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By B. Derin

In this study, the Reddy-Blander model was applied to predict the sulfide capacity (CS) values of FeOx-CaO-SiO2, FeOx-MnOx-SiO2 and FeO-MgO-SiO2 ternary slags, which were experimentally studied in the literature within the temperatures between 1,673 and 1,923 K. As expected, sulfide capacity values of the slags increased with increasing temperature and decreased with increasing acidic content. The model was found to be in agree-ment for all slag systems at the temperature range of 1,773-1,923 K. However, a disagreement occurred when the basic content was relatively high, at 1,673 K for FeOx-CaO-SiO2 and FeO-MnOx-SiO2 slags. The effect on the CS of high amounts of Fe+3 and Mn+3 in the slags is discussed.

Jan 1, 2011

By Wei Li

Carbothermic reduction kinetics of ilmenite concentrates catalyzed by sodium chloride and the microwaveabsorbing characteristics of the resulting reductive products were investigated; the reduction degree of the reaction was deduced to be . Results show that the activation energy is 112.03 kJ/ mol when NaCl is used as catalyst, lowering to 23.11 kJ/mol for the final stage activation energy using sodium silicate as a catalyst. There is a sharp change in the reduction rate constant at temperature ranges of 1,223 K - 1,273 K and 1,373 K - 1,423 K. Microwave-absorbing characteristics of reductive products were measured by the method of microwave cavity perturbation. It was found that microwave-absorbing characteristics of reductive products obtained at temperatures of 850° C, 1,100° C and 1,150° C show sharp changes. Through X-ray diffraction (XRD) characterization, it was found that the formation of Fe occurs at a temperature of 900° C during the reduction process of ilmenite concentrate. The decrease of FeTiO3 content results in the decrease of microwave-absorbing characteristics, while the increase of Fe content gives rise to the increase of microwaveabsorbing characteristics. The decreasing trend is larger than the increasing trend, which is the main reason for the sharp changes in the microwave-absorbing characteristics of reductive products at the temperature range of 850° C to 900° C. When the decreasing trend is smaller than the increasing trend, it becomes the main reason for the sharp changes in microwave-absorbing characteristics of reductive products at the temperature range of 1,100° C to 1,150° C. Kinetics results show that sodium chloride can catalyze the carbothermic reduction of ilmenite, and microwave-absorbing characteristic investigations indicate that microwave heating can be used in the carbothermic reduction of ilmenite.

By Y. H. Zhan

In beneficiation of phosphate ores it is common to use screening to produce the coarse "pebble" concentrate, and flotation to process the -1+0.1 mm size fraction. The -0.1 mm desliming product is treated as tailings. A new partially hydrophobic flocculant, P(MAAA) latex was developed to enhance flotation recovery of fine apatite particles through selective flocculation.

Jan 1, 2002

By R. Dewey

WHAT IS AI? It's very hard to say. Most researchers and practitioners disagree with nearly any attempted definition, but most would agree that A1 does deal with the development of computer-related methods o f problem-solving. Artificial intelligence is a discipline which seeks to emulate human anatomy and/or thought processes by applying computer science, electronics, and mechanical engineering to the development of natural language processing, machine vision, robotics, and knowledge-based expert systems. Integration of these four fields will someday produce the robots of today's science fiction. A1 addresses problems of structuring large amounts of knowledge and representing relationships with rules and semantic frameworks rather than with mathematical equations. A1 is convergent rather than divergent - - conventional conputer applications use relatively small quantities of input to generate large output, but A1 generally reduces large amounts of information to establish a few major conclusions. The development of A1 has prompted greatly increased efforts on the part of scientists and engineers to understand just how humans think, organize information, approach problem-solving, and form conclusions. Some of the more exciting and possibly far-reaching advances in A1 are coming in this more-or-less soft-science area. Thirty years of A1 research (dating from a 1956 conference at Dartmouth College at which the term A1 was coined) has already spawned many widespread, almost ordinary, products: window graphics, hand-held controllers (mouse). function menus, etc., all in an attempt to make computers and people more compatible. WHAT IS AN ES? A1 can be used to develop EXPERT SYSTEMS, which are computer programs or systems which contain knowledge and rules by which problems can be solved. or at least by which possible solutions can be suggested for very complex problems. A1 can be used to better define problems so that solutions can be found. An ES is designed not to process numbers, but to process information according to rules and logic derived from actual practice and experience. WHY AI? WHY ES? Companies are increasingly aware of the value of accumulated knowledge and experience in designing, building, operating, and maintaining the increasingly complex or expensive physical plants in any business. As knowledge branches out and becomes more specialized, the accumulated learning of a veteran operator or manager or engineer becomes a scarce resource well worth preserving. EXPERT SYSTEMS offer a means of doing that, reinforcing, not replacing, human capabilities.

