Search Documents

By René Fernández

Newmont Mining Corporation has been processing refractory gold ore by roasting since January 1995. The ore is refractory due to the association of the gold with iron sulfides, namely pyrite and marcasite, and the presence of carbonaceous components and is oxidized in an oxygen-enriched gaseous atmosphere. The structural characteristics of the calcine have a strong influence on the eventual recovery of gold by cyanidation. These characteristics are strongly dependent upon the roasting conditions, mainly the roasting temperature.

Aug 25, 2002

By Paulo Roberto Pereira

This paper is motivated by the belief that increasing drilling and blasting costs will not necessarily bring about better digging or crushing productivity. As a matter of fact it can be counter productive as the ensuing discussion will show. In the two case studies presented herein when powder factor increased, productivity at a rope shovel and at a primary crusher decreased. Experience has shown that equipment (shovel and primary crusher) productivity increases as the powder factor increases and concurrently operating costs decrease. This is illustrated by Figure 1where the graph shows (assuming drilling costs constant) that for increases in powder factor initially operating costs might fall till a certain point and then they start to go up again. By the same token we need to understand what is the behavior of the operation’s productivity. It seems intuitive productivity goes up for increases in powder factor but when an operation reaches the point of minimum operating cost one could say that productivity reached its maximum. For continuing increases in powder factor can productivity still go up or does it go down? This paper presents two examples where the productivities of a surface coal mine and of a quarry are reduced for increases in powder factor. This indicates that these two operations could be operating to the right of their minimum operating costs and maximum productivity and therefore wasting precious drilling and blasting dollars and resources. Moreover, their productivity is following the red dotted line in Figure 1 and the question becomes can they follow the blue dotted line for increased drilling and blasting costs? The industry owes to itself to determine this minimum operating cost point and what can be done in case that the productivity goes down afterwards despite an increase in drilling and blasting costs. In other words, utilize your drilling and blasting resources correctly. In the two examples that follow single explosive loading strategies make powder factor a valid means of comparing the results of productivity as a function of powder factor. Also, external factors such as equipment operator influence are eliminated due to the long time span considered in the analysis

Jan 1, 2005

By M. McWha

Laboratory bias is a universal problem in all branches of analytical science. It results from differences in methods, techniques, equipment, and calibrations between laboratories. Notwithstanding that it is a property that can be measured by the use of standards or by inter-laboratory testing, laboratory bias remains a material issue for the mining industry. There is extensive literature and clear guidelines on measurement from the International Organization for Standardization (ISO) and its worldwide federation of national standards bodies (ISO member bodies) and from the science of metrology. ISO guides cover the manufacture and use of standards. An accessible source of literature covering laboratory quality control comes from the public health sector, particularly pathology. There is little doubt in financial reporting rules about the meaning of materiality. Public reporting guidelines are clear that material matters need to be disclosed for investors. Unfortunately there is currently no clear guidance what to do about biased assay results in mineral industry public reporting guidelines. This paper reviews the requirements for the manufacture and use of reference materials, public reporting requirements in the mining industry, and presents proposals to improve management and reporting of laboratory biases. Keywords laboratory bias, reference materials, ISO Guides, financial reporting, materiality.

Jan 1, 2014

By R. Sharon

Barrick Goldstrike Mines, Inc. Betze-Post open pit operations, located in northeastern Nevada, have experienced slope instability attributed to the presence of generally weak rock mass conditions, local adverse structural geology and perched groundwater. Ground movements are monitored with acombination of optical survey, extensometers, inclinometers, and time domain reflectometry (TDR).The slope monitoring system at Goldstrike includes two robotics theodolites, which provide real-time coverage for all highwall areas. Survey instruments are housed in specially designed climate controlled shelters in locations where all slopes can be observed. A “remote” computer housed with each theodolite collects data. The “base” computer, located in the mine offices, is used to access data from the remote computers via radio modem.

