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By C. V. G. K. Murty

Sillimanite, chemically named Aluminum silicate, 3Al2O3SiO2 is one of the three forms of alumino silicate polymorphs and commonly encountered in aluminous metamorphic, plutonic, and volcanic rocks and their weathering products. Most of the sillimanite deposits are granular and are of high grade available in coastal areas as associated mineral along with Titanium bearing minerals namely ilmenite, rutile etc. Sillimanite is one of the widely accepted raw materials for the manufacture of high alumina refractories (55-60 % alumina) or bricks. Sillimanite based refractory bricks are used for the lining of Blast furnaces, Arc furnaces, Soaking pits, Reheating furnaces of iron and steel, rotary kilns for cement manufacturing and general kilns for lime production. Considering the vast potential of unexploited sillimanite reserves in India, M/s Trimex Sands Pvt. Ltd., (TSPL)has set up a Mineral Sand Processing plant in 2010 at Andhra Pradesh with a capacity to produce about 50,000 tons of sillimanite per annum besides the production of various heavy minerals such as ilmenite, rutile, zircon and garnet. Traditionally in India, sillimanite is upgraded by froth flotation technique using Oleic acid as a collector cum frother, sodium silicate as depressant and soda ash as pH regulator. At TSPL, Conventional mechanical float cells are installed to float sillimanite. In addition to the usual problems associated with conventional cells, poor flow ability of the sillimanite concentrate is experienced in dry circuit due to the presence of sodium oleate. Fine garnet in the sillimanite concentrate contributes to high iron content in the final product, making sillimanite separation a nightmare for operators (lower recoveries coupled with inferior grades). Various efforts were made to improve the performance of the circuit such as introduction of additional frother like MIBC, optimizing the operating parameters such as pulp density, collector dosage, depressant dosage, air flow rate, pH etc., use of collector aids, stage wise addition of reagents etc. The challenges faced to produce a sillimanite product with stringent quality norms and the efforts made to improve the grade and recovery are described in this paper. Keywords: sillimanite, froth flotation, conventional mechanical cell

Sep 1, 2012

By S. Kelebek, A. Khan, J. Caceres, Beckett. D.

"Pyrrhotite in nickel-copper sulphide ores is nickeliferrous and intimately associated with pentlandite. Due to its low nickel content, pyrrhotite rejection is an important step in processing of these ores. In our laboratory, various reagents were investigated for their effect on pyrrhotite depression. Among these, a combined use of triethylenetetramine and sodium metabisulphite was found highly promising.The work described in this paper has two parts. The firs part is a summary of results obtained on process samples from the pyrrhotite rejection circuit at Falconbridge’s Strathcona Mill. The second part involves simulation of the circuit performance based on the reagent conditions used in the experimental work and the concept of split factors.Two sets of reagent conditions were evaluated. The first one involved baseline conditions, simulating the current reagent performance. The second one simulated the impact these new reagents can have on the circuit performance.The simulation results obtained under baseline conditions indicated a good agreement with the current circuit performance. The simulation results suggest that at practically the same pentlandite recovery and tailing grades, the circuit concentrate nickel grade can be doubled through effective pyrrhotite rejection by these new reagents."

Jan 1, 2003

By O. Guven, I. Karaagaçlioglu, O. Ozdemir, M. Çelik

In this study, the effect of morphological properties such as shape factors and roughness of the glass beads on their flotation efficiency were determined using image analysis and profilometer methods. There is a considerable correlation between the shape factors, surface roughness and flotation behavior of the glass sample. These results indicate that as the particle shape is away from roundness and smoothness, it acquires more hydrophobicity.

