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By Hung-Kei H. Lam

Rubidium and cesium were discovered by Bunsen and Kirchhoff about 100 years ago. These two elements are by no means as abundant as sodium or potassium. Their occurrence in minerals is widespread, but usually as minor constituents. There is no known specific ore containing rubidium, but rubidium is found replacing the. other alkali metals in .some minerals.. Perhaps the highest concentration of rubidium found in one mineral is in lepidolite, KLi(OH,F)2A12Si3010, which contains from 0 to 3.5%*Rb20. 0n the average, lepidolite contains about 0.5% Rb20. Other sources of rubidium are carnallite, KMgCl3?6H20; pollucite, H20.2Cs20.2AI203.9SiO2; rhodizite, R20.2A1203-3B203; biotite, H2K(Mg,Fe)3A1(Si04)3; sea water, rivers, marine and fresh water organisms, soils, and plants. Cesium, even though it is the least abundant. of the stable alkalies, has a specific ore. Pollucites a hydrous cesium aluminum silicate, may con¬tain as high as 42.5% Cs20, although again, the average Cs20 content is about 25% among the handful of known deposits. Other cesium-containing minerals are lepidolite and carnallite. Rubidium and cesium are very much like potassium in chemical properties, consequently, they are hard to separate. Because of the difficulty in obtaining pure cesium and rubidium compounds coupled with the scarcity-of supply, prices were high and the two elements enjoyed little industrial use. Just before the Second World War, the world. supply of rubidium and cesium, from Germany, was a matter of tens of kilograms per year and prices were about

Jan 1, 1959

By Werner Wenzel

Whisker growth during the reduction of iron ores The phenomenon of whisker growth can be observed in a number of solid-state crystallisation reactions, which, apparently, appear in6 the first instance as though they are two independent processes. From such reactions, one can find the whisker type of crystallisation on solid bodies. These examples show, that the whisker growth is neither due to certain crystal forms with predetermined temperature and pressureranges, nor to parameters, which, ad hoc, are necessary for the crystallisation. In all cases the whisker formation seems to depend on nucleation and the availability of crystallizing material in direct environment of such a nucleus, under given parameters of a system. One can generally state, that the research of whisker growth with the aim of establishing proper physical laws, to determine the foundamentals of whisker formation and whisker growth, is at present under active study. We can conclude that, although a great number of hypothesis have been proposed; no concluding theory has yet been arrived at. In the institute for ferrous metallurgy of the technical university of Aachen, research works are undertaken to find an explination to various metallurgical phenomena through help of whisker growth which was observed under varying conditions of iron ore reduction. This was possible by using refined microscopic techniques through which the whisker growth on solid oxyde substrates is detected. This refined technique combines the latest methods of surface examination with the help of stereo-scan-electron-microscope and proper and carefull preparation of surface to be stereo-scanned.

Jan 1, 1971

By S. J. Taylor

The siting, grading and fill usage for leach pads are important aspects of leach pad design. A method is presented that optimizes the cut and fill quantities (i.e. minimizes the cost) required to grade a leach pad with parallel cells; given the desired pad characteristics of maximum and minimum pad slopes, maximum cut and fill depths, etc. and the cut and fill costs. The method allows the variation of the cut and fill costs with depth, which allows the accurate modeling of the cost savings practice of using cheaper fill towards the bottom of a thick fill. This optimization could be incorporated into a CAD package, enabling a designer to simply draw a desired pad shape on a site plan, input the pad and heap characteristics (required heap volume, heap height, heap sideslopes, etc.) and then have the computer report both the adequacy of the pad area and the optimum grading for the particular pad shape. Using this, a designer could quickly and accurately assess the optimum, or cheapest, grading of many shapes and positions for a leach pad. This would be especially useful for large pads that need to be sited on rough terrain.