Jan 1, 2000

By P. B. Demarsh

"Location: - On highway 59, 17 miles east of Val d 10r near junction of Montreal highway in Northwestern Quebec.Life; - Started production 1952, ceased 1965.Ore: - Pyrite, chalcopyrite and small amounts of free gold and goldsilver tellurides in narrow quartz-carbonate-tourmaline veins in granodiorite. Specific gravity 2, 70.Capacity: - 700 tons daily Bevcon ore supply, l 000 tons daily when custom ore available.Assay: - Heads 0 .140 oz. per ton; tails 0. 009 per ton; extraction 92.5%.Grind: - 75% minus 200 mesh at 700 tons; 68% minus 200 mesh at 1000 tons. Detention time 28 hours and 21 hours respectively.Treatment: - Cyanidation process.Reagents: - Per ton. Aero Cyanide (NaCn) 0, 50; crushed unslaked lime 1. 75; zinc 0. 03; litharge 0. 10; steel consumption 2. 25.Water: - Pumped from land-lock spring fed lake l 1/2 miles distant.Cost: - Per ton. Crushing 0. 13; grinding 0 .32; filtration 0. 07; cyanidation 0.14; miscellaneous 0.29; total 0.95.Power: - Hydro-electric, 25 cycle, 12, 000 volts reduced to 550 volts.Labour: - Predominantly French Canadian, nucleus English Canadians.Tailings: - Impounded low lying pond.Personnel: - 15 including supervision.Flow sheet: - Canadian Mining Manual l 9 5 6 .Building: - Wood truss construction: 3/ 4 in. siding, ten test and 1/ 4 in. transite outside. Corrugated galvanized iron roof. Ground level foundations. Internal self induced heating. Wood stave tank equipment."

Jan 1, 1966

By H. R. Kempthorne

"The Property of Bevcon Mines Limited, including a recently acquired adjoining south group, occupies an area of 2,625 acres in northeast Louvicourt township, Abitibi county, Quebec. It is situated 17 miles east of Val d'Or at the junction of provincial highways 58 and 59.Gold was first discovered in the area in 1931 by the late S. B. Jowsey on the present property of Buffaddison Gold Mines adjoining to the west. However, it was not until the winter of 1944-45 that diamond drilling encountered encouraging results on the Bevcon claims. During the period 1946-1948 a shaft was sunk to 1,000 feet and considerable development undertaken from the 500-foot to the 1,000-foot levels. Between 1947 and 1950 approximately 24,000 tons of dump ore and 48,000 tons of ore by stoping were milled at Perron Gold Mines. The favourable results of these tests prompted the decision to construct a milling plant at Bevcon. The mill began operating in July 1952, and presently has a capacity of 800 tons per day. In 1953 the shaft was deepened to 1,600 feet and is currently (1955) being driven to 2,225 feet.Total production of gold to the end of 1954 has been 101,024 ounces from the milling of 697,427 tons of ore of an average grade of 0·163 ounces per ton.GeologyThe Bevcon orebodies occur in a granodiorite stock which has an east-west length of approximately 4 miles and a maximum width of 1 1/2 miles. The property covers the central portion of the stock and its contacts with the Keewatin volcanics. Approximately one-third of the northern contact and one-half of the southern contact are contained within the Bevcon claims. The granodiorite has been cut by acid (feldspar porphyry) and basic dykes trending east-west. A younger diabase dyke, 300 feet wide, strikes northeasterly across the property 1,000 feet east of the shaft.The main ore zone, striking east-west, lies between the more northerly porphyry dyke and the north granodiorite-greenstone contact. It has been extensively sheared, fractured, altered, and mineralized by gold-bearing solutions. It is approximately 2,000 feet Jong from the west boundary towards the diabase dyke. The shaft is centrally located and passes through the south contact of the ore zone at the 500-foot level. The zone increases in width and trends northerly with depth, due to the porphyry and greenstone contacts having average dips of 80 degrees and 70 degrees respectively to the north. Thus on the uppermost or 500-foot level the width is 150 to 200 feet, and at the present bottom level at 1,600 feet the width is 400 to 500 feet.Another gold-bearing zone has been indicated 200 to 400 feet south of the main ore zone by limited surface drilling."

Jan 1, 1949

By A. Dale Wunderlich

In the past, most people have associated gold scams with the sale of non-existent gold mines, an undivided interest in unmined ore or the sale of gold-plated lead bars. These scams are still available to those who want to speculate. Now, though, the mining industry is plagued with a new type of con artist. Many of the new scams involve large, well established mining companies being victimized. Nearly all legitimate mining companies are in search of good mining prospects. This makes them susceptible to modern day con artists. Many professionals from the mining and petrochemical industries are out of work. Some of them have gotten involved with scams or activities that border on the criminal. Mining companies are losing millions of dollars each year to scams. Some of these scams involve venture-capital fraud. Some involve fraudulent mining proposals. And some involve unqualified individuals who are providing services by the precious metals industry. The author estimates that mining scams may be costing precious metals companies as much in dollar losses annually as employee theft. Employee theft is at an all time high, but so are gold scams. Since January of 1990, the au¬thor has been involved in gold theft investigations in which more than $1 million in gold product has been stolen by employees. In the past, most of the gold mine scam operators have concentrated on the general public, which is generally ignorant of basic mining procedures and practices. A scam artist would tell someone from your neighborhood that they have a wonderful underground mine. It produces 62.2 kg/t (2000 oz per st) of gold ore. Your neighbor might think that sounds like a very good investment. Those involved in the mining industry know better.

