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By C. A. Summers

The U.S. Bureau of Mines applied process mineralogy to investigate a lead and zinc deposit located near Story Creek, Colville Mining District, Alaska. Mineralization is hosted by the Kayak Shale in veins, veinlets, and breccia. Sphalerite and galena, with supergene anglesite, occur in symmetrical quartz veins and between breccia clasts. The study sample analyzed 2.11 percent Pb, 5.37 percent Zn, 0.014 percent Cu, and 1.2 oz/ton Ag. Analyses of crushed products showed that 33 percent of the sample weight, and more than 50 percent of the Pb and 65 percent of the Zn, are in the minus 850 µ m fraction. Liberated grains of sphalerite and galena were found in crushed products finer than 300 µ m. Beneficiation tests indicate the material is amenable to processing by traditional gravity and flotation techniques.

Jan 1, 1993

By S. J. Page

The personal dust monitor (PDM) is a combined tapered element oscillating microbalance (TEOM) respirable dust monitor and cap lamp, configured to have dimensions and weight similar to those of a lead-acid miner’s cap lamp battery. The Higgins-Dewell (HD) cyclone design operated at 2.2 L min-1 airflow has previously been reported to have low bias relative to the International Organization for Standardization (ISO) convention. Previous reports have described the PDM as meeting the NIOSH Accuracy Criterion. In order to avoid certain analysis anomalies encountered during these evaluations, a different method of establishing the PDM relative standard deviation was employed. Re-analysis of laboratory data for both the early prototype and precommercial PDMs indicates that the PDM still meets the NIOSH accuracy criterion, and that the precommercial PDMs are more accurate than previously reported.

Jan 1, 2011

By Neil J. Dahmen, Howard J. Handewith

INTRODUCTION Tunneling machines were introduced into civil con¬struction in the 1800s, but their practical applications were not realized fully until the 1950s. As of 1977, tunneling machines were being used on most tunneling projects of substantial size. As in civil construction, the mining applications of tunneling machines have included long drives such as tunneling for long ore-body develop¬ment drifts, long haulage tunnels, longwall access drifts, and long crosscut developments. Tunneling machines ranging from 1.75-m (5.7-ft) to more than I1.0-m (36-ft) diam are available from several manufacturers; machines for mining applications generally have ranged between 1.75 and 6.0-m (5.7¬and 20.0-ft) diam. Tunneling machines usually operate at or near horizontal grades and are supported by a rail-haulage backup system. However, declines and inclines have been made using alternative backup equip¬ment. Either circular or shaped tunnels may be bored, depending upon the particular equipment used. Using tunneling machines to bore openings through rock offers several advantages over the use of the drilling and blasting technique. These advantages include a rapid advance, continuous operation, uniformity of the opening size, smooth walls, and safe working conditions. Compared to drilling and blasting, boring reduces the disturbance of adjacent rock, thereby reducing the ground-support requirements and the exposure to water inflows. The smooth walls provide natural arching and present minimum resistance to the flow of air. A tunneling machine should be considered a spe¬cialized mining tool that is well-suited to certain mining applications. Properly applied and sustained, a tunnel¬ing machine contributes to realizing substantial econo¬mies in the development of underground mines. All costs herein are expressed in 1977 US dollars, unless otherwise noted. The mention of trade names and manufacturers is not intended to imply an endorse¬ment of any specific equipment. TYPES OF TUNNELING MACHINES As listed in Table 1, five principal types of tunneling machines were being manufactured in 1977. Each type of machine offers a special solution to a specific mining problem. Although each of these types of machines is described herein, most of this chapter is devoted to the full-face rotary rock-tunneling machine that has demon¬strated the greatest production in both civil construction and mining applications. Full-Face Rotary Rock-Tunneling Machines As shown in Fig. 1, a full-face rotary rock-tunneling machine consists of a rotating head that is fitted with rock-cutting tools and is forced into the tunnel face. This head is supported by a bearing on a structural support member that, in turn, is held in place by a hydraulically positioned wall-gripping mechanism. Both torque and thrust are reacted from the cutterhead, through the structural support and gripper mechanism, and to the tunnel wall. The rock cuttings fall to the invert at the tunnel face, and they are removed by means of cutterhead buckets or scoops that transfer the cuttings to a conveyor belt. After advancing the cutter¬head through a preset boring stroke, the tunneling machine is advanced by hydraulically pulling the gripper mechanism in from the tunnel walls, stroking forward, and resetting the gripper to the new forward position on the wall; the machine then is set for the next advance stroke. Full-face machines cut only circular openings. Ma¬chines with diameters as small as 1.8 m (6 ft) and as large as 6.1 m (20 ft) have been used in mining applica¬tions, excavating rock with unconfined compressive strengths in excess of 276 000 kPa (40,000 psi). Although special machines have been designed to turn on a radius of 30 m (100 ft) in both horizontal and vertical directions, the conveyors and backup sup¬port equipment generally limit tunneling machines to turns with a radius of more than 60 m (200 ft). The full-face rotary rock-tunneling machines have provided the fastest and most reliable production of any mining method or machine. These machines can be equipped to place any of a variety of ground-support systems, and they can be provided as "open" machines, as shown in Fig. 1, or as "shielded" machines, as shown in Fig. 2. The open machines have the advantage of allowing the ground to be supported as near to the tunnel face as possible. The shielded machines have been designed principally to allow placing precast con¬crete segments. The shielded machines completely pro¬tect the equipment and personnel at the heading, but they are economically limited to permanent long-life haulageways where full lining is required. Partial-Face Rotary Rock-Tunneling Machines As shown in Fig. 3, the partial-face rotary tunneling machine is equipped with a cutterhead that rotates slowly at about 0.21 rad/s (2.0 rpm). The single-disk cutterhead produces the tunnel section shown in Fig. 4 by means of an oscillating motion. These machines work on the undercutting principle, and they are avail¬able in spring-line dimensional increments of 0.1 m (0.32 ft) from 1.5 to 2.1 m (5.0 to 7.0 ft); the vertical dimensions are 2.4 to 3.2 m (8.0 to 10.5 ft), respec¬tively. Depending upon the tunnel width, the cutterhead disk may be fitted with from 8 to 16 drag-bit cutters. Penetration is achieved by means of hydraulic rams that force the tungsten-carbide bits into the rock mass. The operation is cyclic, with cutting occurring only on the upstroke. On the downstroke, the rotating cutter¬head draws the fallen muck from the invert into the panzer-type conveyor for rearward transfer. This feature allows time to either reposition ore cars or to exit the tunnel with muck trains while the machine is cutting, as shown in Fig. 5. Boom-Type Rotary Excavators The boom-type rotary-excavator tunneling machines commonly are known as boom-type continuous miners

