide mineralization. These anomalies show fair-to-good spatial continuity and are in close agreement with the result obtained in the resistivity and chargeability model. This study suggests the presence of exploitable mineral deposits in the AOMD and demonstrates the superior interpretative ability of combined geophysical methods over a single geophysical approach.

Oct 20, 2020

By E. W. Greig

This paper is an account of exploration for bauxite in the Amazon Basin, Brazil, and particularly of the discovery, exploration and development by Alcan of the Trombetas deposit so a general account of the Trombetas Project has already been published in E/MJ (Anon. 1975) to which the reader is referred for details on owner-ship, infrastructure and construction as well as the proposal for mining and treating the bauxite. It is impossible to consider the Trombetas deposits in isolation. A regional account of bauxite in and around the Guyana Shield and the northern portion of the Brazilian Shield is included and it is suggested that these deposits all formed during Tertiary time under similar conditions.

Jan 1, 1977

By J. Fuller, J. Beale, Q. Justice, Z. Agioutantis, S. Hicks, Z. Khademian

Seismic events can be induced by mining due to unstable rock failures or slips along geologic structures leading to the sudden release of strain energy stored within the rock near underground openings. Depending on their intensity and proximity to the working area, seismic events may raise safety concerns, and thus the forecasting of the seismic potential in advance of mining can mitigate safety hazards. The integration of seismic data into geomechanical modeling can provide a tool for identifying areas with elevated potential for seismic activity. In previous works, a methodology was developed to forecast seismic potentials in a pseudo-2D geomechanical model. In this paper, seismic events, ranging in magnitude from about -1.0 ML to 3.7 ML, recorded in a deep longwall mine (> 450 m) in Virginia during mining of six adjacent panels, were evaluated to identify areas where larger magnitude events (> 1 ML) had occurred. A three-dimensional geomechanical model of the same area was constructed in the 3DEC software to calculate the state of energy in the system with the progress of mining along the entire length of each panel. The variation in the energy content of the model was monitored, and zones with potentially damaging slip-type events along bedding planes followed by compressive-type events in the sandstone roof are the mechanism for large seismic events in the studied mine. The locations of anomalous events corresponded to the regions where both compression-type SPI (C-SPI) and slip-type SPI (S-SPI) were elevated. The modeling results were compared with the recorded seismic events to evaluate the model performance in forecasting the seismic potentials. The model was able to forecast 100% of regions with elevated and moderate seismic potential and 89% of regions with low seismic potential. This shows the applicability of energy balance calculations for forecasting the approximate location and timing of destructive seismic events in advance of mining.

Jun 25, 2024

By Stephen L. Bolivar

The Prairie Creek intrusion, near Murfreesboro, Arkansas, is the site of the only commercial diamond mine in North America. Three major lithologies are associated with the intrusion, a hypabyssal peridotite, a volcanic breccia in .which the majority of diamonds occur, and associated tuff. Previous studies, including mining history, geological, geophysical, petrological and whole-rock and mineral chemistry are reviewed. The recent suggestion, by other workers, that this intrusion may be more correctly called a lamproite is examined and supported. This has serious implications for diamond exploration in Arkansas and elsewhere in the U.S.

Jan 1, 1984

By Carl G. Hogberg

To the casual observer there is probably no simpler appearing operation in the mineral industry than a limestone quarry. It might seem that the entire operation - from the drilling, blasting, and loading of the stone, its transport to a mill for crushing, washing and sizing, to loading into boats, railroad cars, or trucks for delivery to customers - can be comprehended at a glance. But no first impression could be more misleading. It is one of the purposes of this presentation to sketch the broad outlines of the extensive limestone industry in the United States which, measured in terms of volume of production since the end of World War II, has grown almost 300 per cent to a national level in 1957 of 384 million net tons.1 Another objective will be to discuss in more detail this industry in the State of Michigan. For this latter purpose, the Michigan Limestone Division plants at Calcite and at Cedarville will be used as examples. These descriptions will, we believe, show that the limestone business has complexities to match its size.