Jan 1, 1990

Attention is drawn to the largest eruptions with dense rock equivalent (D.R.E.) volumes approx-imating 50 km3. These have been strongly clustered during the last 40 000 years, with 11 recognised in the period 35 000 to 22 000 years ago, and 10 in about the last 9000 years, but none in the period 22 000 to 9000 years ago. With the latest such eruption, at Tambora, only 175 years ago, it is likely that we remain in a period of increased activity. During the last 100 000 years, roughly the period during which modern Homo sapiens has existed as a species, there has only been one eruption an order of magnitude larger (>_ 500 km3 D.R.E.). This took place at Lake Toba, Sumatra, about 75 000 years ago, and is estimated to have deposited ash to a thickness of a centimetre or so in parts of Ethiopia, Somaliland, Saudi Arabia and Iran, and to a thickness of a few millimetres in the eastern Mediterranean. The average interval between global eruptions of this magnitude is probably about 40 000 to 50 000 years. Insufficient work on the Quaternary history of volcanoes has been carried out to suggest where the next such eruption might occur. At Yellowstone, which has been well studied, the average interval between very large explosive eruptions is about 700 000 ¦ 120 000 years.As a prerequisite for magnitude-frequency analysis of eruptions, and hazard and risk impact assessments, it is important to classify past eruptions in a consistent manner. In an attempt to find a universally applicable method to estimate order of magnitude D.R.E. volumes from the distribution of airfall tephra, an empirical correction has been derived for the elongation of tephra dispersal fans due to wind. Dispersion distances for various thicknesses of tephra, recalculated for windless conditions, have been obtained from a study of about 40 tephra isopach maps for which D.R.E. volumes have been calculated, and a range of distances derived, equivalent to D.R.E. volumes from 106 m3

Jan 1, 1990

Higher commodity prices and environmental considerations will make selective narrow-vein mining more attractive in future. Unfortunately, hand-held airleg (jackleg) mining is a mature technology that has safety and productivity limitations. Despite decades of attempted innovation, no obvious successor to airleg mining has emerged. A review of some of the possible technologies is followed by a speculative description of the mine of the future, intended to stimulate thinking and discussion during the conference.

Jan 1, 2008

By M J. Davies, R S. Davies

Despite increased expenditure, the global discovery rate of world-class ore deposits has been in decline for over a decade (Schodde, 2017). Mineral exploration has traditionally followed an empirical approach, searching for evidence of mineralisation upon the surface of the planet, then drilling to define the extent of an ore body beneath the surface. As outcropping deposits in well-defined areas are depleted, there is a need for exploration to extend to less well-explored search spaces. One popular new frontier is exploration at greater depths beneath the Earth's surface. However, exploring for deep deposits with limited surficial evidence requires the implementation of predictive targeting methodologies (Hronsky, 2011; McCuaig & Hronsky, 2014). The Mineral Systems Concept (Hronsky & Groves, 2008; McCuaig et al., 2010) provides a framework for predictive exploration targeting. Ore deposit formation is recognised to be a focused mineralising event. These events represent self-organising critical systems and are underpinned by the interaction of complex, non-linear processes. Through the collection and analysis of datasets that map mineralising processes, it may be possible to predict the size and location of resultant ore bodies. CITATION: Davies, M J and Davies, R S, 2018. Beyond below-ground geological complexity: Developing adaptive expertise in exploration decision-making, in Proceedings Complex Orebodies Conference 2018, pp 95–98 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 21, 2018

With the burgeoning opportunities for new gold mines to be developed the opportunity now exists for a reassessment of the optimal processing path for these gold ores. Projects have traditionally followed the path of whole ore cyanidation with either Carbon In Pulp (CIP), Carbon In Leach (CIL) or Merrill Crowe. The challenge ahead is whether these traditional processing methods are the best option for stakeholders, or to go beyond CIP and use a combination of currently available technologies that can be used to provide gold recovery at a significantly reduced capital cost and minimal deleterious impact on the environment. Either stand alone or combinations of gravity concentration and flotation, can produce a gold bearing concentrate that can then be fed directly to a batch or continuous intensive cyanidation unit. Treatment of a gravity/flotation concentrate by intensive cyanidation may be processed by the InLine Leach Reactor (ILR) developed by Gekko Systems of Australia. The advantages of the technology combining gravity/flotation followed by intensive cyanidation are significantly reduced capital costs; improved safety due to reduced cyanide inventories; the majority of tailings un-contaminated by cyanide; less energy required due to an opportunity for an increase in grind size û reducing green house gas emissions; detoxification of concentrate tailings can minimise tailings disposal and containment requirements.

