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By M. A. Mahtab, T. M. Yegulalp

This paper presents the development and application of an approach for clustering fracture orientation data. Data are projected on the surface of the unit upper hemisphere and the clustering approach is applied in three steps: (1) randomness test and identification of dense clusters, (2) estimation of cluster statistics, using Bingham distribution, and (3) rejection of extremal data based on Chauvenet's criterion.

Jan 1, 1982

By Thomas G. Carnahan

The Bureau of Mines conducted research to simulate in situ leaching of a chalcopyrite ore. The purpose was to obtain a direct comparison between moderate-temperature and elevated-temperature in situ leaching of copper trom minus la-inch ore and to analyze the sulfuric acid and oxygen requirements of the leaching system. Experiments employing oxygen were conducted at 35° and 90° C on 362-and 367-1b ore charges, respectively, under flooded conditions and at 400 psig. At 90° C, 47 pct of the copper was extracted in 913 days of leaching; at 35° C, 27 pct of the copper was extracted in 915 days. Diffusion into and out of the ore fragments con-trolled the rate of leaching. Oxygen consumption was 1.46 lb/lb of copper extracted at 35° C and 3.15 lb/lb of copper extracted at 90° C. Sulfuric acid requirements of the ore were 5.49 and 7.48 lb/lb of copper extracted at 35° and 90° C, respectively.

Jan 1, 1982

The determinants of human behaviour are numerous and complex. Many scientific disci- plines focus on various processes which play some part in shaping the actions of individ- uals and groups. Behavioural science attempts to synthesise data produced by these investigations in an attempt to formulate principles by which people's thoughts, feelings and actions may be described, diagnosed, predicted and changed. While no comprehensive account of people and their reactions can be attempted in a brief paper a review of six principles does provide a framework within which managers can establish reliable knowledge applicable to all their subordinates and to themselves. This information may be used to arrange organizational environments and management practices which enable people to discover, release and increase their best intellectual, emotional and motivational capacities.

Jan 1, 1982

By D. E. Kirby

In line with the Bureau of Mines' goal of providing technology to maintain a supply of minerals adequate to meet national economic and strategic needs, a method for recovering chromite from lateritic materials was investigated. Laterites are a large resource of Ni, Co, and Cr, critical metals of which the United States has insufficient domestic sources. A roast-leach method was developed by the Bureau to extract nickel and cobalt from domestic laterites. A concurrent effort was made to recover chromium from either unprocessed laterites or the leach residues. This report characterizes laterites and laterite leach residues. It describes a chromite recovery procedure using conventional industrial beneficiation equipment for sizing, low-intensity magnetic separation, and gravity concentration. Concentrates containing 20.0 to 22.4 pct Cr (29.0 to 32.7 pct Cr203) and with a 1.6:1 to 1.9:1 Cr-Fe ratio were recovered from laterites and residues containing 1.3 to 2.5 pct Cr with recoveries exceeding 50 pct. Because of their low grade and fine size, these concentrates would be suitable for preparing chromium chemicals. The direct beneficiation of laterites for chromite recovery resulted in the minerals containing nickel and cobalt concentrating in slime products. No iron oxide coproducts of acceptable grade were recovered from either laterites or residues.

