Establishing the process mineralogy of gold ores

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This paper discusses the classification of gold ores and gold minerals, mineralogical factors affecting gold extractive metallurgy, and study procedures and techniques commonly employed in gold process mineralogy.A case study of a refractory gold ore is provided to show the need and importance of process mineralogy in gold extractive metallurgy.
From the perspective of metallurgical processing, gold ores can be classified into free-milling and refractory ores. Typically, free-milling ores are defined as those where over 80% of gold can be recovered by conventional cyanide leaching, such as placers, quartz vein gold ores, oxidized ores, silver-rich ores, copper sulphide ores, and some iron sulphide and arsenic sulphide ores. Refractory ores are defined as those that give low gold recoveries or give acceptable gold recoveries only with the use of either significantly more reagents or more complex pre-treatment processes. They typically include iron sulphide ores, arsenic sulphide ores, antimony-, bismuth-, and telluride-bearing gold ores, and carbonaceous sulphide ores.
The deportment of gold in each ore is different and has to be determined individually in order to select the optimum technique or a combination of techniques for gold ore processing. Mineralogically, the extractive metallurgy of gold is influenced by gold particle size, association with other minerals, coatings and rimmings, the presence of cyanicides, oxygen consumers and preg-robbers, and the presence of refractory gold minerals and invisible gold in sulphide and sulpharsenide minerals.
The gold deportment and the various mineral processing requirements of the several ore types can be summarized as follows: (1) gold in placers, quartz vein gold ores, and oxidized ores are easily liberated, and can be recovered by gravity, flotation, and/or direct cyanide leaching; (2) gold in copper sulphide ores is often coarse-grained and associated with copper minerals, and can be recovered into a copper concentrate by flotation; (3) gold in silver-rich ores is often present as electrum or associated with silver minerals, which can be recovered by gravity, flotation, and/or direct cyanide leaching (the problem in recovering gold from silver-rich ores is that the greater reactivity of silver can influence the behaviour of gold in flotation, leaching, and/or recovery processes by the formation of silver sulphide or silver sulphate coatings); (4) gold in non-refractory sulphide ores is medium-to coarsegrained and can be recovered by whole-ore cyanidation, or some combination of gravity, flotation, and cyanidation; (5) gold in antimony, bismuth sulphide, and telluride gold ores often occurs as aurostibite, maldonite, or various gold tellurides, which are somewhat refractory due to their slow dissolution kinetics or association with sulphides. To recover gold from these ores, pre-oxidation and/or ultra-fine grinding are often required; (6) gold in carbonaceous sulphide ores is fine grained and predominantly associated with the sulphides (pyrite or arsenopyrite) that are present in carbonaceous ores. Gold in these types of ores is usually recovered by pre-oxidation to dissolve the host sulphides, followed by cyanidation with or without prior concentration by flotation. Gold recovery from the carbonaceous sulphide ore is more difficult because the gold is “robbed” from the cyanide solution by the native carbonaceous matter.
Gold process mineralogy studies deportment of gold in various ores and metallurgical products and helps address issues and problems related to gold ore processing. It is widely used as a predictive and trouble-shooting tool in gold ore processing, and provides useful information on process selection, flowsheet development, recovery improvement, and reagent consumption optimization.
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The coarse particle recovery (CPR) process captures coarse particles that are not recoverable by regular flotation. Several porphyry copper operations in the world operate analogous circuits that recover non-floated copper from tailings; however, the case presented here for Minera Escondida Ltda. is unique in that extensive underlying test work has allowed the authors to elucidate some fundamental principles behind recovery enhancement.
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Publication: CIM Bulletin
Author(s): B.J. Huls, G.S. Hill
Issue: 2
Volume: 1
Year: 2006
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In underground mines, material handling systems rely on a network of vertical or steeply inclined ore and waste passes. The design and operation of ore pass systems is often based on past experience, which can be anecdotal and, at times, contradictory in nature. This paper provides quantifiable information on ore pass practice and performance in Quebec underground metalliferous mines. The presented field data were derived during a series of site visits in...
Publication: CIM Bulletin
Author(s): J.-F. Lessard, J. Hadjigeorgiou
Issue: 2
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Year: 2006
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Optimization of production schedules in open pit mines is important for managing cash flows. The risk of not meeting planned production targets is a critical aspect of optimization, however, it is not accounted for by traditional schedulling methods. This paper describes a new, probabilistic, mixed integer programming (MIP) formulation. The formulation has been developed so as to minimize the risk of not achieving planned production targets, both ore feed...
Publication: CIM Bulletin
Author(s): S. Ramazan, R. Dimitrakopoulos
Issue: 2
Volume: 1
Year: 2006
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Stereolithography is a well known rapid prototyping technique in the manufacturing sector. Essentially, it is a three-dimensional printing process that produces plastic prototype parts from standard CAD files. At present, Canadian mining companies are not fully aware of the potential of rapid prototyping techniques (RPTs) for their production and mine design systems. Mining engineers and geologists attempt to visualize and understand the characteristics and...
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Author(s): C.P. O’Connor, N. Vayenas, A. Akerman
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Mining has several characteristics, uncommon in other business sectors, which pose additional challenges to the implementation or design of IT and management systems that use the information. Understanding these characteristics would improve the chances of successfully importing new information technology and management techniques to mineral producers. The most important characteristics that should be understood are workplace issues, the industry’s...
Publication: CIM Bulletin
Author(s): S.D. Dessureault, A.P. Schissler
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Electric cable shovels are the most extensively used highvolume excavators in open pit mining. The design of dippers for cable shovels has essentially remained unchanged for the last 100 years. Previous work to improve the production capability of these units focused on updating mechanical and electrical components, and optimizing utilization and operational approaches. Little work has been done to improve dippers and their ground interactions. With the...
Publication: CIM Bulletin
Author(s): N. Shi, T.G. Joseph
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