Jan 1, 1987

By M. Lonoff

G. Campbell The paper by M. Lonoff looks at the importance of byproduct prices on copper production. The paper develops several interesting points on this topic, but there are some points in the theoretical discussion that could use further development. A couple of these theoretical topics will be considered here using the paper's framework of assumptions without concern about how realistic the assumptions are for the copper industry. Lonoff's theoretical model is based on a static, homogenous world where all copper/byproduct deposits are identical, and these deposits are the main source of these metals. Due to the importance of the byproducts to the production decision, the term coproducts will be substituted for the term byproducts to reflect more accurately this condition. The conclusion is drawn that a rise in coproduct prices necessitates a decrease in copper prices because copper production is increased as a consequence of increased coproduct production. The observation that real world behavior does not always follow this pattern is dismissed as "speculation." However, it can be easily shown that within this simple framework market forces might create the observed behavior. The key question to be answered is what causes coproduct prices to rise. Three possible cases will be used as illustrations. The first case is the one implicity assumed by Lonoff. Here, the demand for coproducts increases at all prices (an outward parallel shift of the demand curve) with the demand for copper remaining constant. As reported in the paper, the results are higher coproduct prices, an increase in coproduct production, and lower copper prices due to the resulting increase in copper production. The second case is when the supply of coproducts are constrained-leading to higher market prices. Copper production, as required by the simple model, is also reduced which Reply by M. Lonoff Campbell's comments give me an opportunity to clarify a few points in "Copper and Its Byproducts." That paper examined the affect of byproducts on the copper market and considered the relative riskiness of multi-metal deposits from an investment standpoint. That brief note made no attempt to be exhaustive. Nevertheless, Campbell's comments miss the point of the paper and necessitate a response. My "theoretical model" was static and I freely conceded after introducing the assumption of identical deposits that "none of the assumptions hold." These simplifying assumptions allowed me to bound the possible effects of higher byproduct prices on the copper price by assuming identical deposits and computing average price effects. I took great pains to subsequently explain that since deposits are not identical the identity of the marginal deposit might change due to byproduct price changes. In this case, average price affects will overstate the affect of byproducts on copper prices. According to Campbell, I dismiss as speculation any "real world behavior that does not always follow this pattern" (of metals prices moving in opposite directions). In the byproducts paper I noted that gold, copper, and silver price movements often parallel each other on an intra-day or day-to-day basis. Such movements are largely due to market anticipation of or reaction to changes in interest rates that affect carrying costs of metals stocks. Other movements may be due to anticipated changes in available supply or physical requirements. I loosely grouped these effects as speculative. To distinguish this statement from the main thrust of the paper, I contined "In the long run if gold and silver prices remain high the equilibrium copper price will be lower." The paper set out long run equilibrium conditions rather than attempting to explain price movements on a daily basis or on a year-to-year basis.

