Search Documents

By F. W. Warnaars

The Los Bronces copper deposit is located on the west side of the Andes Mountains in central Chile about 54 km (34 miles) northeast of Santiago. The deposit consists of a hydrothermal breccia complex that was emplaced in the western part of an earlier porphyry copper mineral system. This system exhibits propylitic, sericitic, silicic to potassic hydrothermal alteration with disseminated and stockwork copper-molybdenum sulfide mineralization over an area of about 12 km2 (5 sq. miles). The Rio Blanco Mine, about 800 m (0.5 miles) east of Los Bronces, is an underground block caving mine located in the central part of this system. The mineralization at Rio Blanco is characterized by one of the highest primary copper grades known for porphyry copper systems. Present mining at Los Bronces is from an open pit located in the northern part of a hydrothermal complex that is composed of at least seven different copper-bearing tourmaline breccia pipes. Together these pipe form one large contiguous body about 2 km (1.2 miles) long and 0.7 km (0.4 miles) wide at the surface. This body crops out at elevations of between 3.5 and 4.1 km (2 and 2.5 miles) above sea level. Each breccia pipe has a characteristic shape, matrix, type and degree of mineralization and alteration. Quartz, tourmaline, specularite, anhydrite, pyrite, chalcopyrite, sericite, chlorite, and rock flour are present in significant quantities in most breccia matrices. The clasts consist mainly of quartz monzonite, andesite, and minor amounts of quartz latite porphyry. The seven different breccia pipes are identified, from oldest to youngest, as Ghost, Central, Western, Infiernillo, Fine Gray, Anhydrite, and Donoso. The breccias coalesce, interfinger, or display gradational contacts. In places they form sharp contacts with each other and with the surrounding intrusive or volcanic host rocks. Early breccias are disrupted or cut by subsequent breccia events. Explosive emplacement was followed by collapse after the release of hydrothermal pressures. The Los Bronces breccia complex has sharp contacts with the surrounding intrusive stock and andesites. These contacts dip inward on the north, west, and south margins. The eastern contact is nearly vertical and/or dips slightly outward and suggests a westward tilting of the body of about 15° after emplacement. The breccia complex is not fully explored at depth, but is known to extend at least below the 3 km (2 mile) elevation in its central eastern part, about 1 km (0.6 miles) below the highest breccia outcrop. Primary copper sulfide minerals are most abundant in the Donoso and Infiernillo breccias where the matrix consists mostly of tourmaline, quartz, sulfides, specularite, and/or chlorite with minor amounts of rock flour, sericite, and clay. The volume of the matrix material is mostly smaller than in the other breccias. Secondary enrichment enhanced the primary copper grade in the southern two-thirds of the Los Bronces breccia complex and in much of the surrounding porphyry system. Primary grades of 0.3% to 0.5% copper have been enriched to approximately 0.9%. This enrichment may extend from surface outcrops to a depth of more than 500 m (1, 640 ft) in more permeable parts of the breccia complex. A leached and oxidized capping of variable thickness covers a large part of the enriched layer and exceeds 300 m (984 ft) at one location. The shape and depth of the enrichment blanket and the capping suggest that the enrichment process is still active.

Jan 1, 1983

By J. L. Dion

"A study of the techniques to integrally cast copper tubes in copper tuyeres for use in blast furnaces has been carried out. The work has been performed in support of current efforts to produce two-compartment tuyeres having improved water-cooling capacity. A test pattern corresponding to a vertical section of a two-compartment tuyere, and including a cast-in-place copper tube, was used to investigate such variables as tube preparation, tube coolant, pouring temperature, pouring rate and gating design. Successful castings, either with a good metalfurgical bond or good intimate contact between the tube and the casting, were produced, with all combinations of gating system and position of the tube tried. However, the pouring temperature, the pouring rate and the effectiveness of the coolant are interrelated and must be controlled to produce a good metallurgical bond.IntroductionAs part of its contribution to, and in collaboration with, the Copper Casting for the Steel Industry Committee, CANMET has undertaken research into the methods and techniques needed for the integral casting of copper tubes into high-conductivity copper castings.The objective was to produce two-compartment copper blast furnace tuyeres in which the water-cooled nose compartment consists of a copper tube metallurgically bonded to the wall of the high-conductivity copper casting. This design, developed in the UK, has demonstrated a much extended service life with attendant economies; unscheduled shutdown of blast furnaces due to tuyere failure is a significant problem in the steel industry. The Canadian steel industry believes that this design will replace the currently used single-compartment tuyere in blast furnaces within a few years.The technology to produce these tuyeres does not exist in Canada. One of the main features is the inclusion of a smooth-walled cooling channel in the nose, which permits high velocity cooling water to be employed. A second compartment acts as a reservoir backup, should failure in the nose occur. This would allow continued use of the tuyere for a period of time, permitting a scheduled shutdown for repair s. To assist the Canadian producers of tuyeres to maintain their market, and the Canadian steel industry to have a reliable domestic supply, it is important that the necessary technology for the production of two-compartment tuyeres be developed and transferred to industry."