Jan 1, 1962

By D. S. Dinsmoor

Boron, estimated to comprise about 0.001 percent of the earth&apos;s crust (Fleischer 10), as an element is never found free in nature, although its compounds are found in many localities. the borates are the most important. Sassolite (B(OH)3) and boracite (Mg6C12B1406), non-borates, are-of-minor importance. The crystal structures of most natural borates are still unknown. A classification based solely on the ratio of boron to the total number of cations has been devised (Palache 28). This classification divides the borates into four, sub-groups; anhydrous borates, hydrated borates, borates containing hydroxyl or halogen and compound borates. Only four or five minerals of the hydrated borates group have ever been used commercially. In more recent years, the sodium borates have comprised all but a &apos;small fraction of all borates used. Borax, the hydrated borate compound, is the most important of all boron compounds. It has been used so long and so often that the layman often confuses borax and boron and, applies the terms synonymously.

Jan 1, 1958

By Juan J. Monsalve, Mario Karfakis, AMAN SONI, Nino Ripepi, Jim Hazzard

Pillar collapses are events that due to their severe consequences can be classified as high risk. The design of pillars in underground room-and-pillar operations should migrate to risk-based design approaches. The authors of this work proposed a risk-based pillar design methodology that integrates stochastic discrete element modeling for pillar strength estimation, and stochastic finite volume modeling (FVM) for stress estimation. This paper focuses on the stochastic FVM component for stress estimation. The mining and geomechanical aspects of a case study mine (CSM) are described and pillar stresses are estimated by using three approaches: (1) analytical solutions, (2) 2D finite element modeling, and (3) 3D finite volume modeling. This operation extracts a 30° dipping deposit, which makes current underground stone mine design guidelines inapplicable for this CSM. This work compares results from each stress estimation approach and discusses uses the point estimate method as a simplified stochastic approach to evaluate the effect of rock mass elastic properties variability on pillar stress distribution. Results from this work show that the three estimation approaches lead to different estimations, possibly, due to the wide range of assumptions each estimation approach considers. It was also determined that the horizontal to vertical stress ratio has a significant impact on pillar stress magnitude. Therefore, it is recommended to perform in situ stress measurements, or assume worst-case-scenario values to account and reduce uncertainty due to this parameter. The stochastic stress estimation approach used in this paper provides results that can integrate a risk-based pillar design framework.

Sep 24, 2022

By Mirjana Boskovic

LKAB’s Kiirunavaara Mine is a sublevel caving iron-ore mine located above the polar circle in northern Sweden. The mine has been proclaimed seismically active since 2008 after a magnitude 3 seismic event, according to Swedish National Seismic Network (SNSN). At that time the Kiruna Mine did not have mine-wide seismic system. Since then, the Kiruna Mine experienced several damaging seismic events of which the largest one on the May 18, 2020. The magnitude, based on the moment tensor inversion results on data from the SNSN as well as seismic stations in Finland and Norway, is estimated to 4.2 ± 0.2 moment magnitude. The seismic event on the May 18, 2020 was located in the middle of the one of the productions areas and caused the major damage in the mine, damaging several kilometres of drifts on six mining levels, some of them beyond the practical repair. These damages affected four of ten production areas on several levels, some more some less. Luckily, no person got injured from the seismic event and the very long aftershock series. An important part in the whole process after the seismic event was information flow and decision-making process. It was very important to keep workers and community informed as that contributed transparency of decision-making and decreased the speculations. Resuming the production in the damaged areas in the safe manner, very soon become main focus for the mine management. It was obvious that not only rehabilitation of the areas is needed to resume the production. It was A MUST to understand the factors behind the seismic event and its mechanism to be able to avoid same situation and prevent seismic event of similar size. Mine engineers had to think outside the box to find the solutions to ‘rescue’ every drift that they could to be able to make good enough base for continued mining of the area. The paper describes actions taken in a very complex process of recovering the area that we from the beginning thought need to be abandon. Seismological analyses of the event on May 18, 2020 and past activity in the area, damage mapping, detailed studies of structures and geology, numerical modelling as well as engineering judgement were used as base for all our decisions how to proceed in attempt to restore mining of the area heavily damaged by 4.2 moment magnitude seismic event, in a safe way.

