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By James Y. Oldshue, Paul M. Kubera

Most coillillercial processing applications employing mixers in various types of slurry systems are continuous flow. These applications may also be multiple stage, with the stage number varying anywhere from two or three to ten or more. Two questions that usually come up at the beginning of any proposed pilot plant study are (1) can the pilot plant unit be operated batch-wise, and the results extrapolated both on the basis of scale and fluid motion to the full-scale tank which will be continuous-flow (and probably multi-stage), or (2) does the pilot plant need to be operated in a continuous-flow fashion, and if so, does the exact number of tanks/stages that are proposed for the plant need to be used in the pilot plant? We will consider these possibilities in sequence and present the principles involved in running some of the various pilot-plant arrangements.

Jan 1, 1992

By Hugh K. Herbert, R. John Watling

Laser Ablation-Inductively Coupled Plasma-Mass Spectrom­etry (LA-ICP-MS) has been used successfully to "fingerprint" gold in forensic investigations within Australia and abroad. By comparison of the elemental associations it has been possible to relate gold to specific mineralising events, mines, bullion samples and fabricated articles. The methodology facilitates identification of the provenance of gold thereby providing definitive scientific evidence in criminal investigations. "Gold" samples for analysis span a wide range of materials with many requiring exhaustive prior separation and treatment to present the contained gold in a chemically "unmodified" state, and in a form, suitable for LA-ICP-MS fingerprinting. The quality of the fingerprint, and hence its value in evidence, is directly related to the rigours of prior sample preparation and evaluation, to an appreciation of the history of the gold under investigation, and to the skill of the analyst.

Jan 1, 1995

By H. Mercado G., J. R. Parga T

Mexico continues to be one of the main producers of silver, lead and zinc; although this leadership is ending because of the use of obsolete technologies, which is reflected in low recoveries of these processes. The country therefore requires to develop on new technologies in the field of nonferrous metallurgy, particularly be'cause it is the second most important source of foreign exchange. A novel method, presented in this paper, demostrates that refractory gold and silver can be extracted from a complex sulphide concentrate by a one stage pressure oxidation in an alkaline cyanide solution, this is achieved by simultaneous liberation_ and solubilization of the precious metals. Both gold and silver extractions are greater than 97%. Factors affecting recovery efficiency, such as: pH, lixiviation time in the reactor, temperature, particle diameter, pressure, % of NaCN and pulp density, were investigated. A summary of actual plant operations is also be included.

Jan 1, 1993

By Leonard Harris

Good morning ladies and gentlemen. I would like to thank Hans von Michaelis for inviting me here today to talk to you on the subject of "How to Reduce Capital and Operating Costs at Heap Leaching Projects". The comments I have to offer are based on my experiences in gold heap leaching by Newmont Gold Company in Nevada, by Newcrest in Western Australia (formerly Newmont Australia), by Minera Yanacocha in Peru, by Penmont in Mexico, by Z­Mont in Uzbekistan, by the Hochschild Group in Peru and expe­riences in copper heap leaching by Magma Copper Company in Arizona and as a consultant on several other smaller projects worldwide. These comments are a mixture of technology, ideology, philos­ophy, strategy, logic and opinions and might be looked at by many of you as "one man's view". I like to look at them as "a view from the bridge". Let me add that it doesn't bother me that you may not agree with my comments and that I would be interested in your comments or criticisms at the end of this presentation. I don't intend to discuss the details of the mineralogical and metallurgical test work. I will assume, for this talk, that the test work has been conducted very carefully and that the ore in ques­tion has been determined to be heap or dump leachable. Let's begin with a couple of don'ts! ! First, "don't build the mill until you have a mine". This might sound to many of you as fundamental but believe me it continues to happen. The minable reserves should be well known and established as being economical to mine and leach. NPVs, ROis and IRRs are fine if you can be sure of the gold price you use in your calculations. The best method is to carefully estimate the capital cost and, most importantly, the operating cost per ounce of gold recovered which should include the repayment of the borrowed capital and the interest thereon. For example, if the operating cost under these conditions is $200 per ounce, you have a project. If it is $400 per ounce, walk away f om it. Incidentally, the same prin­ciple can be applied to projects involving other metals such as silver, copper, lead, zinc, etc. The second don't is - "don't be sheep". Don't climb on the bandwagon with respect to design and operation because every­one else does it a certain way. Keep an open mind, be versatile, look for change, look for every possible innovation for reducing capital and operating costs. Beware of those who will tell you "we tried that it won't work" or "it's too expensive" or "that's a crazy idea" , <' ''what do you know about mining - you are a metallurgist aren't you" or "what do you know about metallurgy - you are a miner aren't you" or "only geologists can handle this issue". Be careful about pigeon-holing people according to their basic degree and experience. In these days of low metal prices, we need to consider everybody's ideas, as crazy as some of them might seem.