Jan 1, 1982

By Arthur R. MacPherson

Este capítulo revisa las etapas que deben seguirse desde el momento de considerar la molienda autógena en el desarrollo de un nuevo depósito de mineral o en la expansión de una planta existente, hasta la compra de un molino autógeno. En este caso el término autógeno incluye: semi-autógeno, molinos de pebbles secundarios y molino de bolos (trozos), así como los sistemas de molienda autógena total. También se han incluido las alternativas por vía húmeda y seca. Antes de programar el ensayo debe decidirse cuantas muestras brutas son requeridas para calcular propiamente las posibilidades de molienda autógena del depósito. También ha de tomarse la decisión, de como y donde deben tomarse las muestras, por ejemplo: planta piloto situada en el sitio de localización de la planta o en otro lugar establecido; molienda en húmedo y/o en seco....etc. En el mismo programa del ensayo se obtendrán ciertos datos fundamentales. Los ensayos deberán incluir un trabajo suficiente. para determinar cuál de las moliendas, totalmente autógena o semi-autógena, debe utilizarse; y qué tipo produce la máxima eficacia en la potencia consumida. También, los otros datos pertinentes deben ser recolectados, como por ejemplo: potencias, tonelajes, alimentación, carga, tamaño del producto, carga circulante, etc. Si es necesaria una molienda secundaria para obtener el tamano final, la decisión de qué molienda debe emplearse (molino de pebbles o molino de bolas) puede requerirse un ensayo de trabajo adicional. Finalmente, la concentración del mineral puede jugar un papel importante en la selección del circuito y debería ser una parte del ensayo final una vez que se ha establecido la molienda. Para determinar qué tipo de molinos pueden satisfacer los requerimientos establecidos por la planta piloto, debe tomarse una escala para ciertos datos como: potencia del molino, consumo de acero, simple o doble etapa de molienda, tipo de molino secundario. Para asegurar un posterior entendimiento del depósito de mineral y sus características de molienda, deberán efectuarse algunos trabajos adicionales a pequena escala utilizando pequeñas muestras y molinos para producir unos datos comparables de molienda. También, algunos ensayos tales como medio de molienda óptimo, e índice de trabajo, deberán ser completados.

Jan 1, 1982

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 H. H. Dewing

The Bureau of Mines constructed a process research unit (PRU) to demonstrate new technology for extracting zinc from sphalerite concentrates. Up to 9 kg/hr of sphalerite (ZnS) concentrate was reacted at ambient pressure in the PRU with 80 pct sulfuric acid at 160° to 180° C to produce zinc sulfate and elemental sulfur. The PRU consisted of a three-stage glass reactor system: a 4-liter premix stage in which feed was slurried with 78 to 82 pct H2S04, a 40-liter stirred reactor, and a ISO-liter settling stage in which high reaction conversions were effected and excess H2S04 for recycle was separated from insoluble ZnS04 and sulfur. Evolution of sulfur-containing gases was minimized by sub-surface addition of acid feed slurry to the stirred reactor and by exclusion of air from the reactor to prevent the oxidation of elemental sulfur. Conversion of zinc to zinc sulfate averaged over 99 pct at the optimum acid concentration of 80 pct. Total sulfur losses (primarily S02) were less than 2 pct of the sulfur in the sphalerite. Elemental sulfur remained in the insoluble portion of the settled reactor product after leaching with simulated spent zinc electrolyte containing sulfuric acid. The sulfur residue contained 75 to 89 pct sulfur. Neutral zinc sulfate, required for zinc electrowinning processes, was separated from the sulfuric acid leach solution by crystallization at -15° C as zinc sulfate heptahydrate (ZnS04?7H20). The crystallization operation simultaneously effected a partial concentration of the recycled electrolyte solution by removing water.

Jan 1, 1982

By G. Capello

Carboniferous mining basins are today a non-negligible source of energy. So important in fact that returns now justify high investments and costs even for those deposits that were un-economical in the past. Nowadays, if properly explored and exploited, basins previously considered non-minable due to complex structural and stratigraphical situations may be economically interesting. It is while studying a faulted basin with such features that the Authors developed the described computer-aided methodology capable of constructing a model of the physical structure of coal deposits on the basis of stratigraphical data from drillings. The aim of the procedure is to define coal reserves, the exploitation of a deposit being conditioned by the possibility of identifying zones that are technically minable. This objective is pursued by making as detailed a reconstruction as possible of the geometrical, stratigraphical and tectonic features of the coal-bearing seams of a deposit.

