Search Documents

By Dennis S. Kostick

Introduction Soda ash is known chemically as sodium carbonate, an important inorganic chemical. It has been produced for several centuries by processing certain vegetation and minerals. The US soda ash industry has evolved from several small sodium carbonate mining operations in the West. Now, a nucleus of six companies produce about one-fourth of the world's annual soda ash output US producers currently dominate the world market. But certain international events are occurring that will reshape the domestic soda ash industry in the next decade. Historical perspective Soda ash is used mainly in the manufacture of glass, soap, dyes and pigments, textiles, and other chemical preparations. All of these are the first basic consumer products produced by developing societies. About 3500 BC, the Egyptians became the first society to use crude soda ash. The soda ash was used to make glass containers. It was most likely obtained from dried mineral incrustations around alkaline lakes. Soda deposits were virtually nonexistent in western Europe. So people resorted to burning seaweed to obtain the ashes. The ashes were then leached with hot water and the solute was recovered after evaporating the solution to dryness. The solute, a crude "soda ash" was impure. But, it could be used to make glass and soap. These two products and industries were important to the population and economic growth of the region. About 11.5 t (13 st) of seaweed ash was required to produce about 0.9 t (1 st) of soda ash. Along the coasts of England, France, and Spain, seaweeds with varying alkali contents became important items of commerce and sources of soda ash before the 18th century. The LeBlanc process used salt, sulfuric acid, coal, and limestone. It became the major method of production from about 1823 to 1885. In the early 1860s, Ernest and Alfred Solvay, two Belgian brothers, successfully commercialized an ammonia-soda process to synthesize soda ash. It used salt, coke, limestone, and ammonia. The Solvay process produced a better quality product than the LeBlanc method. In 1879, Oswald J. Heinrich presented to the Baltimore meeting of AIME, a paper entitled "The manufacture of soda by the ammonia process." The paper compared the two processes and foretold the demise of the LeBlanc technique. World production of soda ash in 1880 was 680 kt (750,000 st). Of that, 544 kt (600,000 st) was produced by the LeBlanc process. Of the 2.8 Mt (3.1 million st) of soda ash produced worldwide in 1913, only about 50 kt (55,000 st) was by the LeBlanc method. The LeBlanc process was never used successfully in the US, except for a brief period from July 1884 to January 1885 in Laramie, WY. Previously, soda ash had been produced by burning certain plants, as exemplified by the early Jamestown colonists, or by recovering small quantities of natural sodium carbonate found in alkaline lakes, such as those found near Fallon, NV, and Independence Rock, WY. Before the 1884 startup of the first synthetic soda ash plant in the US at Syracuse, NY, most of the domestic soda ash demand in the East was met by imports, primarily from England. Large-scale commercial production of natural soda ash began in California in 1887 from surface crystalline material at Owens Lake. Production from sodium carbonate-bearing brines at Searles Lake began in 1927 (Fig. 1). In 1938, during exploration for oil and gas in southwestern Wyoming, a massive buried trona deposit, presumably the world's largest, was accidentally discovered. Recent mineral resource evaluation by the US Geological Survey and the US Bureau of Mines indicates that the Wyoming trona deposit contains 86 Gt (93 billion st) of identified trona resource in beds 1.2 m (4 ft) thick or greater. Additionally, there is about 61 Gt (67 billion st) of reserve base trona. Of this 36 Gt (40 billion st) is in halite-free trona beds and 24 Gt (27 billion st) is in mixed trona and halite beds. In 1953, the Food Machinery and Chemical Corp. (later shortened to FMC Corp.) became the first company to mine trona in Wyoming. Soda ash demand increased.