Jan 11, 1983

By Ruipeng Qian, Pengfei Wang, Guorui Feng, XianJie Du, Jun Guo, Yuxia Guo, Tingye Qi, JinWen Bai

"A numerical modeling was conducted to describe the behavior of overlying strata on the longwall top coal caving face for exploitation of a 16.8 m thick coal seam. Three typical structural models, including the Cantilever Structure (CS), Lower Cantilever and Upper Hinged Arch Structure (LC&UHA), and Lower Arch and Upper Voussoir Beam (LA&UVB), were developed. Based on mechanical analysis of the different structures of the key strata, and considering the behaviors of the broken igneous rock strata, a method was proposed and applied to estimate the structures of the overburden strata. The results had been verified by a field micro-seismic monitoring test. The paper provides a foundational method to determine the shield loadings for the top coal caving longwall face.INTRODUCTIONLongwall top coal caving (LTCC) is a highly productive underground mining technology which has been widely applied to the exploitation of the thick coal seams in China and other countries due to its high efficiency (Ju and Xu, 2013; Ju, Xu, and Wang, 2011; Liu et al., 2009). In recent years, a large amount of research on mining pressure forecast, strata control, and mechanical equipment improvement of the LTCC technology has been carried out, which greatly advances the field application of the technology (Liu et al., 2009; Yu, 2016; Dou et al., 2014; Feng et al., 2011; Chen and Li, 2011; Yin, Yan, and An, 2008). In 2006, the LTCC technology was first applied to the exploitation in a 20 m thick coal seam at the Tashan Coal Mine in China (Yan et al., 2011). Ten years of mining at the Tashan Coal Mine has highlighted the importance of the support management in controlling the roof strata on the extra-thick LTCC face. The mining pressure is closely related to the structural features of the overlying strata and its movement laws (Yu, 2016; Dou et al., 2014; Feng et al., 2011). However, the distributions of three zones—caving zone, fracture zone, and deformation zone—on the fully mechanized caving longwalls changed significantly with the increase in thickness of the coal seam (Chen and Li, 2011). The behavior changes of the roof strata led to abnormal pressure in the mining face and resulted in the difficulty of surrounding rock control (Yin, Yan, and An, 2008; Liu et al., 2009; Yan et al., 2011; Gong and Jin, 2008). Therefore, the theoretical research focused on the behavior of overlying strata to reveal the laws of mining pressure has important theoretical significance and practical value.Many classical studies (Qian and Shi, 2003; Feng, 2010; Yu, 2015; Yu, Yan, and Liu, 2012) had been done to describe the behavior of overlying strata in the mining process. It has also been reported that magma intrusion causes an important effect on the surrounding rock, coal, and methane (Wang et al., 2005; Liu et al., 2007). On the one hand, the property and structure of the coal seam was obviously changed by the magma intrusion and resulted in a potential danger of a gas outburst during the mining process (Chen et al., 2012; Wang et al., 2014). On the other hand, the hard igneous strata and the joints occurred with the magma cooled, causing an abnormal behavior of overlying strata and resulting in a series of dynamic disasters during mining (Xuan, Xu, and Lu, 2014; Lu et al., 2016). In fact, many coal fields in China are intruded by igneous sill, including the Datong, Shuozhou, Huainan, and Xuzhou coal fields (Chen et al., 2014; Wu, 2011). The 3–5 coal seam at Tashan Coal Mine in Datong coal field is very thick and is intruded by a large area of layered lamprophyre rock. Face falls and shield failures occurred frequently during the face retreat."