Jan 1, 1982

By Douglas F. Scott

In 1981 the U.S. Bureau of Mines and U.S. Geological Survey conducted a mineral survey of the Pyramid RARE II area (No. 5023) covering 23,500 acres (9,500 ha) of E1 Dorado National Forest and 7,900 acres (3,200 ha) of the Lake Tahoe Basin Management Unit (fig. 1). The Bureau of Mines investigation did not reveal mineral deposits in the area. Samples taken from silicified and limonite-stained metasedimentary rocks and aplite dikes were void of precious or base metals or uranium. Placer samples from stream gravels contained no gold values. Molybdenite occurs in quartz stringers within quartz monzonite near Grass Lake, adjacent to the area; no extension; were found in the area.

Jan 1, 1982

By Joseph R. Hatch

During the past ten years detailed elemental analyses of approximately 8,000 well-documented samples of coils in the United States (including Alaska) have been produced by the U.S. Geological Survey and the various State geological surveys. Examples of data listings include Swanson and others (1976) Gluskoter and others (1977) Hatch, Affolter, and Davis (1979), and Wedge and Hatch (1980). These analyses serve as a basis for evaluating elemental abundances in coals from the various coal province, regions, and fields. When combined with additional geological and geochemical data, some of these analyses give insight into when certain elements were introduced into coals, and which physical and geochemical parameters are most important in determining coal elemental composition.

Jan 1, 1982

By Carroll W. DeKock

Thermodynamic data for selected metal sulfates were critically evaluated and compiled as part of the Bureau of Mines program to provide a scientific base for use in developing new technology and predicting the feasibility of new processes. Values for Cp°, S°, H° - H°298, -(G° - H°298)/T, ?Hf°, ?Gf°, and log Kf as a function of temperature are given in tabular form. Thermodynamic data were compiled for VOSO4, Cr2(SO4)3, MnSO4, FeSO4, Fe2(SO4)3, CoSO4, NiSO4, Cu2SO4, CuSO4, CuO-CuSO4, ZnSO4, and ZnO-2ZnSO4, together with their stable hydrates.

Jan 1, 1982

The detailed engineering of a coal preparation plant is important from the point of view of optimum constructibility, operational security, ease of maintenance, operating costs, meeting environmental goals, safety, plant housekeeping and reduced corrosion and erosion. This paper reviews the several large coking coal preparation plants engineered by Fluor Australia in the past 10 years, and changes and trends apparent for detailed engineering of future plants. Areas of engineering to be covered are coal feed preparation, conveyor design, plant layout, electrics and instrumentation, noise attenuation, erosion and corrosion protection, magnetite handling, rejects and tailings disposal and coal stockpiling and blending.

Jan 1, 1982

By J. M. Stuve

A novel calorimetric solution technique, recently developed at the Bureau of Mines, was tested using synthetic samples of chalcocite (CU2S) and covellite (CuS). The solution of these refractory sulfides was accomplished by oxidation with bromine in a moderately acidic, aqueous solution. The resulting values for the standard enthalpies of formation (?Hf°, 298.15) for CU2S(c) and CuS(c) were -18.1 ±1.1 kcal/mol and -13.3 ±1.1 kcal/mol, respectively. These values are in good agreement with published formation values derived from other methods of physicochemical measurement.

Jan 1, 1982

By H. Saito

To Japan, which is scarce in natural resources, limestone is the only mineral resource comparatively rich in ore reserves and having broadly recognized outstanding quality. Distribution of the limestone deposits extends from Hokkaido in the north to Kyushu and Okinawa in the south, and the deposits are located in a manner of framework formation of the Islands of Japan. Studies of the geological ages of these ore deposits reveals that almost all of the main ore deposits west of Kanto Area belong to the Carboniferous Period - Permian Period of the Paleozoic Era. Also in the east of Kanto Area, deposits belonging to the Paleozoic Era constitute the main part, although recently there are increasing examples of reclassifying the geological age of the deposits heretofore considered as Paleozoic Era to the Triassic Period of the Mesozoic Era by the recent discoveries of the fossils of conodont, etc. Large ore deposits and main ore deposit groups are given in the Figure 1, which shows that the deposits are roughly found well distributed throughout the country.