Jan 1, 1982

By J. Alvarez, S. H. Castro

The feasibility of chalcopyrite-pyrite separation in the flotation of a chalcopyritic copper ore, at reduced surface tensions regulated by methanol, was investigated. It was found that with methanol dosages from 0.5% to 1.5% v/ v, the chalcopyrite might be effectively separated from the pyrite, without use of other flotation reagents and pH regulators. However, under this simple condition, the chalcopyrite recovery was only around 50%, recommending the use of other reagents to reinforce the collector action. Low dosages of different collectors were tested, including SF-323 (Shell Float), S-6588 and S-7251 (Cytec), and S-701 (Molycop). Very promising results were obtained with low dosages of the collector S-701 and 1% v/v of methanol in the pulp, which evaluated against a reference test, gave similar copper recovery, higher Mo recovery and higher depression of pyrite. Consequently, this is an alternative process which does not require the use of lime to depress pyrite.

Jan 1, 1995

Copper waste dump leaching is growing in importance because of the.large tonnages (up to 250,000 ton/day) of low grade waste rock available from open cut mining of copper deposits and proof that controlled leaching of copper from such dumps can be profitable.Overburden or waste rock, ranging in size from large boulders to fines, is dumped as cheaply as possible on sloping sites. Copper is leached from the dumps by applying up to 12,000 gal/min of leach solution (a combination of spent solution from cementation and make-up water) to the top of the dumps by various techniques.Efliuent from the dumps is sent to a cementation plant for copper recovery.Factors which may be controlled, either directly or indirectly, to give a controlled copper content in the dump efliuent (usually 1-2 g/l.) are the cycle of operations (i.e. the alternate wetting and drying periods), thevolume of solution applied to the dump, pH, Fe2+ and Fe3+ content or redox potential, oxygen content, bacteria and their necessary nutrients, and temperature.Dissolution of oxide copper minerals appears to be mainly a function of acid concentration. Copper sulphide minerals need oxidation for dissolution to occur and this is accomplished by a combination of oxygen,ferric ion, and bacteria. Oxidation of pyrite, oxidation of Fe2+ to Fe3 +, and hydrolysis of Fe3+ are of some importance in leaching practice. The presence of gangue carbonate minerals is detrimental.Physical factors connected with penetration of solution into large rocks are important and the treatment of an individual dump usually extends over a period of many years. Recovery of copper from solution is usually achieved by cementation with iron (usually in the form of crumpled cans) but the use of sponge iron is becoming more important. Iron consumption varies from 1 to 4 lbiron per pound of copper. Preconcentration of the copper in the efliuent solution by solvent extraction followed by electrolysis may become a useful method.Application of dump leaching techniques to metals other than copper depends on finding an economic method of recovering the metal from solution...

Jan 1, 1967

By E. O. M. Hanisch

Copper working in the Messina district E. O. M. HANISCH. B.A. (Pretoria) (Visitor) By reference to the available literature, an account is given of the manufacture of metal ingots by the Messina copper workers. These workers are thought to have been Balemba tribesmen, of the Musina Clan, who came from across the lebombo Mountains. A description is given of their methods of mining, smelting, and casting, and of the vlrious types of ingots they produced.

