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By Timothy D. Arnold

Barrick Gold’s Bullfrog underground mine, near Beatty, NV, was established as an after-thought to the main open pit. As open pit ore dwindles, the underground mining became increasingly more important as an ore source, and to the overall economics of the project. This situation is similar to many other mines. Today, there is a move towards underground mining in the United States. There are inherent problems in starting and operating underground mines in the shadow of any open-pit operation. Several attempts were made at the Bullfrog Mine for productive increases. Some were successful, while others were not.

Jan 1, 1996

By Chris Cox, David Green

Outokumpu has developed the HG or High Grade flotation cell over the past decade. This machine gives upgrading and selectivity performance superior to conventional mechanical cells while maintaining their simplicity, ease of operation and recovery characteristics. The HG design is available in a tank cell configuration which provides a number of benefits in plant design and operation. This paper will describe the HG Tank Cell and the "Virtual Column" concept. Results are given from the operation of the HG Tank Cells at Lac Minerals - Est Malartic in Quebec, Canada. Further discussion of applications for gold recovery is also provided.

Jan 1, 1993

By R. J. Pruett, P. I. Prescott

Ground calcium carbonate (GCC) is used in the paper, plastics, paint, rubber and caulks and sealants industries. The favorable properties of GCC include high whiteness and brightness, low hardness and outstanding rheology in water systems. The quality of calcitic GCC ores, which includes chalk, limestone and marble, is dependent on calcite purity and the nature and quantity of the impurity minerals. Wet and dry grinding are used in the processing of GCC. Ore processed by optical sorting, flotation and/or particle-size classification has higher brightness and lower abrasion characteristics. GCC markets are a function of the product's properties, purity and cost.

Jan 1, 1997

By J. Kern, M. Cain, T. Torries

Until recently, the generation of electricity was regulated in all states and the value of generation assets in a regulatory environment for ad valorem taxation were based largely on the book value of the plant plus the rate of return on capital allowed by the state regulatory agency. This method of appraising utility generation assets is inappropriate in a competitive environment because past capital expenditures are not relevant in a competitive environment. However, it is not clear what valuation methods are appropriate after restructuring. This paper identifies key problems and advantages of other appraisal methodologies and makes comments on various valuation and taxation methods.

Jan 1, 2001

By Fathi Habashi

LEACHING IS the process of extracting a soluble constituent from a solid by means of a solvent. In extractive metallurgy it is the process of dissolving a certain mineral (or minerals) from an ore or a concentrate, or dissolving certain constituents from metallurgical products such as calcines, mattes, scrap alloys, anodic slimes, etc. In this respect, either one of two purposes can be achieved: 1) Opening of ores, concentrates, or metallurgical products to recover the metal values. 2) Leaching easily soluble constituents (usually gangue minerals) in an ore or a concentrate in order to have it in a more concentrated form, e.g., the

Jan 1, 1970

By David M. Mchaina, Steve Hardcastle, Michel Grenier

An overview of the process employed to assess arsenic exposure levels at a gold mine is provided together with the recommended control measures. Arsenic and its compounds are regulated in Ontario as designated substances in all workplaces except mines and concentrators. There is a proposal to remove the exemption for mine and concentrators. If the exemption is removed, the mining industry will be required to adopt the proposed exposure Limit of 0.01 mg/m over 40 hours. There are many mines in Ontario which will be affected by this new regulation. To determine the extent of which workers are exposed to Levels exceeding 0.01 mg/m , an assessment program was initiated at the mine. The main objective of the program was to determine the effect of the proposed regulation on underground and surface operations in term of compliance if it becomes Law. The data obtained from the assessment program shared that only 1ML of the workplaces monitored for arsenic indicated levels above the proposed limit of 0.01 ,/yard all workplace levels were below the present Limit of 0.2 mg/m .

Jan 1, 1992

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 J. Kern, M. Cain, T. Torries

Until recently, the generation of electricity was regulated in all states, and the value of generation assets in a regulatory environment for ad valorem taxation were based largely on the book value of the plant plus the rate of return on capital allowed by the state regulatory agency. This method of appraising utility generation assets is inappropriate in a competitive environment because past capital expenditures are not relevant in a competitive environment. However, it is not clear what valuation methods are appropriate after restructuring. This paper identifies important problems and advantages of other appraisal methodologies and makes comments on various valuation and taxation methods.

Jan 1, 2003

By S. M. Khandrika

It is shown that dewatering of fine coal particles (D50 : 21 microns) is enhanced near the point of zero charge. The coal surface is modified by the addition of copper ions and adjusting pH to precipitate surface active metal hydroxy species which promote agglomeration and produce low moisture cakes. Filtration kinetics data are used in calculating filter cake parameters from an integrated form of Darcy's law. The influence of copper ions and pH on filter cake parameters and correlations among them are presented.