Jan 1, 1982

By S. C. Suboleski, C. B. Manula

In a high risk venture such as mining where capital is committed and contracts are signed on a minimum of information, decisions are based primarily on production forecasts derived through consideration of such factors as management-labor relations, mining practice, variations in physical conditions, and the equipment applied. Among these factors, the physical conditions offer the least opportunity for control, and, due to the wide range of mining conditions experienced, little effort has been made to develop objective methods for measuring their effects on mine output. This paper's aim is to demonstrate a method for assessing these relationships that can be applied under a wide range of conditions both in new mines and in working sections where there is a need to determine the impact of proposed operational modifications. Using empirical data from active underground mines, a mathematical model was developed to derive a set of regression equations for predicting production as a function of mining conditions.

Jan 1, 1982

By E. LaRocque

"Long term contracts requiring delivery of 6,000,000 pounds of U308 per year to its customers have made it necessary for Denison Mines to expand its milling capacity from 7,100 tons per day to 15,000 tons per day.Previous papers (1) and (2) described the old leaching and product recovery practice. The flowsheet briefly includes a crushing and grinding circuit, sulphuric acid leaching in a Pachuca plant, liquid-solid separation with wash thickeners and two-stage drum filtration, concentration and purification by moving bed ion exchange followed by two-stage precipitation to produce an ammonia yellowcake.No. 1 Shaft ore, about 4,000 tons per day, will be processed through the truck dump into the old crushing and grinding plant and through the old leaching plant. Ore from Stanrock (No. 3 shaft) will be hauled by truck and also processed through the truck dump as No. 1 shaft ore. Beginning in 1982, ore production from Stanrock will gradually increase until 1985 when some 3,000 tons per day will be milled from the source.A new 8,000 ton per day circuit was designed and constructed to increase the milling capacity to 15,000 tons per day. The new circuit is separate from the old one except that it coins together for the precipitation and tailings neutralization sections of the plant. The feed to the new plant will be from No. 2 shaft.The flowsheet is much the same as the old plant with the exception of the grinding circuit and the ion exchange plant. A semi-autogenous grinding (SAG) plant, unique in the Elliot Lake area, has been installed rather than the conventional crushing and grinding plant; the ion exchange plant is the stationery bed type.This paper describes the major equipment installed for the expanded grinding and hydrometallurgical plant."