Jan 1, 1974

By M. Smit, N. C. J. Dempers, S. Lunkov, C. Saguru, J. Nel

A common method for the recovery of copper is by heap leaching, solvent extraction, and electrowinning. During solvent extraction, the solution is continuously recycled, and it is necessary to remove impurities that build up in the raffinate. For the process investigated in this study, the main impurities include Fe, Co, As, and Zn. Recovery of these impurities can provide economic benefits while adhering to legal and environmental constraints. Such impurities are often removed by precipitation utilizing a neutralizing agent, such as limestone or lime, but it is also possible to remove the impurities by sulfide precipitation. Sodium hydrosulfide (NaHS) is used to selectively precipitate copper, arsenic, and zinc from a solvent-extraction raffinate stream. The resulting sulfide precipitate is bagged and sent to a roaster for further treatment. The design of the sulfide precipitation was investigated to optimize the processing conditions (including temperature, pressure, and residence time), the materials of construction, and the toxicity and explosive nature of the hydrogen sulfide gas produced

Jan 1, 2023

By T. Shellhammer, A. Park

Among all pure metals, copper has the second highest thermal and electrical conductivity, next to silver. These properties coupled with a reasonable cost, make copper ideal for use in metallurgical vessels as a conductor of electrical current, as well as a lining material and protector of refractories and steel superstructures. Treatments of copper to address it’s softness and low melting point, specifically hard surfacing and calorizing, will be discussed. This paper will cover the evolution of copper to its current form, offer comparisons to other materials, and theoretical and empirical evidence on its superior performance in metallurgical vessels such as blast furnaces, basic oxygen converters and electric arc furnaces. Some case studies will be provided and finally a brief summary.

Jan 1, 2015

Rajor intrusion-related Cu and Au dep- osits along the Cordilleran-type central Andean margin and in the western Pacific island arcs constitute a series of discrete, linear belts which correspond to limited (414 m.y.) metall- ogenic epochs. The most important metallogenic belts, all of Cenozoic age, are inferred to have been generated during relatively shallow subduction of oceanic lithosphere beneath con- vergent margins. Geological and isotopic evid- ence suggests that magmatic rocks and associated Cu and Au mineralization were derived from asthenospheric mantle sources, which were enriched in a variety of elements (metals, alkalis, S) by dehydration of subducting oceanic crust. Where exceptionally rapid, low-angle 3ubduction took place beneath very thick (>50 km) continental crust, as in the central Andean Altiplano in the Miocene and southwestern North America during the Laramide, ore-related magmas underwent wholesale crustal contamination. However, the associated Cu-Au mineralization is the same as that developed in primitive island- arc crust. In particular, the by-product Au and So contents of porphyry Cu deposits are inde- pendent of crustal thickness and the degree of crustal contamination as determined isotopic- Ally.

Jan 1, 1987

By Jagdish C. Agarwal

Although copper ranks very low in the order of abundance of elements in the crust of the earth, it has been one of the first metals utilized by mar, at his emergence from the Stone Age, about 10,000 years ago. Use of copper for weapons, tools, utensils and ornaments dates back to the twilight of history, 6,000-5,000 B.C. Native copper outcrops and the malleability of the metal explain its very early use by the cave-dwellers. The working, melting and extraction of copper from its minerals are among the oldest metallurgical achievements of the human race. The oldest complete smelting installations for the extraction of copper from its minerals, dated about the fourth millenium B.C., were recently discovered in the Timna Valley, Wadi Arabah, Israel. (1) The history of the developments of the extractive metallurgy of copper has been adequately reviewed recently. (2,3) The center of copper production migrated from the Eastern Mediterranean to Northern Europe (Mansfeld, Germany, Swansea, Wales) towards the end of the Middle Ages (1500 A.D.). The production of the metal was boosted tremendously in North America since the end of the nineteenth century (Fig. 1).

Jan 1, 1976

By Clinton H. Crane

WHEN I agreed to accept your Committee's suggestion that I talk to you at this meeting on the future of copper, lead and zinc mining, I could not help wondering why I had been chosen to be a prophet. Knowing the pious nature of your committee, I thought I had better look up and see what the Bible says about being a prophet, and what the dictionary definition of a prophet is. The word "prophet" comes from the Greek and is defined as "one who speaks through a divine inspiration." Also, in the Gospel of Saint Matthew, Christ tells us that a prophet is "not without honor save in his own country and in his own house." That gave me pause until I remembered that after all, I had started my professional career as a Naval Architect, not as a Mining Engineer, and consequently, this might be a clue to the fact that the eminent geologists of this society, who know infinitely more about the world's crust than I do, were passed over in this assignment. In thinking back, I then remembered that the first really successful prophet was Noah and that Noah was a Naval Architect. Here then was the answer. One more quotation from the Bible I shall take as my text: In Ecclesiastes, chapter I, verse 9: "The thing that hath been is that which shall be." Now, with this preamble, and not being bound by anything save inspiration, I will proceed to prophesy: As far as the next 15 to 25 years are concerned, from the studies made by