Jan 1, 1998

By Stefan Norgaard

In today's modern gold mining industry in Australia, and the world, more and more companies are recognising the competi­tive advantages gained by implementing an effective training program for operations (processing plant) personnel. Plant operators, or process technicians, are unique amongst all other gold mine employees. They are at work in shifts cov­ering 24 hours a day and their actions can have a profound effect on the operation's economic performance. To a large degree, the minute to minute decisions and actions of an operator can deter­mine whether gold is extracted to bullion in the goldroom or is discharged into the tailings dam. Experience has suggested that most small to medium sized gold operations in Australia, and even some large ones, have not implemented an effective training program. This is not attrib­uted to deliberate negligence or "anti" attitudes against training, moreover mill superintendents and metallurgy managers are technical people not oriented to human resource techniques. Usually the demands of designing, constructing and commis­sioning a gold plant overshadow the need for training in the first instance, In fact some well designed plants treating friendly oxide friable ore have little need for a dynamic well trained oper­ating staff. However, many plants do require a thinking team to optimise production and changing ore conditions towards the end of a mine's life can expose poor competence levels at large expense. Few managers will argue that training is a necessity and results in a win-win situation. The operators win by increased job skills, job satisfaction, clear career development and possibly better pay conditions. Trained personnel usually reciprocate with increased effmt and work ethic. The company wins also by having a thinking team which will maximise gold production and reduce operating costs.

Jan 1, 1998

By Charles A. Horne

Grinding mill circuits used for particle size reduction of mineral ores commonly use cyclones as primary classifiers. Typically, several individual cyclones are installed in a cluster (Fig. 1) where they can easily be added or valved-out of operation in order to balance classifier capacity with fluctuations in tonnage and recirculating loads as ore grades and hardness vary.

Jan 1, 1993

By A. R. Laplante

Ten guiding principles in the design and operation of gold gravity circuits are presented: economic impact, applied mineralogy, gold's behavior in grinding circuits, alternate recovery approaches, reliability vs. performance, gold room operation, scale-up, screening, feed rate and recycling. The principles are explained and their application illustrated with case studies. Conflicts in principle application are also discussed.

Jan 1, 2000

By G. H. Khoe

addressed in a number of studies in the past. In this paper, the stability of a ferrous arsenate compound is evaluated using a solution model and the thermodynamic data which were determined for the system. The environmental stability of the ferrous arsenate precipitate is compared with the literature data for ferric arsenate and arsenate-bearing ferric hydrous oxide.

Jan 1, 1991

By David Humphreys

Assumptions about future commodity prices need to be made with close regard to the purposes for which they are being used. Prices generated for financial planning or trading purposes are unlikely to be suitable for the longer run purposes of project evaluation and reserve estimation. In this latter context, price assumptions need to be realistic, stable and rooted in a rigorous fundamental analysis of long run industry drivers. Amongst the factors to be considered in such analysis are price history, production costs and structural dynamics. It is also important that prices adopted are consistent with other information being used by a company in its decision-making.

Jan 1, 2003

By Dale C. Matthews

Pressure oxidation of refractory gold ores is becoming more popular in what has become an environmentally sensitive society. This article discusses some specific process problems and solutions involved with starting up and operating an autoclave circuit. The Getchell gold deposit is located about 72 km (45 miles) northeast of Winnemucca, NV. The deposit was discovered in 1934 and first production came about in 1938. The oxide portion of the ore body was mined and milled from about 1936 through 1950. Refractory arsenic-bearing sulfide ores had long been known to exist in the Getchell deposit. These ores had been mined concurrently with the oxides since 1938.