Jan 1, 1996

Planning the primary development of a mineral deposit usually is done only once during the life of a mine. As a consequence, not optimizing the primary development of a mineral deposit can cause disadvantages over the whole life of a mine and can lead to higher costs. As a contribution to an improved primary development design procedure beyond the already existing work a study of the identification and quantification of the influence of parameters on primary development based on operational data from working mining operations has been completed. Based upon such a quantification of the influence of parameters a sequenced decision model was developed, that enables to develop an initial concept for the design of the accesses from the surface based upon a few critical parameters. Such a model will not replace detailed planning work within a feasibility study, but it is intended to reduce the amount of planning efforts at an early project stage through providing information what are most likely economic solutions, based on simple rules.

Jan 1, 1997

By James K. Kindig

Hazen Research, Inc., has developed a new process for removing pyritic sulfur and ash from coal. Feed coal is contacted with iron carbonyl vapors, Fe(CO)5, at 190°C which puts a thin skin of magnetic material on the pyrite and ash, but does not affect the coal. Thus, low intensity magnetic separators yield a nonmagnetic coal, low in sulfur and ash, and a magnetic refuse, high in sulfur and ash. Results are given for clean coal produced by this method. A comparison is made between results of the magnetic process and the U. S. Bureau of Mines two-stage flotation process cleaning identical samples of Pittsburgh Coal. Capital and operating costs of the two cleaning methods are discussed.

Jan 1, 1976

By Stephen M. Voynick

Two hours driving time west of Denver, CO and 21 km (13 miles) north of Leadville, Bartlett Mountain rises 4,065 m (13,337 ft) high in central Colorado's Tenmile Range. Bartlett Mountain is one of Colorado's most recognizable peaks, especially when the late afternoon sun casts a surreal, reddish light across its most prominent feature - the Glory Hole. This is a gaping, half-mile-wide, 245-m- (800-ft-) deep crater. Created by subsidence from 60 years of massive underground mining, the Glory Hole is a monument to the Climax Mine, one of the great achievements in American mining and metallurgy. For most of this century, the name Climax has been synonymous with brilliant mining engineering, innovative metallurgical research and entrepreneurial promotion of a once-obscure metal - molybdenum. Climax overcame an array of economic, technological and social problems to become a model for underground development of massive deposits of low-grade ores. It is one of the few mines in the world where cumulative production is measured in the billions of dollars. The Climax mineralization was emplaced 30 million years ago. Magmatic intrusions formed a large, mineralized stockwork within the granite country rock of Bartlett Mountain. Associated hydrothermal events forced superheated metal- and quartz-rich solutions through fracture zones, silicifying the country rock and depositing huge amounts of molybdenite, or molybdenum disulfide. The mineralized rock, a light gray, finely crystalline, silicified granite, is laced throughout with blue-gray quartz veinlets containing molybdenite. Although the richest ores graded only about 1% molybdenite, the Bartlett Mountain deposit contained more than 2.7 Mt (3 million st) of elemental mo- lybdenum.

Jan 1, 1997

By A. Patrick Ryan

To many people, the word cartel implies illegality. However, although it is illegal in the US, cartels are an effective and legal way to conduct business elsewhere in the world. But be-fore we continue, what is a cartel? The American Heritage Dictionary defines a cartel as "a combination of independent business organizations formed to regulate production, pricing, and marketing of goods by the members." However, that definition does not fit many of the "cartels" we are examining today. The International Tin Council is an organization of both consumer and producer nations--no individual companies are represented. The buffer stock is used by the ITC to provide protection for both producers and consumers, and has only been in effect since 1955. (Earlier tin producers groups date back to 1921 when the Federated Malaysia States and the Netherlands East Indies formed the first intergovernmental tin agreement, known as the Bandoeng Pool, which only lasted three years.) The International Bauxite Association only dates back to 1974 when seven nations--Australia, the Dominican Republic, Ghana, Guinea, Guyana, Haiti and Jamaica--agreed to three main objectives: 1) to promote the orderly and rational development of the bauxite industry; 2) to secure a fair and reasonable return on the raw material for the benefit of the nations' citizens; and 3) to safeguard the interests of member countries in relation to the international bauxite industry. 1 Again this organization is composed of nations, not separate firms. This generally follows the pattern that the oil producing countries (OPEC) chose since the nations' mineral product-ion is controlled and often owned by the state. However, the group I am going to discuss fits the more classic mode of a cartel. The informal lead-zinc producers' cartel can be dated as far back as to Roman times when Romans are said to have imposed a quota system on British lead production to safeguard their Spanish lead mines. Also, the lead-zinc producers group is composed only of individual companies, not do not include any lead-zinc consumers. Finally, the activities of the group are not open to public scrutiny, and details are only now available due to a leak in the Australian government. At this point, it is necessary to split the two metals since while many of the members of the cartels produce both lead and zinc they do have different histories and marketing arrangements.