Jan 1, 2004

By J. Nielen van der Merwe

Rock engineering research and technology development in South Africa only received serious attention in reaction to the Coalbrook disaster in 1960. At the time, a number of gaps in knowledge of rock related matters were identified and in the ensuing years, these were progressively attended to. The paper describes the events that led up to the Coalbrook disaster and reviews the developments that took place afterwards. The effectiveness of the research outcomes are tested by referring back to the disaster. It is concluded that tremendous advances were made but that not all the unknowns were attended to at the same level. The strength of nominally square internal pillars is the one issue that received the most attention, but the strength of barrier pillars, overburden behaviour and loading systems are still largely unknown. Due to the complexity of the remaining unknowns, they can and should be addressed by the application of back calibrated numerical models. There are no readily available simple analytical solutions. The state of mining rock engineering research in South Africa borders on an emergency. More than a 1000 years of aggregate research experience has been lost in the last three years and funding is under severe pressure. There are disturbing parallels between the current positioning of the industry as a whole and the Coalbrook mine in the years preceding the disaster.

Jan 1, 2006

By J. A. Porter

This paper uses project examples, primarily associated with large iron ore mines in Brazil, to demonstrate opportunities for the mining industry to go beyond traditional compliance and impact mitigation to proactively operate within the ethics of environmental and economic sustainability.

Jan 1, 1994

By G. R. Luster

In most current practice, the methods that are employed in technical evaluations of cement raw materials are deterministic; i.e., decisions among alternative raw mixes and alternative plant designs are reached with the aid of only "average" compositions and "representative" samples of the available raw materials. Nevertheless, cement plants are sensitive to raw-material variability, and uniformly high-quality raw materials are not so abundant as they once were. Some simple examples will illustrate how geological techniques can be combined with geostatistical and operations-research approaches to customize mining and processing systems to deal with variable raw-material compositions.

Jan 1, 1987

By S Dunham

A cross-discipline approach combining geology, metallurgy and mine planning, geometallurgy is seen as the next logical advance in improving the design and operation of mining businesses. This rapidly evolving field is focused on realising the value that has often been lost in the chasms between the aforementioned technical silos. When successful, the geometallurgical approach promises the ability to tailor mining and mineral processing development and operational options more closely to the characteristics of the resource with resulting lower costs (both capital and operating), improved recoveries and fewer project failures.As with any technological (or managerial) change, there will be side effects from the success of the geometallurgical approach that will impact areas beyond obvious linkages between geology and processing. Some of these effects have the potential to be beneficial to the resource industry and society in general. Beyond the basic geometallurgical promise of closer alignment between processing design/strategy and the multivariate 3D spatial characteristics of the mineralisation, this paper discusses the broader implications and ramifications of the emergent geometallurgical approach: enhancing exploration and discovery; improving project development success; achieving sustainability in an industry working with non-renewable resources; in a world of increasingly hard won license to operate, improving the management of potentially harmful by-products and waste materials (with knock on effects for proactive management of closure issues); smarter approaches to energy management and thus optimisation of projects with respect to carbon footprint; and potential to re-value assets and thus realise a strategic advantage in the area of acquisitions, divestments, mergers and take overs. The authors strongly believe that companies that actively engage with the above issues (and ensure that technical efforts in the area of geometallurgy are not isolated from the larger value chain activities of the firm) will be able to exploit the opportunities that consequentially arise. These early adopters will gain first mover advantages. Firms taking the broad view of geometallurgy will have an opportunity to maximise stakeholder value and win greater success than their less insightful competitors.