Jan 1, 1982

By Fred Leighton

INTRODUCTION Dynamic (seismic or microseismic) methods of determining the stability of structures in rock are based on detecting and analyzing the characteristics of seismic energy that has originated from or traveled through the rock mass. This seismic energy can be in the form of naturally occurring rock noise energy resulting from structural adjustments within the rock or can be introduced into the structure by physical means, such as by blasting or impact. In either case, the seismic energy radiating through the rock mass can be detected using standard equipment and can be analyzed by established techniques to reveal a wide variety of information concerning the condition and stability of the rock mass through which the energy has traveled. In the following sections, the basic instrumentation required for seismic and microseismic studies is described, and some of the presently used applications of these methods are discussed to exemplify the state of the art. INSTRUMENTATION Seismic disturbances in a rock structure generate two types of seismic wave radiation, body waves and sometimes surface waves, which radiate outward in all direc¬tions from the source of the disturbance. Underground mining applications are generally concerned only with discerning the characteristics of the resulting body waves, i.e., the compressional (p-wave) and the shear (s-wave) energy. As these two forms of energy travel through the rock structure, the particles of the rock mass are caused to vibrate, and the vibration character¬istics resulting from each of the two types of wave are distinct. Some important differences are: 1) Compressional and shear waves travel at different velocities through the rock structure. 2) The frequency at which each wave causes particles to vibrate is different, and may range from about 50 to 100 000 Hz. 3) The amplitude or energy level of each wave is different, with the shear energy usually being the greatest. These differences form the basis for equipment se¬lection for individual studies and for modern data analysis techniques. The following sections describe the basic equipment necessary to detect and record seismic wave energy data and show several examples of analysis procedures and how these procedures have been used. In principle, seismic equipment is very simple. It consists of a geophone (or geophones) to detect the seismic energy vibration and convert that vibration to an electric signal, an amplification system to increase the level of that signal, and a means of monitoring and/or recording the signals detected. Fig. 1 is a block diagram of a typical system. The following sections offer a very brief discussion of system components and their individual functions. A more complete discussion is given by Blake, Leighton, and Duvall (1974). Geophones The function of the geophone is to detect the vibrations caused by the passing of the seismic wave energy and to convert that vibration into an electrical signal that displays both the amplitude and frequency characteristics of the vibration. Particle motion or vibration can be quantified and measured by measuring displacement, velocity, or acceleration of the particles. Thus, there are three types of geophones: displacement gages, velocity gages, and accelerometers. The choice of gage depends on the characteristic frequencies of the seismic energy to be monitored and the sensitivities of each type of geophone. In general, displacement gages are used for low-frequency monitoring (periods to 1.0 Hz), velocity gages for medium-frequency monitoring (1.0 to 250 Hz), and accelerometers for high-frequency monitoring (250 to 10 000+ Hz). Experience has shown that in underground studies, the choice of which gage to use lies between velocity gages and accelerometers. An easy, accurate method for selection of gage type is discussed by Blake, Leighton, and Duvall (1974). Once the type of geophone has been selected for use, it must be properly installed, and in the installation procedure the most important step is insuring that the gage is firmly attached to a competent portion of the rock structure. Poorly mounted geophones may entirely fail to recognize low-level seismic signals and will distort the information from signals they do see. Amplifiers Seismic events associated with mine structures occur over a very broad range of energy which results in a broad range of geophone output levels. In general, geophone output levels occur in the microvolt to low milli-volt range, and it is necessary to amplify these signals in order to drive recording or monitoring equipment. Because either an accelerometer or a velocity gage might be used as the geophone, the amplification system must

Jan 1, 1982

By P. R. Kneitz, G. Yoshikado, D. Zayakov

The design and analysis of a circular, domed powerhouse for Pacific Gas and Electric (PG&E) Company's Kerckhoff 2 Project is described. Exploration, geologic stress determinations, mechanical properties, reinforcement and instrumentation are addressed briefly. The analyses of the circular, domed cavern and the comparison of predicted and field deformations are presented in somewhat more detail. The behavior of the completed powerhouse cavern has been found to be substantially as predicted by the analysis.

Jan 1, 1982

By Vaughn E. Livingston

Washington State has a variety of industrial minerals and although not many are produced currently (1982) most have a history of production (table 1). The value of industrial minerals produced in the state exceeds by several times the production value of metallic minerals. In 1981, 15 minerals - cement, limestone, clay, gemstone, pumice, sand and gravel, stone, diatomite, gypsum, olivine, peat, talc, garnet, silica, and dolomite - were produced. Combined value of nonmetallic production for 1981 is estimated at $218,999,000. Cement had the largest estimated value at $102 million, followed by sand and gravel at $47 million, and crushed stone at $29 million. These figures are from the US. Bureau of Mines preliminary production figures for 1981.

Jan 1, 1982

By T. L. Dobecki

Numerous seismic techniques have proven to be important and cost effective aids to both coal exploration and nine planning. Projects conducted by Sandia in recent years have sham seismic refraction is a valuable tool for determining overburden properties while high resolution, 2-0 and 3-D seismic reflection surveys are the primary means of napping coal seam distribution, structure, and continuity. Further, seismic methods utilizing existing boreholes (e.g. downhole, crosshole and guided wave) provide detailed measures of overburden/interburden modulus variation, seam continuity, and calibration for other seismic surveys. Examples include mapping faults of 2-10 m threw in seams 3-15 m thick at depths of 80-300m.

Jan 1, 1982