Jan 1, 1982

By BURCU NILGUN CETINER, Serdar Aktas

Antimony has been used extensively in industry and in everyday life since the 19th century, and antimony sulfides have been known since around 4,000 B.C. Antimony’s most significant applications are as a flame retardant in the manufacture of electronics and textiles, as a catalyst for plastic fabrication, and as paint pigment and fining agent in glassware, opacifier in ceramics and an alloying element in ammunition and battery manufacturing plants. It is also used in vehicle brakes and tires. Brake pads contain stibnite (Sb), the sulfide compound of antimony. In particular, stibnite is used in automobiles as a lubricant, vibration reducer and friction stability improver. Anthropogenic activities are the primary source of antimony in the atmosphere [1,2]. Annual global consumption of antimony has increased to more than 1.4 × 105 t, and China is the most significant producer [2].

By Yao Zhou

Under the United Nations Convention on the Law of the Sea (UNCLOS), the international seabed area (Area) and its resources are the common heritage of humanity (CHH). Patent rights can be incompatible with the CHH doctrine and its underlying principles because patent holders might charge unjustifiably high prices to license patented technology for exploring and exploiting the Area’s resources (creating a "patent holdup" situation), might choose not to license, or might license exclusively when doing so would contravene CHH principles. However, a reasonable patent licensing regime can contribute to sharing the benefits derived from the Area and promote environmental sustainability. Provisions of the UNCLOS that stipulated compulsory technology and financial transfers were removed in the 1994 Agreement relating to the Implementation of Part XI of the UNCLOS (1994 Agreement), but to promote equity and sustainability I propose a voluntary licensing regime modeled on the concept of reasonable and non-discriminatory patent licensing (RAND) that has been used in other contexts. The International Seabed Authority (ISA) or another entity will need to coordinate and promote this licensing regime through governance of intellectual property (IP) derived from the Area. This proposed approach can better effectuate the CHH doctrine and its underlying principles.

