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By B. Waquet

The genesis of a hydrothermal subsea mound, by chimney debris heaping and mineralizing fluid circulating upward, induces a vertical maturation gradient. Connected porosity is easy to measure and, after mineralogical evidence, can be use as a maturation index. Thus, to understand how a rock property evaluates with maturation, it is possible to plot it against connected porosity. Results are that uniaxial compressive strength, Young's modulus, and in a lesser certitude tensile strength, abrasivity and hardness, increase very weakly with maturation until a maturation threshold (equivalent to a connected porosity equal to 0.2), and rocket to much higher values after it.

Jan 1, 2011

By L. A. Clark

Although vein-, syenite-, and pegmatite-type deposits are known in Saskatchewan, recent intense exploration stems from discovery of several exceptionally high grade uranium and uranium-nickel deposits locallized near the basal unconformity of the 1.3-1.4 b.y. Athabasca Sandstone Formation. Graphitic basement rocks and post-Athabasca faulting or brecciation coincident with the unconformity are important in locallizing uranium deposits which form as tabular, shoe lace-like bodies with grades averaging over two percent and containing up to 50,000 tonnes U308. Some deposits have similar nickel contents. A few published sandstone analyses average 0.8 ppm uranium while basement granitoid and meta-sedimentary rocks vary from 0.5 to 20 ppm. In the proposed genetic model, traces of uranium are leached from these rocks by oxidized formation waters sweeping through the sandstone and along faults. Solutions are reduced and uranium is precipitated as basement graphitic meta-pelites are encountered along brecciated fault zones.

Jan 1, 1979

By Salim Akhtar

The operation of a mineral processing plant with a complex flowsheet is represented by a mathematical operator. Such a representation permits a quantitative evaluation and monitoring of the separation processes in different sections of a processing plant, and gives an overall separation efficiency of the plant.

Jan 1, 1973

By André Vervoort

At the 2017 ICGCM-conference in Morgantown, WV, a case study was presented with measurements of the upward surface movements or uplift after the closure of two neighboring coal mines (Winterslag and Zwartberg, Belgium). One was closed in the sixties, and the other closed in 1988. The study was based on satellite data (Radar-interferometry or InSAR). The analyses showed both a significant variation of uplift values above the mined area and the surrounding zones, and a variation of the uplift rate as a function of time. In other words, the phenomenon of uplift is complex. At that time, it also was clear that more research was needed to better understand this phenomenon, e.g., an identification of the various mechanisms that are relevant for the process of uplift and the quantification of the various impacts. A systematic analysis of all relevant parameters resulted in a framework that forms the basis for the analytical calculations of uplift values. These calculations show that the main impact is due to changes in the hydrostatic pressure. However, the expansion of the softest parts, i.e., the collapsed or goaf material, is not only important, but the expansion of the (stiffer) non-collapsed strata layers due to a change in pore pressure also must be integrated into the model. For the case study, the partial flooding of the underground after closure of the mine that was abandoned in the sixties is integrated into the model. Larger stiffness values also are applied for this mine, in comparison to the values of the more recently closed mine. Overall, a very good correlation is observed between the InSAR-measurements and the calculated values along a north-south transect.

By Patrick Linehan

Vibration and air blast noise from blasting were evaluated during a research program which was sponsored by the U. S. Bureau of Mines. Blast variables were studied using small scale model (SCM) tests to evaluate specific variables as well as interactive effects, followed by experiments with production blasts at the surface coal mines. Experimental data showed that the primary variables affecting the ground vibration amplitude are the charge weight per delay and the length of the delay interval. Blast variables having a significant effect on the overpressure amplitude include the charge weight per delay, the length of the delay, burden and spacing, stemming amount and type, direction of initiation, charge depth and amount of detonating cord and cover.