Jan 1, 1991

By A. J. Douchane, J. M. Shirley

The high grade gold and silver Ken Snyder Mine is located in north-central Nevada, in Elko County, adjacent to the town of Midas, approximately 240 miles to the east­northeast of Reno and approximately 60 miles to the northeast of the town of Winnemucca. The Midas Joint Venture (MJV), an equal partnership between Franco-Nevada Mining Corporation, Inc. and Euro­Nevada Mining Corporation, Inc. with Franco-Nevada Mining Corporation, Inc. being the joint venture manager, owns the mine. In May 1997, Kilborn Denver, now SNC-Lavalin America, completed a bankable feasibility study and proceeded with detailed design, procurement and construction management. In mid December 1998, MJV not only poured their first gold several months ahead of schedule, but were already operating at full production. In addition, the construction of this US $84 million mine, mill and related facilities were completed on budget. Operating cash costs are US $78/oz. This paper describes how this was accomplished.

Jan 1, 1999

By A. R. Laplante

In this paper, the performance of the Knelson Concentrator and of the batch and continuous Falcon Concentrators are compared. The units are based on different operating principles, and perform quite differently. The Knelson yields very high free gold recoveries over a wide size range of both the recovered and rejected species. It is less effective in recovering very fine (<15 μm) or very flaky gold, as encountered in flotation feeds, concentrates or tails. It is the preferred unit for gold recovery from grinding circuits. The batch Falcon is effective in the fine range, typically less than 37 μm for gold. Its recovery zone is quickly saturated when there is significant heavies in the feed. It works best as a pre-concentration unit, or when sulphide content is low. The continuous Falcon is a versatile unit which is capable of recovering fine heavies (density down to 5 g/cm 3), especially from coarser gangue.

Jan 1, 1993

By J. Searls

The potash review arrived too late to appear in the June issue. Potash is a general term that includes several water soluble potassium salts: potassium chloride (muriate of potash), potassium sulfate (sulfate of potash), potassium magnesium sulfate (sulfate of potash-magnesia), potassium nitrate (niter) and sometimes potassium carbonate. Potassium carbonate was the original potash when it was leached from wood ashes and dried in large, cast iron pots to black-to-gray crystals (ash) to form "pot ash." "Pearlash" was potash roasted to white crystals. In modern terminology, the great preponderance of "potash" is the mined forms. It is estimated that 95% of the potash mined around the world is used as fertilizer. In 1840, Justus von Liebig demonstrated to the scientific community the importance of potassium to the growth of plants. But there was no low-priced source of potash available at that time. In the winter of 1851-1852, minable potash was discovered near Stassfurt,

Jan 1, 1991

By P. Whincup, T. Showell, B. Marchant, R. Dunne

An oversupply of copper on world markets in the early 90' s, coupled with a decrease in demand, resulted in a "tight" market for the sale of copper concentrate. In these conditions small producers of low grade copper concentrates found it difficult to sell their products. The situation was exacerbated for those producers also having reasonable quantities of penalty elements (e.g. As, Bi). The Telfer Gold Mine bulk copper gold concentrate, produced from treating underground sulphide ore, fell into this category (i.e. 16% to 20% copper, 30% to 35% sulphur and 3500ppm to 4500ppm arsenic). The concentrate sulphide minerals are predominately chalcocite and pyrite. Although a higher grade copper concentrate was attainable a substantial decrease in gold recovery ensued. Under the prevailing market conditions a decision was made to stockpile concentrates pending either an easing of market conditions or alternatively finding an on site method for treating the concentrate to recover both the contained gold and copper.

Jan 1, 1995

By A. Dan Rovig, C. Kevin McArthur

Technical and managerial innovations in the minerals industry have allowed continuing mining activities in the United States, and elsewhere, as gold orebody quality has diminished or has become more refractory. Of course, world markets, permitting requirements, and political processes also have created a need for innovative practices that contribute to the survival of the mineral industry. The gold industry has been transformed, during the past approximately 40 years, from a predominantly underground mining and milling type of exploitation and extraction to the large-scale, relatively low-grade type of extraction that is common in the United States today. Indeed, with the introduction of gold heap-leaching technology and the development of mines that produce from large, relatively low-grade gold orebodies in the western United States, a "new" industry was born and continues to prosper today. It is worthwhile noting, however, that Dobra (1997) has reported that one of the major trends in the North American gold industry is a movement back toward underground developments.

Jan 1, 1998

By Robert C. Dunne

Nearly one third of Australia's total gold product is produced in the Kambaloa - Kalgoorlie - Leonora Goldfields. There are presently some 25 gold mines in the area with the possibility of another six plants being constructed in the next year. Details of the gold extraction techniques used on these mines will be discussed and certain innovative technologies and problem areas will be highlighted.

