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By C. E. Larson

Man's use of 'glass predates recorded history. Although early man had no knowledge of how to form glass, artifacts have been found near naturally occurring glass formations where molten rock had been rapidly cooled. In areas where volcanic activity is evident, primitive people fortunate enough to have lived in that area used the naturally formed glass to make arrow heads, knife blades, tools and ornaments. These glass artifacts have been found all over the world. In fact in todays modern society there are recorded cases of aboriginal tribesmen in Australia fabricating arrowheads from glass bottles. 2. A Brief History of Glass The first evidence of man made glass were beads made around 2500 BC by the Egyptians. The Mesopotamians also made glass beads at about the same time.

Jan 1, 1986

By Stanley V. Lachmansingh

Bauxite can be regarded as a mixture of hydrated aluminium oxides the predominant constituent - and oxides of iron and titanium, silica and silicates. Heterogeneous and non-crystaline, most bauxites vary in average composition from one deposit to another both in terns of impurities as well as the proportion of Gibbsita and the Monohydrates Diaspore and Boehmite. Iron levels (as Fe2O3) can vary from less than 1% to as high as 30% with the alumina content ranging from 40 to 6o%,. Gore than 90% of all bauxite mined in Guyana is used as feed for the - production of refractory grade calcined bauxite. There are -however, several speciality grades used in various industrial applications and these are characterised by the quality of the bauxite in particular ;,with regards to iron and silica levels which generally have to be low. The main speciality grades are designated Refractory, Abrasive and Chemical. Bauxitte is also used in the production of nigh alumina cements,, activated bauxite end in the manufacture of electrical insulators.

Jan 1, 1977

By G. Davis

Mineral properties and mineral firms often trade at a market value that is significantly greater than the value indicated by discounted cash flow (DCF) techniques. A possible explanation is that DCF analysis does not consider the value derived from managerial flexibility. Presumably, then, at least some of the difference between DCF value and market value is due to managerial flexibility. This paper surveys the recent attempts to empirically quantify the value of managerial flexibility using option pricing theory. The results indicate that managerial flexibility, at least as measured by the option pricing methodology, falls well short of explaining the gap between DCF value and market value.

Jan 1, 1995

By Saul J. Escalera

Mechanisms involved in the depression of the sulfides: pyrite, chalcopyrite, galena and sphalerite with potassium permanganate have been investigated. Flotation tests were conducted using potassium amyl xanthate, Z-6, and pine oil in the absence and presence of potassium permanganate at around pH = 6. 5 naturally yielded by the sulfides in the pulp. On the basis of crystal chemistry considerations, the amount of xanthate adsorbed by the sulfides depends on the amount of sulfur and metal ions present on the surface; thus, the avidity of the sulfides for xanthate should increase in the order: sphalerite C chalcopyrite 4 galena 4 pyrite, and the ease of depression response to the permanganate action should be in the same order. Depression of the sulfides in the system occurs primarily due to the removal of the collector ions by the permanganate ions to form manganese dioxide and dixanthogen according to the reaction: 3 M(RX)2 + 2 Mn04 + 4 H20 2 ? MnO2 + 3(RX-XR) + 3 M+2 8OH where M represents the metal ion, RX the xanthate ion and (RX-XR) the dixanthogen molecule. Results seem to indicate that the permanganate ions play a triple role in the system: (1) they convert xanthate ions into dixanthogen, (2) they further oxidize the mineral surface and (3) if present in excess, they may oxidize the xanthate beyond the dixanthogen stage with the formation of CO2, H20 and SO4. All sulfides, except for chalcopyrite, showed a depression response in the order predicted regardless of the order of addition of xanthate and permanganate reagents. Chalcopyrite did not depress as easily; this behavior may be due to the avidity of the colloidal MnO2 to adsorb Cu+2 ions on its surface, this would destabilize the colloid making it coalesce with the formation of a layer of precipitated MnO2 on the surface of the mineral. The presence of this layer would prevent further action of the permanganate ions on chalcopyrite.

