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By Antonio Peralta

Mining activity in Mexico began in the 16th century when the Spanish realized the mining potential of the new territory. Since that time, mining has evolved into a strong and vital industry for the country. Good professionals in the mining-related fields are fundamental to the growth and improvement of this industry. Since the end of the 18th century, formal education in mining has been available at the University of Guanajuato, in Guanajuato, Mexico. This school created one of the first schools of mines on the North American continent in 1828. In recent times, some other programs have been created at other universities. Universities offering mining related programs Listed here are the seven universities in Mexico that offer mining related degrees. They are the University of Guanajuato, UNAM, the University of Zacatecas, the University of Chihuahua, the University of Sonora, the University of Coahuila and the University of San Luis Potosi. The University of Guanajuato is the only Mexican university that offers graduate studies at the master's level. No PhD programs in mining engineering are offered at any Mexican university. Programs at each university are of different duration. They are: • University of Guanajuato-Five-and-a-half years, divided into five years of classroom instruction and six months in the working place. • University of Zacatecas - Five years of classroom instruction.

Jan 1, 1994

By V. T. McLemore

The Wind Mountain (WM) nepheline syenite deposit is part of the alkalic complex in the Cornudas Mountains, which ranges in age from 34.6 ± 1.5 Ma to 36.8 ± 0.6 Ma. The WM deposit consists of a complex, zoned pluton that ranges from syenite porphyry to nepheline syenite porphyry. The WM deposit has potential use for ceramics and dark-colored beverage containers and consists of nepheline, k-feldspar, albite, and varying amounts of other minerals. Analcime also is present locally but must be avoided because it is unsuitable for ceramic and glass. Chemically the deposit consists of 56-63 % SiO2 17-21 % Al2O3 and 4.0-5 % Fe2O3. Although initially iron is high, when the crushed rock is passed through a specialized magnetic separator, the iron content drops to below commercial maximum standards of less than 0.5% Fe2O3. The WM deposit is currently under exploration and testing to determine marketability.

Jan 1, 1994

By H. Suharyono, R. Hogg, P. Bunnaul

The flocculation of fine-particle suspensions by polymers is a nonequilibrium process whose performance is strongly influenced by physical as well as chemical variables. A standardized test procedure has been developed that provides quantitatively reproducible measurements of process performance in terms of the floc settling rate, supernatant turbidity and sediment compressibility. The procedure provides information on the development of flocs in response to polymer addition and on their degradation behavior during subsequent handling. Extensive experimental observations using a variety of solids and flocculant types have been used to develop criteria for reagent selection and process design. It is shown that the appropriate choice of reagent(s) is determined primarily by chemical factors (solid type, solution chemistry, etc.). However, actual performance depends more on physical variables, such as agitation intensity and the rate of flocculant addition. Some general guidelines for flocculant selection and process design in industrial applications are suggested.

Jan 1, 1994

By B. J. Arnold

Coal blending inherently means homogenizing a mixture of coals so that, overall, the properties of the blend meet some specifications for maintaining power plant performance and emission requirements. In common practice, however, coal blending is at best coal mixing. If necessary, more sophisticated blending systems can produce a more homogeneous feed by using accurate weighing devices and on-line coal analyzers coupled with sampling systems. Blending can be accomplished at the mine, on stockpiles, and from bins, bunkers, and silos.