Jan 1, 1998

By Steve Kral

The Northwest Mining Association (NWMA) has been an advocate for the U.S. mining industry since 1895. For several decades, the organization has represented mining members located mostly in the Northwest and some southwestern Canadian provinces. Today, though, the NWMA?s membership is located in 42 states and seven provinces and has become a national voice for the mining industry. So, during the association?s 119th and final meeting as the NWMA, a name change was announced. The organization is now called the American Exploration and Mining Association (AEMA). But that?s not all that has changed, according to the association. The new name reflects more closely the diversity and location of the AEMA?s membership. It will still be an advocate for the mining industry, dealing with land, environmental and community issues on state and federal levels. The conference, held in December 2013 in Reno, NV, attracted about 2,500 attendees. And the accompanying exhibit included 230 equipment and service suppliers in 246 booths. Technical programming ran the gamut of mining industry issues and technologies, including surface and underground mining; high technology systems and automation in mining, metallurgy and exploration; along with social issues, finance and safety. The following is a sample of some of the sessions.

Mar 1, 2014

By F. Lincoln & B. Rodier, G. Poniatowski, N. Kawashima, T. J. White, J. H. Kyle, G. F. Eaton

The history of Australia is a narrative of the discovery and development of its mineral wealth. The gold strike at Ballarat, Victoria, in 1851 transformed the colony by triggering the first great influx of migrants to Australia, and the development of subsequent mineral discoveries lead to a vast resource industry. However, beneficiation of base and precious metal ores carried with it an environmental penalty, not addressed until the last quarter of this century. In particular, the extensive deposits of gold, silver, lead, copper and zinc reside in sulphurous ores which often contain arsenic, antimony and mercury as significant contaminants that are released as unwanted by-products during smelting and refining. Until recently, these toxic concentrates were discharged to the atmosphere or receiving waters, collected in tailings ponds close to the smelters, or dumped at sea. Although such procedures . were acceptable in the past, more stringent environmental controls have required a re-examination of these practices and encouraged intensive efforts to develop enduring solutions to the disposal of these wastes. From this research has emerged a promising new generic technology called Xtaltite (pronounced crystal-tight). In this approach, geochemical principles are employed, first, to reduce the toxicity of heavy metals to low levels, and second, to identify and engineer suitable repositories for the permanent disposal of the consolidated waste form. In this paper, we emphasise the application of Xtaltite to the disposal of arsenious smelter fumes derived from gold winning. The principles ofXtaltite will be described and its technical and economic performance compared with conventional technolo­gies.

Jan 1, 1995

By H. W. Gussmann, R. G. Rohrs, E. van der Merwe

Salinity in Effluents carries a high penalty as a result of toxic­ity, corrosion, limited re-use potential, scaling and environmental impact. Although the high TDS, such as Calcium sulfate, other than metals are still being dealt with a low key non issue basis, they are receiving more and more attention from regulators. Traditional solutions to solve these problems are costly and inefficient and create therefore severe constraints on the prof­itability of mining operations and out-price in general the finan­cial resources for environmental clean up operations. Going up the technology versus cost curve the most econom­ic solution to pollution is dilution but which is difficult in a coun­t1y shoti of water. If this can't be done, the second best, at least in sunny areas, is, to pump the whole effluent on a tailings dam for evaporation. Depending on the contaminants, one may have to pond the efflu­ent to avoid re-dissolution and seepage into the ground. The next most common solution to pollution is the addition of lime to remove and concentrate any dissolved metals and then dump the product, hidden in a mass of gypsum in a convenient place. Again ponding may be required to avoid ground pollution. However the treatment costs start to rise steeply if it is not allowed to discharge the limed overflow solution because of its high calcium sulphate content. Further treatment is then required in the form of high cost and high tech membrane process tech­nology such as reverse osmosis or dialysis or even mechanical driven evaporation.

Jan 1, 1998

By James Y. Oldshue, Paul M. Kubera

Ore processing requirements in the gold industry are similar to those in other sectors of the minerals industry. In all cases, the processes revolve around the handling of large volumes of ore slurry, incorporating either physical processing or chemical processing steps which are related to distinct mixing application classes as defined in Table 1. From this standpoint, the complexity of the applications range from the simple (blending, solid suspension, etc.) to the complex (e.g., multi-phase reactor systems). The large volume of material to be processed dictates the large equipment size which is characteristic of this industry, and the often remote locations place a premium on both mechanical and process reliability.

Jan 1, 1992