Apr 26, 2022

The Colorado portion of the Rio Grande rift is clearly defined physiographically from the south in the San Luis valley northward to the latitude of Leadville where sediments of the Dry Union Formation (Tweto, 1961) accumulated within the subsiding rift zone. To the north of Leadville is a system of faults active in the late Tertiary, including the Mosquito fault that offset a portion of the Climax mineralization (Wallace et al., 1968). Tweto (197B) describes remnants of Dry Union Formation against the Mosquito fault north of Dillon in the Blue River valley, so it is apparent that the rift and associated sediments extended well to the north of Leadville. Kelley (1952, 1954, 1956) and Chapin (1971) have noted in New Mexico that the Rio Grande rift is a series of en echelon basins, offset to the east, with constrictions connecting them (Fig. 1). In Colorado the structural basins are offset to the west. The net effect of all the rift zone basins in New Mexico and Colorado is an arcuate pattern (Fig. 1) abutting the Colorado Plateau and Sari Juan Volcanic Province on the west. The width of the rift system gradually decreases northward to about Leadville where rift definition is not apparent.

Jan 1, 1987

By Wen H. Su

This paper examines the intrinsic mechanisms of cutter roof by combining field investigation, laboratory testings, underground instrumentations, and numerical modelling. Cutter roof developed during the development of a set of longwall panel entries in a West Virginia coal mine was presented as a case study. Mining alternatives applicable to the mine are recommended. Cutter roof occurred in two other West Virginia coal mines were also investigated Detailed comparisons were made among the three cases. As a result of the extensive investigation, intrinsic mechanisms of cutter roof failures under various conditions are presented from the practical and theoretical points of view.

Jan 1, 1985

By Walter E. Heinrichs

Early history of the district is typical of many, particularly in Southwestern United States. The usual early Spanish influence was felt; Marcos de Niza, Coronado and Father Kino are most notable, but authentic records regarding Spanish mining activities are sparse. About 1769 the Indian village of Tucson became a Spanish settlement. During the next century prospecting attempts were largely interrupted by the Indian, Mexican and Civil Wars. By 1870 Tucson had a population of 3200 and by 1880 the Southern Pacific Railroad extended all the way from Los Angeles. Pyrometasomatic copper ore was first produced with some local direct ore smelting done during the late 1800s. By 1907, a rail line was built from the Twin Buttes mines to Tucson by the Twin Buttes Mining and Smelting Company. World War I was a very active period, with mixed copper, lead, zinc, gold and silver production. This came mainly from underground replacement and contact metamorphic deposits and from practically all portions of the district. Some of these operations continued intermittently until the 1929 depression.

Jan 1, 1976

By J. Philip Neal

Feldspar is no example of special mineralization in isolated spots: it can usually be found within a mile or so of almost anywhere. Along with silica sand, it is a major part of our world&apos;s total mineral composition. This fact imparts to it an economic status different from a sulfide ore, or potash, or phosphate. While every feldspathic "stringer" does not possess economic potential, the generous distribution does yield a high statistical frequency of good feldspar ore bodies: the adjective "good" being subject to some flexibility of interpretation. The strong chemical bonds of this alkali aluminum silicate give it certain use advantages, but under present technology its individual elements cannot practically be separated to create aluminum, potassium, sodium, silicon - or their oxides. Its present uses rely upon chemical inertness - as in fillers; and on its physical melting characteristics and their effect in glass, enamel, or ceramics.

Jan 1, 1973

By Hans von Michaelis

The renaissance in extractive metallurgical practices for gold and silver recovery is far from over. This is one conclusion of a three year investigation into innovations in Cold & Silver Recovery by Randol International Ltd. (1981, 1983). The six volume reference report reviews a host of new processes and innovative applications of older metallurgical practices. Some of these were summarized by von Michaelis (1982, 1982a). There are several reasons to expect this renaissance to continue. One reason is the nature of gold and silver deposits. The list of known occurrences of These metals is very extensive. There are literally tens of thousands of prospects but over 99% of these are too low grade, too small or too refractory for a viable operation employing conventional processing.