Jan 1, 1978

By K. S. Gritton

The U.S. Bureau of Mines has investigated methods for extracting metals from a variety of arsenic-containing smelter flue dusts. One proposed flowsheet includes a sulfuric acid leach, a cooling step to precipitate hydrated copper sulfate, and a reduction-precipitation of As2O3. Arsenic extractions greater than 90 pct were achieved, while copper extraction ranged from 50 to 85 pct under the conditions examined. Copper was removed from the leach solutions by crystallization followed by SO2 precipitation of arsenic which resulted in a 98 to 99.9 pct As2O3 product. Other metals, such as lead and zinc, were concentrated in the leach residue or in other byproduct streams for recovery of their valuable metal contents.

Jan 1, 1990

"Foreword by Ren BryceSenior engineer, Freeport-McMoRan, Oro Valley, AZ, USAThe eighth annual Mineral & Metallurgical Processing Division (MPD) student poster contest was held in February at the national SME Annual Conference & Expo in Denver, CO. A total of 33 students presented their work at the poster competition. The competition started in January when the students submitted a one-page abstract for judging. In February, they prepared and presented a poster that explained their research. A panel of judges went to each student and listened as the students explained their research in five minutes.The students worked hard at their research and then set aside time to complete all the necessary steps to enter the competition. The MPD recognizes the effort required to enter and as a result, provides monetary rewards to all participants. The first-place winner receives $1,000; the second, $500; the third, $250; and the fourth through seventh, $200. All remaining students receive $100. All of the students also receive a complimentary ticket to the MPD Luncheon. As in past years, there are separate levels of competition for undergraduates and graduates.Graduate winnersKaustubh Shrimali won first place for researching “The influence of starch in amine adsorption by quartz in the reverse flotation of iron ore.” Venkata Atluri received second for studying “The effect of polysaccharides on bubble attachment at talc surfaces.” Jennifer Galvin placed third for investigating “A novel approach to alkali pug bake for the extraction of rare earth elements from monazite concentrate.” In the fourth through seventh places were Amy Richins, Sumedh Gostu, Brett Carlson and Chris Vass.Undergraduate winnersNestor Santa earned first place for exploring “Copper recovery from waste printed circuit boards.” Cassidy O’Connell received second place for conducting “Performance analysis of CMC in high talc copper sulfide flotation systems.” Catalina Vanegas won third place for examining “Cyanidation tests and pretreatments to recover gold from a refractory ore in Colombia.” Kylie Boyce, Michael Archambo and Pritam Sinha were in the fourth through sixth places.Everyone benefits from attending the student poster competition. The students are able to display their work to future employers, and industry professionals can talk to up-and-coming engineers. Next year, there will be another competition for more posters and networking. Come and enjoy the event and the posters."

Jan 1, 2017

By M. Spangler

FirstMiss Gold installed a supervisory control system based on Pavilion Technology's Process Insights neural network software and Oil System's PI data historian. The primary goal of the system was to control the acid preconditioning circuit. However, our first successful control loop was on the limestone feed rate to the neutralization circuit. The information gained by modeling these circuits and the better control provided by the system has resulted in reagent savings of over $80,000 per month.

