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By Louis I. Briggs

Evaporite rocks, salts of the more soluble ions in seawater, are deposited when seawater becomes concentrated by excess evaporation in marginal basins having restricted circulation with the open sea. The simple conceptual model of an evaporite basin (Figure 1) has a single inlet connecting the basin to the open ocean, the restriction to open circulation being caused by a bar or reef near the mouth of the inlet. As the oceanic water flows from the inlet into the basin it tends to form a thin layer of brine that spreads out over the surface of the basin brine, and as it does so, the salt concentration In the surface layer gradually increases owing to continued evaporation of the water. When the solubility products of the salts in the surface layer are exceeded, the salts precipitate and settle to the bottom of the basin, The order of precipitation follows their order of least solubility. Normally the carbonates separate first, followed by the sulfates and chlorides and the more complex double salts. In nature there is considerable overlap in their ranges of precipitation. The water flow in the basin, also shown schematically in Figure 1, diverges from the inlet essentially perpendicular to the lines of' equal salinity in the surface brine. The distribution of salts deposited in such a model will parallel the isosalinity lines, being arcuate and concave toward the inlet (1)

Jan 1, 1967

By I. J. Dowdeswell

Perspective Man is a model maker. Throughout recorded history man has-used models both to provide insights into the workings of the processes which surround him and as a step towards the eventual control of those processes. These models have covered the field from extremely large systems (solar and celestial. models) to infinitesimally small systems (sub-atomic .and atomic models). Models have been developed for social systems, ecological systems, biological systems and economic systems: all fields of human endeavour contain the fruits of this restless model-making. The Role of Models Since the evidence of mans' industry in formulating models is so abundant, it is worthwhile stating some of the reasons. Based on the simple definition that "a model is a convenient and useful representation of some facet of the 'real' world", then a model provides a means for: 1. Understanding the thing being studied. 2. Communicating that understanding to others. 3. Manipulating the thing being modelled. The common denominator implicit in these reasons is that- improved control is the. objective off all modelling or simulation work. Improved control shows itself either directly by the development of devices which perform the control functions or indirectly by improvement in the decision making process itself. For example, in a process plant, a suitable model of part of the process could lead either to the use of automatic control devices such as set-point controllers or to the implementation of instructions (pre-defined decisions) which permit the operator to better control the process. Typical process control systems use both of these since fully automatic control is restricted to processes where the required information can be effectively measured.