Jan 1, 1994

By Arthur C. Pincomb, Alan R. Shapiro

A public awareness of and commitment to abate pollution of water, air, and soil continues to stimulate demand for industrial minerals and rocks capable of neutralizing strong and weak acids. The role of acid neutralizing agents is 1) to treat acidified water and soil until the desired pH is attained and 2) to remove acid-forming compounds from industrial processes to mitigate the formation of acidic discharges. Environmental applications for these agents include: acid rain mitigation, neutralization and prevention of acidic industrial process discharges, and treatment of acid mine drainage and coal refuse. Desulfurization of industrial flue gases involves removal of sulfate compounds capable of combining with hydrogen to form acids. Details of flue gas desulfurization are covered in the previous chapter on Flue Gas Desulfurization. Ideally, the neutralization of acids results in an upward adjustment of effluent pH 7, or neutrality. The final pH value for many acid treated wastes, especially industrial discharge streams, is commonly over neutralized to pH 8.5 to 9.5. The Clean Water Act sets the upper discharge limit at pH 9. ACID NEUTRALIZATION REAGENTS Acid neutralization is accomplished by adding alkali metal and alkaline earth metal compounds to acidic water or soil until the desired pH is attained. The commonly used alkali ions are calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K). Sodium hydroxide, high calcium and dolomitic hydrate, high calcium and dolomitic lime (quicklime), high calcium and dolomitic limestone, soda ash, and magnesium oxide are the compounds most commonly applied to raise the pH of acidic waters or soils. Limestone and dolomitic limestone, which are calcium and magnesium carbonates, and their equivalent oxides and hydrates formed by calcination, are the industrial materials most commonly used in the manufacture of reagents for acid neutralization. Approximately 327 kt of high calcium and dolomitic lime were consumed for acid neutralization purposes in 1988. Magnesite and brucite are industrial minerals that compete with dolomitic limestone for the magnesium-oxide market. Production of caustic calcined magnesia for neutralization purposes exceeded 6 kt in 1990. Soda ash is an industrial mineral gaining increased acceptance in the neutralization of acid waste discharges. Approximately 182 kt of soda ash were consumed in 1990 for acid waste treatment or acid prevention by flue gas desulfurization. Other mineral products either consumed in minor quantities or receiving attention as future neutralizing agents include zeolite and hectorite. In some cases, waste products have been found to be suitable and cost effective for neutralization of acids. Common wastes gaining acceptance include basic slag, phosphate mining refuse, cement kiln dust, fly ash, and mine tailings.

Jan 1, 1994

By J. R. Batista

Leachates from gold heap-leaching mines contain selenium concentrations as high as 2 mg/L. Previous studies report satisfactory selenium adsorption by activated alumina when using relatively "clean" drinking waters. However, the findings of these studies cannot be directly applied to the treatment of mine leachate where other ions compete for the alumina adsorption sites. This study evaluated the adsorption of selenium from a mine leachate to develop design parameters for full-scale activated alumina processes. The study revealed that 68% of the selenium in the leachate could be removed by alumina at pH > 5.0. Silica adversely affected the selenium adsorption capacity. At pH values < 4, silica was poorly adsorbed by alumina and selenium adsorption was improved.