Jan 1, 2014

Calaverite is a gold telluride found in the Kalgoorlie region, Fiji, Cripple Creek Colorado and numerous other locations. It is known that a high pH is necessary for calaverite cyanidation, with the leach rate increasing substantially above pH 12 due to the hydroxide ion concentration. In most circumstances lime is used to achieve high pH, however lime saturates at approximately pH 12, limiting the maximum pH obtainable in a critical region for calaverite leaching. Plant observations, laboratory experiments and thermodynamic modelling show that the maxi-mum hydroxide ion concentration that can be achieved with lime (CaO) is strongly dependent on common ions. The presence of calcium, as commonly found in saline waters, substantially diminishes the maximum pH that can be obtained with lime. Conversely the presence of sulfate ions, as generated through oxidation of sulfides, substantially increases the maximum pH that can be achieved with lime. Sulfide oxidation during cyanide leaching of complex ores may generate acid and sulfate ions, making overdosing with lime at the front of the circuit, or staged addition down the leach train, important to maintaining the maximum hydroxide concentration.

Jan 1, 2014

By Kari Niiranen

LKAB (Luossavaara-Kiirunavaara AB) is operating iron ore mines, concentration plants and pelletizing plants in Northern Sweden. The largest of the apatite magnetite deposits and the mines are Kiirunavaara with annual production rate of approximately 27 Mt crude ore underground. LKAB produces two varieties of pellets: blast furnace pellets and direct reduction pellets (LKAB DR Oxide Pellets). Meanwhile the concentration process in a sequence of the low intensity magnetic separation (LIMS) and flotation at the concentration plant. In spring 2007 there were noticed great fluctuations of SiO2 grade in the crude ore. The high SiO2 grade is particularly problematic in the case of direct reduction pellets. In consequence, a project was started (called Silica in the Mine) to define exactly the problem related with silica and to find out, if possible, the reason for the great fluctuation of SiO2 grade in the crude ore going to the processing plant. A further target of this project was to develop a simplified method at the laboratory scale, to predict SiO2 grade in the magnetite concentrate in the future, but also predict the physical properties of the ore with respect to mineral processing. The essential stage of systematic characterization of the ore body for mineral processing properties is the estimation and simulation of different parameters from the laboratory scale to the large scale at the concentration plants using empirical data collected at the mineral processing by LKAB in Kiruna. Further a target was also to find useful physical parameters for mineral processing and implant those parameters into the existing geological 3D-model of the deposit. This information will be used for making prognosis of the future mining and the quality of the crude ore. It will also give better control and improve the production planning in the mine and the performance at the concentration plant in Kiruna concerning the decrease of the SiO2 grade of the magnetite concentrate.

Sep 1, 2012

Calcium carbonate has three polymorphs: calcite, aragonite, and vaterite. Needlelike aragonite CaCO3 with a high ratio of length to diameter (aspect ratio) is widely used in plastics, rubber and ceramics as a filler and in pigments and paints as a carrier. This paper investigated the influence of H3PO4 dosage, reaction temperature, CO2 flow rate, and initial Ca(OH)2 concentration on formation of needlelike aragonite CaCO3. It was found that the presence of H3PO4 in Ca(OH)2 suspension resulted in rapid formation of (Ca5(PO4)3(OH)) crystal nuclei, which facilitated nucleation and growth of aragonite CaCO3 on the formed (Ca5(PO4)3(OH)) crystal surfaces. The results revealed that H3PO4 addition of P/Ca of 0. 2~0. 3, high temperature of 75~85 °C, low CO2 flow rate and initial Ca(OH)2 solid concentration of 1. 5 %~5. 6 % are beneficial to formation of aragonite. Well crystallized needlelike aragonite CaCO3 whiskers with length > 20 µm and aspect ratio > 15 were directly synthesized.