Jan 1, 1972

By I. S. Parrish

Locating and defining an ore body with minerals or metals that can be recovered at a profit is the objective of minerals exploration. Direct exploration involves examining and sampling rocks either in outcrop, underground exposure, drill core, or cuttings. Indirect exploration infers the measurement of some physical, chemical, or biological factor that reflects the possible presence of the metal or mineral of interest, or a structure that may act to collect, concentrate, or otherwise favor the presence of the desired commodity. Included here are all forms of geophysical, geochemical, or geotech-nical prospecting. In recent years, indirect exploration has given rise to an impressive number of specialists and a variety of techniques. Less impressive is the success rate or productivity of the modern explorationist. Exploration Productivity Losing Ground Judging from the low number of mine openings or mine discoveries in recent years, the exploration industry is not as productive as it once was. Many will take umbrage at this judgment, but a review of the literature will support this statement. In Canada, from 1951 through 1960, there was an average of 5.6 discoveries a year. From 1961 through 1976 there were only four a year. This nearly 30% reduction occurred despite a massive increase in exploration funding. From 1950 to 1955, the Canadian mining industry spent $5 million (1975 dollars) for each minable deposit found. During the period 1970 to 1975, the cost was $25 million for each one found. The industry was spending five times as much and finding 30% less than a generation earlier. This is not indicative of a productive endeavor. The loss in productivity is even more apparent to explorationists who wander the western US, and are awed by the thoroughness and discovery rate of those early prospectors who explored from 1850-1920. The "old-timers" missed very little. They used pans and crude chemical tests in place of plasma or X-ray fluorescent assay techniques. But, they found ore bodies that led to mines. Today, the best prospecting areas are pockmarked by the hand dug pits, trenches, and shafts left by our predecessors. The success or productivity of the old-timers may be attributed to any or all of several factors. Granted, they were looking at virgin ground and at deposits that in many places were exposed. The factor most critical is, however, that they employed direct exploration methods. They walked over areas of interest, traversed swamps and mountains, and followed "colors" in stream gravels to their source. They also chipped rocks, dug pits, trenched along structures, and followed the "leads." Many of today's explorationists, on the other hand, adopt a more sophisticated approach. A geologic model is conjured up so the exploration team "knows" models, but the model should be applied at a later stage in the exploration effort. J. D. Ridge has written an excellent article on the role and timing of models. Geologists should collect and assemble data, facts, and observations and fit these into a model and not conceive a model and seek data to prove their vision. Further, many exploration managers are adept and talented at devising exploration programs. They can program and use modern exploration techniques and tools. They can apply these and their modeling capacity to assemble a glittering array of targets. It would appear that in all too many instances, creating targets has been equated with and is considered being productive. As noted, finding ore bodies is being productive in exploration. Creating targets may or may not lead to ore bodies. As an end result, locating targets is not productive exploration. How then does one foster productivity in exploration? Some suggestions are to increase the use of direct methods, follow the methods and philosophies of old-timers, look at more rocks, do more field work, use foot traverses, and do more drilling. It may be argued that this is what the old-timers have done and we would then be hoping to find

Jan 11, 1983

By D. R. Forshey

Although the United States has the world's largest coal reserves, most of those reserves will require underground mining. Unless underground injury and fatality rates are reduced, the number of disabling injuries and accidental deaths will grow as coal production increases. The Bureau's Mining Research Program, designed to reduce the exposure of workers to hazards while improving productivity, is described. Major program thrusts are 1) re- moving the hazards or removing miners from the areas in which hazards exist, 2) developing ways to improve management decisions and mining skills so as to reduce the incidence of situations requiring human involvement in hazardous, emergency, or corrective tasks, and 3) improving, or at least maintaining, productivity so that both the tangible (dollar) and intangible (human) costs are reduced. In these ways, projected demands for coal can be met using resources without an increase in human suffering.

Jan 1, 1987

By John C. Cook

In reasonably dry rock, long-wave radar can theoretically explore to distances approaching 75 meters (250 ft). High-resolution radar reflections have already been demonstrated through 13 m of hard limestone, through 9 to 18 m of coal in place and through 225 m of rock salt, using only low-power experimental radar equipment. Radar reflections have been received through the rock from rough pillar walls, from faults, and from a slim, uncased, vertical drill hole. In three years of intermittent experimentation, the feasibility of rapid radar exploration of large volumes of rock, with portable equipment, in deep, wet workings has been demonstrated. With future, improved equipment the theoretical working range, of the order of 75m, is expected to be attained in most hard rocks. THE TECHNIQUE Fig. 1 illustrates an early "monocycle" radar system (1) set up in a coal mine. This radar equipment is entirely different from that employed for detecting distant objects through the atmosphere. However, the basic principle is the same: a pulse of electromagnetic energy is radiated by the transmitter, a portion is reflected by some "target" object embedded in the surrounding medium and some of this energy is collected by the receiving antenna. In the receiver, the pulse is amplified, is "stretched out in time" by a sampling process, and is displayed on the screen of a cathode-ray oscilloscope. It may also be recorded on paper or magnetic tape. Fig. 2 illustrates a

Jan 1, 1997

By Viktor Tokle, C. W. Dawson

The Devico directional core drilling system and its capabilities are described, with reference to other directional drilling technologies and the advantages and disadvantages of these systems. The advantages and disadvantages of a number of borehole navigation systems are also presented. A discussion of the applications of the technology follows, illustrated by case histories. Finally, the environmental impacts and benefits of the technology, in comparison to more conventional systems, are presented.