Sep 1, 2014

By Angela K. Braden

Igneous rock exposures occupy only a minor portion of surface area (<18 mi2) in Arkansas, and are divided into two major groups: nepheline syenite (7 mi2) and syenite complexes (8 mi2), with various dikes and sills representing the remaining surface exposures. The syenite complexes have been the sites of major vanadium and minor titanium production during the past 50 years. Nepheline syenite exposures were important in the early production of locally used building stone; however, aggregate and roofing granules have now become the principal market for the production of nepheline syenite in Arkansas. Nepheline syenite intruded into a sequence of Paleozoic sedimentary rocks in Arkansas and is exposed in two areas: in Saline County near the town of Bauxite, and in Pulaski County at Granite Mountain, just southeast of Little Rock. Although the central Arkansas region had been investigated thoroughly for bauxite by the early 1950s, the nepheline syenite resources of the region have yet to be evaluated systematically by the state. Arkansas nepheline syenite was evaluated for its ceramic uses in 1952. Some recent industry interest has revolved around its potential use as a sand-blast abrasive. The largest exposed areas of nepheline syenite, located at Granite Mountain, currently are being mined by the Minnesota Mining & Manufacturing Company (3M) and McGeorge Contracting (Granite Mountain Quarry). 3M has been in operation since 1947 and mainly produces roofing granules. A fine powder produced by 3M during crushing that is marketed under the name Donnafill? recently has seen use as filler in self-compacting confined construction and as an additive (frit) in common brick. Since the early 1960s, Granite Mountain Quarries has produced a variety of aggregates, ranging from riprap to industrial sand, and recently constructed a computerized hot-mix-asphalt production facility. Approximately 4.5 million tons and 1.2 million tons of syenite were produced from Granite Mountain and 3M, respectively, during 1979. No production values are available after this date; however, combined production from both quarries is estimated to be at least 6 million tons annually.

Jan 1, 1999

By III Sadler

Processing bauxite and clay ores to reduce Iron content to levels low enough for the ores to be suitable raw materials for such products as refractories and abrasives has long been regarded as a diffi9ult problem. Standard magnetic separation processing of the untreated ore has been attempted by previous investigators with only limited success due to the finely divided state and weak magnetic susceptibility of the iron minerals (hematite, geothite, etc.) present in these ores. The new process described in this paper consists of calcining the finely crushed ore at 500 to 800 C and then reducing (with hydrogen, carbon monoxide, etc.) the iron oxides present to magnetite or elemental Iron. The magnetic susceptibility of iron in these forms is enhanced 40-to 100-fold over that of hematitie and is readily removed by simple magnetic separation. Starting with a 2.7% Fe20s Alabama bauxite ore, a 1.5% Fe20s product was produced in one pass through a Davis tube magnetic separator with 95 + % recovery of the iron-free bauxite fraction and a 20% Fe20a magnetic product. These findings suggest that with the addition of light calcination, reduction and magnetic separation steps to the conventional refractory grain production process, the large U.S. reserves of high-iron bauxites could be used.

Jan 1, 1990

By W. T. Walter

High-G centrifuges from five preparation plants were sampled to determine and quantify the various operating factors affecting performance. The operating factors that were considered include feed rate and percent solids, size of feed material, screen-basket type, hardness of coal and age of the flights. The performance parameters that were measured include product surface moisture, recovery and degradation of the coal. Regression equations with good significance levels were developed.

Jan 1, 1982

By W. Hustrulid

In the mid-to-late 1800’s the U.S. mining industry was on the threshold of nearly a century of golden times. Nearly every state had a prosperous and growing mining sector. The importance of the industry was reflected in the creation of the state school of mines. Today, with the depletion of readily available mineral reserves, much of the U.S. metals mining industry is considered to be in a sunset phase. The same is true with the mining schools that serve the industry. However, the United States is still a major consumer of the world’s minerals and requires a dependable supply of both minerals and minerals professionals. In his 2002 Jackling Lecture “You Can’t Make a Silk Purse Out of a Sow’s Ear” the author presented a list of concerns, propositions and recommendations. In this follow-up paper, the author further explores the subject through the presentation of a detailed case example focusing on the iron mining industry of Minnesota and minerals education at the University of Minnesota.

