Study of the material composition of refractory gold-bearing ore to assess effective technological solutions

The study of the material composition of gold-bearing ores includes the determination of quantitative chemical and mineral composition, forms of noble metals, granulometric composition, and physical and mechanical properties to choose the direction for the development of an effective technology of their complex enrichment. This work is devoted to the study of the material composition of refractory gold-bearing ore of Aktobe deposit. It was determined that the content of gold is 1.55-1.6 g/t, the mass fraction of silver is 42-43 g/t, and the content of sulphur is low and is 1-1.1% respectively. Of non-ferrous metals, zinc 0.17%, and lead 0.15% are present in insignificant amounts, and the content of harmful impurities antimony and arsenic are insignificant and amounted to 0.01 and 0.05%. The ore sample has a relatively uncomplicated mineral composition: rock-forming minerals represented by quartz, potassium feldspar, calcite, and mica predominate significantly. Ore minerals are represented by pyrite up to 10 %, limonite up to 0.5 %, galena 0.15-0.2 %, sphalerite 0.17-0.2 % and gold. Physical and mechanical properties of the ore were determined. According to the category of crushability, the ore belongs to the category of medium hardness. According to Bond's method, the "index of network Wi" of ball milling was determined for the initial ore, which was 19.3 kW∙h/t∙μm0.5. Based on the obtained data on the study of material composition, further research will be directed to the study of gravity and flotation enrichment.

PURPOSE. Today the development of an efficient technology of refractory ore processing is quite problematic, therefore the achievement of high degree of gold recovery is a relevant problem. The purpose of the research includes investigation of mineral and chemical composition of the gold-bearing ore of the Taror deposit, performance of the series of tests on ultrafine grinding (UFG) of ore prior to cyanidation and pulp processing after UFG by the method of atmospheric oxidation followed by cyanidation, study of the ground particle size effect on the degree of Au recovery under conventional cyanidation and search for an alternative technology of gold recovery from refractory gold-bearing ores. METHODS. Diffractometric and quantitative methods are applied to analyze the mineralogical composition of the ore. Optical emission, atomic absorption, phase, IR-spectroscopic, gravimetric, titrimetric and photometric methods are used to study the chemical composition of the sample. Gold and silver contents are defined using direct fire assays. RESULTS AND THEIR DISCUSSION. The obtained results have shown that the Taror ores refer to refractory ore type. It means that traditional cyanidation method without application of any additional process operations fails to present any acceptable results on gold recovery. Application of the UFG method followed by atmospheric oxidation has increased gold recovery by 7.33% for this type of ore. CONCLUSION. Application of UFG followed by atmospheric oxidation enables efficient processing of refractory ores, which was considered earlier economically unviable. It is planned to study this type of ore further by flotation concentration methods, carry out a series of tests on flotation concentrate UFG and atmospheric oxidation of ultrafine ground pulp with the following cyanidation in the sorption mode.