Jan 10, 1985

By J. Tuzson, H. McL. Clark

Introduction Wear of pumps, wet cyclones and pipelines by suspended solid particles will impact their operating economies by limiting their useful life, reducing their reliability and increasing the amount of servicing. Erosion is considered a materials problem. The empirical solution consists of testing different materials in field applications. Such tests are time consuming and expensive. The prediction of localized wear rates, life estimates and appropriate material selection demand a better understanding of the slurry wear process in environments corresponding to those found in working equipment. Key words: Wear, Slurry abrasion, Coriolis erosion tester The slurry wear process Solid particles suspended in liquid generally move with the flow, but such particles deviate under the centrifugal and Coriolis forces encountered in pumps. The concentration of particles will increase, and a solid layer or bed may accumulate if the acceleration is directed against the flow passage wall. Large particles in dilute suspensions may impact the wall. dissipating their kinetic energies and removing material. However, particles smaller than about 11)(1 µm encounter great drag when moving through the liquid. and such par¬ticles have little kinetic energy left when they reach the wall. They cannot penetrate the stagnant boundary layers present in pumps. Therefore, small particles tend to form beds that slide along the wall, removing material by a process that could he called sliding erosion or wet abrasion. Wear by impact erosion from large particles in dilute slurries can he predicted by appropriate analytical and empirical methods. However, laboratory tests and calculations of wear rates that correspond to sliding erosion are more likely to correlate with field experience from wear under similar conditions. Specific energy Data from laboratory slurry erosion experiments have shown that the amount of material removed is approximately in proportion to the energy expended in the erosion process. Thus. the specific energy-energy expended in removing by erosion a unit volume of material-offers a simple, practical measure for the erosion resistance of materials. The concept was found to also apply to sliding erosion (Clark et al.. 1997). Generally, the study of the material-removal process in slurry erosion continues to remain a subject of research. Conceptually, if the flow velocities and accelerations could be calculated in a pump or pipeline, the energy dissipated at the passage walls could also be estimated, and the material removal rate would become known from the specific energy determined by laboratory tests. Slurry erosion testing Laboratory devices made specifically for slurry erosion testing may be grouped into the following: jet erosion devices, slurry pots and the Coriolis test machine (Pagalthivarthi and Helmly, 1992). Jet erosion devices use a slurry pump and nozzle to produce a high-velocity slurry jet that is directed at a flat material specimen, either perpendicularly or at some acute angle. Combined impact and sliding erosion are produced. but the processes cannot be separated, and the wear is difficult to assess except by weighing. Slurry pots consist of a cylindrical vessel containing the slurry of interest. In the slurry pot, test specimens are attached to a rotating arm. The samples are rotated in the slurry and experience local flow conditions that result in combined impact and sliding erosion. Wear depth measurements from detailed laboratory experiments have been successfully correlated with results from an analytical model of the process, and specific energy values have been calculated (Wong and Clark, 1995). In industrial use, the samples are weighed to determine the total material loss. Materials are ranked with respect to some reference material. The Coriolis erosion tester (Tuzson, 1984) consists of a rotor with a central cavity, from which two opposing radial passages lead out (Fig. 1). The slurry is fed to the centerof the rotor in one pass from a stirred overhead tank. The slurry particles are subjected to the Coriolis acceleration as they flow out through the radial passages. The material specimens are mounted into the radial passage walls facing the direction of rotation and are eroded by the particles that are pressed against them as they flow out radially. A narrow groove is worn into the sample within a few minutes, using a few gallons of slurry. Material removal is estimated accurately from profilometer traverses across the wear scar at different locations. The energy dissipated by the particles can be estimated, which leads to a well-defined experimental value for the specific energy.

Jan 1, 2000

By A. D. Davis, C. J. Webb, A. Heriba

Introduction The disposal of spent ore from cyanide heap-leach processing facilities is of concern to the mining industry, the regulatory agencies and the general public. The disposal of an additional several hundred million tons of spent ore from heap-leaching operations is planned in the western United States during the next decade, and this amount could increase if gold prices rise. In the past decade, more than fifteen million tons of spent ore have been disposed of in the Black Hills of South Dakota. The criterion for offloading spent ore was set by the South Dakota Department of Environment and Natural Resources at 0.5 ppm weak acid dissociable (WAD) cyanide. South Dakota's nitrate offloading limits vary for each mine, depending on ore type and other factors. Concentrations of nitrate in the leachate from spent ore depositories could be the result of conversion from other nitrogen-containing species. One likely source of nitrate is residual explosives from the blasting of ore. Previous work on the combustion products of nitrogen explosives has shown incomplete oxidation (Johansson and Persson, 1970). Another likely nitrate source is the degradation of cyanide to ammonia, followed by oxidation to nitrite and nitrate. A third possibility may be leaching of background nitrate from soil or rock. Objective The primary objective of this research was to investigate laboratory procedures for predicting nitrate concentrations in effluent after the disposal of spent ore at heap-leach gold processing operations. Laboratory tests were performed to define the concentrations of nitrate and nitrite in leachate as a function of time. Sources and species conversions were examined by investigating the nitrogen contributions from cyanide neutralization and from blasting with ammonium nitrate/fuel-oil (ANFO) explosives. Ore processing at cyanide heap-leach facilities Gold mines in the northern Black Hills of South Dakota normally use the following steps in their heap-leach cyanidation processing: Blasting. Surface gold mines in the Black Hills use ANFO explosives (approximately 95% ammonium nitrate and 5% fuel oil). Field evidence and studies show that explosives often fail to ignite or burn completely in shot holes. One reason is that ammonium nitrate absorbs moisture readily, which reduces blast efficiency. Ferguson and Leask (1988) cited a study conducted at the Fording coal mine in southeastern British Columbia. In that study, the total nitrogen released to surface and ground water was estimated to be about 6% of the slurry explosives. However, Ferguson and Leask (1988), in a later analysis of water quality near coal mines in the Kootenay coal fields, indicated that this is likely an overestimate of the nitrogen release. Mines that used ANFO explosives in dry conditions released 0.2% of the nitrogen from blasting. Cyanidation. At surface gold mines in the northern Black Hills, cyanide species from heap leaching can be classified into free cyanides and simple ions, weak complexes, moderately strong complexes and strong complexes (Scott and Ingles, 1981). Degradation of cyanide and disposal of spent ore. Methods of destroying cyanides include hydrogen peroxide oxidation, natural degradation and evaporation, water leaching and alkaline chlorination. Hydrogen peroxide is used to oxidize cyanides in the northern Black Hills mining area. The hydrogen peroxide oxidation reaction forms cyanate, which can hydrolyze to form ammonium and carbonate ions. After formation of ammonia or ammonium ion, further oxidation to nitrite (NO2-) and nitrate (NO3-) can occur. Spent tailings from gold processing in the Black Hills normally are disposed of in tailings facilities constructed in nearby drainages. Infiltrating rainwater with a typical pH of about 5.6 is an additional component introduced into the spent ore after disposal. Methods Field sample collection. Spent ore samples were collected from conveyor belts (or other convenient points) at heap-leach mines by personnel from the South Dakota Department of Environment and Natural Resources. The samples were placed in black plastic bags that were contained within 5-gal buckets and sealed to prevent exposure to ultraviolet light. The samples had a minimum head space to limit evaporation and contact