Jan 1, 1980

By Aaron Jones, Guy Reed, Russell Frith

"In 2017, one of the international authorities on coal bursts, Dr. Chris Mark, published a paper entitled “Coal Bursts that Occur during Development: A Rock Mechanics Enigma,” in which several relevant technical issues were identified, the most pertinent being:i.whilst development coal bursts are commonly associated with geological faults, understanding which specific faults result in burst-prone development mining conditions and why, remains undefined.ii.conventional wisdom in relation to strong roof and floor geology of the coal seam might be limiting, based on certain burst examples in Colorado.iii. development coal bursts can occur without the local ground stresses being substantially elevated from their in situ levels.This paper outlines what is considered to be a credible, first-principles, mechanistic explanation for these three current development coal burst conundrums by reference to early published coal testing work examining the significance of a lack of “constraint” to coal stability and an understanding of how very specific structural geology and other geological features can logically cause this to occur in situ, albeit on a statistically very rare basis. This basic model is examined by reference to published information pertaining to the development coal-burst that occurred at the Austar Coal Mine in New South Wales, Australia, in 2014 and from the Sunnyside District in Utah, USA.The “cause and effect” model for development coal bursts presented also offers a meaningful explanation for the statistical improbability for what are nonetheless potentially highly-destructive events, being able to explain the statistical rarity being just as important to the credibility of the model as explaining the local conditions associated with burst events.The model could also form the basis for a robust, risk-based approach utilising a “hierarchy of controls” to the operational management of the development coal burst threat. Specifically, these include the use of pre-mining predictions for likely burst-prone and non-burst-prone areas, the use of the mine layout to avoid or at least minimise mining within burst-prone areas if appropriate, and finally the development of an operational Trigger Action Response Plan that reduces the likelihood of inadvertent roadway development into a burst-prone area without suitable safety controls already being in place."

Jan 1, 2019

By W. J. C. Venter

The use of activated carbon to improve the selectivity in the separation of base metal minerals from bulk concentrates played an important role in the development of separation techniques employed at Tsumeb Corporation's Tsumeb and Kombat mines. In this paper the Kornbat mill flowsheet and metallurgical data are given with particular reference made to the separation techniques using activated carbon. The mine's historical background, geology and mining methods are described briefly.

Jan 1, 1973

By Ben H. Daud

The systems optimization approach to mine planning has led to the adoption of a number of mathematical and computer models for short, medium and long range planning of mining operations. In the realm of open pit mine planning, the most common uses of such an approach have been in the areas of optimal pit design and planning of materials handling operations. Since a truck-shovel combination is the most widely used method of materials handling in open pit mines, a number of models have been presented in the past to analyze and optimize such systems. Broadly, these models can be divided into two categories. The simulation model, which is primarily used as an aid in analyzing the performance of either an operating or a proposed haulage system under the influence of externally alterable parameters, and the linear or integer model which is used as a tool for short or medium term optimization of the system under the operating constraints. In the first part of this paper, a brief discussion is presented of the linear/integer optimization models presented in the past, and in the second part a new model is described which is actually a combination of the simulation and the integer programming models. In its bare essentials, the model consists of an integer optimization algorithm, but the constraints are regularly and dynamically updated by incorporating the conclusions drawn from a stochastic simulation model of the mine haulage system. Since the successive optimization is performed by the mine operator who manipulates the constraints to guide the model towards the optimum, the mystical black box approach is minimized and should help in adoption of the model by the mine personnel. Also, by combining the stochastic simulation model and the deterministic integer model, some of the advantages of each are acquired.

Jan 1, 1976

By J. J. Snodgrass

Faults, sandstone channels, and abandoned mine workings present severe safety hazards, disrupt mining, and necessitate costly precautions or discontinuance of operations. In addition to fault detection, mining companies have a need to map discontinuities such as seam thinning and previously mined areas in both longwall and room-and-pillar operations. Initial field tests demonstrated successful generation and propagation of higher order guided wave modes. Theoretical studies indicate potential for improved resolution by sensing small details in the coal seam and roof structure. Controlled- waveform source transducers and specialized detectors are particularly useful to preferentially excite and detect the Love (SB) and Rayleigh-type (P-SV) waves, including the higher frequency modes. The distinct observation of reflections using the transducers in the shear wave mode makes feasible the detection of the water-filled voids.