Summary While some fractions of the uranium ores from Crownpoint, NM, are amenable to leaching with mild chemical reagents such as hydrogen peroxide or high-pressure oxygen in sodium bicarbonate solution, other ores are refractory to this treatment, possibly because the uranium mineral is embedded in a kerogenic organic matrix. Such refractory ore occurs only in selected areas of the general Crownpoint properties. Previous papers have described the use of chemically severe leaching systems (sodium hypochlorite, oxygen/sulfuric acid) to recover uranium from such refractory ore. In this paper we report results of an experimental study on the effects of heating refractory Crownpoint ore at moderate temperatures in the presence of a mild (oxygen/sodium bicarbonate [O2/NaHCO3] or hydrogen peroxide/sodium bicarbonate [H2O2/NaHCO3]) chemical leaching system. peroxide/sodium bicarbonate [H2O2/NaHCO3]) chemical leaching system. When a composite sample of refractory ore from the Crownpoint uranium properties was leached with high-pressure (600 to 800 psig [4140 to 5520 properties was leached with high-pressure (600 to 800 psig [4140 to 5520 kpa]) O2/NaHCO3 at ambient temperature in batch or pack tests, only 30 to 40% recovery and slow reaction rates were observed. However, this same leachate, when heated to 140F [60C], gave 60 to 65% recovery in batch, pack, and core studies at much more rapid rates. Several other pack, and core studies at much more rapid rates. Several other temperatures were studied, but 140F [60C] appears to be close to optimum for the group of ore samples tested. When we used rough kinetic approximations, relatively low apparent energies of activation were observed. The uranium recovered with heated leachate was accompanied by dissolved organic matter, which suggests oxidative attack on and breakdown of the highly aromatic organic carbonaceous matrix. Some trace quantities of organic molecules identified in the effluent were consistent with kerogen degradation products. Some dissolved silica also was produced. Reservoir heat balance estimations suggest that the concept of using heated leachate for in-situ leaching can be technically feasible in reservoirs such as Crownpoint, particularly if injection rates are high and ore bodies are reasonably thick. Thus, this technique represents a possible alternative for recovering uranium from refractory ore. possible alternative for recovering uranium from refractory ore. Introduction Previous work has shown that uranium ore from the Crownpoint region of Previous work has shown that uranium ore from the Crownpoint region of northwest New Mexico has been amenable to leaching with a variety of chemical leachates. In these ore samples, both uraninite and coffinite have been identified, and Rhett has described a cryptocrystalline or possible organometallic form of residual uranium. Coffinite, when present, frequently is encysted or otherwise embedded in kerogenic organic material with crystallite size ranging from less than 1 to 30 microns [less than 1 to 30 mu m]. The uranium-bearing sandstones are classified as arkosic, and contain detrital quartz, feldspar, and other rock debris, with some clay and carbonate. Overall, we have observed considerable heterogeneity in ore characteristics, even within a relatively small area, and noted wide variation in leaching rates when a chemically mild leachate (O2 or H2O2 in NaHCO3 solution) was employed. Ore from a number of areas at Crownpoint did not leach efficiently or to high recoveries with such mild leaching systems and has been termed "refractory." In the ore samples that displayed this refractory or "intractable" nature, the coffinite was shown to be at least partially encapsulated in the carbonaceous organic matrix. We also observed that when chemically more powerful leachates such as sodium hypochlorite (NAOCl) or O2/sulfuric acid (H2SO4) were used, rapid leaching and high recoveries were obtained with Crownpoint refractory ore samples. Another way to introduce severity into a chemical reaction is, of course, to increase the temperature. That this is an effect of considerable magnitude at temperatures near 77F [25C] can be seen by simply proportioning temperature coefficients, for reactions at 77 and 95F proportioning temperature coefficients, for reactions at 77 and 95F [25 and 35C] (EA is the apparent energy of activation, kcal/mol [kJ/kmol], R equals 1.987 cal/K-mol, and T is temperature, K). For "typical chemical reactions" with EA = 15 and 20 kcal/mol [62 220 and 83 680 kJ/kmol], reaction rates are approximately doubled and tripled, respectively. JPT p. 2228

The article presents the results of a study on the possibility to assess refractory gold-bearing ores using thermal analysis data. It studies the flotation concentrates obtained during the enrichment of double refractory sulfide gold-bearing ores. This type of ore is complicated by the fine impregnation of gold in sulphide minerals and the presence of sorption-active scattered carbonaceous matter, which is in close association with sulphides. The results of thermogravimetric and mass spectrometric studies of refractory gold-bearing ores are presented.The obtained fragments for kerogen CH (m/z = 15), C2H (m/z = 29) and C3H (m/z = 43) indicate the presence of various types of carbonaceous matter in the studied samples. It is justified that the degree of sorption activity of carbonaceous matter depends on the presence of kerogen and bitumen in the ore. High sorption activity of scattered carbonaceous material significantly affects the processing technology of ores and concentrates, both flotation and pyro- and hydrometallurgical methods.Thermogravimetric and mass spectroscopic analyzes can be used to determine the degree of preg-robbing of refractory gold-bearing ores. The obtained results predetermine the direction of creating new methods and technologies in the field of decarburization of refractory gold-bearing ores in the integrated development of solid minerals in the mining regions of Russia.