Jan 1, 1997

By G. T. Newell, J. G. Stone, V. M. Mejia

Introduction Advances in drilling have reached a point where large diameter cores can be recovered from "tight," or weakly indurated placer gravels. In such ground, core drilling can provide more reliable data regarding tenor than can be obtained using churn drilling or similar classical techniques. It can also provide metallurgical and geological information that is not available from samples obtained through alternate methods. In 1985, Coastal Mining Co, a subsidiary of M. A. Hanna, and Western Gold Reserves began to review a Tertiary placer deposit owned by San Juan Gold at North Columbia, CA, about 14 km (9 miles) northeast of Grass Valley. The deposit is one of the largest remaining unmined portions of the formerly extensive early Tertiary ancestral Yuba river system. It has been known since the 1850s, has been the subject of much technical literature, and has been the object of at least four previous drilling programs. The eastern one-third of the 6 km (3.7 mile) stretch of the channel between North Columbia and Badger Hill was partially stripped by large scale hydraulic mining in the late 1870s and early 1880s. Mining ceased in 1884 when the Sawyer Decision prohibited further discharge of hydraulic tailings into the Sacramento and San Joaquin Rivers. By that time, about 30 to 45 m (100 to 150 ft) of relatively low grade upper gravels had been removed over some 81 hm2 (200 acres). About 90 to 105 m (300 to 350 ft) of higher grade middle and lower gravels were left at least partially stripped. In 1914, a few churn holes were drilled along a widely-spaced line. In 1938-1939, Selection Trust conducted an extensive drilling campaign to evaluate the deposit. Particular attention was directed toward the partially stripped eastern portion. In 1968, the US Geological Survey drilled three churn holes in the eastern part of the deposit. The US Bureau of Mines conducted experimental mining and drilling in the Badger Hill area. In the late 1970s, Placer Service Corp. acquired a lease on the deposit. Between 1979 and 1984, Placer Service drilled 28 large diameter BADE (a German-manufactured machine) drill holes on the eastern portion of the deposit. The surviving records from the widely-spaced 1914 drilling program are fragmentary and the reported grade not well substantiated. The 1968 holes were drilled for scientific purposes. Again, drilling details are not available. However, detailed records for both the churn drilling program and the BADE program were available and formed the basis for the initial evaluation of the property. Geology The geology of the auriferous Tertiary gravels of California have been described by Whitney (1880), Lingren (1911), and, more recently, Yeend (1974). In general, the Tertiary gravels in the North Columbia area occupy a broad channel cut into pre-Tertiary igneous and metamorphic rocks. The upper, or white gravel is overlain conformably by volcanic tuffs and volcaniclastic rocks. A middle gravel is characterized by the presence of silicified and carbonized wood. A lower blue gravel unit has relatively coarser cobbles and contains a higher proportion of igneous and metamorphic cobbles than the other units. The upper gravel consists of interbedded pebbly sand and silty, or clayey sands with prominent cross bedding. Most of the pebbles are well rounded and consist mostly of white vein quartz and quartzite. The upper unit is moderately well compacted. Exposures in the walls of the old hydraulic mine pits stand at 45° and 50° angles. The gold content of the unit is well below an economic cutoff. The middle gravel - included with the upper unit by Yeend (1974) - is coarser grained, with carbonized wood, and 75 to 100 mm (3 to 4 in.) cobbles of metased-imentary and metavolcanic rocks in a sandy matrix containing abundant lithic fragments. The upper contact appears to be conformable, but the lower portion of the unit appears in places to consist of reworked lower gravels. The unit contains less clay than the upper unit and is somewhat more friable than the underlying lower gravels. The gold content, while somewhat higher than the upper level, is too low to be of ore grade. The lower gravel averages between 30 to 45 m (100 to 150 ft)