Jan 1, 1984

By Ernst Langer

INTRODUCTION Morro do Niquel is located near the small town of Pratdáolis in the southwest part of the State of Minas Gerais, Brazil, about 300 km in a straight line north of São Paulo and 300 krn west of Belo Horizonte. The deposit is known since 1935. Systematic exploration started, however, only in 1957 and production with one furnace in 1962. Since 1969, after the installation of a second furnace, the mine produces about 2 500 tons of nickel, contained in ferronickel, per year. This production is now consumed totally by the Brazilian steel industry. The "Morro do Niquel" is a serpentinite stock of 900 by 400 m which rises 200 m high above the surrounding metamorphic rocks of Algokian age (see Figure 1). On top of the hill there is a leached barren zone of about 200 by 400 m, generally 20-30 m deep, which consists practically only of a boxwork of quartz colored brown by limonite. Surrounding this zone on the sides of the hill is weathered, decomposed serpentinite which contains about 213 of the economic nickel mineralization. Roughly 113 of the ore reserves lie below the leached overburden representing ore of a different type. The geological map and cross-section, Figure 2, give a clear picture of the occurrence.

Jan 1, 1979

By C. W. Matthews

Introduction Screening is an art, one of the oldest in the process field today, and one of the most widely used in our present age. Screening is being applied to an ever-increasing number of assignments, in an ever-expanding circle of industries. Screening is defined precisely as a mechanical process which accomplishes a separation of particles on the basis of size and their acceptance or rejection by a screening surface. Particles are presented to apertures in a screening surface and rejected if larger than the opening, or accepted and passed through if smaller. Screens are machines with screening surfaces used to classify materials by size. The screening surface is the medium containing the apertures for the passage of the undersize material. Screens are put to many uses - size separation, dewatering, desliming, media recovery, scalping, trash removal, washing, dedusting, conveying, concentration, and many combinations of these functions. It is interesting to note that screens are used for handling commodities

Jan 1, 1985

By Alex G. Sciulli

According to recent estimates, nearly 30 percent of the material from underground coal mining in the United States is rejected on the surface as waste. This accumulation of almost three billion tons of coarse and fine coal refuse is primarily from coal cleaning operations. The marketable coal is intermixed with sandstone, clays, shales, and carbonaceous rocks, which must be removed and disposed of in an acceptable manner. The disposal of mineral wastes is a major environmental concern. The most common types of environmental problems associated with coal refuse disposal are acid formation, erosion, and sediment control. Other areas of concern include air and water quality, combustion control, mine sealing, and reclamation. This paper focuses on these topics and attempts to outline special environmental features which can be incorporated into the design and construction of a coal refuse facility. Often these measures can minimize and possibly eliminate the potential environ- mental hazards. It is imperative, however, that these measures be adopted prior to and during construction, because of the relative ease and cost savings compared to post-construction implementation.

Jan 1, 1983

By Duluth Engineers' Club, Engineers' Club of Northern Minnesota

"During the last ten years great strides have been made, on the Mesabi Range, in the practice of beneficiating low grade iron ore material. By .beneficiation is meant all methods of removing impurities, and raising the iron content to a point where it can be sold in open market, the principal impurities being silica and moisture. The • general processes to which low grade iron ores are amenable are as follows:1. Thermal(a) Drying ; removes hydroscopic or atmospheric moisture. .(b) Calcining; removes carbon dioxide from iron carbonate, molecular water from hydrated hematites, and atmospheric moisture.Roasting; removes sulphur, carbon dioxide, molecular water and atmospheric moisture.Agglomeration; primarily for the purpose of preparing finely divided material for blast furnace; briquetting and sintering.2. MechanicalScreen sizing; removes rock and sand.Classification; removes sand by means of currents of water of varying velocities.Log washing; removes fine sand.Jigging; removes larger particles of impurities than is possible by log washing. Certain types of jigs remove fine sand.Reciprocating tables; recover fine iron particles from sand discarded by above processes.Magnetic separation; applicable to the commercial separation of the magnetic oxide of iron from gangue material. From a scientific standpoint it is possible to separate certain hematites and limonites from their gangue:(g) Miscellaneous processes; comprise dry concentration, electro-static separation and other processes."