Jan 1, 1994

By Ken Santini, Ronald R. Bauer, Joseph R. Copeland

Wollastonite, named after W.H. Wollaston, an English chemist and mineralogist, is a calcium metasilicate having the chemical formula CaSiO2. Although it is a unique mineral, wollastonite has a short history of industrial use. Wollastonite is the only naturally occurring, nonmetallic, white acicular mineral. Its acicularity is the main reason for its ascendancy in the late 1970s and 1980s as a reinforcing filler and as a replacement for short-fiber asbestos and short-fiber milled fiberglass. Wollastonite is used in applications ranging from bowling balls to automobile fenders, from ceramic tile to automobile brakes, and from thermal insulation board to protective industrial coatings. The United States is the largest producer of wollastonite, with China, India, and Finland as the other three major sources. The United States, Europe, and the Far East are where most of the production is consumed. Geology Mineralogy and Physical and Chemical Properties Wollastonite, a member of the pyroxenoid mineral group, has the theoretical composition of 48.3% CaO and 51.7% SiO2. Iron, manganese, magnesium, or strontium may substitute for some of the calcium. Commonly associated minerals include garnet, diopside, calcite, quartz, epidote, apatite, and sphene. Some of the physical properties of wollastonite are listed in [Table 1]. Wollastonite is largely chemically inert; however, it can be decomposed in concentrated hydrochloric acid. Some wollastonite will fluoresce under shortwave or longwave ultraviolet light, or both, with colors ranging from pink-orange to yellow-orange and, more rarely, bluish green. In addition, wollastonite may show phos¬phorescence. Because of its unique cleavage properties wollastonite breaks down during crushing and grinding into lath-like or needle-shaped particles of varying acicularity. This particle morphology imparts high strength and is therefore of considerable importance in many of the markets for wollastonite. The acicularity of particles is defined by their length:width, or length:diameter, ratio (i.e., aspect ratio). Individual particles, even the smallest ones, commonly ex¬hibit an aspect ratio of 7:1 or 8:1 and have an average diameter of 3.5 gm. Low aspect ratio products (powder wollastonite, or milled grades) with 3:1 to 5:1 aspect ratios are used as general fillers, in ceramics, and in metallurgical fluxing. High aspect ratio products with ratios of 15:1 to 20:1 are used as functional fillers for rein¬forcing thermoplastic and thermoset polymer compounds and as a replacement for asbestos. The dry brightness and whiteness of wollastonite are also important in determining its suitability for certain filler and ceramic applications. When pure, the mineral is brilliantly white, but impurities may color it cream or gray. Brightness is determined by measuring the reflectance of finely ground powder against a stan¬dard that is assigned a brightness of 100. Magnesium oxide and barium sulfate are the two standards used. G.E. brightness, a term used in North America, refers to brightness measured with a Gen¬eral Electric reflectometer. Commercial wollastonite products usu¬ally have a G.E. brightness ranging from 85 to 95. The Hunter method is also used to measure the brightness of wollastonite. Loss on ignition (LOI), another important property in determining applications for wollastonite, is the amount of volatile matter driven off when the mineral is heated to 1 000°C. Com¬mercial wollastonite products have an ignition loss ranging from 0.5 to 2.0%. Wollastonite&apos;s naturally high pH of 9.9 (10% water slurry) is of major importance to its use in the coatings industry. Coatings formulators use milled grades as a pH stabilizer in interior and exterior PVA (polyvinyl acetate) and acrylic latex paints. There are two polymorphs of calcium silicate: wollastonite, a low-temperature form, and pseudowollastonite, a high-temperature form. Conversion of wollastonite to pseudowollastonite occurs at about 1 120°C and results in an increase in the coefficient of expansion and a color change. Pure white wollastonite may change to a cream tint or to various shades of red or brown. This color change is thought to be due to the presence of iron and/or strontium.

Jan 1, 1994

By F. E. Kottlowski

Widespread high-calcium limestones in New Mexico region are low -in magnesium, but some units include shale interbeds deleterious for sulfur removal usage. Thick limestones in Mississippian Escabrosa, Lake Valley, and Leadville, Pennsylvanian Madera and Hermosa, Pennsylvanian-Permian Horquilla, Permian Hueco and Capitan, Cretaceous U-Bar, and some Cenozoic travertines are high-calcium units. Significant outcrops are in mountains of southwestern, south-central, central, southeastern and north-central New Mexico, southeastern Arizona, southwestern Colorado, and northwestern Chihuahua. Coal-fired powerplants are mainly in northwestern New Mexico and eastern Arizona, thus transport is mainly by railroad.

Jan 1, 1994

By Ihor A. Kunasz

Lithium minerals occur predominantly in pegmatites that contain mineral assemblages derived from the crystallization of post- magmatic fluids or from the metasomatic action of residual peg- matitic fluids. They have been the traditional sources of raw material for ceramic and chemical industries. With the discovery of the Searles Lake deposits, brines became new sources of lithium, and, today, two brine deposits satisfy nearly one-half of the free world demand for lithium chemicals. Indeed, lithium production from pegmatites has been superseded by brines sources. In the United States, the brines of Clayton Valley, NV, have been exploited since 1964 by Cyprus Foote Mineral Company, a subsidiary of Cyprus Minerals Company. In Chile, Sociedad Chilena de Litio Ltda., an affiliate of Cyprus Minerals Company, is now producing lithium carbonate from the brines of the Salar de Atacama. Recently identified brine deposits suggest that these may well become the prime sources of lithium chemicals. In Bolivia, the government is negotiating the rights to exploit the brines of the Salar de Uyuni. The Salar del Hombre Muerto in Argentina is being evaluated as a future center of chemical production. The brines of the Great Salt Lake of Utah, the Smackover Formation, and the Imperial Valley geothermal field have been defined as important resources of lithium. In Tibet, high concentrations of lithium have been reported in several saline lakes. In the People&apos;s Republic of China, lithium may be produced from the brines of the Dabusan playa in the Qinghai Basin. The 1950s saw a great number of lithium companies develop. However, following the termination of the Atomic Energy Commission purchase program in 1959, several companies, such as Maywood Chemical Co., American Lithium Chemicals, and Quebec Lithium Corp., were forced to close their operations. Nevertheless, with the development of new applications in glass ceramics, air conditioning systems, synthetic rubber, and metallurgy (aluminumpotlines), the lithium industry grew steadily. With the potential application of lithium metal in batteries, nuclear reactors, and fuel cells, a steady growth can be foreseen. New products and new applications are likely to stimulate exploration for expanded reserves as well as the search for new sources from which lithium could be extracted economically. Presently identified reserves and production capacity are sufficient to satisfy the conventional market growth of lithium.