Jan 1, 1947

By Jon J. Connor, Richard J. Ebens

The trace element geochemistry of the cherty clay-rich carbonate residuum cover in much of southern Missouri and adjacent parts of Arkansas was investigated during the earl 1970's as part of a statewide geochemical survey of Missouri.1-8 The study was environmentally oriented and focused on the character of the "natural" geochemical environment of the state. A great deal of effort was made to collect samples that would represent the geochemical variability of the near-surface environment in an unbiased way. In general, this was accomplished by use of randomization procedures in both collection and analysis. Most of the sampling sites were selected randomly to prevent personal bias from entering into sample selection. In the laboratory, samples were analyzed in a randomized sequence to circumvent the effects of any systematic bias that may have entered into the laboratory procedures. Several residuum samples contained 1000 parts per million (ppm) or more of lead, zinc, and barium. All these samples were collected in Washington County in or near the barite district. The frequency distributions shown in [Fig. 1] indicate just how unusual the residuum in Washington County is with regard to these three metals and copper. The shaded parts of the histograms represent the samples from Washington County. The histograms are based on analyses of 141 samples from 38 localities scattered over the subcrop of the Cambrian and Ordovician formations of southern Missouri and northern Arkansas. Eight localities were selected randomly from over each of four bedrock units-Bonneterre dolomite; Potosi and Erninence dolomites; Roubidoux formation; and the Jefferson City, Powell, and Cotter dolomites. Six localities were selected randomly from over the Gasconade dolomite. The geochemical "background" for these elements in residuum is defined by samples from outside of Washington County (unshaded part of the histogram); lognormal distribution curves have been fitted to the corresponding parts of each histogram. Clearly, these lognormal models (curves) describe well the background distributions of zinc, barium, and copper. The background histogram of lead concentrations is notably skewed to the right compared to the model. Lognormal distribution curves were also fitted to the data on lead, copper, and zinc in the residuum of Washington County. No model was fitted for barium in Washington County because of the distinct bimodality in the data. All samples containing more than 1000 ppm were collected in the barite mining district and obviously reflect the elevated levels of barium in the district. The frequency distributions for Washington County are clearly anomalous with respect to the background data, those for lead, zinc, and barium being exceptionally so. The models for anomalous lead, zinc, and copper seem to fit reasonably well, although the scatters in the lead and zinc anomalies are considerably larger than the scatters in the corresponding background data. The copper anomaly, although probably real, is greatly subdued compared to that of lead and zinc. Also, it has a scatter similar to that of the copper background, rather than being enhanced like the scatters of the lead and zinc anomalies. On the basis of techniques described by Miesch,4 the chemical abundance of copper, lead, and zinc in residuum in

Jan 1, 1980

By Tomas Astorga

APEC, the Asia Pacific Economic Cooperation is the forum of 21 countries having approximately 56% of the total world income, and over 45% of global trade. In 1997, APEC economies produced 67% of the world copper output, 55% of gold, and over 45% of other base metals. Mining in APEC captures more than 60% of the total mining investment in the world. New and emerging economies are now appearing in the demand scenery, such as China. New trends in the international environmental regulations are posing questions related to the use of copper in different industrial and consumption applications. These may have a strong impact on future trade of copper. New applications are also appearing based in new technology fields. The paper examines the growth potential of the copper market in main consumer ad highly populated economies of APEC, incorporating analysis of various interrelated factors. It also analyses the outlook of the copper supply. Its conclusions point to the need to implement demand outlook models. Finance and economic reforms will open important avenues for trade growth in basic metals, particularly copper. Changes in the consumption patterns of highly populated countries will add to better perspectives of copper demands. The recovery of a fast pace of economic growth in the APEC region will bring new demands for copper, especially as a consequence of high tech applications. More extended policies focused in the need for developing energy efficiency programs and schemes will add to this picture.

Jan 1, 1999

By A. Block-Bolten

Copper concentrates from northern Peru contain large amounts of arsenic and antimony in the form of sulfosalts like enargite, tennantite and tetrahedrite. These impurities affect up to 30% of Peruvian copper production. Under the sponsorship of the Instituto Geologico Minero y Metalurgico in Lima a project to separate copper from arsenic without pollution of the environment is being carried out at the National University of Trujillo in Peru. The U.N.T. process is unique in the respect of using .low melting salts as solvents, and sulfides of metals with high cation potential as destructors of the complex sulfosalt molecules. Laboratory scale experiments have given encouraging results but interesting and difficult problems developed on scale-up. The process is pyro-hydrometal-lurgical and under certain circumstances its economics are promising.

