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By K. Anderson

There is a credible, cogent, and responsible argument that mining can be part of a sustainable future in countries with freely elected governments, transparent and enforceable laws, a closure plan with an adequate bond, and a small handful of other measures. This perspective, built largely upon the understanding of mining as a temporary use of the land, is coupled with a growing understanding of economic diversification as a tool to level out the ‘bust’ side of the boom and bust cycle. There are verifiable signs of progress that the sector has, at least in some venues, begun to embrace this view of ‘sustainability’ both in philosophy and practice. While laudable, there remains a conundrum not yet fully explored. It is conceivable that companies can fulfill all legal requirements, practice corporate responsibility in its broadest and most liberal interpretation, and yet leave behind, after the gates are closed and the lights turned off, a situation which is not only unsustainable, but far worse off than before mining started. Having observed this outcome, repeatedly, some critics have concluded that all mining should be stopped. Others recommend that it be vastly curtailed until regulatory regimes are re-vamped, communities fully empowered, and companies brought to heel. Yet others, including many within the industry, are looking to hold back this dark prospect with peer pressure, branding and competition for good will. In this paper, I propose to focus on this discontinuity, that gap wherein the chain of logic breaks and reasonable policies, reason-able choices, reasonable actions, may fail to deliver expected results. I suggest that any meaningful definition of post-closure sustainability must include the concept of human welfare, and increasingly, human security, over and above meeting the requirements of law, beyond retaining shareholder value and reputation, beyond discussions of subsequent land use and diversified employment. I suggest that self-determination, that ability of a people to hold for themselves the vision of their own future, and to have a sense of their power to implement it, may be both the most difficult and the single most important determinant of long-term sustainability in a community. The particulars will vary; a Canadian junior or an Australian multinational, a highly regulated state in the American west or a ‘failing state’ in Africa’s west, gold or sand and gravel. But the recommendation is the same: this must be a collective endeavor, a shared responsibility involving some combination of government, companies, communities, local and international NGOs (non-governmental organizations), each contributing in the ways most able.

Jan 1, 2004

By Ammar Henchiri

INTRODUCTION A current need of the phosphate industry is the development of process technology for treatment of high carbonate content ore. About 75 to 80 percent of the world phosphate reserves (1) are associated with carbonate gangue, which is not amenable to treatment by the existing techniques. Numerous laboratory and pilot plant studies have been devoted to carbonate-phosphate separation. Different techniques were involved (washing, sieving, attrition, flotation, calcination, and leaching). For technical and economical considerations, flotation appears to be an efficient process for this problem. Separation of carbonates (calcite and dolomite) from igneous phosphate is applied in industrial plants in Brazil, Finland, and South Africa. But, for sedimentary phosphate, no industrial realization exists at this time, with the possible exception of some plants in China. The main problems with sedimentary phosphates are: • high substitution by CO3-2 and F- for P04 -3 in the apatite lattice. • larger surface area of the phosphate particles because their surface is porous and irregular. • tendency of sedimentary minerals to produce more slimes in conditioning than the crystalline minerals, hence, larger dosages of collectors are required for sedimentary minerals. Investigations reported in the literature indicate that most processes developed for sedimentary carbonate-phosphate separation involved inverse flotation of carbonates using fatty acids as collectors (2), (3) associated with phosphoric acid (4), monosodium phosphate (5), F- (6), or SiF6 -2 (7) as phosphate depressants. Later investigations, conducted by A. Henchiri and G. Baudet (8), (9), (10), (11), (12), (13) in the BRGM technology department, of phosphoric esters revealed that these reagents are selective collectors for carbonate-phosphate separation. The above investigators developed a process which used phosphoric esters to collect carbonate minerals and sulfuric acid or sodium fluorosilicate as depressants for phosphate. Extensive comparative tests for different processes on the same phosphate sample show that the process developed at BRGM is one of the most promising methods proposed for sedimentary phosphate-carbonate separation. It should be pointed out, however, that phosphoric esters make abundant froths. The handling of these excessive froths will be a problem in an industrial-scale plant. This paper outlines test work performed in order to optimize and to improve the efficiency of the flotation process on a sedimentary phosphate ore selected from the Sra Ouertane orebody. The Sra Ouertane flotation process, illustrated on Figure 1, first removes carbonate minerals by inverse flotation and then recovers phosphate as a froth product, leaving quartz as a cell product.