Jan 1, 2019

By Brian E. Davies, Bobby G. Wixson

INTRODUCTION The mining, extraction and refining of metals into useful materials is an honorable profession with an ancient and productive history. Civilizations have long depended upon metals for their implements, structures and machinery necessary for survival, growth, and development. Today, as in the future, metals and minerals are essential to the progress of mankind as we approach the 21st century with technologies and concepts that will require new concepts and production from the metal mining and processing industries. Today is the tomorrow we talked about yesterday and the implementation of new ideas is essential if we are to achieve "Frontier Technology in Mineral Processing". Unfortunately, the state-of-the-art mining, processing, smelting and refining methods historically employed were less than desirable environmentally, which has caused todays public to view the metal mining and processing industry with concern. Presently the ancient rock and chat tips connected with old Roman lead-zinc mines which were worked in Wales are causing stream contamination problems that must be corrected at considerable expense to the local governmental agencies (Firth, J.N.M., et al., 1981). However, improved progress has been made and the environmental control and clean-up procedures utilized by modern lead-zinc operations in the "Viburnum Trend" or "New Lead Belt" of South East Missouri may serve as a model to illustrate how alternative technologies, environmental concerns and cooperative efforts contribute to efficient mineral production within the confines of a U.S. National Forest region without significant environmental impacts. This area received international attention when it was opened within the boundaries of the Clark National Forest in the mid 1960's. By 1970 it ranked first in the world by producing 432,576 short tons of lead ore and has since continued in this position producing 451,153 short tons of lead ore in 1983 representing 91% of the total United States lead production (U.S. Bureau of idines, 1983). This production comes from a mining area approximately 40 miles long by 10 miles wide extending in a north-south direction. Geologically the lead is disseminated throughout the Cambrain age Bonneterre Formation, mostly a dolomite, at depths ranging from 700 to 1200 ft. (213.4 to 365.8 m). Galena (lead) is the principal ore mined with lesser quantities of sphalerite (zinc), chaleopyrite (copper) and silver being recovered as economic co-products. This new mining development in one of Missouri is most scenic areas could have led to a classic confrontation between industries and environmentalists. Instead, through the cooperation of industries, governmental agencies and university researchers, the Ozark environment has been protected, and may serve as a model for future coexistence of the mineral industry with the environment. Cooperative Program Development As early as 1965 five new mines and two lead smelters were being prepared for production and environmental concern was an essential part of that planning. All the mining companies became acquainted with representatives of the various federal and state agencies and scientists from the University of Missouri-Rolla (UMR). During the next six years, St. Joe Minerals Corporation, American Metal Climax, Inc., Cominco American Incorporated, Ozark Lead Company (Kennecott) and American Smelting and Refining Company participated in cooperative research efforts. The companies also participated in information exchange meetings, the development of improved analytical methods and the utilization of research findings in the modification or construction of pollution-abatement facilities. Early on research was carried out to determine background values and to establish natural baselines of trace metals in the surrounding environment. The unusual topography and drainage pattern of the mining area were helpful since it was possible to establish control sites and test sites below individual mine-mill operations to study waste-water effects on the receiving streams. The location of the ‘New Lead Belt', mines, mills,

Jan 1, 1985

With the dawning of a new century came the beginning of a new era in the coal industry. Instead of the traditional practice of only buying and selling produced coal in the United States, a coal futures market was established. The New York Mercantile Exchange began trading coal futures in July 2001. But, even in this new era, many of the old is-sues that have beset the coal industry still remain, as was evident in2001. Coal production increased to are cord level during 2001, according to preliminary data from the US Energy Information Administration(EIA). Production in 2001 rose by4% to 1.01 Gt (1.12 billion st), compared with 2000 (Table 1). This barely surpassed the previous record level of 1 Gt (1.11 billion st)set in 1998. Coal consumption remained unchanged. The additional production was used to replenish the depleted stockpiles that had resulted after two years of declining coal production and increasing coal consumption.

Jan 1, 2002

By F. Freme

Coal production in the United States increased in2004 by 36 Mt (39.7 million st) to end the year at 1 Gt(1.11 billion st), according to the U.S. Energy Information Administration (EIA). This was a 3.7-percent in-crease from 2003’s 971.6 Mt (1.07 billion st) (Table 1).(All percentage change calculations are done at the short-tons level.) Although U.S. coal consumption rose in 2004, not all coal-consuming sectors had increased consumption for the year. Coal consumption increased in the electric power sectors by 1 percent and declined slightly in the other industrial sector, while coking coal consumption dropped by 2.4 percent. U.S. coal exports rose for the second consecutive year, while coal imports again increased to record levels. Coal stocks declined during the year, as electric generators used their stockpiles to helpmeet increased demands and missed shipments. Coal producers used their stockpiles to supplement their production levels.