Jan 1, 1994

By Louis M. Schlesinger

KMG Minerals, Inc., a mica-feldspar-quartz producer in Kings Mountain, N.C., uses about 50% of its plant&apos;s -200 mesh slimes to manufacture brick. However, the company is unable to market the remaining 50% of this fine mineral mixture. The NCSU Minerals Research Laboratory operated a pilot plant to process these slimes to produce an additional product. The process, consisting of blunging and hydraulic sizing, was designed to separate a kaolin-enriched -270 mesh product from the bulk of the coarser +270 mesh "grit" minerals. Size analysis showed that this product was 80% finer than 20 microns and 50% finer than 6 microns (in equivalent spherical diameter). An evaluation indicated that it is a hydrous aluminum silicate that might be suitable in the filler and extender markets for traffic paint, some types of plastics, joint cements, and dusting compounds. Because of its high viscosity, it will be difficult to use more than a small percentage in cast ceramic bodies. However, it might be possible to use up to 10% in extruded ceramic bodies (i.e., electrical porcelain). The 15.2 cm (6 in,) diameter Linatex Hydrosizer was tested using a range of teeter water flowrates, so that the net rise velocity was varied from 0.10 cm/s to 0.40 cm/s. The solid feed rate to the sizer was maintained at approximately 1.1 t/hr/m2 (0.12 ton/hr/ft2). Tests were run using both "shallow" (i.e., 6 in.) and "deep" (i.e., 15 in. teetered beds. The best overall result was obtained when the sizer was operated with the "deep" teeter bed and a net rise velocity of 0.10 cm/s. About 97% of the +270 mesh material was rejected and approximately 79% of the -270 mesh material was recovered in a 14% solids slurry.

Jan 1, 1994

By P. Muduli, Y. Xi, T. M. Yegulalp, A. J. Arias

A short review of current practices and recent developments is followed by a description of a newly developed approach for solution of the optimum, ultimate pit limit problem. The new approach utilizes network modeling of the problem for solution by maximum flow algorithm. The latest developments in the implementation of maximum flow algorithm present significant time and memory savings as compared to initial development due to Ford and Fulkerson (1956). Results of a series of computational tests are presented to demonstrate how this approach performs as compared to the well-known Lerchs Grossman algorithm. It is also shown that the solution by the new method automatically includes several optimal solutions based on a predetermined number of benches to be included in the analysis.

Jan 1, 1994

By M. E. Smith

Chile is the world&apos;s largest copper producer and as such sets the standard of practice in copper SX/EW design. The authors summarize the liner systems used at many of Chile&apos;s major copper producers both operating and planned. The evolution in the state of the art is also discussed, considering both economic factors and Chile&apos;s burgeoning environmentalism.

Jan 1, 1994

By R. K. Rajamani

The theoretical model based on fluid mechanics, in conjunction with the laser-Doppler velocimetry (LDV) measurements, elucidate the size-classification mechanisms in an industrial hydrocyclone. The model has no adjustable parameters and involves solving the Navier-Stokes equations to predict the liquid-phase velocities. The spatial-concentration gradients were determined considering the particle phase in the Lagrangian frame and the classification curve was determined by balancing the forces acting on the particle. The force balance requires liquid velocities, which in turn depend on the local volumetric concentration of the particles. Hence, complete modeling work involves coupling both the concentration and liquid-phase velocity calculations until convergence is reached. Finally, the experimental and predicted classification curves were presented for 250-mm hydrocyclone operating at high-percent solids.