Jan 1, 1993

By R. L. White

Classification of Mills Mills may be classified under four categories that relate to the type of action utilized to grind the material: Tumbling. The most important of these to the minerals processing industry are tumbling mills. Grinding media is actuated in a free¬form pattern in a rotating drum causing it to tumble, material being ground passing through the tumbling media. Work is done by a combi¬nation of attrition and impact. Impact. Grinding media is actuated in a distinctive pattern so that it impacts the material being ground. Work is done by impact. Roller. Grinding media is actuated in a distinctive pattern, mate¬rial being ground passing under or between the media. Work is done by compression. Fluid Energy. There is no grinding media as such. Energy is imparted to the material by transfer of kinetic energy from the fluid to the material. Grinding is accomplished by interparticle impact and attrition. Tumbling Mitts The main physical arrangement consists of a lined cylindrical drum mounted on trunnion bearings driven by a ring gear and pinion, in turn connected directly or through a reducer to the electric motor. Variations to this general arrangement include: (1) Drum mounted on rollers instead of trunnions. (2) Bearings on the drum directly, not on trunnions. (3) Utilization of multiple pinions on the gear. (4) Trunnion-type drive arrangement through a gear reducer with¬out the use of a ring gear. (5) Motor rotor mounted directly on the drum with stator around the drum, thus eliminating the gearing. The drum consists of a shell and heads lined with replaceable liners of various types and configurations. Various types of tumbling mills are tabulated; illustrations of some are shown. The types are so designed for specific purposes. Media utilized include steel rods, balls, or rock of the same material as being ground or of special material in the instance where iron contami¬nation is detrimental (see Figs. 9 and 10 and Table 2). Impact Mills Although there may be some overlapping of interpretation of terms, impact mills are considered those in which the media is actuated in a distinctive manner, at relatively high speed, impacting the material to be ground. There is an overlapping also in what may be considered to be crushing equipment rather than grinding equipment. Hammer Mill or Impactor. Material is fed into the equipment; inside hammers of impactors revolve at a high speed, breaking the material on impact with the hammers (see Fig. 11). Material is also thrown against the periphery of the mill, causing impact grinding to occur. Equipment is normally lined with replaceable abrasive resis¬tant metal; hammers are also

Jan 1, 1985

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 Duane B. Jorgensen

The two calcium sulfate minerals, gypsum and anhydrite, occur in many parts of the world, and gypsum has long been of economic importance in the family of industrial minerals. Gypsum, the dihydrate form of calcium sulfate (CaSO, . 2H20) and anhydrite, the anhydrous form (CaSO,) are frequently found in close association, and it is seldom that a calcium sulfate deposit will consist exclusively of one mineral or the other. Although known gypsum deposits are extensive, anhydrite makes up the larger part of total calcium sulfate resources. Although it has very minor economic use, it is important to the understanding of gypsum deposits and is referred to frequently in the following discussion. Calcium sulfate is one of the principal constituents of evaporite deposits, and when pure, has the following composition: [ ] Deposits of pure gypsum or of pure anhydrite which are large enough to be considered commercial have not yet been found because of both the metastable relationship between the two minerals, and the presence of impurities such as calcium or magnesium carbonates, chlorides, other sulfate minerals, clay minerals, or silica. Most gypsum produced ranges from 80 to 95% pure and beneficiation is normally limited to selective mining or quarrying or upgrading by crushing and screening during mill processing. END USES The largest use for gypsum is based upon the unique property which calcium sulfate has of readily giving up, or taking on, water of crystallization. With the application of a moderate amount of heat in a process known as calcining, gypsum is converted to plaster of paris, the hemihydrate of calcium sulfate (CaSO4 ½ H2O), which when mixed with water will set or harden as the calcium sulfate returns to the stable dihydrate form. This semifinished product, usually called stucco, is then manufactured into a large variety of plasters, wallboard, and block for construction use, or into plasters for industrial applications. About 75% of the gypsum used in the United States is calcined for these purposes. Uses of uncalcined gypsum are principally as a retarder for portland cement, as a soil conditioner, as a mineral filler, and other minor industrial applications. About 25% of the gypsum mined in the United States goes into these markets; however, in other countries with building practices different from those in the United States and Canada, relative usage varies widely. Calcium sulfate deposits are the world's largest sulfur resources; minor quantities of gypsum and anhydrite have been used to produce sulfur or sulfur compounds. This use is accompanied by a unique site-specific set of economics because sulfur is generally available from non-gypsum sources at lower cost.