Jan 1, 1995

By D. K. Adjei, G. Ofori-Sarpong, R. K. Amankwah

"Mercury (Hg) is toxic and has long-term effect on the muscle tissues, the brain and the central nervous system functions due to its bioaccumulation and biotransformation effect. Hg pollution around the world is high and this has attracted much global concern such as the Minamata Convention on Mercury, held in 2013. For several years, mercury has been the chemical of choice for Artisanal and Small-Scale Mining (ASM) gold extraction, accounting for about one-third of the global mercury consumption. A greater percentage of this ends up in the environment through open burning of amalgam, spillage and indiscriminate disposal of waste. To break this wall of mercury pollution, it is very important for the mercury used to be recycled through the use of mercury retort units. This brings into the limelight, the Lantern Retort which tries to synergise the high conductivity of steel and the see-through effect of glass, thus, improving the amalgamation process. A research conducted on improving the original Lantern Retort arrived at an appropriate distillation length of 5.08 cm which was used in redesigning a more efficient retort. The improved Lantern Retort recovered about 98% of the mercury used. INTRODUCTION Artisanal and Small-scale mining (ASM) is an informal mining activities which employ quite simple tools such as pickaxes, sluice boxes, shovels, chisels, metal bars, mattocks and water pumps for mining and processing of gold ores. The artisanal and small-scale mining (ASM) sector has served as source of employment for many people in developing countries including Ghana (Aryee, 2001; Hilson and Potter, 2003; Amankwah and Anim-Sackey, 2004; Amankwah et al., 2010) and has provided a substantial amount of foreign exchange through its activities (Hilson, 2001; Styles et al., 2010). Hentschel et al. in 2003 estimated that about thirteen (13) million people are said to be engaged directly in the small-scale mining activities worldwide. However, an estimated 100 million people are said to depend on this sector for their livelihood mainly in developing countries. In China alone, a projected number between 3 and 15 million people are engaged in artisanal and small-scale mining activities (Hentschel et al., 2003), whilst in Ghana, it is estimated that more than 1,000,000 people are employed directly or indirectly in the artisanal and small-scale mining activities, with 10% being women (Amankwah and Anim-Sackey, 2004; Amankwah and Ofori-Sarpong, 2014). In Ghana, ASM gold production has grown from a low of 2.2% in 1989 to a high of 34% in 2014. This figure is estimated to increase with proper documentation. This indicates that the sector has made significant socioeconomic impact on many individuals and communities as a whole. Notwithstanding the above positive contributions, the sector has also contributed to negative impacts on human, aquatic life and the environment in general due to indiscriminate mercury emission. This ‘pollution wall’ needs to be broken, and several interventions have been put in place including the use of retort units like the lantern retort (Adjei et al., 2014; Amankwah and Ofori-Sarpong, 2014)."

Jan 1, 2017

By John J. Simmons

Federal and state regulations, in an effort to reduce acid rain, are becoming increasing more stringent regarding sulfur content of fossil fuels. Whereas coal from Illinois and Ohio contains between 1.5 and 37. sulfur, Wyoming has billions of tons of coal reserves containing less than O.5/% sulfur. However, much of Wyoming's coal is high in moisture, 25-30%, and low in energy, 8,200 to 8,900 BTU, vs. 10,500+ BTU for Illinois and Ohio Basin coals. Wyoming currently ships in excess of 130 million tons of coal to utilities as distant as Michigan, Wisconsin, Minnesota, Iowa, Nebraska, Louisiana, Oklahoma, and Texas. With freight charges ranging from $12.00-$20.00/ton, more than $1.5 billion a year is spent to transport water. A test shipment of more than 50,000 tons of Wyoming coal has recently been made from Mobil's Cabello Rojo Mine, south of Gillette, by Burlington Northern to the Robert's Bank British Columbia coal terminal for transloading and shipment to Taiwan Power Company. This coal assayed approximately 8,400 BTU/lb. and 277. moisture. Carbontec Energy Corporation feels the future availability of dried coal containing 11,000+ BTU could substantially enhance the potential export as well as the domestic market for Wyoming coal. Large and small utilities, along with industrial furnaces require tens of millions of tons of Wyoming, West Virginia, and other Eastern The federal government is encouraging the expenditure of hundreds of million of dollars by utilities to retrofit their boilers to allow them to burn higher sulfur coal. This program, if carried to completion, would cost many tens of billions of dollars, with the net result being high power costs sustained by the utilities. These costs will be passed on and paid for by the American consumer. A sensible alternative would be the burning of low sulfur coal by the utilities, without costly capital and operating expenditures. Carbontec Energy feels the successful operation of a Carbondry Coal Drying Plant in Wyoming will be the forerunner to other similar and larger operations in the State. CARBONTEC RESEARCH The activities of Carbontec's personnel to develop a viable process to dry sub-bituminous and lignite coal goes back some 14 years; in fact, for some of us it goes back to 1962 when we were involved in a program under which lignite coal from Truax Trayer's Velva mine was placed in low sulfur coal, which are burned alone or blended with high sulfur, Midwestern coal. Carbontec believes that a high BTU. reasonably priced, shippable coal fuel produced in Wyoming and delivered at costs competitive with Eastern low sulfur coal, could offer substantial benefits to Wyoming coal producers, utility customers, and to the State of Wyoming.