Jan 1, 1970

By Paul A. Rittenhouse

Its a pleasure to be with you this afternoon and to talk briefly on one of my favorite subjects -- the U.S. sulphur industry. As our Chairman mentioned, I have been associated with the sulphur industry either directly or indirectly for the last twenty years, both on the production side and as a consumer. Sulphur, while unseen and relatively unknown to most people, is like margarine ... that ubiquitous spread ... that is yellow and nearly omnipresent in the industrial world. It is because sulphur, in some form, is required in nearly all aspects of our economy that makes its study so interesting to me as a researcher. An analysis of the sulphur outlook requires examination of such industries as fertilizer, paints and pigments, copper and zinc, uranium, petroleum, chemicals, pulp and paper and textiles - just to name a few. Of course, because its use is so widespread and ever-changing it is difficult to develop and maintain a good understanding of the sulphur industry. It is also a problem to cover the industry in a short discussion and to project its really dynamic nature. Hut, if you will bear with me, I will attempt the task. First of all, let me say that sulphur today is a world commodity and to a large extent moves freely in world trade; nearly a third of the world's sulphur or something over 15 million tons in 1974 entered international trade. However, today our interest is in the current changing sulphur picture in the U.S., with particular emphasis on the western part of the country.

Jan 1, 1975

By Vas Choudhry

The eighties are likely to witness the first commercial-size coal-to-gasoline plant(s) in the U.S., although uncertainty regarding crude prices and cautious involvement of the Federal Government in the synfuels development are evident. The formation of The U.S. Synthetic Fuels Corporation with passage of the Energy Security Act is projected to pave the way for some of the projects on a moderate scale. The corporate objectives (1) are to provide funds for supporting a number of feasibility studies and loan guarantees for the construction of at least some commercial-size plants and the possibility of product price supports or purchase commitments. There are a number of coal conversion processes (2) currently under evaluation for producing either gaseous or liquid plus gaseous fuels, the other processes such as SRC I are for producing desulfurized deashed clean solid fuel for commercial use.

Jan 1, 1982

By Ray Nivens, Umit Turunc, Caroline Sui, Nick Morrison, Douglas Steiner

"In most copper mines and concentrators, mill water is continuously recovered and reused, with fresh water added to make up for losses. When mixed, these water chemistries can lead to severe scaling, especially in pipes, tanks and pumps on the mill water supply side, reducing flows and causing significant production losses.At KGHM Robinson Nevada Mining Company, increases in the fresh water addition ratios resulted in severe scaling problems and premature pump failures thereby jeopardizing plant production. What initially appeared to be a few isolated scaling events eventually unfolded into a recurring pattern of water supply-related production losses with increasing severity. Through completion of detailed root cause analysis, chemistry modeling, laboratory work, in-plant testing and system engineering, the mechanisms of scaling were identified and addressed.Advancements in fresh water addition practices and antiscalant application methods resulted in a stepwise reduction of the mill water scaling. Cost savings and production benefits were significant to the plant’s financial metrics.IntroductionThe production of mineral and metal concentrates using the flotation process requires large quantities of water. Flotation is utilized as the primary means for beneficiation with sulfide ores. Mined ores are crushed and ground into a slurry of 20-55% solids. For each ton of ore, 400-900 gallons of water1 are needed to supply the grinding mill. Additional water is needed in the flotation circuit as well. With many modern mills operating at2 11,000-165,000 tons/day, water supply volumes can be upwards of 3,000 gpm to 100,000 gpm of flow.For plants operating at or above capacity, disruptions and restrictions in water supply flow can have a direct impact on the production and recovery of the metal. Water supply flow can be limited for a wide variety of reasons but of interest are those limitations that are due to mineral scaling. Mineral scaling is the selective point precipitation of inorganic species above saturation concentrations. Precipitated species form flow-restricting deposits in the mill water system (tanks, pumps, pipe and valves), that will eventually impact water supply to the concentrator."

Jan 1, 2017

By John J. Dran

In recent years, market rates of interest have risen well above their historical long-term average. Also during this period, the short-term variability of interest rates has been greater than in prior years. Interest rates have a significant effect on the operation of our economy. They influence the extractive industries in a number of ways. Their major long- range impact is on investment decisions - specifically the valuation of mineral deposits. An understanding of the factors that influence interest rates is important to the engineer or businessman who makes the investment decisions for the mining company. The effect of changes in the market rate of interest on the value of mineral reserves is critical to the future financial success of the mining enterprise. The most common simplification of the factors determining the level of interest rates is that they are a function of the demand for and the supply of money. While this is an oversimplification, most businessmen would be hard- pressed to provide a better explanation. The purpose of this paper is to explore certain fundamental economic aspects of interest rates and to examine their effect on the analysis of investment in mineral deposits.