Jan 1, 2005

By J. C. Norman

The United States was the world’s largest producer and consumer of boron compounds during 1995. According to estimates from the US Geological Survey(USGS), boron mineral concentrate and chemical production in the United States totaled an estimated 1.1 Mt(1.2 million st) yielding 602 kt (663,000 st) of B2O3 for an estimated value of $462 million. This level of production exceeded 1994 revised production figures by about 9%. The United States continued to provide nearly all its own boron supply while maintaining a strong position as a source of sodium borate products and boric acid to foreign markets. During 1995, about 900 people worked in domestic boron mines and plants, about the same as in1994. USGS estimated total world production of boron during 1995 to be about 3 Mt (3.3 million st), yielding about 1.6 Mt (1.8 million st) of B2O3. World production in 1995 was about equal to revised 1994 levels.

Jan 1, 1996

By Larry A. Enloe

The 16-to-1 milling operation is Sunshine Mining Company's first new silver and gold producing facility. The 16-to-1 underground mine and mill are located approximately 64 km (40 miles) southwest of Tonopah, Nevada. Ore re- serves in the epithermal vein deposit are estimated at 0.91 Mt (one million st) of ore, at an average silver grade of 206 to 240 g/t (6 to 7 oz/st) and an average gold grade of 1.2 g/t (0.035 oz/st). The underground mine uses a large diameter blasthole stoping system of mining using highly mechanized rubber-tired equipment. The mill uses conventional cyanide leaching with countercurrent decantation and Merrill-Crowe precipitation. The mill start-up was in February 1982 resulting in the first pour of dore' in March 1982. The mill's present annual production is approximately 31.1 t (1.0 million oz) of silver and 264 kg (8500 oz) of gold.

Jan 1, 1984

By Daniel E. Walsh

A pilot scale study was performed to evaluate the potential for gravity concentration of gold from -13 mm (-1/2"), crushed ore from Ester Dome, Alaska. 9.04 tonnes (9.94 tons) of crushed ore were sampled and processed through a Pan-American jig -Wifley table pilot plant. Plant products were sampled for assay and material balance calculations. Gold recovery through one stage of jigging and two stages of tabling was 17.4% at a concentration ratio of 615:1. Concentrate grade was 766.3 g/tonne (22.4 oz/ton). The feed grade to the plant was calculated at 1.71 g/tonne (0.050z/ton). Jig tailings, primary table tailings and secondary table tailings grades were 1.44 g/tonne (0.042), 1.30 g/tonne (0.038), and 5.47 g/tonne (0.16 oz/ton) respectively. Significant, coarse, free milling gold values were shown to remain in the jig tailings. Concentrate mineralogy is discussed.

Jan 1, 1991

By J. A. Dlas Lima

Alunorte is a metallurgical-grade alumina refinery located in northern Brazil. This plant which was designed to produce 1.1 million mtpy of calcined alumina, started operation in July 1995. A process information system was installed before refinery start-up. It has been a main factor in process improvements, which resulted in an increase in production from 1.1 to 1.5 million mtpy. This system has been particularly useful for analyzing data and allowing retrieval of data by process engineers. This paper describes how a quality monitoring system to evaluate all aspects and stages of production, as well as alumina silo level and blending percentage, was developed. This system was designed to give support to ISO 9002 certification, which happened in December 1998. The quality monitoring system was developed using Microsoft Excel 7.0 and makes extensive use of VBA macro. The primary users of the system are shift foremen, managers and engineers, who use it to track the process and avoid variations in alumina quality.