Jan 1, 2004

In parallel work, the cyanide/silver impregnated activated carbon system was studied for the purpose of developing an alternate cyanide removal system. It was found that free cyanide can be reduced from 20 ppm to below 10 ppb with a fixed bed of silver impregnated activated carbon, since such cyanide removal might be applicable to gold mill effluents, the investigation was extended to the cyanide/gold impregnated activated carbon (GIAC) system. Batch tests were conducted varying the gold content of activated carbon, carbon/CN ratio, stirring speed, pH of the initial solution, and the reaction temperature. The adsorption isotherm of cyanide/gold impregnated activated carbon system was also studied. The results of these batch tests show that the behaviour of the cyanide/GIAC system is very similar to the cyanide/silver impregnated activated carbon system variation of the gold content of the impregnated activated carbon has some influence on the cyanide adsorption rate. The latter is mainly increased, however, by increasing the GIAC/CN ratio. The activation energy was determined to be 3.12 kca1/mole (13.08 kj/mole) and the Au(CN)2 saturation at 194 µ M/g NORIT ROX O.B. The experimental results of reaction temperature and stirring speed show that the adsorption of free cyanide on such activated carbon is controlled by pore diffusion inside the activated carbon particle or by surface reaction. The adsorption isotherm follows the linear model and it is favourable for the cyanide/gold impregnated activated carbon system.

Jan 1, 1994

By T. Payne

Underground heat issues are mainly focused on the detrimental effects to a workers health. However, working in hot, humid conditions has other negative effects. Studies have shown that safety, productivity, workforce morale and operating cost are also worsened in these conditions. The human body has several mechanisms for rejecting heat and remaining cool. However, once the air temperature exceeds about 34°C, the only effective mechanism is by evaporation of sweat from the skin. This is assisted by acclimatisation which is the human body?s enhanced ability to combat extended exposure to heat. The body has to remain well hydrated when working in heat as even small degrees of dehydration cause significant decreases in the ability to work in heat. There are two ways in which heat load can be reduced: Through use of refrigeration/vent/cooling to reduce thermal stress on workers; Reduce the contribution that heat sources have to underground heat load (e.g. reduce idle time, fleet size, etc). Some of the sources of underground heat have the potential to be more manageable than others. Geothermal heat and heat from autocompression will be found in all mining situations in varying degrees depending on geothermal gradient and surface temperature, however, the use of equipment and blasting may be streamlined to reduce the underground heat load. It is through a combination of the available options that most mines will successfully control their heat related problems. Mt Isa, which has been a focus for heat related study in Australia, has successfully implemented protocols for working in heat. Through combining these with the installation of a surface bulk air cooling plant, Mt Isa has consistently reduced the incidence of heat illness. This is likely to be the most cost effective method of reducing heat load for deep mines in Australia. Shallower mines which may only occasionally encounter hot conditions should consider more portable cooling options. This study will review the heat issues in underground Australian metalliferous mines.

Jan 1, 2009

By Robert H. Scott

Developments during the past few years have brought coal-based composite fuels to commercial readiness. During the next few years, composite fuels will become available from a number of suppliers. Potential users must evaluate the combustion properties of these fuels to determine equipment and operating changes required for their use. Most work to date has been done with boiler applications. However, many potential non-boiler applications exist in the metals and minerals industry. These applications require specific evaluations appropriate for the processes involved.

Jan 1, 1982

Adverse ground behavior events, such as convergence and falls of ground, are some of the most significant challenges and hazards in underground mines. Our goal is to work toward mine-wide, digital, and real-time three-dimensional geotechnical situational awareness and predictive capabilities in complex underground mining operations. This will benefit operators, engineers, and management by enabling them to develop a more proactive approach to ground control. To this end, and inspired by research in the field of remote sensing and autonomous robotics, this paper assesses the potential of mobile light detection and ranging (LiDAR) data acquisition for high-frequency, high-accuracy monitoring tasks in Global Navigation Satellite Systems (GNSS) deprived underground mines. Limitations of current monitoring practices are reviewed. Relevant academic and commercial developments in the fields of indoor mobile mapping systems (MMSs) and simultaneous localization and mapping (SLAM), robust autonomous robotic platforms, and automated remote sensing data processing are highlighted, and their current shortfalls are evaluated. To conclude, the ramifications of this work for the development of future autonomous underground mine monitoring solutions are discussed.