Jan 1, 1983

By Keith Wallace

Although systematic control of ventilating air currents in underground mines dates back to the Greek and Roman empires, quantified analysis dealing with the cost of providing airflow did not appear until about 1860 when the first fans with acceptable efficiencies became available. Initially, these were introduced to avert methane explosions initiated by shaft bottom furnaces. However, discussions arose on how much coal the steam driven fans consumed in comparison with shaft furnaces in order to produce the sane amount of airflow. Ventilation economics had arrived. In 1981/82 a project was funded by the Department of Energy and carried out at the University of California, Berkeley in order to analyze and compare alternative ventilation designs from the viewpoint of economics and systems efficiency1. This paper highlights some of the results of that study.

Jan 1, 1983

By Bruce R. Lipin

Chromite, the only ore of chromium, occurs almost exclusively in mafic-ultramafic rocks and their weathering products. However, not all kinds of mafic-ultramafic rocks are favorable hosts for possible low-grade chromite deposits. For instance, chromium-bearing basalts are not favorable because they commonly contain < 0.3% Cr2O3, and chromite is almost always less than 50 um in diameter, if it is present at all. Chromite-bearing ultramafic rocks in stratifonn and alpine complexes tend to be either ore grade (> 25% Cr203) or very low grade (< 2% Cr203); intermediate rocks are scarce. In most complexes large tonnages exist only in the < 2% Cr2O3 group and the composition of the chromite is commonly unsuitable for metallurgical use. Some nickel laterite districts contain more than 108 tons of material with 2.0% to 5.5% Cr2O3, and hence, chromium could be a byproduct of nickel in some laterite districts.

Jan 1, 1982

By L. R. Stoiser

The mineral resource potential of the Los Bronces deposit was successfully evaluated by an intense, coordinated program over a 37-month period (April 1978-May 1981) as part of an economic feasibility study. The program included more than 120 km of core drilling, 63 km of access road construction under adverse topographic and climatic conditions, detailed geological mapping, plus other related activities. This Tertiary-age copper-molybdenum deposit is composed of an earlier mineralized porphyry-type body intruded in part by a large complex of mineralized hydrothermal breccia pipes. Both intrusive and extrusive igneous rocks are present. Erosion, oxidation, leaching, and supergene enrichment of copper have resulted in a deposit now exposed at the surface that contains more than 368 Mt grading about 1% copper equivalent as sulfides.

Jan 1, 1982

By G. K. Derby

Paper presents project results investigating current techniques for dragline wire rope removal and the development of less hazardous means of performing the task. The cannon is the most prevalent method used in American surface mines. A cannon test program was conducted that used 40-and 50-grain primer cord to establish force produced using a 56-pound projectile. Socketlwedges were separated to establish separation force data. Two alternative removal methods, pendulum ram and portable hydraulic pusher, were developed and tested. Both provide sufficient force to effect separations under normal conditions on draglines with up to 78- cubic yard buckets.

Jan 1, 1984

By William R. Bond

The pressure/vacuum lysimeter is being used as an effective vadose zone monitoring device for mining heap leach facilities, tailing disposal ponds and tailing waste sites. Their use has proven reliable for baseline data collection, early warning leakage detection and analyzing geochemical variations in the vadose zone. The lysimeter structure utilizes a closed cylindrical chamber made of PVC or inert material. The soil water intake portion of the cylinder is made of a porous material of low permeability. The application of vacuum or pressure to the unit is via two access tubes from the ground surface. Available soil moisture is drawn by vacuum through porous material into the lysimeter chamber and then collected from the access tubes. Case studies show their usefulness for monitoring around a uranium tailing pond constructed in glacial till material, under heap leach pads and pregnant, barren, and overflow ponds, and investigating the movement of contaminant moisture through old tailing deposits. Relatively easy to install and sample, regulatory agencies and facility operators are accepting and negotiating for their application as a site integrity monitoring device and unsaturated zone research tool. Their use at heap leach facilities lends credibility to solution balance calculations when considering a leachate loss of 5 or 10 percent can make or break a mine&apos;s profitability.

Jan 1, 1984

By Lancelot E. Kun

The high-rate floc blanket clarification process developed by the Anglo American Corporation of South Africa is capable of continuously clarifying gold and uranium pregnant solutions containing 200-2500 mg/L suspended solids to below 25 mg/L solids at an average rising velocity of 8 m/h at the low process cost of R0,001-0,002 per ton of liquid treated. Overall process cost savings are mainly due to increased polishing filtration cycle times.

Jan 1, 1984