Jan 1, 1999

By John L. Bolles

The mineral processing engineer must have some knowledge of mineral identification, and the greater his knowledge in this field, the greater will be his potential to do his own specialty well. Most metal-bearing ores and industrial minerals require processing of some kind to produce a salable product or a material suitable for further processing. The types of treatment are many, but each one is aimed at separating a mineral or family of minerals from others. Obviously, then, it is basic to all mineral processing to identify the minerals present in the raw material and in intermediate and final products resulting from processing. Very often the mineral processing engineer will enter planning while exploration of a mineral prospect is going on. He will examine hand specimens, drill cores and cuttings, bulk samples, and materials in place. He must identify the valuable minerals, their occurrence and associations with other minerals, and the identity of diluents or host rock. An exact and detailed knowledge of the raw material will usually suggest the treatment processes that should be investigated in the development of the most suitable scheme for that particular raw material in that particular location. Physical properties of a mineral often lead directly to a process for separating that mineral from others. Some well-known examples of these are: magnetic separations for such minerals as magnetite, rutile, ilmenite; gravity separations for gold, silver, galena. cassiterite; flotation separation for most sulfides; distillation of mercury from cinnabar; and selective dissolution in specific solvents such as halite or sylvite in water, gold and silver in cyanide solutions, copper oxides, carbonates, sulfates and silicates in dilute sulfuric acid. These processes and many others are described in detail elsewhere in the Hand¬book and so it is not appropriate to give details here, except to emphasize that processing is aided greatly by complete mineral identi¬fication. Developing a treatment scheme for a new mineral discovery is an exciting assignment fag the mineral processing engineer, but much more of the usual work relates to quality control in existing plants. Here too, mineral identification is important. Some processing is aimed toward producing an end product which will meet exacting specifica¬tions regarding purity or allowable diluents. In this situation it is vital that contaminants be identified so that the process can be adjusted

Jan 1, 1985

By N. I. Fedunets

The development of variousworks on automatising of operational processes at coal¬extractive and coal-mining enterprises introduces an ever growing necessity to carry out investigations in the wide range of problems concerning the possibitity of joint functioning of different levels, which seems impossible without the use of integrated systems of passing on and prossessing the information on the basis of modern calculating machines and other means of automation. This view on the problem of automation of the enterprise operation presupposes that the structure of automated operational dispatcher control (AODC) should be very closely connected with that of integrated data processing system! In this case the AODC structure from the point of view of automation of its functions (or operations), i.e. from the point of view of informational techniques coinsides in general with the structure of dispersed information and calculating network (ICN), realizing the passing on and processing of the information as well as solving the functional tasks on the basis of local calculating networks of electrical calculating machines with correspond to different levels of AODC and located with regard to productional hierarchy of operational dispatcher control (ODC). In this approach however the use of dispersed, ICN gives opportunity to. realize the possibility of action only with realisation on the CM of algorithmic' task of ODC, when a dispatcher 'is the lastto make a final decision.. At the mining enterprises it's rather difficult for a dispatcher to make a final decision because of the great variaty of productional situations, the presence of contradictions and a number of other subjective factors which often lead to the dispatcher's mistaks causing great material losses of the enterprise. Hence the necessity arises to automize and formalize making a decision and including the expert systems (ES) into the ontour of AODC, which enables the dispatcher 2to get a neeessary advice in different situations, especially in case ofemergency on the basis of establishing the mechanism of logical layout of non-formalized data base (DB) procedures relying upon the background knowledge and experience of experts. The presently presented in this paper theory of establishing the. ISAODC on the basis of dispersed ICN and expert systems is aimed at trasformation ofoperational' tasks of the higher level into the technological ones, at solving the tasks of diagnostics and forseeing of the process of production, with a dispatcher getting an opportunity of making qualitative and effective decision concerrning the choice of operational impacts in actual time on the basis of generalization the realisation of presented conception must, as has been already mentioned, be accomplished only on the basis of the foundatoin of the united dispersed informational - calculating network of electrical calculating machines.. This includes ICN which would be operating in . different operational contours. . From what has just been said it followsthat the ISAODC Structure will conside with that of DICN (in our case) and hence all the problems of ISAODC structure would be regarded as the questions of DICN.