Jan 1, 2000

By Mahmut Altiner

Magnesium is listed as a key critical raw material in a report by the European Commission that evaluated raw materials based on supply risk versus economic importance [1]. It has extraordinary properties, such as nontoxicity, inertness, high melting point, stability, low weight, chemical resistance, electrical insulation, optical transparency, corrosion-resistant behavior and refractory nature. It is widely used in the areas of agriculture; the environment, for antibacterial and water-purification purposes; electronics; automotive; drug delivery; ceramics; construction, as filler in brick; and concrete production, in the forms of magnesium oxychloride and magnesium oxysulfate. Magnesium oxide (MgO) particles can be produced through the calcination of magnesite ore at different calcination conditions depending on the desired quality of the product, classified as fused (2,800 °C), dead-burned (>1,400 °C), hard-burned (1,000–1,400 °C), or light-burned MgO (700–1,000 °C) [2]. However, the global availability of magnesite ore is limited.

By Matthew J. DeMarco, Anthony T. Iannacchione

Coal bumps have presented serious mining problems in the U.S. throughout the 20th Century. Fatalities and injuries have resulted when these destructive events occur at the working face. Persistent bump problems can result in abandonment of large reserves or lead to premature mine closure. Through the years, a1ternative techniques such as artificial supports, extraction sequencing, destressing, pillar design changes and specific pi1lar retreat practices have been successful1y imp1emented to mitigate coal mine bumps. Several techniques have evolved for room-and-pi1lar operations that control the way the roof rock breaks, regulating the manner in which stresses are redistributed in the mined section. Special mine layouts employed in longwall mines have also proved to be successful in safely redistributing or containing excessive loadings. However, with ever increasing production rates, greater overburdens and new mining systems, the need to evolve even more effective bump control designs will continue to challenge the U.S. coal mine industry.

Jan 1, 1992

By P. D. Rao, D. E. Walsh

A pilot-scale study was performed to evaluate the potential for gravity concentration of gold from -13 mm (-1/2 in.) crushed ore from Ester Dome, AK. 9.04 t (9.94 st) of crushed ore were sampled and processed through a Pan-American jig-Wilfley table pilot plant. Plant products were sampled for assay and material balance calculations. Gold recovery through one stage of jigging and two stages of tabling was 17.4% at a concentration ratio of 615:1. Concentrate grade was 766.3 g/t (22.4 oz/st). The feed grade to the plant was calculated at 1.71 g/t (0.05 oz/st). Jig tailings, primary table tailings and secondary table tailings grades were 1.44 g/t (0.042 oz/st), 1.30 g/t (0.038 oz/st), and 5.47 g/t (0.16 oz/st, respectively. Significant coarse, free-milling gold values were shown to remain in the, jig tailings. Concentrate mineralogy is discussed.