Jul 28, 2020

By C. Fuellenbach, J. Brune

"INTRODUCTION Mining activities must be safe and profitable. These two requirements influence each other. The purchase and implementation of safety improvements costs money. Injuries and illnesses at mines stop or delay production and may result in additional costs or a loss of profit. Other effects of injuries and illnesses include the negative influence on employee morale, corporate reputation and conflicts with contract partners. Based on this researchers asked the question: are mines with lower rates of injuries and illnesses more profitable than mines with a higher frequencies? One aspect of this research is the evaluation of the safety situation and the measurement of benefits of safety improvements in the German mining industry. In the following paper, this part of the research will be examined. The main aim is the evaluation of injury rates in different German mining sectors and regions in Germany. SELECTION OF GERMAN MINING OPERATIONS The research team decided to focus the study on the salt and potash and the aggregate and industrial minerals mining industries in Germany. These two mining industries are different in the number and size of operators, structure of the industry, pricing and markets. The selection of two different industries adds to the clarity of the evaluation. Salt and potash mining industry The German salt and potash industry is primarily located central Germany. All salt and potash mines in Germany are underground operations. In 2015, the German potash industry employed 8,100 employees and generated a total revenue of 2 billion Euros. German potash reserves include magnesium compounds like kieserite (MgSO4·H2O), in addition to sylvite (KCl) and carnallite (KMgCl3·6(H2O)). The German salt industry employed 2,300 people in 2015 and generated revenue of 800 million Euros (Krueger, 2015) There are seven mining companies with salt and potash operations: esco-european salt company GmbH & Co. KG, K + S Kali GmbH, Saline Luisenhall GmbH, GSES Glückauf Sondershausen Entwicklungs- und Sicherungs-gesellschaft GmbH, Südwestdeutsche Salzwerke AG, Wacker Chemie AG and Südsalz GmbH. In this way, esco – european salt company GmbH & Co. KG is an affiliated company. Esco was founded as a joint venture of K + S and Solvay in 2002, since 2004 K + S is the sole holder (esco - european salt company GmbH & Co. KG, 2016). Likewise, the Südwestdeutsche Salzwerke AG has a controlling interest in Südsalz GmbH (Südsalz GmbH, 2016). Aggregate and industrial minerals mining industry The aggregate mining industry in Germany is comprised of many small mining operations and relevant companies. According to the German Department of Economics (BMWi, 2015), the following industrial materials are classified as aggregates: fluorite, barite, kaolin, quartz and quartz sand, quartzite, silica, loamy and foundry sand, pegmatite sand, shale, clay, bentonite, schistose, limestone and dolomite, gypsum and anhydrite, basaltic lava and lava sand, gravel and split, pebble and silicic sand and peat."

Jan 1, 2017

By Joel Nonnweiler, Rafael Castro, Ross Webb

The three thousand foot long 66-inch diameter Folsom East Interceptor Section2B was completed accident free, on time and under budget with no measurable surface settlement. The tunnel passed through nested cobbles, highly abrasive sands and gravels, and abandoned mine workings with less than five-feet of cover at times. Preventing settlement was critical since the tunnel passed under a heavily traveled state highway. A pilot project to test microtunneling and pipejacking methods in the same ground conditions abandoned both drives before completing the planned drive lengths. This paper discusses performance of the conventional tunneling method selected to excavate the ground and the effectiveness of the ground modification techniques employed.