Jan 1, 2014

By M. Saghaeian, R. Hejazi, H. Abedini

Vertical ring and Pulsating Wet High Intensity Magnetic Separator (VP-WHIMS) is widely used for week magnetic mineral beneficiation or ferrous impurity removal from non-metallic minerals. Because of the complexity of this machine, mathematical modelling of its process is complicated and time consuming. In this paper, artificial neural network (ANN) and response surface methodology (RSM) were applied to evaluate the VP-WHIMS performance and optimize its main operating parameters in beneficiating of the Chadormalu hematite sample. The operational parameters of this magnetic separator are considered as: magnetic field intensity (2500-8500 gauss), pulsating frequency (20-100 %max), ring rotation speed (0.6-4.6 r/min) and slurry concentration (15-35 w/w %). Concentrate grade and recoveries (weight and Fe) are monitored as responses. Centre composite design (CCD) was used for experimental study. Four process variables were set using small CCD. Eight star points (a=±1), eight axial points (a=±2) and five replicates at the centre point (a=0) were chosen as experimental points. In ANN system, the best network topology was obtained as (4-5-3). The weights connection and biases were obtained using batch back propagation (BBP) method for 21 experimental data points. The results indicate that ANN

Jan 1, 2014

By S. H. He

This paper focuses on the influence of pulp oxygen content on the separation of pentlandite and pyrrhotite contained in two different process streams in the Clarabelle Mill, operated by VALE INCO. The two process streams are (i) the scavenger cleaner feed, the product of regrinding the thickened, scavenged concentrate and the B cleaned tail produced from treating the non-magnetic fraction of the milled run of mine ore, and (ii) the magnetic concentrate which is the magnetic fraction of the milled run of mine ore. In the Clarabelle Mill, sulphite (SO32-) and TETA (triethylenete-tramine) are together used to selectively depress pyrrhotite from pentlandite. These depressants pre-ferentially decompose collector and/or sulphur enriched species at the pyrrhotite surface, an appar-ently essential mechanism in pyrrhotite depression from the scavenger cleaner feed stream. Selectivity in depression may originate from differences in the electrochemical rest potential of pyrrhotite and pentlandite. As both minerals are susceptible to oxidation, aeration in conditioning and flotation plays a key role in selective flotation. Important differences in the flotation behavior of pentlandite and pyrrhotite from the magnetic concentrate and the scavenger cleaner streams are highlighted in

Jan 1, 2014

By C. Perez

In mineral processing plants it is important to estimate rock composition, size and grindability to improve control of the grinding process. It is well known that variation in ore grindability and size distribution directly affects mills power consumption and throughput. This paper extends a general machine vision approach for on-line estimation of rock mixture composition using color information. Our proposed rock lithological recognition method requires the following steps: division of each image into sub-images, color feature extraction using the Binary Quaternion-Moment-Preserving thresholding technique (BQMP) and support vector machines (SVM) for classification. The BQMP thresholding technique splits the image in two and chooses representatives of each half using the histogram as features. The statistical parameters of the color data can be expressed using the quaternion moments into the representatives. This method can be recursively applied to the sub-images, obtaining 5x2n features in n iterations. Once the feature vector has been computed, each vector is assigned to one of three classes using a classifier. The method was tested on a database containing 20480 sub-images (64x43 pixels) of five ore types as follows: massive sulphide (MS), disseminated sulphide (DS), net textured (NT), gabbro (G), and peridotite (P). These ore types were assigned to three grindability classes: soft (MS), medium (DS and NT) and hard (G and P). The database was divided in 2 subsets: 15360 sub-images used for training and cross validation and 5120 sub-images used for test. The classification accuracy was compared with a method previously published based on a mixture of principal components analysis (PCA) for color, and wavelet texture analysis (WTA) for texture feature extraction. WTA-PCA approach reached a 76% accuracy in test while our BQMP method reached 90% of classification accuracy using only color features. Experimental results show that our proposed method yields excellent results compared to previously published results. Keywords: rock classification, lithological classification, grindability estimation