Jan 1, 1994

By James W. Stewart, A. C. Colvine

Introduction Precambrian shield terrains the world over are experiencing an unprecedented level of concerted exploration for lode gold deposits. Reasons for this include: • The increase in the price of gold (following 40 years at $1.13/g or $35 per oz) has transformed targets that were once unattractive into viable exploration propositions. • The relatively suppressed market for other metals produced from shields (base metals, nickel, iron, and uranium) has further focused exploration attention on gold. • The preeminence of gold production from rocks of early Precambrian age, as shown in Fig. 1. • The relatively high grade of gold in these mines (averaging about 10 Wt or 0.29 oz per st) permits profitable extraction even under depressed gold prices. A number of these mines have been in continuous operation for more than 50 years. • The recent discovery of the major Hemlo deposit, in well exposed rocks adjacent to the Trans Canada Highway, has had a world-wide impact. This demonstrates that a major new deposit can be found even in an accessible, well exposed area of a shield; gold mineralization is susceptible to rational exploration; and new target types for gold exploration exist. This paper reviews exploration activity for gold in shield terrains worldwide (Fig. 2), excluding Early Proterozoic paleoplacers of the Witwatersrand type. Emphasis is on the Archean, which is traditionally the most productive part of the Precambrian shields. There is also an emphasis on the Canadian shield (Fig. 3) because of its vast areal extent and exceptionally broad range of mineralization styles. Geological Approach A basic problem exists in gold exploration when compared to exploration for base metal massive sulfides that predominated during the 1960s and 1970s. Gold concentrations cannot usually be detected by airborne geophysical instruments. The majority of massive sulfide deposits were detected using airborne electromagnetic detectors and magnetometers. A full 75% of Canadian gold discoveries can be credited to surface prospecting. The percentage is even higher in other countries. This observation allows for great optimism for two reasons: • Large areas of shield terrain are obscured by either surficial deposits (glacial tills, clays, and desert sands) or deep surface weathering. This makes them inaccessible to prospectors. Logic dictates that such obscured areas should have the same potential for gold concentration as has exposed bedrock. • The Hemlo style of mineralization, a roughly tabular ore body where gold is associated with disseminated sulfides, is different from the traditional prospecting target. The gold is hosted by discrete quartz veins. While it is true that limited discoveries were made at Hemlo more than 30 years ago, and this style of mineralization is present elsewhere, recent

Jan 12, 1984

The following errors were inadvertently included in "How millisecond delay periods may enhance or reduce blast vibration effects" by R.M. Wheeler in the September issue of Mining Engineering.

Jan 1, 1987

By A. H. Hassan

Stibiotantalite is a relatively rare mineral not commonly found in the major tin districts of the world, and its separation characteristics have not been documented adequately in the literature.

Aug 1, 1979

By Raúl Castro, René Gómez

In underground mining, rock fragment size is a key variable for productivity because it impacts equipment selection and mining structure design. This study characterizes granular material fragmentation during its flow to understand its characteristics and mechanisms. Tests were conducted using a laboratory setup to emulate various heights where material is drawn. The fragment-size distribution was measured before and after tests for clay, concrete fragments, and gravel. Results showed that fragmentation mainly occurs in minor sizes, with significant increases in fine material as travel distance increases.

Jan 10, 2022

By Rahul Bhaduri

Mercury levels in Twin Creeks Vista pit ore (previously Chimney Creek, North pit ore) increased substantially since plant start-up in November 1987. Consequently, modifications were necessary to minimize industrial hygiene hazards and potential operational problems. The original plant design included mercury control measures. With progressive increases in mercury levels, the issue had to be re-addressed. Modifications to operational practice, industrial hygiene and management philosophy will be discussed. Additionally, a detailed examination of the mercury vapor suppression system currently employed at Twin Creeks will be presented.

Jan 1, 1994

Previous models describing the aggregation of polymer coated particles fail to take into account the fact that there are a limited number of sites onto which a polymer segment can adsorb, called ?active? sites. Thus, the collision efficiency is a factor not only of the fractional surface coverage, but also of the number of active sites. In this study, a physical model of the flocculation system was devised in which the number of these sites could be varied, in order to study the effect on particle aggregation.