Jan 1, 1981

By Dachun Liu, Baoqiang Xu, Bin Yang, Yong Deng, Heng Xiong, Xiumin Chen

"In this paper, vacuum distillation technology has been employed to study the possibility and regularity of separating copper and enriching lead, silver and other valuable metals from copper- based multi component alloys. The result of experiment indicated the practicability of vacuum distillation dealing with copper base complex multi-component alloy to separating lead and silver, when the vacuum distillation temperature was 1637K, distillation time was 60min; residual gas pressure was 20-30Pa, the removal rate of silver was 95.86%, of lead was 99.63%; the evaporation rate of copper was 0.745%. The removal rate of arsenic, antimony and tin respectively were 83.09%, 48.12% and 24.54%. Vacuum distillation method is applicable for dealing with the copper-based multi component alloys, silver and lead can realize effective recovery.IntroductionCopper generally go with lead mineral, therefore, to remove copper from lead becomes an inevitable link in lead smelting. Dross from removed copper usually contains lead, arsenic, antimony, tin and noble metal silver. In abroad, soda ash-iron dust is adopted to process copper dross of this kind. The outcomes of this process are lead matte, wet lead, scoria smoke dust etc[1~5] The dominant components of all the outcomes are copper and lead. Moreover, in the process of tin smelting, copper contained by-products are produced, such as, crude tin alloy, tin lead electrolytic anode slime and so on. Copper content of all the products are ranging from few percentages to several tens percentage. Those products, no matter merge into main producing process, or separate treatment cost losses of valuable metal. For one hand, the containing of copper of outcomes from pyrogenic attack is less than 50%, for the other hand, a lot of valuable metal need to be processed, which increase the cost of retrieve."

Jan 1, 2013

By J. Kent Smith

THE object of this investigation was to ascertain the effect of varying percentages of beryllium upon pure copper and the properties of the resultant alloys in their softest condition, the effect of heat hardening on them, and the extents to which these properties could be augmented by different combinations of heat hardening and cold rolling. The data compiled in this paper represent partial results of continuing work done by the writer during the years 1930 and 1931, which was a continuation of the unpublished ground work incepted in the laboratory of the Beryllium Corporation of America by H. B. Pulsifer in the year 1926. A short bibliography on beryllium alloys is appended to this paper. It has, of course, long been known that copper subjected to cold work is hardened and strengthened to a considerable extent, furthermore it had been qualitatively noted in previous experiments that copper-beryllium alloys seemed to take on hardness and strength as the result of cold work at a greater rate even than does plain copper. It was decided therefore to endeavor quantitatively to determine such rate of increase, as also the relative increases by combinations of cold working and heat hardening. The results are summarized in Tables 3, 4 and 5. A preliminary series of experiments had indicated that by an exposure to the heat of 575° F. for 2 1/2 hr. age-hardening of a 2.50 per cent beryllium-copper alloy took place. Slab ingots of nine different beryllium-copper alloys were prepared under identical conditions by means of the addition of a previously prepared 12.5 per cent beryllium-copper alloy to well melted and deoxidized pure copper. The ingots were then reduced by hot rolling to 12 gage (about 0.080 in.). These strips were heated to 1450° F. and quenched in cold water, and thus brought to their softest condition. (See Table 1.) Strips were next "precipitation-hardened" by reheating to a definite temperature. Similar strips to those itemized in Table 1 (which had been quenched from 1450° F.) were reheated for varying periods of time at 575° F. The hardness figures show that a metastable condition, of which the range of stability is dependent entirely upon time at the given temperature, begins to be noted in copper samples containing as little as 0.85 per cent beryllium. It is extremely noticeable in samples containing

Jan 1, 1932

By Zay Jeffries

AN acute current shortage of copper, with the prospect that conditions may become worse, indicated by Office of Production Management information. Present estimates of copper requirement for defense indicate that nearly all the available metal will be required in the future for this purpose. Severe dislocations are, expected, but the objective is to distribute the copper available for civilian use in such a manner as to minimize these dislocations. The advisory committee on metals and minerals has been asked for a suggestions which may be helpful in meeting this situation.\