Sep 1, 2012

Optimising flotation designs and innovations is a complex process involving many parameters, one of which is ensuring sufficient testwork is carried out at plant level before these innovations are launched in the marketplace. This paper will describe how modern design tools are utilized, what are testwork phases at various plants and how results and observations have helped to validate and optimise flotation design innovations. Scale-up of equipment has long been the prevalent trend, but how long can it continue? Are there other means for pushing the boundaries of present technology? Some present challenges and future directions are given in the light of theoretical criteria for scale-up and how it has been applied in practice. Very large flotation cells of 300 m3 size have been installed in New Zealand, and relevant results from the metallurgical and mechanical aspects are presented and discussed. Utilization of the cell volume is also important. New innovations in the hydrodynamic domain are presented and discussed. Means to enhance flotation of coarse and fine particles are shown with results from plant testwork. Accurate control of large flotation cells is vital to optimize yields and grades. Froth image analysis and intelligent level control are presented ? again - with relevant plant results.

Jan 1, 2014

By Agnieszka Surowiak, Tomasz Niedoba

The paper presents a way of determining relations between ash content in coal, particle size and particle density by means of regression, multidimensional Morgenstern distribution functions and kernel approximation. The three-dimensional random vector (D, ?, ?), where D is a random variable describing particle size, ? - random variable describing particle density and ? - random variable describing ash content, where function ?=?(d, ?) is obtained by means of regressive function. The multidimensional Morgenstern distribution functions and kernel estimators with the use of Gauss function were applied to approximate the functions f(d, ?, ?) and f1(d, ?). This approach is a new way of multidimensional description of grained materials such as coal and it also allows to evaluate material features more properly than the classical statistical approach. The results were verified statistically.

Jan 1, 2014

By E. V. Zelinskaya, V. U. Starostina

"The Irkutsk region is a raw material region. There are a lot of big enterprises for extraction and processing of oil, gas, coal, iron, gold and rock salt. Besides of it, refractory clays, limestone, mica, gypsum and talc are mined in the region. The most important type of mineral raw material is a gold. More than 8.5% of the total mining in the Russian Federation is extracted in Irkutsk region. It is about 0.7% of the world production. The environmental problems of mining and processing enterprises are a complex set of issues that requires of the searching of effective methods to be solved. One of the key environmental problems remains the reduction of waste generation and the introduction of environmentally safe waste management. After analysing different methods of environmental impact assessment it is established that the method of Life Cycle Assessment is one of the most effective methods for mining production. This method base? on the material balance of flows of raw materials, products and waste. The method of Life Cycle Assessment allows to identify the effects of environmental pollution under the influence of mining and processing at a quantitative level and to show real quantitative forecasts of the possibility of managing the flows of raw materials and waste.INTRODUCTION The Irkutsk region is a raw material region. There are a lot of big enterprises for extraction and processing of oil, gas, coal, iron, gold and rock salt. Besides of it, refractory clays, limestone, mica, gypsum and talc are mined in the region. The most important type of mineral raw material is a gold. More than 8.5% of the total mining in the Russian Federation is extracted in Irkutsk region. It is about 0.7% of the world production. The main provider of precious metal is the Bodaibo region. This is a main location for the major ore companies such as “Vysochaishy”, which produces about 5.0 tons a gold per year; “Pervenets”(PJSC Polyus, the largest gold producer in Russia) - 4.5 tons/year, “Druza” - 0, 5 tons/year. Placer gold is extracted by more than 40 enterprises. In connection with this, there are many plans about a building of new and reconstruction of concentrating factories. Consequently, an increase in the volume of processing is expected. The main projects are the construction of a new mill of the Mining and processing plant GOK “Vysochaishy” with a capacity of 2.6 million tonnes of ore per year; the development of the “Uhakhan” gold-field - 23 km from the “Goltsa Vysochaishy” gold-field; the opening in the Bodaibo region the next parts of the gold-deposit ""Pervenets"". Additional, the growth in a gold production can be achieved by a store of gold in the “Sukhoi Log” deposi"