Jan 1, 1993

By Berthold Pilz

The importance of a power economy that is efficient both in technological and economic terms has been clearly recognized in recent years. In 1977 the German Federal Government therefore introduced its Energy Research and Energy Technologies Program 1977-1980, which consolidates the government activities in the field of nuclear and non-nuclear energy research. The priority objectives of this program can be summarized as follows: safeguarding the medium- to long-term energy supply in the Federal Republic of Germany at reasonable overall macroeconomic cost, taking into account the requirements of environmental protection and the safety of the population. In the field of coal mining technologies, about 200 research projects are currently under way. A total of DM 1.7 billion is earmarked for research to be conducted in this area between 1977 and 1980.

Jan 1, 1979

By Paul Hosford, B. Thrall

There has been a surge of exploration activity and interest in mineral properties located in cold Northern climates, with gold and copper properties as the two most attractive targets. There are already a number of mining operations located in the Arctic, for example, Red Dog, Polaris, and Lupin, all located in the Canadian Arctic. The logistics of sustaining operations, the engineering design and construction methods for such inhospitable regions are now relatively well understood. However, at least three of the proposed new mines in the Yukon Territory, Canada are designed to be heap leach operations. Rescan Engineering has recently completed Feasibility studies for two heap leach operations in the Yukon, one of which, the Brewery Creek Mine, is now in operation. The purpose of this paper is to explore some of the engineering and operating concepts that have been developed to make heap leaching an appropriate process method for gold recovery in a cold climate. Many of the readers will be familiar with the general and specific details of heap leaching, and it is not the intention of the authors to deal with any of the established "do's" and "don'ts" that have been addressed in numerous previous papers, but only with those pertaining to cold weather operations. This paper also examines these design concepts in specific relation to the results of the first winter's operation at Brewery Creek Mine, the first "far" North heap leach operation.

Jan 1, 1997

By A. Bascetin, A. Nieto

One of the most difficult problems in mining operation is how to determine optimum cutoff grades of ores at different periods over the lifespan of the mine that will maximize the net present value (NPV) of the mine. Cutoff grade optimization maximizes the NPV of a project subject to capacity constraints in the mine, mill and the market.. This paper describes the determination of a cutoff grade strategy based on K. Lane’s algorithm adding an iterative optimization factor calculated for every year during the live of the mine to maximize the project’s NPV. The introduced algorithm is a windows based program developed at Virginia Tech which coded in visual-basic within a spreadsheet environment (Excel). The resulting cut-off windows based program is a user-friendly tool which calculates interactively different mining cutoff grade scenarios. The benefits of the methodology are demonstrated using a hypothetical case study. The authors have observed an improvement of the total NPV using this iterative approach using a year by year optimization factor.

Jan 1, 2007

By D. Krzyszton, P. Czaja

Mining explosions in rocks originate stress waves of great intensity, which crush the surrounding rocks and are then propagated as a seismic wave. Seismic waves are the cause of dynamic loading of pillars and their subsequent destruction. In calculating safe dimensions for inter-room pillars, not only the stresses conditioned by overburden pressures should be taken into consideration, but also the dynamic stresses caused by explosion. This is of particular importance for pillars with great specific acoustic impedance which have been destroyed mainly by the reflected seismic wave. It is possible to take dynamic loading into consideration in the calculation of pillars when the parameters of the propagation wave, the dynamic elastic constants of rocks, the strength properties of rocks, the strength properties of rocks subjected to dynamic loads and the parameters of the blasting charge are known. An example of the calculation for the safe width of an inter-room pillar subjected to the seismic effect of an explosion is given and the possibilities of reducing the dynamic loading of pillars are discussed.

Jan 1, 1982

By Adrian Smith, Debra W. Struhsacker

13.1 INTRODUCTION Cyanide is, a generic term indicating the presence of the cyanide ion (CN-). Cyanide is a very common, naturally occurring compound produced by many biochemical reactions. Many plant species synthesize organic compounds which contain cyanide in the form of cyanogenic glycosides (Knowles, 1976). For example, trace amounts of cyanide are present in the seeds and leaves of many members of the Rosaceae (rose) family (Kingsbury, 1964). Many common items such as lettuce, maize, sweet potatoes, kidney beans, (Oke, 1969) almonds, and cigarette smoke contain cyanide. As examples, a recent chemical analysis of chocolate-covered almonds measured a total cyanide content of about two ppm (Steffen Robertson and Kirsten, 1987); and the U.S. Surgeon General (U.S. Department of Health, 1964) has shown that cigarette smoke contains up to 1,600 ppm total cyanide. The chemistry of cyanide solutions is complicated because the cyanide ion forms compounds and complexes with many elements. Some cyanide species are highly toxic whereas others are relatively inert and harmless. Molecular hydrogen cyanide (HCN) is the most toxic form of cyanide. Under most conditions, HCN exists as a gas which readily dissipates or reacts with the environment to form less toxic or nontoxic forms of cyanide. Thus HCN is an ephemeral toxin, and many naturally occurring geochemical processes reduce the HCN concentration of a heap system with time. As discussed below, free cyanide includes the two species, ionic cyanide (CN-) and molecular hydrogen cyanide. Free-cyanide toxicity in man, mammal s, and aquatic species is we1 1 documented (Doudoroff, 1976; Ecological Analysts, 1979; Towill et al., 1978). The lethal doses reported for human adults vary with the type of exposure as follows: • One to three mg/kg body weight if ingested; • One hundred to 300 ppm if inhaled; and • One hundred mg/kg of body weight if absorbed. Acute toxicity of free cyanide to freshwater invertebrates ranges from 0.028 to 2.295 mg/l, depending on species and test conditions. Generally, free-cyanide concentrations greater than 0.1 mg/l are expected to kill sensitive species in freshwater or marine environments (Doudoroff, 1976;