Jan 1, 1992

By W. A. Crosby

The ability of open pit mines to steepen overall final wall angles allows significant cost reductions as a result of reduced waste movement requirements. Final wall angles are principally controlled by three factors: geological conditions; hydrological conditions; and wall control blasting practices. The first of these factors is not controllable by the mine operator, the second can be influenced to some degree, but the last one certainly can be controlled, hence the current interest in final wall blasting practice at many mining companies. This paper discusses common blasting techniques employed to steepen final pit walls and outlines the attractiveness of moving from small hole high cost systems to the use of full size production drills as a means of reducing wall control blast costs. Attempts to make this change have been limited at many mines by the physical size of the drills and their inability to reverse drill. In the past, pres pi it, pre-shear or trim holes have had to be drilled vertically, at considerable distance from the upper bench toe, with the result that inter-berm face stability is reduced and final wall angles have to be made somewhat more shallow than desirable. The paper concludes with a description of how these problems can be overcome by utilizing the new Bucyrus 39R which has the capability of drilling at a ?15 degree angle underneath the machine. It is concluded that the resulting wall control blast designs will offer large mines improved final wall angles with resulting significant overall cost reductions.

Jan 1, 1998

By I. M. Stewart

In a proposed rulemaking regulating asbestos, nonasbestos varieties of Tremolite, Anthophyllite and Actinolite would be excluded from the regulations controlling permissible exposure to asbestos fibers. This proposed rulemaking is perceived as improving the scientific basis of the regulation of asbestos because it recognizes that there are no scientific data, either mineralogical or health related, which support the regulation of nonasbestos Tremoiite, Anthophyllite and Actinolite in the same manner as asbestos fibers. However, the proposed regulation, while representing a major advance in the treatment of AT A for regulatory purposes, does not provide an adequate analytical method for distinguishing between asbestos and nonasbestos particles, nor an adequate description of the regulated minerals. This paper addresses those topics, recommending that OSHA include an appropriate mineralogical definition, and implement a discriminate counting procedure to distinguish asbestos from nonasbestos particles.

Jan 1, 1992

By G. E. McCormack

The Development of Water Gel Explosives Water gels are the most recent development in the evolution of commercial explosives. They are replacing dynamite, having proven themselves to be excellent alternatives to this standard explosive. Water gels have steadily displaced dynamite over the past two decades. In 1959, they accounted for only 1 percent of the market they share with dynamite. By 1965, the share taken by water gels had grown to 21 percent. In 1970, it was more than 40 percent, and today it is nearly 70 percent. Black powder, the first widely used explosive, revolutionized mining and quarrying in its day. However, when nitroglycerin dynamite became available about a century ago, it rapidly displaced black powder because it provided greater energy for a given weight, much higher velocity for better rock shattering performance, and water resistance for easy use in wet conditions. During the past 50 years, ammonium nitrate has played a dramatically increasing role in explosives. First, it was used as an ingredient in dynamite, and then as the main component in nitrocarbonitrate blasting agents. About a quarter of a century ago, it began to find use in a simple and inexpensive mixture with fuel oil that has revolutionized the explosives industry and today fills about 80 percent of the requirements for explosives in the U.S., and certainly the bulk of blasting requirements worldwide. Water gels and dynamites share the remaining 20 percent. Water gel explosives based on ammonium nitrate have also been developed during the past quarter century. These explosives contain