Jan 1, 1975

By A. Durnan

Barrick Goldstrike Mines Inc. (Goldstrike) operates a six circuit (train) pressure oxidation plant for the pretreatment of gold bearing sulfide ores. The property is located 27 miles north of Carlin, Nevada. Since the commissioning and start-up of the first circuit in 1990 until the present total plant availabilities have exceeded 90%. The discussion that follows will detail the maintenance practices employed to consistently achieve this goal.

Jan 1, 1994

By M. L. Bricker

The Jim Bridger Mine is operated by Bridger Coal Company and is located in Sweetwater County, 35 miles (56 km) northeast of Rock Springs, Wyoming (USA). The general location of the mine site is shown on Figure 1. Bridger Coal is a joint venture of NERCO Coal Corp, the operator, and Idaho Energy Resources Company. The permit boundary encompasses in excess of 20,000 acres (81 km2) and is nestled against the western side of the Continental Divide. Production started on July 3, 1974, and the mine has produced approximately 90 million tons (82 million t) while moving approximately 450 million cubic yards (344 million m3) of virgin earth. Annual production averages 5 to 7 million tons (4.5 to 6.4 million t) of run-of-mine coal. Coal is consumed on site by the Jim Bridger Power Plant, a 2,000-megawatt generating station, and the electricity is transmitted to the Pacific Northwest power grid (Oregon, Idaho, Northern California, etc.).

Jan 1, 1991

By Y. C. Guan

In an attempt to replace the traditional cyanide process of extracting gold, a new technology using ammoniacal solutions has been developed. In this study, the electrochemical behavior of gold in ammoniacal solutions at temperatures above 100°C has been investigated. An electrochemical cell in an autoclave has been introduced to carry out this study. The system consists of a gold working electrode, a platinum counter electrode, and an external saturated calomel electrode (SCE) which is connected to the autoclave system through a Birch wood plug. Techniques used in this study included potentiodynamic polarization, galvanostatic polarization, cyclic voltammetry, and Tafel polarization. The electrochemical reaction mechanisms governing the dissolution process are presented.

Jan 1, 1996

By Raul A. Deju

This paper shows how one can relate the chemical reactions between water and a silicate bed to the equations of flow. First the reaction mechanism is studied both theoretically and experimentally. Once the reaction mechanism is established, the equations of flow are solved and a solution (under physically reasonable side conditions) is obtained. Experiments to substantiate the solution are also presented.

Jan 1, 1969

By C. Zhou, R. Jacksha

This paper reports measurement results for radio frequency (RF) propagation around 90° corners in tunnels and underground mines, for vertically, horizontally and longitudinally polarized signals. Measurements of signal power attenuation from a main entry into a crosscut were performed at four frequencies — 455, 915, 2450 and 5800 MHz — that are common to underground radio communication systems. From the measurement data, signal power loss was determined as a function of signal coupling from the main entry into the crosscut. The resultant power loss data show there are many factors that contribute to power attenuation from a main entry into a crosscut, including frequency, antenna polarization and crosssectional entry dimensions.

Jan 1, 2016

By Roland W. Merwin

The Bureau of Mines has studied the possibility of using the heap leaching process for treating the gold ores in the sedimentary beds of northeastern Nevada. This paper summarizes all available information on the technical and economic feasibility of heap leaching oxidized ores from these beds, past industry application of vat leaching, results of recent Bureau of Mines and industry tests on heap leaching ores from this region, and requirements for planning the proper application of heap leaching. Preliminary tests on representative samples of ores from the region show that a satisfactory recovery of gold can be obtained by heap leaching the ores with cyanide at a relatively coarse size. Significant deposits of gold ore occur in sedimentary beds of various locations over an extended area 40 miles wide and 200 miles long in northeastern Nevada. The area is centered 40 miles west of and runs parallel to the leading edge of the Roberts Mountain thrust fault system, a prominent geologic feature in the area. The general locations of past and present gold mining operations are shown in figure 1. (slide 1)