Jan 9, 1988

Let’s start off with your assessment of the mining industry. Today, the status of the mining industry is stronger than it has been over the previous few years. While mining continues to be a major part of the world’s economic foundation, the industry is gaining strength due to rebounding metals and minerals prices. And now, with these rising prices and the changes the industry instituted during the years when mining-related commodities were selling at low prices, our stronger, more productive and internationally competitive industry should flourish. Mining remains an essential business and the industry is far ahead of the game when it comes to the trend of globalization as a key to sustained growth. Also, the industry continues to realize increased productivity through technological innovations. And an increasing number of countries are moving towards capitalism, which opens doors for exploration and mining within their borders. After looking at all of these factors, I believe that the mining industry will only continue to gain momentum in the future.

Jan 1, 2004

By K. P. Black, G. W. Sevick, D. E. Hockley, K. S. Sexsmith, J. T. Chapman

Mineralogical analyses of carbonates in depyritized tailings and pyrite concentrate (from depyritization of the tailings) were completed as part of the tailings characterization for the Crandon Project, a massive sulfide deposit in northeastern Wisconsin. The mineralogical study was designed to determine the proportion of calcium and magnesium carbonates, and therefore the effective buffering capacity of carbonates in the tailings. The depyritized tailings are net acid consuming and will be stored in a surface tailings management area. The pyrite concentrate is net acid generating and will be used as backfill in the underground mine workings. The majority of carbonates in the depyritized tailings were ferroan dolomite containing 10 to 15% iron (by weight) and lesser amounts of siderite and magnesian siderite. The proportion of calcium and magnesium-rich carbonates corresponds to several independent tests of carbonate neutralization potential (CO3-NP) availability. The pyrite concentrate had less CO3-NP, indicating segregation of the carbonates during pyrite flotation. These carbonates reported higher iron contents, consistent with the relatively lower availability of CO3-NP in the pyrite concentrate.

Jan 1, 2002

Introduction The objective of the design and operation of a mine is to make as much money as possible within certain reasonable and responsible constraints. The imposition of constraints on the objective of maximizing profits can result in an optimum mine design. This paper deals with the maximization of profits. Optimization will be discussed in a future paper. In the mining industry, it is generally accepted that the maximum economic recovery is defined by identifying the reserves and the sequence of mining that results in maximum net present value (NPV) or discounted cash flow-rate of return (DCF-ROR), as indicated in Fig. 1 (see Lemieux, 2000). Current parametric analyses techniques, such as varying the mining costs; profit reservation; sales price or metal content, to define pit limits and mining sequence technically referred to single, double or triple parameterization, do not assure that the curve in Fig. 1 will be maximized. In defining the sequence, the first material to be mined should be the first grouping of recoverable mineral that has the highest after-tax unit value and that forms a feasible mining unit. The assumed mining of the first pit should be followed by the assumed mining of the second most profitable and practical pit or pit expansion. If this process of grouping and sequencing is followed until the profitability approaches zero, the general sequence required to extract the maximum economically recoverable reserve is identified. The curve in Fig. I is constructed by calculating the NPV for a series of sequences, each assuming operations are terminated on successively lower profit pits. If the operation ceases on a pit with too high of a profit, opportunity is lost, and the NPV is lower than the maximum. The NPV curve peaks and then starts to decline before the zero-profit pit is assumed mined. This occurs because the money invested in advanced stripping would have produced a greater return if it was invested at the dis¬count rate. The maximum economically recoverable reserve is defined by the pit limit corresponding to the maximum NPV or DCF-ROR. Pit and phase definition The real challenge of reserve definition is identifying the phasing and after-tax profit per ton, so that the curve in Fig. 1 can be plotted. The after-tax profit cannot be properly addressed until after the pits are designed, the production is scheduled and the cash flow is estimated. Throughout the years, many investigators have ad¬dressed this problem. A major thrust of the famous paper in which Lerchs and Grossman (1965) presented their algorithm was to identify a sequence that would produce a result similar to that identified in Fig. 1. Whittle's (1988) four-dimensional analysis is designed to address this issue. The author addressed this same issue in a paper presented to the 1968 Canadian Institute of Mining national convention (Lemieux, 1968). Without a relatively simple methodology to con¬struct the curve in Fig. 1, the number of iterations in a trial-and-error method becomes prohibitively burden-some. The pit designer seeks a simple pit-planning parameter that will serve as a proxy for the after-tax profit per ton used in defining the curve in Fig. 1. The designer's goal is to apply this pit-planning parameter using standard pit-wall location techniques to design a series of pits that will provide a guide to the sequencing. Common techniques used to position pit walls are strip-ratio limits, highwall incremental analysis, floating-cone methods or "maximizer" applications1. Costs, revenues, noncash charges, taxes and profits are usually structured on a unit basis for use in the pit-wall location analysis. Application of the proxy parameter using the pit-design tools should, ideally, result in the definition of pits and sequences that will maximize the curve in Fig. 1. 1 The pit-design tool frequently referred to in the literature as an "optimizer" defines a pit boundary that maximizes the value contained within based on the input parameters and the safe pit-wall angle. The optimization of the pit design involves selection of rate of production, cutoff grade, product quality and other considerations. These considerations constrain the maximization of value. Therefore, pit-design tools that maximize value should be called "maximizers."