Jan 1, 1920

By Howard M. Wells

Investment in minerals development usually entails big financial outlays. which will remain at risk for a long time before the venture can begin to generate a return cash flow. Before 'committing himself to such a venture the investor would be wise to carefully examine the possible consequences of his exposure to risk. In this context risk is defined in multiple terms, which relate the magnitude of possible loss with the probability that such loss may occur--normally the probability will decrease as the amount of possible loss increases. The analysis of risk is an essential component of the decision making process, especially so in the case of low grade high tonnage mining ventures where a very real possibility exists that future unfavorable circumstances may lead to losses that could cripple or ruin even the richest corporation. Wells (1979) postulates a rationale for making the investment decision under uncertainty based on the comparison of two independent risk criteria: 1) the risk inherent in the venture represented by the negative portion of the cumulative distribution of the net present value (NPV), as derived by a stochastic evaluation procedure, 2) the limits of risk the decision maker is willing to accept, taking account of the financial capacity-of the 'firm to absorb various levels of future cash shortfall should the venture prove disappointing. The chance the investor would be prepared to accept can be expected to decrease as the amount of the possible shortfall increases. The limits of acceptable risk are-defined by a curve called the "LL-curve" which can be directly compared with the cumu¬lative NPV curve. A positive investment decision is implied if the limits of acceptable risk are not exceeded.

Jan 1, 1982

By Michael R. Birkos

A new electrotelluric prospecting technique allows the mapping of ore body distribution, lithologic contacts, and voids with accurracy comparable to core drilling. Data is available almost immediately and presented in a format similar to a downhole log. This is done with a passive surface receiver that transduces electrotelluric radiation into an audible signal. Changes in the character of the audible signal lends insight into lithology, porosity, fluid type and medium. Three case histories are presented. The first delineated a paleochannel within a coal seam. The second traced old mine workings and backfill areas. The third identified a high-pressure karst void.

Jan 1, 1986

By Daniel C. McLean

Chemistry plays a more important role in milling operations than is generally recognized, particularly in fluid- solid separation processes. Chemical aspects are also very important insofar as plant water quality is concerned, and in the manner in which this water quality effects plant design and operation. Aside from the inherent chemical characteristics of plant water, the mineral preparation industry is becoming increasingly more dependent on the use of mining chemical reagents--relatively new to the coal industry, but items of I standard usage in complex metal recovery plants. These chemicals have many useful properties and can produce significant improvements in operations and metallurgical efficiencies when used properly and intelligently. They can produce poor results and sometimes severe losses when used improperly. Most reagents are relatively expensive on a per pound basis, hence costs can be excessive if they are used wastefully or inefficiently.

Jan 1, 1968

By Jean-Marie Deschamps

In an approach to the complicated study of bauxite from Les Baux de Provence it is necessary to consider the paleogeographical context of all the bauxites in southern France. These bauxites are of Karstic type, belonging to a metallogenic area extending from the Pyrenees Mountains to the Alpine Massif. Within this area each deposit does not always correspond to the same geological period. There are differing opinions regarding the origin of Karstic-type bauxite and a discussion of these various theories is beyond the scope of this paper. Bauxite of Les Baux, in Provence, was discovered in 1821 by the chemist, Berthier, near this picturesque village located in the region of Arles. It is Les Baux from which the name of bauxite originates. For a long time this bauxite was of no interest because of high silica 'and mediocre alumina content. Besides, the calcium carbonate content is somewhat high and is one of the main characteristics of Les Baux bauxite. The problem of exploration of the Les Baux deposit has been to prospect minable zones according to traditional norms where silica and carbonate are low.