Jan 1, 1989

By P. James

"INTRODUCTION High sulfate (SO4-2) levels often occur in MIW (mining influenced water) either as the result of oxidation of sulfide minerals exposed by mining activity or by deliberate addition – commonly by sulfuric acid (H2SO4) use in hydrometallurgical leaching activities. Increasing regulation of sulfate discharge is creating new pressure to treat or mitigate sulfate release to prevent its entry into the environment. Current treatments include precipitating as gypsum during lime treatment, filtration separation using membranes such as reverse osmosis and nanofiltration technology, and biological elimination via methods like constructed bioreactors. Blue Planet Strategies (BPS) focuses on improved resource utilization targeting electrolytic treatment and waste conversion into resources and has now demonstrated that its proprietary DEMET™ (Dynamic Electrolytic Metal Effluent Treatment) platform can also remove sulfate from target streams as a byproduct of its usual primary treatment focus points of metal species elimination and/or pH adjustment.[1-6] This powerful new capability can mitigate sulfate contamination and recover the sulfate in a useful and potentially saleable form as a byproduct of improved primary treatments focused on enhancing production or treating waste. This provides a new treatment opportunity and value proposition for lowering overall sulfate consumption/addition or creating new revenue to defray conventional treatment costs. The DEMET Alternative DEMET utilizes a patented electrolytic technology platform employing proprietary dynamic high surface area electrodes in innovative configurations to achieve a variety of novel selective chemistries. DEMET‘s unique elements can yield higher processing rates at practical efficiencies, lower energy consumption, plus improved processing stability and lower maintenance requirements due to enhanced resistance to cell fouling and shorting; while also thwarting cross stream (catholyte vs. anolyte) contamination. Consequently, DEMET can provide a superior, extremely versatile, and cost-effective electrolytic treatment option where a multitude of FEED and PRODUCT stream combinations might be employed in comparison to traditional tankhouse electrolytic cells. Secondary reactions (Figure 1A) which could also occur at the cathode (plating/electrowinning, precipitation/scale formation, etc.) are controlled through process tailoring and operation parameter selection. Additionally, DEMET‘s innovative dynamic system mitigates potential fouling and electrode occlusion or shorting challenges which could occur when process particulars demand some of these secondary side reactions occur."

Jan 1, 2015

By H. R. Hammond

The situation of The Consolidated Mining and Smelting Company of Canada Limited, or Cominco, may be somewhat unique in that the Company is not only a manufacturer of ammonium nitrate, but as a mining company is a major user of its own product. This situation has resulted in highly successful application of ammonium nitrate-oil explosives. Several noteworthy techniques have been developed and others have been improved. Use of this material in the mining industry has led ammonium nitrate producers to adopt the term nitro-carbo-nitrate or INN for ammonium nitrate-oil blends. A small blending plant at Cominco's largest mining property, the Sullivan Mine, at Kimberley, B.C., is producing more than 80% of all the explosive used at the Sullivan, and is supplying two other Cominco mines. Application has required intensive research to determine the best forms of ammonium nitrate for use in small holes drilled for development and long-hole stoping. It has led not only to experiments to determine the best blending oil, but also to development of loading techniques to the point where NCN is being moved through loading tubes over 700 feet. It has required research into mining practices such as hole arrangement and blasting of development cuts. It has resulted in the development of a special product for secondary breaking. All this has been accompanied by the recognition of the importance of insuring safe practices at every stage.