Jan 1, 2000

By Robert L. Cheek, Sid McIlveen

Sodium sulfate is an important industrial chemical. As recently as ten years ago it was produced and consumed in the United States in quantities exceeding 1 Mtpy. Since then, both its production and use have declined; however, approximately half the production still comes from natural sources. [Fig. 1] illustrates the history of production of natural sodium sulfate in the United States. Production of natural sodium sulfate from various types of deposits is the main source of this chemical in Canada and Mexico, and probably in Argentina, Chile, Iran, Spain, and the Russian Republics. MINERALOGY AND PHYSICAL PROPERTIES Sodium sulfate is widespread in occurrence and is a common constituent of many mineral waters, as well as seawater. Atmospheric precipitation contains sulfate; it is one of the major dissolved constituents of rain and snow (Davis and Dewiest, 1966). Many of the saline lakes throughout the world contain varying amounts of sodium sulfate. Because sodium is usually the dominant cation, some workers make an anionic distinction, referring to lakes containing predominantly sulfate as bitter lakes and those containing predominantly carbonate as alkali or soda lakes (Bateman, 1950). Sodium sulfate in its natural form is found in two principal minerals, mirabilite and thenardite. Mirabilite, the hydrous form, is commonly called Glauber's salt. It was discovered by the German chemist, J.R. Glauber (1603-1668), who derived its name from the Latin, sal mirabile, meaning wonderful salt. Thenardite, the anhydrous variety, was named for the French chemist, Louis Jacques Thenard (1777-1857) of the University of Paris (Mitchell, 1979). The largest quantities occur in the form of mirabilite. Sodium sulfate is found in varying degrees of purity, from theoretically pure efflorescent crystals of mirabilite to combinations and admixtures of other salts and impurities. It is a common constituent of some brines; from this source much is extracted commercially. Sodium sulfate also is found in compounds, such as the minerals glauberite, the double salt of anhydrous sodium and calcium sulfate, bloedite, the hydrous double-salt of sodium sulfate and magnesium sulfate, and burkeite, the anhydrous double-salt of sodium carbonate and sodium sulfate. Over 40 minerals contain sodium sulfate in varying proportions; many are of special interest because of their frequent occurrence. Table 1 lists some sodium-sulfate bearing minerals. The reader is referred to other publications (Cole, 1926, Dana, 1932, Grabau, 1920, and Dietrich, 1969) for descriptions of these minerals. Only mirabilite and thenardite will be described herein. Mirabilite Na$04.10H20, contains 55.9% water of crystallization. It is noted for its efflorescence or spontaneous loss of water. On dehydration it changes to the anhydrous form, Na2S0,. Mirabilite is an opaque to colorless, water-soluble mineral that tastes first cool, then slightly bitter. It has a specific gravity of 1.48. It frequently forms as efflorescent, needlelike monoclinic crystals, but generally is found in the massive form. Thenardite, the anhydrous mineral, Na2S04, contains 43.68% Na20 and 56.32% SO3. It ranges from colorless to white and may be tinted shades of gray or brown. It is a water soluble mineral with a slightly salty taste. Its specific gravity (2.67) and hardness (2.5 to 3) exceed those of mirabilite. It commonly occurs in the massive form without visible crystals. Its crystals are frequently tabular pyramids of the orthorhombic system. Sodium sulfate also occurs as a heptahydrate, containing seven molecules of water, but this is unstable and has not been found in the natural environment. The solubility of sodium sulfate has an important effect on the crystallization of the salt in nature, as well as in its production. Its solubility in water generally increases as a nonlinear function of temperature. Below 1.2°C, ice and mirabilite form. As the temperature is increased above O°C, increasing amounts of sodium sulfate become soluble. At 32.4°C, a transition point on the solubility curve is reached, as the decahydrate melts in its own water of crystallization and the anhydrous form crystallizes. With in- creasing temperatures, solubility decreases somewhat. The presence of other dissolved salts changes the transition temperature and solubility characteristics of sodium sulfate.

