What is the gold content in pyrite?

Object of study. Using modern methods, crystals of pyrite, one of the main gold-concentrating minerals at the Berezovskoye deposit, were studied. Materials and methods. The material for analysis was selected from ladder sulfide-quartz veins and accompanying beresites of the Ilyinskaya, Pervopavlovskaya, and Vtoropavlovskaya dikes of the Berezovskoye deposit. The ores were studied using optical microscopy, X-ray microanalysis (X-ray microanalysis), scanning electron microscopy (SEM), and also (mainly pyrite) by LA-ICP-MS. In addition to pyrite, fahlore, galena, and rare aikinite, cosalite, tetradymite, and tsumoite were studied. Results. According to point and profile analysis, as well as mapping by grain area, the main impurity elements are Co, Ni and As, their distribution is zonal with a tendency for the amount of Co and Ni to increase and As to decrease towards the center of the grains. Cu, Zn and Pb are noted in pyrite in the form of micro-ingrowths of their sulfides and as a uniformly distributed impurity. In the late generation of pyrite of the Pervopavlovskaya dike, gold content was established with a zonal distribution of Au in an amount of up to 22 g/t. The gold-bearing variety of pyrite is characterized by abnormally low Co and Ni contents and high As contents (up to 8000 g/t). Conclusions. The general distribution of the main trace elements in pyrite from the Ilyinskaya, Vtoropavlovskaya and Pervopavlovskaya dikes indicates similar conditions of its crystallization. The presence of late-generation pyrite with finely dispersed gold in the ladder veins of the Pervopavlovskaya dike indicates a heterogeneous distribution of gold mineralization, probably due to its multi-stage nature, and may be an indicator of concentrated ore columns, but this requires additional study.

Keywords

Supported by: The work was supported by the Russian Science Foundation project No. 14-17-00693-P.

About the authors

Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry RAS (IGEM RAS).
Russia
119017, Moscow, Staromonetny lane, 35. Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry RAS (IGEM RAS).
Russia
119017, Moscow, Staromonetny lane, 35. Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry RAS (IGEM RAS).
Russia
119017, Moscow, Staromonetny lane, 35. Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry RAS (IGEM RAS).
Russia
119017, Moscow, Staromonetny lane, 35.

References

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Text of the scientific work on the topic “Flotation fractionation of gold-bearing pyrite into products of various qualities”