Jan 1, 1963

By D. Tahija

"Hecla's Greens Creek silver-gold-lead-zinc mill began using carbon dioxide rather than sulphuric acid to control pH in April, 2015. High pH levels in the grinding and lead flotation circuits are caused by the presence of re-mined cemented paste backfill in mill feed and need to be lowered to achieve good flotation response. Carbon dioxide has proven to be quite effective at controlling pH in the lead circuit with greatly improved pH target attainment. The allowable amount of carbon dioxide used is not limited by effects on lead-zinc selectivity and by poor froth characteristics, as was the case with sulphuric acid. Startup and implementation went smoothly, with few operational issues needing to be resolved. Early results from implementation of the system and its effects on mill performance will be presented. INTRODUCTION Hecla Greens Creek is a silver-gold-lead-zinc mine producing flotation lead and zinc concentrates, as well as a gravity gold concentrate. Besides their base metal contents, both the lead and zinc concentrates carry precious metals. The circuit is largely conventional, with SAG and ball mill grinding being followed by graphite removal preflotation, then conventional lead flotation and conventional zinc flotation. Both rougher concentrates are treated in regrind steps, followed by cleaner flotation. The cleaners tails are treated in an unorthodox bulk circuit to produce a low-grade zinc-lead concentrate marketed to Imperial Process smelters (1). BACKGROUND Backfill and Flotation pH The Greens Creek mine is an underground operation in which mined areas, after ore extraction, are backfilled, using rammed paste or pumped slurry. The backfill consists of mill tailings to which approximately five percent Portland or similar cement is added to enhance its compressive strength. Later mining near backfilled areas inevitably results in a considerable amount of old backfill being mixed with new ore before being shipped to the mill. Depending on orebody geometry, mining methods etc., the amount of backfill in mill feed is often 20% to 25% and sometimes even higher. Commercial cement, and consequently backfill prepared using it, contains excess lime. Because of this, backfill in mill feed is indistinguishable from the addition of a large amount of lime, so mill natural pHs often range above 10 or even 11. Similar situations have been recognized for many years at mines throughout the world (2)."

Jan 1, 2016

By Lena Paar

"Underground construction poses certain challenges for all parties involved because the actual ground conditions are often unpredictable. Highly complex projects like tunnel construction are affected by various uncertainties. To address this complexity, the construction contract has to be flexible enough to be adapted to the actual conditions (e.g. divergent ground conditions, work delays). However, the adaptation of a tunnel construction contract does not guarantee the absence of a margin of interpretation. The perfect construction contract is an illusion because ex ante statements of the actual ground conditions are not feasible. This paper will discuss contractual parameters that must be considered in order to enable an effective adaptation of the contract during excavation. It is therefore necessary to discuss the following topics: decision-making competence, variable remuneration, fair-risk allocation, value engineering and partnering between client and contractor. INTRODUCTION Thinking of tunnel construction processes, engineers’ first (or at least second) association is about ground conditions. When constructing under the surface, the project is directly related to the ground conditions; however, ground conditions are known fairly well in advance. The estimated conditions can be the same or can also differ from the existing ones. A clear view of the conditions is possible only by driving through the section. What Hoek calls “Geological unpredictability which is guaranteed to provide some surprises in even the simplest tunnelling job” is, in addition to contractual issues, one of two critical aspects of modern tunneling (Hoek 1982). Almost no research tries to figure out, what flexibility in this context means and how to approach it in the contracts. Papers dealing with the New Austrian Tunnel Method (NATM) pose some principles to meet the requests for flexibility (cf. Austrian Society for Geomechanics 2011). However, it remains unclear how to create contracts in order to make them “flexible” enough to react to divergent ground conditions."