Jan 1, 1977

By J. Richard Kyle

Salt domes, their cap rocks, and the adjacent sedimentary strata represent a major economic resource in the Gulf of Mexico basin. Gulf Coast salt diapirs formed in response to sediment loading of the "mother" Louann evaporite sequence of middle Jurassic age, an effect that is caused by the buoyant nature of the lower density salt. Halokinesis progresses from nonpenetrative deformation that creates broad "pillow" structures into discrete high-amplitude diapirs. Because of its buoyancy, the top of the salt diapir remains near the land surface or the seafloor during much of its history as the basin floor subsides. The salt within the Gulf Coast diapirs is deformed complexly and commonly shows subvertical banding that represents modified sedimentary layers with different contents of nonhalite components. The most abundant impurity is anhydrite, which occurs as individual millimeter-scale crystals or as deformed clasts that generally form about 5% of most salt stocks. Many mature salt diapirs are mantled by a "cap rock" that consists of a lower anhydrite zone and an upper calcite zone, commonly separated by a discontinuous gypsum-bearing zone. The anhydrite zone forms as accreted layers of anhydrite grains and clasts that are left after episodes of halite dissolution. The calcite zone is a product related to petroleum destruction accompanying bacterial reduction of aqueous sulfate. Calcite-cemented siliciclastic strata occur above or alongside diapirs. The mineral resources of the salt-dome setting are remarkably diverse. Major economic products of the salt-dome environment are salt and cap-rock-hosted native-sulfur deposits, as well as petroleum resources that occur on the dome flanks and in the cap rock. Native sulfur forms as a result of bacterial sulfate reduction accompanying petroleum destruction to form hydrogen sulfide, which is subsequently oxidized to elemental sulfur, major amounts of which have been produced by the Frasch process from Gulf Coast salt-dome cap rocks. Some cap rocks have produced limestone, gypsum, and anhydrite for a variety of construction uses. Although traditional industrial-mineral resource production from Gulf Coast salt domes is shrinking, some cap rocks host potentially commercial concentrations of celestite and barite, as well as the metals Zn, Pb, and Ag. Furthermore, caverns, excavated within the salt stocks, serve as major storage facilities for crude oil (including the Strategic Petroleum Reserve), liquefied petroleum gas, and natural gas. These resources are products of fundamental geologic processes that are integral to the evolution of the Gulf of Mexico basin. Whereas production of some industrial-mineral resources, such as elemental sulfur, has declined in recent years, ample reserves of salt will allow production to continue into the foreseeable future. Further, there is potential for other mineral-resource production from cap rocks under favorable economic circumstances. Expanded use of caverns, excavated in the salt masses for material storage and disposal, is likely to continue into the next century.

Jan 1, 1999

By D. D. Young

During the 1970's a number of covered storage facilities were constructed in North America to store and handle large quantities of bulk, solid materials. This trend, away from outdoor storage piles, will probably continue at a stronger pace in the 1980's. This paper attempts to answer some of the questions often raised about the economics of large covered storage facilities. The paper is in four parts: 1. Why Build a Storage Facility? 2. 2. Common Components of Storage Systems With Details of Six Storage Facilities 3. Results of a Study for 50,000 Mg Clinker Storage 4. Guidelines for Conducting a Study to Select a Storage System.

Jan 1, 1980

By H. T. Kang

Various geological anomalies are encountered in underground longwall mines, and they cause stability problems. In this study, a number of detailed two-dimensional finite-element models were made, consisting of mine floor, roof, coal seam, shield structure, gob, etc. to analyze the influence of geological anomalies on longwall shields. Two different categories of anomalies were simulated. The first ones are shear zone and sandstone channels, with variable sizes and locations in the roof. The second category is fault or fracture plane, with variable friction factors, locations, and orientation of the fracture plane. The results of the analyses are' integrated with an artificial intelligence system for developing a forecasting guideline for prevention of underground hazards due to the existence of geological anomalies.

Jan 1, 1996