Jan 1, 1988

By Abdullah Arik

The resource classification methodologies have always been a topic of research and debate. There are both traditional and Geostatistical methods used in practice. Because of the uniqueness of each ore deposit, it seems almost impossible to have a single industry-accepted norm for resource classification. Therefore, some practitioners have adapted the methodologies to suit the deposits they are working on, but many simply use the methods they are comfortable with. Another reason for the existence of varying classification methodologies is the lack of an easy and established way to measure the confidence in the estimates. Therefore, their classification becomes a subject of debate. In this paper, a new approach is offered to classify the resources using a "Resource Classification Index." The approach using this index takes into account the local variation, the spatial data configuration around the block being estimated, as well as the traditional distance measures. A case study for a gold deposit is presented to demonstrate how this new index can be used to classify the resources. The results from this approach are compared to those from two popular classification methodologies.

Jan 1, 2002

By Robert E. Mclvor

Classification system efficiency (CSE) is a simple metric that can be used to measure and increase ball milling circuit efficiency. It is defined as the percentage of the ball mill energy being used to grind target (oversize) particles. This paper describes CSE analysis conducted for a variety of operations with related improvements in circuit efficiency ranging from 3 to 30 percent. The achievable CSE for any given ball milling circuit is described, providing the means to determine the extent to which every plant can benefit from increasing grinding circuit CSE.

By Ellen S. Forbus

Reduction bleaching is used to improve the brightness and color of the kaolin pigments sold to the paper and speciality industries. The bleach re¬duces the iron oxide associated with kaolin deposits to a colorless form by the following reaction: Na2S2O42+ 6Fe+3 + 4 H2O -> 2 NaHSO4 + 6Fe+2 + 6H+ (Conley et al., 1964). At present, sodium hydrosulfite is used by the kaolin industry as the reductive bleach. It is often purchased commercially as a liquid solution and added into an acidified slurry. Before the use of commercial sodium hydrosulfite, kaolin plants manufactured zinc hydrosulfite on site by adding zinc dust to sulfurous acid made by passing SO2 gas into water. This process was abandoned in the 1970s due to environmental concerns about zinc in waste waters. In the 1970s, Engelhard patented a process that made sodium hydrosulfate from an iron hydrosulfate (Tiethof, 1978). Difficulties with separating the iron hydroxide byproduct from the bleach and a decrease in the cost of commercial bleach caused the project to be abandoned.

Jan 1, 1993

By R. V. Ramani, K. V. K. Prasad, M. Swaminathan

Engineering design involves, in addition to numerical calculations, considerable amount of expertise and judgement. The expertise and judgement is required to conceptualize and idealize the problem, select a suitable mathematical model for the problem and to interpret the model results in terms of stipulated design constraints. In recent years, knowledge based systems (KBS) have provided the capability to integrate the qualitative experiential and expert knowledge with the quantitative knowledge for improved analysis and design of systems. A possible KBS architecture for mine ventilation system design was discussed by Ramani and Prasad (1987). The expert system (ES) component of the KBS supports the analysis and interpretation phases of the ventilation design process with an algorithmic program used for the solution of alternate designs. The purpose of this paper is to discuss the data and knowledge needs for developing such a system and a formal means of their representation on the computer. A number of ES shells were evaluated to explore possible development and delivery environments for the system. A brief summary of this evaluation is also provided.

Jan 1, 1989

By A. J. Getz

Major precious metals projects are underway in Australia, Papua New Guinea, Indonesia, the Philippines and New Zealand. This article reviews the status of those projects. Included in this review are project location, reserves, method of resource exploitation, anticipated production, and other unique conditions. The article is limited to major precious metals projects in the Western Pacific region. This is not meant to negate the attractiveness or importance of the many other projects in that area. The geographical setting of these five countries are shown in [Fig. 1]. The gold output of the countries has increased dramatically during the 1980s. [Table 1] compares 1980 and 1988 production figures. The compound growth rate is 120%. That reflects the attractiveness of the region’s resource base as well as the impact of price increases, new exploration models and processing technologies, and changes in government policies. If the 10 projects discussed here are all brought onstream, their combined output - at about 130 t (4.17 million oz) - would amount to an increase of greater than 50% over 1988 production from this region. Table 2 shows indicative production levels for each of the 10 projects. Dollar amounts are in US currency unless otherwise specified. Australian dollars have been converted to US dollars at the rate of 1.28: 1.00.

Jan 1, 1990

By Mark W. Cadwallader

Heap leach mining requires liners in order to contain leaching solutions for both economic and environmental incentives. The use of HDPE geomembrane liners for heap leaching is discussed in this paper. Comparison is made to clay liners, with inclusion of economic considerations. Several heap leach projects incorporating geomembranes are discussed.

Jan 1, 1987