Jan 1, 1994

By I. Demers

Doyon mine, Quebec, Canada evaluates the possibility of desulphurizing their tailings to produce material to be used in as cover over the acid generating tailings disposal site. Laboratory tests were conducted and showed that a single-layer cover made of desulphurized tailings placed over reactive tailings can prevent the generation of acid mine drainage. Modelling with the software Vadose/W was undertaken to optimize the design parameters, namely cover thickness, water table position, and residual sulphide content of desulphurized tailings following laboratory work. It was found that the optimal configuration includes a 1 m desulphurized tailings cover containing 0.8%S, with the water table kept at the interface between the reactive tailings and the cover. To maintain the cover performance to reduce oxygen flux towards acid-generating tailings even in the event of a long dry period, a sand layer is suggested to protect the cover from excessive evaporation. It is possible to reach the environmental objective chosen for Doyon mine (10 mol/m2/year) with the protective sand layer, even in extremely dry conditions.

Jan 1, 2008

By C. F. Curry

In the early 1940's Humphreys Mining Company in Florida pioneered heavy mineral mining with a dredge in the United States, In 1948 Du Pont, in conjunction with Humphreys, opened their first of two mining operations recovering a titanium dioxide product in Florida. Later on in 1952 Du Pont opened their second plant, both of which used a cutterhead suction type of operation. This process is also used in heavy mineral mining in Australia and Africa. In 1957 ASARCO started prospecting in New Jersey. Test borings indicated a large deposit of ilmenite bearing heavy mineral sands had been deposited and concentrated in an area near Lakehurst in central New Jersey. Humphreys Mining Company was contacted about the possibility of mining the ASARCO New Jersey property in much the same way as Du Pont and themselves were doing in Florida. An extensive study was made to determine the economic feasibility of mining the ASARCO property. During this study, extensive test drilling and samples for a pilot plant were taken.

Jan 1, 1975

By H. Lawson

The Mine Safety and Health Administration (MSHA) issued Program Information Bulletin P09-03in April of 2008, providing formal guidance on using programs that model the redistribution of stress during underground mining of coal. A key part of this guidance is visual observation and mapping of ground conditions. If a correlation between ground conditions and model output can be established, the model is considered to be verified, and can be used to guide mine design in similar ground. A simple scale is recommended for ranking observed roof, rib, and floor conditions. This paper discusses optimization and implementation of a ground condition rating scheme in the gateroads of a deep underground longwall coal mine. Roughly 80% of each gateroad length deteriorated in a fairly uniform manner. However, this manner varied between gateroads, as did pillar size. The implementation of a ground condition mapping program, similar to that recommended in PIB 09-03, was successful in characterizing the ground response to mining in gateroads of a longwall coal mine.

Jan 1, 2012

By John C. Ruckmick

Elemental sulfur deposits generally can be classified as either volcanogenic or biogenic. The latter can be divided into biosyngenetic and bioepigenetic deposits. Essentially all economically important sulfur deposits are bioepigenetic replacements of anhydrite or gypsum in basins containing evaporites and hydrocarbons. Anaerobic bacteria utilize the oxygen of sulfate ions to oxidize hydrocarbons to C02 and reduce the sulfate to H2S. Sulfur deposits are formed by concomitant and subsequent oxidation of the H2S. These bacterial systems can operate on enormous scales, producing deposits containing over 200 million tons of elemental sulfur. There are no known "old" sulfur deposits; almost all known deposits are younger than Miocene and most are still actively forming today. Therefore, it is probable that, with burial and time, sulfur deposits are converted to sulfide deposits. Perhaps more important, bacterial oxidation of hydrocarbons and resultant production and trapping of large quantities of H2S appears to be the logical explanation for the location of many important metal sulfide deposits such as the Mississippi Valley type lead and zinc deposits.