Jan 1, 1987

By H. Salamanca

The electric operation and design features of the 11.000 H.P. variable speed SAG mill gearless drive is presented. The function of the frequency converter, control system drive and lubrication systems are described. An analysis of the harmonic characteristic in the Supply System and Motor is presented, and the dynamic development of the stator current, speed and the magnetic flux in the start-up process of the drive is evaluated. Besides, the most important aspects in the commissioning and maintenance of the drive are analyzed.

Jan 1, 1991

By J. W. Leonard

By using physical and chemical method to increase the bulk density of newly mined coal, the productivity of a mine can be significantly increased. Greater amounts of coal can be placed in fixed volume shuttle car by increasing bulk density. This can increase mine productivity by about 15%. Small, easy to achieve changes in mining operations are required to obtain the increased productivity. This article deals with chemical methods used to increase coal bulk density, the results and discussion are based on experiments performed in the laboratory.

Jan 1, 1992

By Takashi Goto

In 1968 three historical rockbursts had occurred at Bibai Coal Mine in Hokkaido. At the time they had been observed by several seismic observatories as natural earthquakes away more than 100km from Bibai City. These facts taught us that the occuerrence of failure yielded in underground opening that was accompanied with seismic wave could be observed by seismometer on the surface. After two years from this desaster, the study concerning to microseismic events generated from underground mining panels has been begun by researchers with heart-throb.

Jan 1, 1982

By . A. J. Erickson

The Park City District, one of three major mining districts in Utah, is located approximately 20 miles southeast of Salt Lake City on the eastern slope of the Wasatch Mountains. The district has been in near continuous production since 1869. Production has been sustained from exceptionally long bedded replacement ore bodies in the Thaynes, Park City, and Humbug formations and also from several major veins. District production is summarized below. TABLE NO. 1 Park City District, Total Production, 1869 thru 1968 (Source r Various Company Records) [ ]

Jan 1, 1970

By John Dasher

In 1980, some US cars were designed and built to metric dimensions; wine and gas were sold by the liter; and the March of Dimes Walkathon was measured in kilometers. Although the US Congress has taken a ''soft" approach to metrication, and public resistance to the idea remains strong, the use of metric units is becoming more and more widespread. As the minerals industry becomes more international in scope, US mining companies are converting to the metric system-particularly those companies with business interests overseas.

Jan 2, 1981

By P. Harris, G. Groenmeyer, L. Parolis

The effect of molecular weight, charge and the presence of the cations Ca2+, Mg2+and K+ on the adsorption of carboxymethyl cellulose on pure talc obtained from Balmat, New York have been investigated. Higher adsorption densities were obtained in the presence ofCa2+ and Mg2+ ions than with K+ ions and higher ionic strength solutions resulted in higher adsorption densities. Changing the molecular weight did not influence the adsorption however increasing the charge (DS) of the polymers resulted in lower adsorption densities.

Jan 1, 2004

By William R. Yernberg

SME’s Arizona Conference was held at the Doubletree Hotel at Reid Park in Tucson on Dec. 4 and 5, 2005. The annual conference is organized by the Arizona Conference Board of Directors, which represents SME sections in Arizona and adjacent areas. The conference provides an opportunity for individuals and corporations associated with mining in the region to get together once each year to discuss the status of the industry. Important topics discussed among the attendees included the price of copper, community relations and education.

Jan 1, 2006

By A. D. Davis

Limestone-based material shows great promise for removal of arsenic from water. In laboratory tests, it has removed more than 95% or arsenic and more than 99% of cadmium and lead. In addition, the waste material appears to be suitable for recycling or disposal in an ordinary landfill. However, the efficiency of limestone for arsenic removal could be improved. Recent research has shown that iron treatment of limestone can enhance its arsenic-removal efficiency greatly, increasing its attractiveness as an alternative to other methods.

Jan 1, 2012

By S. K. Mukherjee, M. M. Singh, N. I. Jayaramn

In underground mining operations, ventilation and water sprays are the common methods of controlling dust. In recent years, there has been a proliferation of technical literature dealing with water sprays for dust control. However, guidelines for the design of an effective water spray system have not been presented to the mining industry. This paper recommends guidelines for water spray systems to control dust in underground mining operations. These guidelines suggest type, number, location, and orientation of nozzles; desirable operating water pressure; and associated filtration system.

Jan 1, 1987