Jan 1, 1994

By J. G. Groppo

Lowering of filter cake moisture of ultra-fine coal to a 20 percent level using conventional vacuum filtration could be achieved using a combination of metal ion and surfactants. Pretreating coal slurry with about 0.2 Kg/ton of a surfactant and 50 ppm of copper or 10 ppm of aluminum ions provided filter cake containing 22.8 percent moisture. The lowering of moisture is explained due to formation of hydrophobic micro-agglomerates which facilitates dewatering.

Jan 1, 1994

By G. D. Hood, C. E. Jordan

The US Bureau of Mines investigated rapid froth flotation through more efficient bubble-particle collisions that improved the overall flotation kinetics. An in-line static mixer efficiently mixed the bubbles, water and ore, selectively attaching these bubbles to the hydrophobic mineral&apos;s surface. As the mixture entered the flotation chamber, the hydrophobic mineral was already attached to the bubbles and was quickly floated away from the remaining ore pulp. The rapid flotation system was evaluated for beneficiation with a western porphyry copper ore containing 0.67% copper and with a phosphate-bearing amine flotation tailings sample containing 9.5% P2O5 in a quartz matrix. Over 88% of the copper was recovered from the ore in a rougher concentrate containing 5.9% copper at a rate seven times, faster than conventional flotation. Sixty percent of the quartz in the phosphate-bearing sample was floated at a rate four times faster than conventional flotation. The unfloated product retained 80% of the phosphate in a 16.9% P2O5 concentrate.

Jan 1, 1994

By Joyce A. Ober

Strontium occurs commonly in nature, averaging 0.034% of all igneous rock; however, only two minerals, celestite and strontianite, contain strontium in sufficient quantities to make its recovery practical, and these minerals are found in sedimentary rocks. Of the two, only celestite has been found to occur in deposits of sufficient size to make development of mining facilities currently attractive. Celestite, the most common strontium mineral, consists primarily of strontium sulfate (SrSO,). Strontianite, the second most common mineral, consists primarily of strontium carbonate (Sr CO3). Strontianite would be the more useful of the two common minerals because strontium is used most commonly in the carbonate form, but few deposits have been discovered that are suitable for development. The physical properties of strontium ores are listed in [Table 1].

Jan 1, 1994

By J. E. Bevan

Once mining compromises the stability of a rock mass, the dangerous task of roof bolting begins. Many attempts have been made to automate this process, but there are still many refinements that need to be made. In the past, roof bolting modules were designed around the abilities of a human operator. Currently, researchers are taking a new approach that focuses on designing modules that can utilize bolting methods that are easily automated. A non-rotating anchor that is locked into position by a linear force (as opposed to a rotational force) was designed by researchers at the U.S. Bureau of Mines. Once the bolt is secured in the bolt-hole by the anchor, the bolt is tensioned and a collet is used to secure the other end of the bolt. This process replaces the traditional bolt-nut fastening method. This program is part of an effort at the U.S. Bureau of Mines to automate the coal mining process.

Jan 1, 1994

By S. K. Kawatra

It is common in coal-cleaning operations to produce a fine waste stream which contains a considerable amount of coal, but which is not economical to recover both because it is mixed with large amounts of difficult-to-remove clay slimes, and because the fines are often heavily oxidized. Conventional froth flotation machines cannot produce an acceptable product from such material in a single stage of flotation, and even flotation columns often have difficulty cleaning this type of feed. A new type of flotation column was designed specifically to deal with these problems, and was installed and tested in a coal-cleaning plant in Ohio. The feed coal contained 39.8% ash as fine clay, and 2.83% total sulfur, and was 80% passing 176 micrometers. The coal was a thickener product which had oxidized for some time, and was very difficult to float. However, using the new column it was possible to recover up to 85% of the calorific value in a product containing less than 11% ash, and up to 60% of the calorific value in a product of less that 8% ash. The bulk of the pyritic sulfur was rejected from the coal as well. Multistage flotation tests showed that the flotation column was able, in a single stage, to produce the best froth flotation product that it was possible to recover from this coal.