Jan 1, 1979

By Raj K. Rajamani

In ball milling the rates of breakage vary primarily with the size distribution of powder in the mill. In wet grinding viscosity of the slurry varies continually as size distribution changes and hence the breakage rates change. In this study a simpler estimation scheme is used to determine breakage rates in batch grinding. Using an approximate solution to the batch grinding equation, acceleration and deceleration of breakage rates of all individual size classes is determined when the grinding environment is varied. Experimental results with limestone and copper ore show time-dependent breakage rates under both dry and wet grinding conditions. In general the breakage rates increase for coarse sizes and decrease for fine sizes with increase in the fines present in the mill. Such variations have strong implications in closed-circuit grinding.

Jan 1, 1991

Conventional logging tools such as density, neutron, and acoustic have ranges of investigation of tens of centimeters. The borehole gravimeter, however, has a range up to hundreds of meters. For example, from the center of a cylindrical ore body 0.20 g/cm3 denser than its surroundings, one can detect the boundary of the ore body at a radius as large as five times its height. More complex structures can be investigated with computer programs. We can predict the usefulness of proposed gravity surveys, or decide which suggested structure is most likely to have caused the results of existing surveys.

Jan 1, 1988

By J. A. Ehler

Speed and torque control of standard A.C. induction motors can be accomplished using a variety of devices ranging from mechanical, hydraulic, and electrical. Also, the motor can be specified as an A.C. wound rotor or D.C. motor using the associated controls. Normally, any one of these drive types can be adequately used to provide the torque control necessary to accelerate a conveyor belt system. The selection will depend on the economics, experience, and preference of the designer or end user. These drive types will be presented from a functional and performance viewpoint to assist in the understanding of the available technology.

Jan 1, 1998

By Dominic F. Howarth

Groove deepening (deepening of a groove in rock by successive passes of a rock cutting tool) is a potential operational feature associated with tunnel boring machines. Little research has been undertaken in this area which is of direct practical relevance to the design and application of tunnel boring machines. Laboratory experiments using single, double and triple disc arrays have revealed an important fundamental cycle of events associated with disc cutters when progressively deepening a groove. Furthermore, in contrast to pick cutters, groove deepening by discs is shown to be an efficient operation. This can be directly attributed to the increased interaction between disc cutters due to the increase in magnitude of lateral forces generated as a groove is deepened.

Jan 1, 1981

By Michael F. Werneke

While the use of synthetic polymers for solid/liquid separation is not raw technology (1)(its history goes back to the mid 1950's), its importance has increased dramatically over the past decade. This can be attributed to two major factors. The first of these was a change to mechanized mining (strip mining and continuous underground miners) which resulted in a lower quality (higher reject) preparation plant feed, as well as a higher percentage of smaller size particles in the feed. The second factor has been the greater restrictions imposed by governmental agencies on effluent discharge and solids impoundment, requiring pre-treatment of recirculating water before reuse and treatment of refuse before disposal. Today, synthetic polymers find utility in almost all applications requiring separation of solids from aqueous suspension, including "in-process" as well as waste treatment applications. In spite of the fact that there are over several hundred commercially different flocculants available in the marketplace (2), there are a limited number of chemically different materials available which are useful from a cost/performance standpoint. The potential reasons for using flocculants in a coal preparation plant are summarized in TABLE 1.

Jan 1, 1979

By D. S. Young

The random variable transformation technique was introduced to make probabilistic structural analysis simple for such structures as slopes, dams, foundations, or retaining walls, where two shear strength parameters are required to analyze their stability by deterministic engineering methods. The Gaussian transformation was performed by using the Hermite orthogonal polynomial function. This transforms the experimental histogram into the standard normal distribution, whose mean is zero with a variance of one. Then, the transformed standard Gaussian variable was used for the bivariate normal probability analysis on the structure. The Gaussian transformation technique and the Hermite polynomial functions were chosen because the bivariate joint normal distribution is well-known and easily available for engineers. The binormal probability analysis was made on the probability region of a certain confidence level by superposing the critical line on the same probability region that divides the region into two zones: stable and unstable zones. The critical line was determined from the back calculation of the deterministic engineering method of the structural design. Finally, the probability of structural failure at a desired confidence level was calculated by simply integrating the volume of the binormal density surface above the unstable zone in the probability region. A simple case of slope analysis is introduced to illustrate this probabilistic approach, and its effectiveness and simplicity is demonstrated.