Sep 5, 2011

By A Weeks an, R Bertinshaw, S Khosrowshahi

Good mining is central to any approach to value tracking. Good mining occurs where the ore is correctly delineated, measured and fed to the mill. This process is usually referred to as grade control, ore control or quality control. There are now ways to measure the efficiency of this process, such as by using conditional simulation, and a brief synopsis is presented. Resource estimation is the foundation of ore reserve estimation, which should enable useful prediction of the expected metal to be recovered from mining and milling. Significant improvements have resulted from applying new techniques such as the Chain of Mining (CoM) method, which models the mining process. Again, a brief synopsis is presented. Tracking value from the mine through the mill implies a linear sequence of processes that can be modelled. Reality is more complex and there are error components, feedback loops and breaks in the Chain of Value. Modelling the total production process in a number of operations is considered, including the various impacts on producing reconciliations. Procedures are also discussed for handling a number of difficult issues such as: different data supports, stockpiling strategies, blending from multiple ore sources, blast movement and underground ore extraction.

Jan 1, 2002

By A R. Bye

Energy comes at great cost to our world and societies and therefore we should use it wisely and optimally. Societal pressure is enforcing this and the industry must respond by being proactive.The mine-to-mill approach to integrated mine and semi-autogenous grinding (SAG) mill optimisation demonstrated that throughput gains of up to 20 per cent could be obtained through a closer match of blasted run-of-mine ore to the feed best treated by a SAG mill. Since that approach was developed, new drivers have risen to prominence including environmental costs and impact of energy, water, waste. This is set against a backdrop of reducing ore grade and increasing demand that is pushing up our impact on the environment. The new challenges demand new approaches.This paper explores the opportunities in taking traditional approaches to optimisation to new levels of two-way integration and incorporating potentials for ore upgrade into circuit design. The new mantra may be æflexible circuitsÆ û designing and building for the present and the future by allowing for the uptake of new and future technology.

Jan 1, 2009

By D Brereton, C J. Moran

In this era of rising focus on the social and environmental costs and benefits of mining operations, the valuation methodologies used to assess such impacts become increasingly important. Within an industry dominated by an engineering culture that places emphasis on net present value (NPV) calculations using high discount rates, difficulties often arise when attempting to justify projects with longer-term, harder to quantify benefits. This is particularly so when these benefits fall in the social and environmental domains and involve other stakeholders. In this paper, we summarise the results of a recent literature review on this subject, which focused on the valuation of æBeyond ComplianceÆ initiatives in the mining sector. We discuss a range of approaches including the quantification of hidden internal costs, financial methods of incorporating risk into calculations, the integration of quantitative and qualitative information, and also the valuation of æexternalitiesÆ or costs and benefits borne by others. We then use a series of examples relating to the management of water in the minerals industry to illustrate how some of these approaches could be applied. There are high-level commitments from both individual companies and groups such as the ICMM to incorporate sustainable development criteria into decision-making processes within the industry. We conclude the paper by arguing that, to meet these commitments, there is a need for the industry to adopt a broader range of valuation methodologies than appears to be the case at present.

Jan 1, 2006

By Y. S. Roditis

Traditionally, open pit optimization has been used to produce a single outline which can guide the pit design. This paper describes how a series of optimum nested pits are utilized to: a. produce different mining sequences and to help in mine planning and phase design; b. evaluate different metallurgical processes, production scenarios and equipment size; c. investigate the sensitivity of a project to prices, recoveries, production rates, costs, ultimate pit slopes etc.

Jan 1, 1993

Anyone who has driven backwards using only their rear view mirrors knows how difficult it is to avoid spinning the steering wheel the wrong way. So why run your mine that way? Traditionally Reconciliation has focused on the past performance of the mine. In this paper we make a case for Prognostication û the act of forecasting or predicting something in the future from present indications or signs. Reconciliation is a common activity carried out at most mines around the world. Countless geologists and engineers spend hours poised in front of spreadsheets diligently comparing how their resource/reserve model, grade control, and survey pick ups compare to what was actually produced. The result is usually a group of factors, which are applied to future estimates in an attempt to better predict how the operation may perform. Unfortunately, if the road ahead isnÆt the same as what you have just been down, youÆll be æoff-roadingÆ in no time! An alternative is to constantly collect and analyse key measurements that are used to calibrate critical estimates in an iterative process. When variations occur, they are analysed and corrective action is taken to ensure the estimates and measurements realign. In this way the estimates become forecasts and can then form the basis for decision making to ensure that what does happen in the future will match the plan or schedule. By automating this process, some mines have been able to be proactive on a daily basis in order to improve the overall performance of the operation. This paper outlines the key estimates and measurements used for reconciliation, details the characteristics of an automated web based information management system to facilitate the process and provides some insights about how mining operations might move beyond reconciliation.

Jan 1, 2003