Jan 1, 2016

By David Butts

Solar ponding to crystdlize sodium chloride has been used for thousands of years.1 The systems used were inefficient and usually small compared to the large 25,000 acre pond areas seen today. It has only been in the last 25 years that any real effort has been applied to develop solar ponding technology. Many large solar pond systems have been constructed without much thought to efficient and optimum production rates. The recent high costs of labor, of equipment and of energy have forced producers to take a closer look at their solar pond systems in an attempt to squeeze out the highest possible yields. Other companies such as the Arab Potash Company, the Dead Sea Works, Texas Gulf (Moab, Utah) and San Francisco Salt Companies have no more land area in which to expand and therefore efficient ponds are essential. This paper is written to show how the subdivision of solar ponds can result in production increases of up to 20% and beyond.

Jan 1, 1984

By Vas P. Srinivasa

A comminution circuit is an important integral part of a mineral processing plant. Nearly 40% of the capital cost and 30 to 40% of the operating cost are taken up by the crushing and grinding circuit. Therefore, considerable care should be given to the design and selection of this circuit. Several factors affect the selection of a comminution circuit--energy consumption, avail- ability of the equipment, the remoteness of location, and availability of trained personnel, to mention a few. Each of these factors influences the choice. Selecting a comminution circuit strictly on lower capital cost may not be optimal. Crushing and grinding circuits are usually site specific and should be selected - only after careful analysis of all the factors involved. The objective of this paper is to show the effect of these factors, which are extranious to capital cost. Usually, the capital cost of a semiautogenous grinding circuit is lower than that of an equivalent conventional circuit. However, due to lower equipment availability and high power costs in certain locations, the economic advantage of lower capital cost is lost. Analysis indicates that a break even point occurs at a power cost of 5¢/kWh. This paper describes the procedure utilized for selecting the most economic comminution circuit and states the conditions applicable for each cominution circuit.

Jan 1, 1983

By A. M. Anthony, A. Y. Atta, S. S. Magaji, U. Abubakar-Zaria

There are two major gold recovery methods: the hydrometallurgical technique, which employs cyanide solutions, and amalgamation method, which involves mercury (Hg). These methods present considerable health, safety, and environmental concerns. Past applications of alpha-cyclodextrin (α-CD) on gold scraps show that α-CD is not only inexpensive, but is also environmentally friendly. This research work used α-CD to recover gold from gold ores instead of gold scraps. The gold ore was sourced from Shanono gold deposit site Kano State,Nigeria. The gold ore was characterized by fire assay (FA) for the precious metal. The concentrate was digested with aqua regia (AR) for 24 h. Modified AR, where hydrochloric acid was replaced with hydrobromic acid, was used for the gold digestion due to the good match in molecular recognition between gold bromide ion (AuBr)− and α- CD in a second sphere coordination complex. The digestate was characterized using atomic absorption spectroscopy (AAS). Gold recovery using this technique is pH sensitive, and five pH values (2.0, 3.6, 4.0, 5.4, and 6.0) were investigated. FA analysis showed the Shanono gold ore deposit contains an average of 4.71 ppm of gold, AAS analysis showed highest gold recovery of 69% at pH 4.0, which is lower than recoveries from the metal scraps. This could be due to the presence of other gangue minerals closely associated with the ore. However, gold recovery using α-CD on Shanono gold ore has shown to have a higher yield of 69% compared to 35.5% yield obtainable by Artisan Small Scale Miners using mercury.

May 5, 2020

By H. V. Scotland III

Lafarge Corporation's Texas Quarry, in Baltimore MD, achieved a substantial expansion of pit reserves by removing an inactive underground mine. The day lighting program, designed, and completed in 1997, open pit mined more than 400 meters of room and pillar workings which were originally developed to recover high brightness Calcium Carbonate. The project proved to be a challenge throughout its course as the pit plan was modified and successful daylighting techniques were developed to remove the mine without adversely affecting the safety of the operation, quality of the stone recovered, or negatively impacting the surrounding community. The design parameters and techniques developed and implemented at Texas may prove of interest to other operators as they are faced with daylighting opportunities. This article will detail the challenges we faced and the solutions which made the project a success.

Jan 1, 1999