Jan 1, 2013

By W. Collingwood

As open pit mines continue to grow deeper and productivity continues to increase, the management of respirable dust and noxious gases can become a challenge. The natural wind flow in open pit mines is often recirculatory. This recirculation traps dust and gases in deep open pit mines. This problem is particularly acute in high latitude open pit mines due to a phenomenon known as an atmospheric inversion. In the winter, arctic and subarctic regions experience short days and long nights. This deficit of solar radiation creates a situation in which cold, still air accumulates near the bottom of the pit. In open pit mines, this can result in unhealthy accumulations of gases and other contaminants in the open pit mines. In this study, the natural wind flow patterns in and around open pit mines were investigated using a computational fluid dynamics (CFD) program. Two dimensional models were created for a variety of pit geometries. The effect of depth, slope angle, and wind speed on the recirculation pattern in the pit was examined.

Jan 1, 2011

By S. D. Bearden

Color enhances expression and communication in all physical objects experienced in life. Pigments provide color and in some applications have a specific additional function. Natural iron oxides are widely distributed throughout the world but only a few deposits are sufficiently pure and possess acceptable color and brightness properties to merit their processing into pigment form. Ochre, the common name for goethite ore, is the best and most under used material in the buff colored pigment market. The geological occurrence of ochre in the basal Shady Formation of the Cartersville Mining District (Georgia) is described. Exploration, processing, and product applications of New Riverside Ochre Company, Inc. are discussed. An overview of the worldwide pigment market is presented with emphasis placed upon the North American activity in iron oxide production and application. The purpose of this paper is to increase the awareness of ochre and its potential market in the colored iron oxide pigment industry, encourage research on the origin of ochre deposits, and stimulate interest in new applications of this unique substance.

Feb 27, 2013

By Henry S. Brown

At least two dozen massive sulfide deposits in the southern Appalachians have supported significant mining operations. Literally hundreds more deposits are known to exist, but are too small to be of commercial interest. Essentially all that are being, or have been, mined are those deposits that were exposed at the surface when first discovered. It is reasonable to assume that many more massive sulfide deposits, large and small, exist hidden not far beneath the surface. The ideas I am sharing with you here today are based both on my personal studies of some of the deposits and on descriptions of deposits in the literature. An attempt will be made to account for the genetic interpretation problems raised by many of these deposits posessing both "syngenetic" and "epigenetic" features. In addition, an examination will be made of the possible relationships between the massive and the not-so-massive sulfide deposits in this region. Hopefully, these observations added to those of others will eventually lead to the synthesis of a better model on which we can base exploration programs in the southern Appalachians.

Jan 1, 1976

By R. J. Weege

Conventional underground mapping methods and diamond drilling are being applied in a study to determine the nature of the copper ore occurrences near the footwall of the Osceola lava flow top, commonly referred to as the Osceola Amygdaloid. Our work to date suggests that structures formed by relatively impermeable barriers, created by flowage and injection of still-molten lava from the interior of the flow into the solidified, brecciated crust, acted as the ore receptacles. Ascending hydrothermal fluids traveling near the footwall contact were trapped and confined in these barriers which retarded the direct upward movement of the ore fluids and caused deposition of copper. Oreshoots located near the footwall appear to have been formed spatially' independently from the hanging-wall oreshoots by fluids traveling simultaneously, but along different channelways. The barrier concept as advanced by earlier writers to explain the concentration of the ore-bearing, fluids into broad shoots con¬stituting entire ore bodies is found to be equally as applicable for the localization of smaller oreshoots within the Osceola ore body.

Jan 1, 1962

By Steve Kral

Mining is a risky business. The cost of exploring for new mineral deposits is high and the success rate of finding one worthy of development is relatively low. And once a deposit is identified, there is no guarantee that it will become a mine. Mining companies have to spend a lot of time and money on due diligence, prefeasibility and feasibility studies, and sustainable development and environmental issues before deciding whether the deposit will become a profitable mine. And then there are the millions of dollars spent in developing the deposit and building a mine. No wonder the mining industry has trouble attracting investment capital. Companies take a large risk in developing reserves and investors take a similar risk in investing in them. So mining companies must be as accurate as possible in determining mineralization that makes it to reserve status. After all, reserves are a company’s most important asset and one of the critical factors analysts and funding sources look at when determining if a mine or mining company is worth the risk.