Jan 1, 1987

By J. Hupka

The limited effectiveness of the original hot water process for recovery of bitumen from certain Utah tar sands containing bitumen of higher viscosity (e.g. Sunnyside, Tar Sand Triangle)1,2 indicated that bitumen viscosity strongly' influences the separation efficiency. In this regard, there should exist a critical value of bitumen viscosity above which the effectiveness of the hot water process decreases significantly. Apparently certain tar sands contain bitumen of such high viscosity that even a digestion temperature of nearly 100°C is insufficient to lower the viscosity below the critical value. In addition it seems that differences in physico-chemical forces which act between sand and bitumen are negligible in comparison to the difference in visco-mechanical forces. Predominantly mechanical forces hold viscous bitumen on the rough surface and in the pores of sand particles, resulting in strong adhesion. This phenomenon is a critical feature in the phase disengagment of oil-wetted domestic tar sands with viscosity control by temperature. Besides increasing the temperature for viscosity control the effectiveness of the original hot water process could be enhanced by control of bitumen viscosity with diluent additions. Strictly speaking this appraoch is the only possibility for heavy bitumen for which the high temperature of digestion does not lower the viscosity sufficiently. As a result of viscosity control by diluent addition the digestion temperature can be lowered which is important from an industrial standpoint. Another important consideration is that effective phase disengagement occurs only when the entire bitumen phase has the same viscosity. This means that some time (penetration time) is necessary for complete and uniform dilution of the bitumen. If the viscosity of bitumen, which is a function of temperature, diluent addition and penetration time, controls the separation efficiency, hot water processing of many different kinds of tar sands should be possible, assuming that the sand phase consists primarily of quartz-type minerals.

Jan 1, 1982

By John Litz

The term "refractory gold ores" refers to a wide number of ore types which are not readily amenable to direct cyanidation. A number of processes have been used commercially, and a number of others have been proposed and in many cases pilot tested. The selection of the appropriate process for an ore should not be arbitrary. Ore grade may preclude some processes, but a good understanding of the ore mineralogy can guide the selection. Many present gold operations and many potential gold operations have faced or are facing problems with refractory gold mineralization. We at Hazen Research have had the opportunity to perform bench testwork and in some cases, pilot plant testing on a number of refractory ores. The data included in this paper are excerpted from the testing of fifteen ores which cover a wide range of mineralogical compositions. This paper is not intended to be a treatise on the processing of refractory gold ores. In many of these gold projects, not all of the standard process alternatives were evaluated, nor was adequate mineralogical work performed. Such is the dilemma of contract research. "If I believe that I don't need it, why should I pay to have it done." The intent of this presentation, therefore, is to show how different ores respond to the various processes, and to demonstrate that one must have an open mind when developing a process for a specific refractory gold ore.

Jan 1, 1998

By Fredrick C. Kruger

We can confidently predict such obvious long-term trends affecting the minerals industry as - increasing consumption, exhaustion of easily discovered near-surface ores, and sharp limitations upon open pit mining by environmental considerations. There- fore, we must intensify the exploration for, and the development and exploitation of, deep bodies of potash and other ores. This paper examines the state of the art of the search for, and the evaluation of, potash from both a geological bias and a mining practicability. The use of indirect geological methods and geophysical techniques, followed by expensive deep drilling, are the conventional approach to evaluation and development of mining plans. The geologist and the geophysicist will have to find ways to perform both of these tasks better and cheaper.

Jan 1, 1973