Jan 1, 2001

By J. D. Patsey, G. T. Lineberry

Introduction A computer program was developed for analyzing drum-type hoists before modifying an existing system or designing a new one. Its use permits the preliminary evaluation of a system before seeking technical assistance from mine hoist designers and manufacturers. The user-friendly program accepts a variety of data and analyzes hoisting systems for any balance state. The program can be used to calculate skip capacity to yield a desired production rate, solve for drum face width, select a permissible wire rope, estimate total horsepower of the hoist plant, and estimate annual power cost. Whether required for a large mining complex or for a relatively small operation, a hoisting system must be carefully designed to ensure the efficient, reliable, and safe flow of material. Because shaft sinking and hoist installation can total between 2.5% and 3% of the cost of opening a deep mine, proper hoist selection is critical. Today&apos;s mining engineer has at his disposal the most powerful design and analytical aid ever, the micro- computer. There is, unfortunately, limited software for the study of hoisting systems, unlike that for other materials handling equipment (Manula and Albert, 1980; Prelaz et al., 1964; Bucklen, 1969; Thompson, 1985). HOIST reduces a time-consuming set of calculations to a concise package of interrelated subprograms. A literature review revealed no common-user pro- grams to analyze hoisting systems, although at least four major hoist designers/manufacturers/installers have their own in-house programs. To provide a tool with which the mining engineer could preliminarily analyze a materials hoisting system or could check the calculations of a hoist contractor, a computer program was developed. HOIST was written in BASIC for the IBM-PC for ease of program adaptation and to en- courage field use on compatible systems. Details of program development are omitted, since the basic principles of hoisting analyses are relatively straightforward, simple, and readily accepted (Har- mon, 1973; Nordberg, n.d.; Adler, 1957). Program features, intended usage, and benefits of the com- puterized solution are emphasized over theory development and mathematical rigor. Background The mine hoist system that is selected and installed at a mine is the "lifeline" of that mine, with installations lasting 20 years or more. Thorough study is warranted to ensure that productivity demands are met at a minimum cost per ton. The increased cost of a large, powerful, high-speed hoist must be offset by increased production to justify its selection. To optimize this tradeoff, an extensive hoisting analysis should be performed. The analyses to properly size the skip (or cage ) , the drum, and the hoist drive are conducive to computerization, permitting rapid evaluation of changeable operating and design parameters, such as velocity, acceleration, state of balance, and productivity demand. The program is particularly useful in conducting sensitivity trials, such as investigation into the effect of change of productivity on skip capacity and on horsepower of the hoist drive. HOIST is currently limited to the study of drum-type hoists with cylindrical drum(s). However, only minor changes to the program would permit analysis of friction hoists and conical drum configurations. Model development and testing The program is based on accepted equations and physical relationships. Examples of manual calculations formed the basis for decision points and program branching. Data is input in the order that it would be needed if the problems were solved manually. The choices are arranged likewise. HOIST was developed in sections, with manual solutions performed to check program logic. The testing became more rigorous as sections were completed. Output from one section becomes input for following sections, as appropriate. The simplified flow diagram of HOIST is given in Fig. 1.

Jan 1, 1988

By LeRoy D. Loy

Would you believe me if I told you the constant battle between Government regulatory agencies and industry could be won by both sides? No, I&apos;m not crazy, nor have I been soaking up any of that fine Kentucky whitelightning. But I have recently been a participant in a battle where both sides won. Actually, I&apos;m using the term "battle" loosely because, in reality, it wasn&apos;t a battle at all - despite the fact that all the ingredients were there for a monumental struggle; i.e.. government, industry, special interest groups and a controversial issue - the development of effluent limitations. I&apos;d like to tell you about it. Historically, on one side of the battle, government has always been ac¬cused of adopting regulations with limited evaluation of existing technologies; and then with seemingly no regard for the economic consequences. On the other side, industry gets punished by government&apos;s harsh actions because of their past "do-nothing" attitude toward pollution control. Recently, this battle seems to be losing steam, because both government and industry are beginning to realize that, ultimately, they both will lose. Even more important is the fact that both sides are, or should be, working for industrial expansion compatible with environmental protection.

Jan 1, 1977

By L. Martins

To increase zinc recovery in the concentrate, this investigation performed mineralogical characterization, dispersion studies, bench and pilot-scale flotation experiments and an industrial flotation trial. The objective was to verify the flotation behavior of the silicate zinc ore (calamine type) in the presence of slimes, with the aid of dispersing agents. Characterization studies identified the major minerals in the flotation feed as hemimorphite (calamine), quartz and dolomite. Dispersion tests showed that enhanced dispersion of the particles in the pulp in the absence of reagents occured at a pH range between 8.5 and 12.0. Bench-scale flotation experiments were planned using the statistical tool of complete factorial design at two levels, replicated once. These experiments showed, and were confirmed at the pilot-plant scale, that higher doses of sodium sulfide and polymeric dispersant combined with sodium silicate favored a higher metallurgical recovery. At 6,800 g/t (218 oz/st) sodium sulfide and 6,992 g/t (224 oz/st) polymeric dispersing agent combined with sodium silicate, a zinc grade of 38.4% in the final concentrate was achieved, at an average metallurgical recovery of 72.4%. The industrial trial confirmed the pilot scale results, leading to zinc recovery of 76.1% and a 37.3% zinc grade in the concentrate. Key words: Froth flotation; Flotation reagents; Flotation depressants; Zinc/ zinc ores