Jan 1, 1994

By R. A. Holmes

Although manganese is a metallic element and is widely dispersed in nature, it never occurs except as a compound in combi¬nation with other elements. Use of such compounds in the production of glass is known to have occurred in early Egypt. The dioxide of manganese was considered a compound of iron until 1774 when C.W. Schule first recognized it as an element. In the same year, a Swedish mining engineer, J.G. Gahn, became the first to isolate manganese. In 1856 development of the Bessemer process of steelmaking gave economic importance to manganese, and later, in 1882 Robert Hadfield discovered the benefits of high manganese steels. GEOLOGY Physical Properties Elemental manganese is a silver-gray metal, resembling iron but harder and more brittle and used primarily in alloys (both ferrous and non-ferrous) and a wide variety of chemical compounds. Some of the physical properties of manganese include: melting point¬1 245°C; boiling point-2 150°C; density at 20°C-7.43 g/cm3; specific heat at 25.2°C-O.115 cal/g; latent heat of fusion-63.7 cal/g; hardness on Mohs scale-5.0; linear coefficient of thermal expansion from 0 to 100°C-22 x 10-6. Mineralogy There are over one hundred minerals that contain manganese. These minerals vary from those with compositions that are pre¬dominantly manganese to those having only minor percentages of manganese. Distribution of Deposits Manganese ore deposits are found worldwide and were formed in various geological environments, but only a rather limited num¬ber of deposits have high grade manganese ore in sufficient quan¬tities to be mined and utilized economically on an industrial scale. It is worth noting the fact that almost all of the significant deposits can be classified into two types of deposits: marine chemical sed¬imentary deposits, and residual (secondary) enrichment deposits. There are, however, a much larger number of geological types but these are not of commercial significance at this time. Sedimentary deposits are the most common and are usually stratiform or lenticular. Manganese minerals were formed by a chemical process during the deposition of marine sediments. They usually contain manganese oxides and carbonate minerals, some¬times interbedded together or with other sedimentary rocks such as limestone or shale. Examples of this type of deposit are the Russian ore bodies of Nikopol and Tchiatoura, as well as the Kalahari deposits in South Africa and deposits of Groote Elyandt in Aus¬tralia. Residual deposits were formed in a different way: by alteration of existing manganese deposits or by concentration of the manga¬nese minerals when other minerals were washed away by weath¬ering or ground water processes. The Nsuta deposit in Ghana, the Amapa deposit in Brazil, the Moanda deposit in Gabon, and nodules in the residual clays of the US Southern Appalachians are examples of this type of geological process. In the case of the Ghana and the Amapa deposits, this is only true for the outer layers of the deposit containing oxide minerals, the inner part being comprised of car¬bonate minerals including manganese carbonate, probably from marine origin. Some sedimentary and residual-type deposits have been metamorphosed, giving rise to small high grade ore bodies. These deposits are regionally metamorphosed, occurring in mar¬bles, slates, quartzites, schists, and gneisses. Some of these deposits, such as the Franklin, NJ, deposit are rich enough to be commercial without secondary enrichment; however, most of the exploitable deposits have been secondarily enriched. Due to the diversity and complexity of manganese deposits, both with respect to deposition and chemistry, a wide range of impurities are almost invariably present in the ores. Table 1 shows that the reserves (i.e., a measured resource that can be economically and legally extracted) are estimated at 814 x 106 tons of contained Mn, which equates to more than a 100 year supply at the current level of production. The reserve base is made up of the marginally economic reserves and sub-economic re¬sources and are some 4.5 times greater than the proven reserves. Also apparent from study of Table I is the fact that some 75% of manganese reserves are found in two countries, the USSR and South Africa. On the other hand, North America (i.e., the United States and Canada) have few significant deposits. The largest deposit, or at least one of the largest, in the United States is located at Chamberlain, SD. This deposit is sedimentary

Jan 1, 1994

By J. Bacho

The modern drilling fluids industry is a dynamic, evolutionary environment. It is continuously striving to satisfy and anticipate the ever-changing needs of the oil and gas industry. The predominant driving forces in the industry over the past decade have changed dramatically. Health and environmental issues, coupled with economic and performance requirements, demand innovation and change from the drilling fluids industry. Emerging drilling fluid technologies will demand environmental considerations from mined components with additional emphasis on cost and performance criteria. Drilling fluids providers continue to search for and identify environmentally sensitive components which meet or exceed the performance of their more toxic predecessors. These changes have and will impact the components of drilling fluids that are mined.

Jan 1, 1994