Jan 1, 1992

By Steve Karl, Rock Jenkins

The mining industry appears to be slowly rebounding. But many individuals and company officials are still smarting from the beating they received during the recent recession. As a result, companies have taken the "lean and mean" approach. As pointed out at the Oct. 24-26, 1984 SME-AIME Fall Meeting in Denver, CO, companies are placing more emphasis on optimizing their operations through more efficient mining and processing technologies and equipment. Empathizing with the mining industry's woes was the meeting's welcoming luncheon speaker, John D. Withrow, Jr., executive vice president product development for Chrysler Corp. Withrow paralleled Chrysler's problems of a few years ago with the current problems facing the US mining industry. He said Chrysler's come-back centered around its engineering and technical personnel, who regained "their seat at the head table." "In short," Withrow said, "we had lost the competitive edge. By cutting costs and people and improving our products we got everybody to believe we could." The 2700 participants at the Fall Meeting attended technical sessions geared toward turning mining back into a productive and profitable industry. Sessions and symposia included papers on precious metals extraction, crushing and grinding innovations, geomechanics, environmental control, health and safety, and various commodities. This article briefly highlights some of the papers presented. To order preprints of these technical papers, see ME, December 1984, pages 1620 and 1621. Computers Gain Mining Acceptance High tech has reached mining. As evidenced by many papers, computers have become valuable tools in many applications. These include tailings ponds operation and waste management; truck dispatching; mine design, simulation, and scheduling; monitoring; and reclamation. Mine planning is generally labor intensive and requires a considerable amount of the planner's time. P. K. Chatterjee, X. Chung, and Y. Jianjy described a computer-generated interactive graphics approach to under-ground coal mine planning that lessens the manhours involved in producing plans. The computer program examined exploratory borehole information. This included coal seam thickness, tonnage, quality constraints, and the nature of their distribution. Layout designs were then initiated and a probabilistic simulation performed to determine production levels of different extraction strategies. The interactive graphics approach gives planners the ability to quickly evaluate several layout alternatives and select the best one. For surface coal mines, M. A. White, of Arch Minerals Corp., explained several computer programs that aided in his company's surface mine plans. Several drill hole database and modeling pack¬ages are available. But Arch tech¬nicians developed specific pro¬grams for model strip areas. They were used to form long-term pro¬jections for various area and semi¬area stripping operations. They also generated reports on yard¬age, tonnage, quality, and ratio in¬formation. The information is used in budgeting, to compare mine plans, and to analyze acqui¬sition candidates. While computer-based truck dispatching systems have been used in mining for some time, earlier systems were run on ex¬pensive mainframe or high per¬formance minicomputers. As such, computer-based truck dis¬patching systems have been too expensive for all but the largest mines. Recently, however, a microcomputer-based system, af¬fordable to smaller mine opera¬tors, has become technologically feasible. Y. C. Kim and W. E. Kolb re¬ported on a simulated microcom¬puter system that uses strategi¬cally placed signposts in the pit area to automatically detect truck movements. A microprocessor in the signpost sends information to the microcomputer. The computer determines the truck's assign¬ment and alerts the dispatcher. He radios the driver his assign¬ment. In addition to the technical pa¬pers, an introductory short course on microcomputers was offered at the meeting. L. M. Kass and J. P. Stone, from the US Bureau of Mines, walked participants through the uses of microcom-