Jan 1, 1941

By W. H. (Bill) Jay

The destruction of cyanide creates a significant impost on the financial returns of gold mines. These losses increase substantially when ores containing cyanide-soluble copper are treated. Failure to remove or destroy free or WAD cyanide before it is discharged into tailings dams has, on a number of occasions, led to significant fish, bird and animal deaths. Thus, the retention of cyanide within the leach circuit and the recovery or removal of stable metal cyanide complexes needs to become standard practice for all gold mining operations. Furthermore, reducing cyanide purchases will minimise the quantity of cyanide transported to the mine site thereby reducing the opportunity for spillage of this chemical. Many different physical and chemical methods have been investigated for the removal of cyanide from process solutions. All cyanide destruction methods create a financial impost on the economic viability of the gold mine. To reduce these costs, the recycle of cyanide and the economic recovery of the metals solubilised by cyanide is of prime importance. The alternative methods currently in use, or under consideration for the treatment of copper cyanide, entail high reagent costs, produce the recovered metal in a contaminated form and require the safe handling of hydrogen cyanide. These processes will be briefly discussed within this report Environmental and financial benefits are enhanced by recent laboratory and pilot plant studies conducted by Oretek Limited. The Oretek CPC process for the recovery of copper and the recycle of cyanide from copper cyanide-containing solutions does not require pH adjustment to the alkaline cyanide leach conditions. Copper ions are coordinated to a water-soluble and/or an organic soluble polychelating agent under alkaline conditions and the cyanide ions are displaced Membrane separation, or phase separation of the polychelated copper from the cyanide ions enables the cyanide ions to be recycled and the copper to be directly electrowon from the polychelating polymer. The polychelating polymer is then recycled. Ion exchange resins and solvent extraction systems which may be incorporated into the above process will also be discussed in detail.

Jan 1, 1998

By Wong PLM, Hsu YJ, Nguyen HH

The treatment of copper-gold ores has been plagued by several problems because of the interaction of copper minerals with the cyanide leach solution and the dissolved gold cyanide. Apart from the higher consumption of cyanide caused by the dissolution of various reactive copper minerals such as azurite, malachite, chalcocite, cuprite and bornite, native copper also causes the loss of gold due to its cementation reaction with the soluble gold cyanide. This interaction however is complicated by the strong dependence of various copper-cyanide species on the solution pH and free cyanide concentration.By understanding the effect of various operating conditions (pH and cyanide concentration), several treatment processes could be implemented to minimise the copper-gold interaction and to separate copper from mixed copper-gold cyanide solutions.

Jan 1, 1997

By LaBrooy S. R, Ritchie I. M

Problems with the cyanidation of copper-gold ores Copper-rich gold ores are becoming increasingly important both within Australia and overseas (Dayton, 1982; Deng and Muir, 1994; Muir et al, 1993; Sceresini and Staunton, 1991; Solis, Hefter and May, 1995; Wall, Hornby and Sethi, 1987). In Australasia alone over 30 copper-gold deposits have been reported (Muir et al, 1993). Table 1 lists several of the deposits that have been processed. TABLE 1 Examples of copper-gold deposits in Australasia. Name

Jan 1, 1997

By Steve R. La Brooy

Techniques for dealing with copper-gold ores are reviewed. Cyanide has little selectivity of gold over copper, and depending on the reactivity of the copper minerals cut-off grades for gold recovery by direct cyanidation are generally below 0.5% copper for oxide ores and 1 % for sulfide ores. Non-cyanide gold leachants also tend to be reactive to copper. The cheapest option for sulfidic ores is to produce a flotation concentrate for smelting, while transition ores generally need a sulfidisation pre-treatment. The requirement for the concentrate to have a high enough copper grade to be acceptable to a smelter may compromise copper and gold recovery. This can lead to significant gold grades in the flotation tailing, and copper levels in the tailing that are too high for direct cyanidation to be able to recover the gold. Oxidised ores, flotation tailing or other material not amenable to flotation represent the greatest grey area for gold recovery. Copper removal by acid, alkaline or ferric pre-treatment is possible though not generally used. Cyanide pre-leaching to remove copper, followed by copper and cyanide recovery represents a potential option that has been installed at one Australian gold plant, where copper is recovered onto carbon, ahead of the slower leaching gold. Actual cyanide recovery depends on ore mineralogy, allowing for losses as cyanate, thiocyanate, carbonate and ferrocyanide. Alternative options for gold recovery following cyanide leaching include precipitation, ion exchange and solvent extraction of the gold. Ammonia-cyanide leaching may offer another option for more selective gold dissolution from flotation tailing and oxidised materials. A plant is currently under construction in Mauritania.

Jan 1, 1992