Oxidation of sulfide mineral and metal extraction analysis in the microwave-assisted roasting pretreatment of refractory gold ore

The use of thiosulfate to extract gold from refractory ores is promising because of its non-toxicity and high selectivity. Sulfide minerals (i.e., pyrite, arsenopyrite, chalcopyrite), major gold carriers in refractory gold ores, however, hinder gold extraction due to the high consumption of a lixiviant. In this study, a new method to improve gold extraction from sulfide bearing gold ores is proposed based on the model experiments using a mixture of gold powder and arsenopyrite-bearing sulfide (HAsBS) ore. The effects of HAsBS ore on gold leaching in ammonium thiosulfate solutions were investigated, and it was found that gold extraction in the presence of HAsBS ore was suppressed because of the unwanted decomposition of thiosulfate on the surface of sulfide minerals. To improve gold extraction in the presence of the sulfide minerals, this study investigated the effects of the pretreatment of HAsBS ore using ammonium solutions containing cupric ions and confirmed that HAsBS ore was oxidized in the pretreatment and its surface was covered by the oxidation products. As a result, thiosulfate consumption was minimized in the subsequent gold leaching step using ammonium thiosulfate, resulting in an improvement in gold extraction from 10% to 79%.

Mesophilic bacteria were enriched from samples collected from acid mine drainages in La Carolina (San Luis, Argentina). Two enrichments, E1 and E2, showed suitable rates for iron or sulphur oxidation, respectively. Both enrichments were characterized by FISH analysis. They were mainly composed by Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans respectively. Studies with both, mixed and individual enrichments, showed biooxidation (measured as iron solubilisation) of a refractory gold-bearing pyrite ore from Hualilán (San Juan, Argentina). Pyrite and sphalerite were the main mineral species in the ore with 7% w/w and 8% w/w of iron and zinc and approximately 25 ppm of gold. Leaching experiments (2% w/v ore, 1.8 initial pH, 180 rpm and 30°C) were carried out with the addition of different alternative energy sources (6.67 g/L sulphur powder, 1 g/L ferrous iron, 0.02% w/v yeast extract). Redox potential, pH, ferrous iron concentration and total Fe and Zn were measured regularly. A 100% of iron leaching (after 28 days in the best experimental condition) was observed in some of the cultures. In other systems high zinc release was obtained (100% of dissolution after 28 days in the best experimental condition). Our results strongly suggest that under the correct operating conditions, biooxidation pre-treatment can be used to recover zinc as a subproduct of gold extraction from refractory ore.

Treatment of carbonaceous refractory gold ores

Bacterial oxidation of refractory sulfidic gold ores and concentrates can be used as a pretreatment process to enhance the recovery of gold. Sulfide minerals that occlude gold, such as pyrite, arsenopyrite, pyrrhotite, and marcasite, are biooxidized by acidophilic, chemolithotrophic bacteria. The biooxidation process results in the solubilization of the sulfide minerals with increased exposure of gold for subsequent recovery using standard metallurgical processes such as cyanide leaching. The mineralogy of the refractory gold ore determines the effectiveness of the biooxidation process. The ore must possess sufficient iron sulfide to support the bacterial growth and carbonate minerals, which can consume the acid, must be absent or present in such low concentrations that the biooxidation will result in a net production of acid. Several mining operations currently utilize biooxidation as a pretreatment process for refractory gold ore concentrates. Research and development are in progress to extend the use of biooxidation for pretreatment of lower grade sulfidic, refractory ores.

The mining sector, in particular gold mining, plays an important role in the economy of Tajikistan. Today, the issue of optimizing gold mining mechanisms, increasing its efficiency and expanding the resource base is of topical importance. The depletion of easily accessible gold deposits is stimulating the development of methods for extracting gold from refractory and low-grade ores. One of the promising methods of pre-treatment of such ores is gravity enrichment. The aim of the study is to characterize the Pakrut gold deposit, to determine its mineralogical and chemical composition, and to develop an optimal gravity enrichment scheme for gold recovery. Research objectives are as follows: to study the mineralogical composition and geochemical characteristics of gold-bearing ores, and then to develop a technique for their gravitational enrichment. The object of the study is the gold-bearing ores of the Pakrut deposit (Central Tajikistan). Materials and methods of research: analytical work and enrichment in laboratory conditions were carried out in the chemical laboratory of the Pakrut Joint Venture, the ore enrichment laboratory of the V. I. Nikitin Institute of Chemistry of NANT, the Central Committee of the Main Geological Directorate under the Government of the Republic of Tajikistan. It is found that gold in the Pakrut ores is mainly represented by native gold and electrum. The main gold-bearing minerals are pyrite, arsenopyrite, sphalerite, galena, jamesonite and some vein minerals. The gold content in the ore is about 6 g/t. The granulometric composition of gold is extremely uneven. Most of the gold particles are less than 10 μm in size and are coated with gold-bearing minerals, which hindered their release during grinding. In accordance with the characteristics of the gold deposit, gravity enrichment method has been used to extract the liberated coarse gold. Studies have shown that the gravity separation process is used for the primary processing of ore to recover coarse gold particles. The gold content and recovery in the gravity separation concentrates are 46.58 g/t and 44.59 %, respectively.