Jan 1, 2010

By Derek J. McCracken, William G. Holroyd

Emery is a rock that at one time held a large share of the abrasives market. The introduction of synthetic abrasives, however has forced it to settle for only certain niches in the marketplace. This loss of market share is due mainly to the higher amounts of impurities and weaker internal structure that naturally occurring minerals have compared to manmade materials. The use of rocks and minerals as abrasives dates back to early man, who used flint, quartz, and other natural materials to fabricate various tools. During the 19th century, with the Industrial Revolution imminent, the character of the abrasives industry was changed forever as synthetics were introduced. Frank B. Norton is credited with producing the first manmade abrasive when, in 1855, he manufactured a vitrified grinding wheel using emery grit and clay. Before Norton&apos;s accomplishment emery had been the only commercially available abrasive. The latter part of the 20th century has seen synthetics capture an increasing share of the abrasives market from natural materials. The term emery is believed to have been derived from the words emeri (French), smeriglio (Italian), and smiris (Greek). The term corundum, for the principal mineral of emery, seems to have originated from kauruntaka, the Indian name for the mineral. GEOLOGY Emery is a gray to black, granular rock comprised of various minerals including corundum (A1,0,), an iron-bearing mineral (usually magnetite-Fe,O,, hematite-Fe,O,, or hercynite- FeAI,O,), and several trace impurities such as mullite, titania, silica, and magnesia. The hardness of emery normally ranges between 7 and 9 on the Mohs scale, depending on its mineral com- position and level of impurities. Corundum, the hardest mineral in emery, typically has a hardness of 9. The specific gravity of emery ranges from 3.2 to 4.5, also depending on mineral composition and purity. The crystallography of each mineral contained in emery differs somewhat. Corundum exhibits an hexagonal crystal structure, whereas magnetite forms within the isometric system, frequently as octahedral crystals. Hercynite, an iron spinel, is also isometric. Hematite has an hexagonal structure but often is found as botryoidal and reniform masses. Principal deposits of commerical emery are found in the United States, Turkey, and Greece. In the United States two emery producers in the Westchester County-Peekskill area and one in the Cortlandt County area of New York closed their mines in the late 1980s. Commercial production in the United States now comes only from the western Cascade Range in Oregon. The emery in New York has a typical A1,0, content of 41.5%. Most of the rock is not true emery because it contains a mixture of spinel and magnetite but very little corundum. The deposits are of Late Ordovician-Early Silurian age and consist of veins in which emery is mixed with olivine, pyroxene, and hornblende. The veins evidently were formed by contact metamorphism and are surrounded by Precambrian schists that contain mica, sillimanite, cordierite, garnet, and quartz. The deposits in Oregon were formed during Miocene time by the contact metamorphism of ferrunginous bauxite by intrusive lamprophyric dikes and plugs. Emery is found in thin layers bordering these tabular dikes, which are usually oriented perpendicular to bedding, and in "surficial placer deposits. The emery deposits in Turkey occur as small, massive, lens- shaped bodies and as surficial placers. They are believed to have formed during Permian and Triassic times. In Greece the principal site of emery production is at Cape Emeri on the Island of Naxos. These deposits consist of lenticular masses of emery surrounded by marble. They originated during Mesozoic time, evidently by metasomatic replacement. Smaller deposits on several other Aegean islands were formed by the metamorphism of bauxite or other alumina-rich materials.

Jan 1, 1994

By John William Carlson

The Y2K or "Millenium" bug is a tiny critter, comprising no more than two digits in a date field. This bug, like its' more lethal cousins of biological and computer virus fame, has the potential to derail the economy of the U.S. and the rest of world. Whatever the reader's perception, rest assured that you will be affected by Y2K along with every person in the civilized world. How did we get to this position? It is really quite simple. The Y2K problem is a creation of computer programmers who, in an effort to conserve valuable memory in the early days of computer development, used two digits as shorthand- to define the year in date sensitive applications. Instead of typing in "1982," our experts employed "82." They believed-correctly­that the problem of limited memory would be solved by technology and assumed (nasty word) that software would be modified to take care of any problems associated with a date rollover in the year 2000. Their assumption resulted in the problem facing us today.

Jan 1, 1999