Jan 1, 2003

By T. S. Golosinski

Introduction Typical dragline rigging includes several sets of ropes: hoist ropes, drag ropes, dump ropes and boom suspension ropes. The drag and hoist ropes contribute most to the dragline operating cost. Both work in very difficult conditions and wear out rapidly. As a result, frequent rope changes are required resulting in substantial cost and productive time loss. Although performance of rigging has a profound impact on dragline efficiency, there are no common, industry accepted standards related to its selection, operation and maintenance. Little information on the subject is available and the practice differs widely throughout the industry. The performance of drag and hoist ropes depends on: •rope construction that should closely match requirements of the specific application, rope operating conditions and its maintenance and • correct definition and application of the rope discard criteria so that full advantage of the rope can be taken without endangering safety of its operation. This paper reviews the present practice related to all these factors. Its findings are based on the wide survey of the present industrial practice. Field survey In total, 33 North American dragline applications were surveyed of which 17 were Bucyrus-Erie machines, 10 were Marion and six were Page (now P&H). Most of the draglines were stripping overburden in coal mines, but the survey also included some unique applications such as phosphate mining in Florida and oil sand mining in Alberta. Hoist drive power of the surveyed machines varied from 300 to 7775 kW (400 to 10,400 hp). Drag drives varied from 300 to 5815 kW (400 to 7800 hp). Boom lengths varied from 37 to 110 m (120 to 360 ft). Bucket sizes varied from 5 to 96 m3 (6 to 115 cu yd). The hoist and drag ropes installed on the surveyed machines were supplied by 10 rope manufacturers and differed widely in type and construction. Most common rope strand constructions included standard strands, Seale, Warrington, Warrington-Seale and Filler-Seale. Results of the survey [ ] Working conditions Working conditions of hoist and drag ropes are quite different. The first cope primarily with bending on rope drums, point sheaves and deflection sheaves, and with tension force imposed by the bucket and its load. The drag ropes are exposed to severe abrasion at the pit crest, and to severe bending and crushing at fairleads, all while coping with tension forces imposed by resistance of the bucket to dragging. Bending of drag ropes at house rollers and at rope drums is of minor importance for their performance. Differences in working conditions result in different wear patterns, which make it feasible to install discarded hoist ropes to further serve as drag ropes. The hoist ropes wear primarily due to fatigue breaks of wires, while the drag ropes are subject to severe abrasion of outside wires, rope deformation and internal wire-strand breaking. The last is often indicated by the reduction of rope diameter. The summary of working conditions for the surveyed draglines is shown in Table 1. For simplicity, Table 1 does not include the data on rope bending at the fairleads, nor at the deflection rollers and house rollers. Similarly, Table 1 does not include the data on drag rope bending (other than that on the rope drum), as its influence on rope life is insignificant in view of severe abrasion and internal wear taking place elsewhere. The following abbreviations are used in Table 1: [D - diameter of rope drum. DP - diameter of boom point sheaves. d - rope diameter x - mean value of the measured parameter. s - standard deviation of x B/d - average bending ratio of ropes B/d =(D+ DP)/2d n - operational safety factor of the rope (rope stength) x (number of ropes) n(bucket load + bucket weight)] In terms of D/d ratio, the working conditions of hoist and drag ropes are similar to that in other related industrial applications. However, the safety factors of the dragline ropes are lower, which requires them to carry relatively large tension forces. The last explains the fact that the life of dragline ropes is low when compared to other industrial rope

Jan 1, 1995

By J. Burgess Winter

It is an honor to present the lecture in honor of Daniel C. Jackling, the developer of the technology of copper mining that we continue to use 100 years later. He made a dramatic breakthrough in the early part of this century in the development of bulk-mining methods for large, low-grade porphyry copper-sulfide ore bodies. At Magma Copper, we are particularly proud that the Jackling Award states we have "made significant contributions to technical progress." Before Jackling's time, copper mining had exploited with primitive equipment very high-grade underground ore bodies and high-grade open pits. During the 20th century, the situation changed. Three significant innovations occurred within about 10 years around the turn of the century. In 1903, Jackling's concept of large-scale mining with steam shovels and rail haulage was implemented at the Bingham Canyon mine in Utah. Eighty years after the introduction of rail haulage, the mine converted to truck haulage with large-capacity high-efficiency haul trucks and reduced the stripping ratio from 3.5:1 to less than 1:1.

Jan 1, 1995

By W. Rogers

Blast-induced rock mass displacement can have a significant impact on ore loss & dilution. The mischaracterisation of the grade boundaries both prior to, as well as a result of blasting can lead to significant financial losses on account of ore loss and dilution. Ore dilution occurs when waste material is miscategorised as ore and sent for processing or stockpiling, diluting the run of mine head grade and recovery. Ore loss takes place when valuable mineral is miscategorised as waste and sent to the waste dumps, thus never being processed and recovered. Extensive research has been conducted at the University of Queensland over the last fifteen years to understand the impact of blast movement on ore loss and dilution. Recent outcomes of this research have developed innovative tools and techniques to measure and model blast movement. These techniques have been implemented at Ahafo gold mine in Ghana to understand blast movement dynamics and to implement solutions to reduce blast-induced ore loss and dilution. These solutions are validated through controlled trials and have been incorporated into site standard operating procedures to sustain the benefits.

Jan 1, 2012