The article studies the material and mineralogical composition of the refractory gold-bearing ores of the weathering crust of one of the deposits in Eastern Siberia. It is revealed that, according to the textural and structural features, ores are multi-mineral and have significant differences in the composition of the detrital, granular material and the loose component. All ore is saturated with iron hydroxides and limonite crusts with clay components. The results of the analysis showed that large classes contain an insignificant amount of a valuable component. Increased gold content is noted starting from -4 + 0 mm size. In the free state are about 3-5%. Processing of these types of raw materials is a rather complicated task. Analysis of the enrichment methods showed that the use of new solvents of noble metals with their subsequent concentration is promising. Of practical interest are alkaline solutions obtained by dissolving sulfur in an aqueous suspension of calcium hydroxide. The reagent is non-toxic and environmentally friendly. Leaching was carried out in a wide range of concentrations of the solvent used. The optimum solvent concentrations and the duration of the leaching process for extracting the valuable component into the filtrate were determined to be 97–98%. Chemical analysis of cakes showed that the reagent does not enter into chemical interaction with other elements that make up the ore. As well as the content of elemental sulfur in dump cakes averages 0.64%, that is, it corresponds to a content in the raw material of up to 0.8%. At the same time, cakes are not environmentally harmful and can be stored on special platforms.

Reserves of high-grade gold ore worldwide are decreasing, and some industries have started processing refractory gold ore. Refractory gold ore contains sulfide minerals such as pyrite (FeS2), chalcopyrite (CuFeS2), galena (PbS), and sphalerite (ZnS). Gold in refractory ores occurs as fine-size gold-bearing sulfide minerals. In this study, the microwave-assisted roasting method has been investigated as a pretreatment for a refractory gold ore. This method can provide rapid heating radiation, cause micro-cracks, and trigger the decomposition of sulfide minerals. The presence of additive helps in the oxidation of sulfide minerals. The microwave-assisted roasting was carried out using variations in microwave power and time. Microwave power between 300 - 600 watts significantly affected the increase in roasting temperature and weight loss of refractory gold ore. The highest temperature reached 567°C in roasting at 800 watts for 30 minutes. The optimum condition for microwave roasting was achieved at 400 watts of power with a roasting time of 30 minutes. Metals extraction of Cu, Zn, Pb, and Fe reached 97.2%, 82.7%, 16.1%, and 2.1% in water leaching.

The paper considers the results of the application of dry magnetic separation on samples of ferruginous quartzites of the Kostomuksha ore field, represented by refractory ore, free-milling ore, and their mixture. The assessment of the influence of the ore texture on the technological parameters of dry magnetic separation indicates their insignificant changes: the yield of the non-magnetic product varies from 12.4 to 13.5%, and the Fetotal content in the magnetic product increases by 1.11–1.14 times. A decrease of at least 15% in the number of harmful impurities was found: S by 16.2–17.3%, SiO2 by 15.5–21.1%, and Al2O3 by 39.1–48.4%. The authors have performed a comparative assessment of the granularity of the initial ore and the magnetic product with the measurement of energy consumption, as well as an analysis of the magnetite liberation on particle sizes of less than 2 mm. It was found that due to the release of a non-magnetic product in the amount of 12.3–14.5%, represented by non-magnetite or weakly mineralized rock varieties, energy consumption for the crushing process is reduced by at least 5%. The mineral liberation assessment showed that mainly free magnetite is contained in the −0.4 mm fineness class. It was found that in the magnetic separation product of the refractory ore sample, the amount of liberated magnetite in the size class −1 + 0 mm increases by 12.1% compared to the initial ore sample. For the free-milling ore sample, the opposite trend is observed: a decrease in the amount of free magnetite by 30.9% in the magnetic product. Analysis of the magnetite liberation in the mixture indicates deterioration in the results obtained during the separate crushing of refractory and free-milling ore and a decrease in the amount of liberated magnetite in the magnetic product by 60% compared to the initial ore.