Jan 1, 1985

By J. E. Moyle

Introduction In October 1983, Rio Algom Ltd. decided to develop the East Kemptville tin deposit. This decision was the result of intensive geological and metallurgical evaluation work, as well as careful studies of environmental and marketing aspects. The property is located about 54 km (34 miles) northeast of Yarmouth, Nova Scotia, near the village of East Kemptville. Geology The geological setting is a granitic intrusive at the contact with metasediment. The tin mineralization is in the form of cassiterite (SnO2), which is about 80% tin. Sulfides are associated with the deposit containing silver, copper, and zinc, which are recoverable as byproducts. The mineralization is associated with quartz veins and greisen alteration. In the center of the deposit, the zones are so close together they have the appearance of a massive or porphyry type deposit. Ore Reserves The mine plan is based on 56 Mt (62 million st) at 0.165% tin. Up to the ninth year, mill feed will average about 0.2% and lower grade material will be stockpiled. In later years, the average grade will be 0.16% tin. A 0.08% cutoff grade is planned for the entire 17 years of production. East Kemptville is a relatively low grade tin deposit, and only a combination of favorable circumstances has made it economic. • The ore body is situated at, or very close to the surface, permitting mining by open-pit methods at a very low stripping ratio. • The tin occurs in relatively large crystals that allow for good recovery by gravity techniques. • It is ideally located in a well-settled area, with all essential infrastructural requirements already in place. • The positive and cooperative response from various governmental agencies involved are encouraging. Mine Plan The mine plan incorporates an initial pit, followed by three expansions to the ultimate pit. Mining will be at 14 kt/d (15,000 stpd) and will include 9 kt (10,000 st) of ore plus 5 kt (5,500 st) of waste and low grade. After five years, the mining rate will increase to 21 kt/d (27,500 stpd). It is planned to drill vertical 165-mm (6.5-in.) blast holes on a 6-x 6-m (20- x 20-ft) pattern. Bulk slurry explosives will be used to break the rock. Loading will be with hydraulic shovels into 70 t (77 st) haulage trucks. The trucks will deliver the ore to a 13 x 20 m (42 x 65 ft) gyratory crusher, where it will be crushed to 150 mm (6 in.). Secondary and tertiary cone crushers will be used to further crush the ore to 13 mm (0.5 in.). Process Design Tin extraction technology is practically unknown in North America, but Rio Tinto Zinc, which has a 53% ownership in Rio Algom, is involved in tin production in the UK. Rio Algom has used this experience and expertise in metallurgical evaluation work and in tin-related aspects of plant design. Mineralogical and metallurgical test work have been performed, both on laboratory and pilot plant scales. Mineralogical work was done largely in the UK, the laboratory test program was carried out at the Lakefield research facility in Ontario, and pilot plant work was conducted in Australia. This program has resulted in significant improvements in recovery and concentrate grades, over best projections that could be made before this work was carried out. Concentrating Process The concentrator is being designed to process about 9 kt/d (10,000 stpd). The first step is to reduce the size of the ore to -700 µm (-24 mesh) in a rod mill/ball mill grinding circuit. The ball mill will operate in closed circuit with high capacity banana-type screens. The screened product will be deslimed to 30 µm (560 mesh) with cyclones, then passed over the pri-

Jan 4, 1984

By Vern Miller

The Bureau of Mines developed a detector for controlling sorting devices to separate the copper-bearing fragments from the barren portion of Michigan native copper and western porphyry copper ores. A successful sorter could be used to preconcentrate the ore and eliminate costly hoisting or hauling of waste. An induction balance unit was developed and used in sorting tests on crushed sized -1+1/2-inch (-2.5+1.3-cm) ores from the Kingston (0.9 pct CU) and Centennial (1.6 pct Cu) mines of Upper Michigan. Concentrates of 4.0 pct and 7.5 pct Cu, respectively, were obtained at recoveries of 85 and 80 pct of the copper in the feed. Eighty percent of the sorted ore was rejected as tailing. Sorting larger fragments improved the separation efficiency. Tests on -4+2-inch (-10+5-cm) sized Kingston (1.6 pct Cu) and Centennial (2.1 pct Cu) ore samples yielded concentrates of 4.3 and 4.5 pct Cu, respectively, with corresponding recoveries of 92 and 91 pct. About 60 pct of the sorted ore was discarded as tailing. Porphyry copper sulfide ores also responded to electronic sorting but at a lower separation efficiency. Sorting response was affected by the degree of segregation.

Jan 1, 1976

By Donald Towse

Portland cement is a basic building material in every country in the world, and, fortunately, the raw materials required in its manufacture are widely distributed. It is a low-priced bulk commodity (price one cent a pound or less, with a density of 100 pounds per cubic foot.) Table 1. Approximate price per pound of selected mineral products. Copper 48 cents per pound Aluminum 27 Lead and zinc 15 Asbestos 3 to 18 Pumice 6 Sulfur 2 Bauxite (abrasive) 1.8 Barite 1 to 1.6 Cement 1 Primitive regions may get along without any Portland cement, but most countries use some, and it is one of the most widespread building materials, even if used in small quantities. Use of cement begins early in a country's development, and, because of local availability of raw materials, cement manufacture is one of the first heavy industries many countries desire. Use and manufacture of cement usually precedes other industrial materials such as steel and heavy chemicals, and consumption levels off for a long period during development of infrastructure and an economic base. With a mature economy comes a very high consumption. Per capita consumption varies ten times or more between nations (Figure 1).

Jan 1, 1970