Jan 1, 1969

By Burke Trafton

An earlier paper1 introduced a rapid solution for mine ventilation network problems, employing the digital computer. In this paper, refinements and additions to the computer program which expand its scope of application and a solution to a ventilation network having a coal-mine configuration are presented. Specifically, the revised program--written in FORTRAN for the IBM 7074 computer in Penn State's Computation Center--is applicable to any mine ventilation network employing natural splitting and having its fan located externally. It accomplishes the following; 1. Distributes an assumed total quantity of air flow among all air- ways of the network, performing iterations until an acceptable level of error is attained and the flow in each airway is known. 2, Computes the pressure drop (head loss) in all airways and the overall network and mine head losses. 3. Determines the operating point for the mine and a given fan, adjusting all air flows and head losses to the actual values.

Jan 1, 1964

By Allen D. Graham

The coal industry in South Africa is briefly outlined. Test- work carried out on bulk samples of coal in the laboratory and used in the design of the Van Dyks Drift washery are described. Factors affecting the selection of equipment and the designed capacity of the plant are discussed. A description of the crushing plant, washery and load out section is given together with performance data obtained in the final acceptance tests. New features incorporated in the Van Dyks Drift plant and in more recent plants of the Group are outlined.

Jan 1, 1982

By P. Jonsén

Understanding mill charge motion is important. In the charge, the centre of gravity is shifted from the rotational centre of the mill system, and its motion is induced by rotation of the mill, while at the same time the charge creates a torque into the mill system. Breakage of ore particles and wear of liners/ball media are closely linked to the motion. To study these phenomena in a physically correct manner, numerical models for different parts of the mill system are needed. Validations of such models are scarce, because of the difficulty to measure in a tumbling mill. Experimental measurements in a lab mill were done for diverse load cases: varying feed materials, mill fillings, mill speeds and pulp liquids. The mill is set up to directly measure the charge-induced torque. The accuracy is good with relative uncertainty smaller than ±2% for relevant load cases. A full three dimensional numerical model of the whole mill is used to predict induced torque. Agreement between predicted and measured torque at steady-state is good. In addition, the model can accurately predict the mill start-up behavior for torque and mill power. This proves that the model is physically correct, and can be used for full-scale mills.

Feb 27, 2013

By M. T. Ityokumbul

Flotation columns and their variations are increasingly replacing conventional cells in mineral processing circuitry. While the operational characteristics of columns differ from those of conventional cells, the same scale-up methodologies are being employed in design. This practice may be attributed to poor understanding of the factors controlling throughput. The use of tall flotation columns is frequently justified on the requirement for increased particle residence time. It is shown that longer particle residence times in the column cell alone do not translate into increased recoveries. Throughput data from several industrial flotation column installations is presented. An attempt at using dimensional analysis to provide scale-up methodology for the factors controlling column throughput is made.

Jan 1, 1995

By D. R. Lanners

Samples of the same coal measure overburden spoil were obtained from three different mine sites. Site A used a 27-m3 tub-mounted dragline, Site S used a front-end loader and truck combination, and Site C used a 6-m3 crawler-mounted dragline. The spoils were analyzed in the laboratory for the strength parameters using drained triaxial tests conducted on 150-mm diameter specimens. Regression analysis was utilized to determine the appropriate failure criterion for the strength data from each site. Spoil obtained from Site S yielded higher shear strengths than Sites A and C.

Jan 1, 1993

By Mark Van Dyke, Ted Klemetti, Jake Beale, Zoheir Khademian, Joe Wickline

In 2016, a 3.7-ML magnitude event caused by mining activity occurred at a longwall mine in southwestern Virginia which was recorded by the United States Geological Survey (USGS) and felt by local residents. The event was the largest of its kind since a global mine design change by the operator was instituted in 2008 following three large events in 2005, 2006 and 2007 (3.4, 4.3, and 3.4, respectively). Two of the three pre-2008 events (2005 and 2007) damaged ventilation controls in the mine which fueled a mine fire. In 2016 the mine’s management requested researchers from the National Institute for Occupational Safety and Health (NIOSH) to access geological data and determine what parameters could possibly lead to events of a magnitude of 1.0 ML or greater. Evaluation of 2,152 geological data points and modeling revealed three major geological factors in common with the majority