Актуальность исследования заключается в том, что проведенные детальные минералогические исследования с упором на электроннозондовый микроанализ дают информацию о составе руд и форме нахождения благородных металлов (группы платины), редких и редкоземельных элементов, что может значительно повлиять на экономическую ценность рудопроявления Майке. Цель: определить распределение и формы нахождения благородных, редкоземельных и редких металлов в поликомпонентных медноколчеданных рудах проявления Майке. Объекты: метасоматиты линейно-трещинного типа и генетически связанные с ним медноколчеданные руды на правобережье реки Майке в пределах Маятасского рудного поля. Методы. Состав медноколчеданных руд и породообразующих минералов метасоматитов был изучен в лабораториях минералогии и физических и химических методов исследований ТОО «ИГН им. К.И. Сатпаева» (г. Алматы). Элементный состав определен методом электроннозондового микроанализа на JCXA 733 c применением энергодисперсионного спектрометра INCA ENERGY. Проведены атомно-эмиссионный полуколичественный спектральный анализ, рентгенодифрактометрический и термический анализы. Результаты. Рассмотрены основные критерии петрографии и минералогии метасоматитов линейно-трещинного типа и генетически связанных с ними медноколчеданных руд, впервые выделенных в пределах Маятасского рудного района. Доказывается, что основные рудные тела медного колчедана локализуется в составе кварц-рутил-сидерит-хлоритовых и сидерит-мусковит-хлоритовых сланцах, являющихся составной частью силицит-карбонат-углеродистого комплекса. На основании детальных минералогических исследований показано, что медноколчеданные руды являются источниками платиноидов, редкоземельных элементов и рения. В составе медноколчеданных руд проявления Майке выделены виоларит, пирит, сфалерит, пирротин, микровключения кобальтина, никелистого кобальтина, феррокобальтина, герсдорфита, теллурида серебра, акантита, теллурида свинца, галенита, тестибиопалладита, висмутистого тестибиопалладита, мелонита, вавринита. Показано, что зональный никелистый кобальтин является источником платиноидов (Pt, Ir, Ru, Rh, Os), образующих поликомпонентные твердые растворы. Рений входит в состав сульфидов меди, железа, никеля, свинца и висмута. Теллур был обнаружен в составе теллурида серебра, теллурида свинца, тестибиопалладита, мелонита и вавринита. Эрбий встречен в составе незонального никелистого кобальтина и виоларита. Кадмий обнаружен в виде изоморфной примеси только в сфалерите. Элементы цериевой (легкие – La, Ce, Pr, Nd, Sm) подгруппы и Y входят с состав фосфатов, фторфосфатов и являются источником образования водных фосфатов в зоне окисления медноколчеданных руд проявления Майке.

Gold extraction is a vital process in the mining industry, as gold is a valuable and highly sought-after metal. A detailed mineralogical and characteristics study of refractory gold ores from PT XYZ was conducted. The primary components of refractory ores were silicates, carbonates, oxides, carbon, and sulfides. Because refractory ore contains contaminants that impact gold recovery, pre-treatment is necessary before processing to maximize gold recovery. To maximize the percentage of gold recovery, the refractory ore type in this study will be subjected to a pre-treatment technique called roasting, which attempts to reduce the sulfur content and alter the porosity of the ore. The hydrometallurgical method of extracting gold used in this research is cyanide; this technique was selected since it is the most technologically efficient way in the mining sector to date. Five ores were employed in this study: A, B, C, D, and E were obtained from PT XYZ in Indonesia. Based on laboratory and experiment testing using XRD, XRF, ICP, LECO & DLT (Diagnostic Leach Test), it concluded that sample A was free milling ore with a percent extraction of Au 95%. However, samples B, C, D, and E are refractories of the ore type, which need to be roasted before processing. Sample B had the highest percentage of gold extraction (89%), in the refractory type ore after roasting.