UDC 622.7 E.L. Chanturia FLOTATION FRACTIONATION OF GOLD-BEARING PYRITE TO PRODUCTS OF DIFFERENT QUALITY ~I~T loss of gold during enrichment of copper-zinc sulfide ores is 40-90%. Previous studies [1, 2] revealed the presence in the ore of the Gai deposit of copper-zinc gold-bearing pyrite ores of four mineralogical and technological varieties of pyrite, differing in habit, content of gold and other impurities, and forms of gold occurrence (table). The fourth mineralogical – technological variety of pyrite is pyrite grains with inclusions of native gold and characterized by its high content (from 9 g/t to 1650 g/t with an average value of 93 g/t). Changes in the gold and silver contents of this variety of pyrite are closely related to each other. The particle size of native gold found in pyrite is 2-7 microns. Gold particles of this size cannot be opened during grinding (Fig. 1). The mass fraction of pyrite of this mineral-technological variety in the total mass of pyrite is 14.6%, the mass fraction of gold associated with it is 85% of the total gold associated with pyrite. Pyrite of this group, even in fine size classes of -0,074 mm, is found in intergrowths with sphalerite, and many grains are in fine intergrowth with quartz (impregnation). The information obtained suggested that the high losses of gold observed during the processing of sulfide copper-zinc ores are associated with this variety of pyrite. And, if until now all losses of gold with pyrite during the processing of such ores were classified as “inevitable” losses, now these losses can be avoided if pyrite with a high gold content is extracted into a separate product and sent for processing using a special technology [ 3]. Mineralogo – technological varieties of pyrite from the Gai deposit Range of Au content in pyrite, g/t Pyrite yield (mass fraction), % Element content, ppm (g/t) Au distribution (mass fraction), % 0,5 – 1 15,2 210,78 830,32 474,260 4,933 0,302 0,89 0,842 1 – 5 70,0 203,42 1561,99 1474,206 15,514 17,674 3,32 14,427 > 9 14,6 106,66 2798,85 2084,408 34,268 5,703 93,34 84,727 Average 100,0 15,3 100,0 Currently, the Gayskaya Concentrator is stably operating according to the scheme of collective-selective flotation, which provides for the separation of the “copper head”, the collective flotation of sulfides into a collective copper-zinc-pyrite concentrate, the separation of copper-zinc concentrate from it into a foam product and the production of pyrite concentrate by a chamber product ( copper-zinc flotation tailings), subsequent selection of copper – zinc concentrate with the production of zinc concentrate as a chamber product. The scheme may include a gravity unit for separating free gold from grinding products using conical hydrocyclones and gravity tables, the discharge of which is fed to flotation. It is generally accepted that noble metals are extracted into copper, zinc and pyrite concentrate, according to the extraction of gold-containing sulfides and free gold of flotation size into concentrates. However, V.A. Bocharov emphasizes that, “based on data from repeated testing of technological processes of enrichment factories, the distribution of gold among sulfur enrichment products Rice. 1. Grains of native gold (white) in pyrite (gray) from the Gai deposit. Large-scale fid, copper and copper-zinc ores, is determined by the degree of extraction of pyrite sulfur in them, which, in turn, depends on the flotation scheme and mode and, above all, the pH of the environment and the concentration of depressing ions” [4]. From the above, we can conclude that sulfide gold “comes” with pyrite, but not with its entire mass, but with part of the pyrite with a high gold content. Where this part of pyrite is released, gold is concentrated there. Calculation based on data provided by Gaisky GOK OJSC (with a gold content in ore of 1,5 g/t) shows that gold losses from the original ore – with general silicate tailings (yield 60%) can range from 10% with an Au content in the tailings of 0,25 g/t and up to 44% with an Au content of g/t. – with a pyrite chamber product (copper-zinc flotation tailings), with a yield of 15%, can range from 7% with an Au content of 0,7 g/t and up to 23% with an Au content of 2,3 g/t. Total gold losses can fluctuate, respectively, in the range of 20% – 70% of the original ore, i.e. gold recovery ranges from 80 to 30%. In general, we can confidently say that gold losses during ore processing are determined by pyrite, both in collective tailings and in copper-zinc flotation tailings. Further studies were carried out to • identifying the causes of losses of pyrite with high gold content (9 g/t and bo- lee) according to the existing technological scheme; • establishing the possibility and conditions for selective flotation separation of a mineralogical-technological-logical variety of pyrite with a high gold content from its total mass for further processing using special technology; • reducing gold losses during the beneficiation of copper and zinc ores at the Gayskaya concentrator and increasing the complexity of their processing. Objects and methods of research The studies were carried out on mono-mineral pyrite products isolated from the concentrate of gravity tables (106.8-116.2 g/t Au and 30.8-26.7 g/t Ag) of the Gai concentration plant by enriching them (finishing) by gravity, magnetic and electrical methods. The study was carried out using optical microscopy, non-destructive film structural etching, scanning electron microscopy (8BM), energy dispersive and X-ray microanalysis, a method for determining resistivity and thermopower, gravity, magnetic and electrical separation, flotation, instrumental neutron activation analysis (INAA), atomic adsorption analysis. Pyrite flotation was carried out with butyl xanthate (BX). The results of the studies showed that pyrite flotation under environmental alkalinity conditions (pH 10, created by lime milk), close to the actual conditions of collective sulfide flotation of the enterprise (pH 9 -10, 200 -260 CaO b.) leads to depression of pyrite with a high gold content and its transition into a chamber product (Fig. 2) and, accordingly, under factory conditions, into dump tailings. With an increase in the concentration of BKs and an increase in the yield of pyrite in the foam product, the gold content in the chamber flotation product, and, accordingly, its recovery, increases. As a result, pyrite with a high gold content of up to 333-564 g/t Au can be concentrated in the chamber product with a gold recovery of 98-99%. The results obtained indicate very high losses of sulfides and, in particular, pyrite in the process of collective copper-zinc-pyrite flotation. The control flotation of tailings provided at the enterprise with the return of the concentrate to the head of the process allows for additional extraction of some of the sulfides of copper, zinc and pyrite, leaving pyrite with a high gold content in the chamber product. To extract metals and sulfur from collective flotation tailings, Gin-Tsvetmet, together with Unipromed and the Gai concentrating plant, developed and implemented a technology using a three-product hydrocyclone. According to this technology, “collective tailings are supplied to post-flotation of sulfides at a pH of 9 – 10,5, created by lime at the beginning of the collective cycle. What is new in this technology is the use of modified reagents – a xanthate collector with an electrolyte (consumption 10-15 g/t) and an acidifying activator based on phosphorus-containing copper salt for flotation of sulfides passivated with lime (consumption – up to 50 g/t). After post-flotation of sulfides, copper losses decreased by 1,6-2,2%, zinc – by 2-8%, sulfur – by 2,3-20,5%” [5]. As mentioned above, the pyrite content in collective tailings ranges from 5 to 10%, i.e., from 3 to 6% of the original ore, and the gold content in them ranges from 0 to 25 g/t. Apparently, such a small content of pyrite in the collective tailings did not attract due attention to it. ■ yield of the chamber product gold recovery in the chamber product gold content in the chamber product arsenic content in the chamber product silver content in the chamber product