Jan 1, 2018

By Maurício Torem, Gabriela Huaman, Antonio Merma

The purpose of this review paper is to succinctly present the most significant works related to Mineral Processing and Environmental Bioremediation and developed by the Mineral and Environmental Technology Group (METG) of the Materials Engineering Department of the Pontifical Catholic University of Rio de Janeiro (PUC-Rio). In mineral processing it was emphasized the use of the Rhodococcus opacus bacteria as a bioreagent in the bioflotation of some mineral samples (magnesite, calcite, hematite, quartz and apatite). The adsorption of the bacterial cells on the mineral surface can be due to specific and/or non-specific interactions, which will depend on several factors, as their surface charge and hydrophobic character. The zeta potential evaluation of the mineral particles before and after interaction with the R. opacus cells showed that the biomass modified the zeta potential profiles of the minerals, which confirm the adsorption of bacterial cells on the mineral surface. Moreover, the bacterial cells adsorbed caused a change in the mineral flotability which is related to a change in their hydrophobic character, thus, the mineral bioflotability was found to be dependent on the pH and the bacterial concentration. On the other hand, the environmental bioremetiation assessed the biosorption potential of three metal ions (lead, copper, and cobalt) by four different biomass Streptomyces lunalinharesii, Rhodococcus opacus, Rhodococcus ruber and coconut shell powder. For this purpose, biosorption process was characterized under different operating conditions such as initial pH and biosorbent dosage. The Freundlich and Langmuir isotherm models were applied to the equilibrium data obtained at different concentration.

Jan 1, 2014

By D. Pirouzan

It is customary to use more than one stage of flotation to obtain an acceptable level of separation of valuables. Flotation circuit design is usually accomplished by applying empirical rules which usually results in operations not working at their optimum conditions. Given the capabilities of genetic algorithms (GA) in finding an optimum solution in a very disturbed search spaces, they can be used to obtain the desired flotation circuit configuration. In flotation circuit configuration and optimization problem, a combination of metallurgical parameters such as yield and concentrate ash content could be used as the fitness function for the genetic algorithm. The multi-objective nature of the problem justified to use Pareto method to arrive at a set of solutions. The appropriate configuration based on technical or economical considerations could then be chosen. To obtain the fitness function for any given configuration, it is necessary to model every flotation stage. The proposed method was used to find the optimum circuit configuration for a coal washing plant. The objective was to arrive at the highest yield while producing a concentrate with a certain ash content (< 11%). The feed to the flotation circuit was characterized based on the size fractions and their flotation rate constants. Results showed that with a 95% confidence, the absolute difference between the modeled and measured values were 2.9-5.5% for yield and 0.4-1.1% for concentrate ash content. When the proposed GA-based circuit configuration was implemented in the plant, the yield increased from the original value of 57.6% to 65.7% while producing concentrate ash content (10.9%) within acceptable limits. By adding one stage to the current three-stage circuit, it was predicted that the yield could further increase by 3.8% while keeping the quality of the concentrate within the appropriate level. Keywords: modeling, optimizing, flotation circuit configuration, genetic algorithms

Sep 1, 2012

By M. S. Prithvi

Over the decades, mine and mineral processing plant operations for the most part, have been found to have had adverse impacts on the environment. At the same time, mineral processing and mining operations produce mineral products that are indispensable to modern society. Thus, the sector has desirable and undesirable attributes simultaneously. The situation presents itself as a contradiction (i.e.) the mineral processing and mining operations are wanted by society, and at the same time unwanted by society. The existing methods of addressing the issues raised above have evidently not been very successful in reducing the opposition to new projects and to the related activities such as land acquisition. This paper attempts to show the relevance and applicability of TRIZ for addressing the issue. TRIZ, or Teoriya Rezheniya Isobretatelski Zadach, is a Russian acronym meaning Theory of Inventive Problem Solving. TRIZ is a powerful tool that can be usefully applied to resolve such contradictions, using resources usually available within the system of interest. Accordingly, this paper introduces the issue background, followed by an introduction to some key concepts of TRIZ such as the 40 principles, separation principles and directed evolution. The paper goes on to apply the 40 principles to two case studies. The results show that TRIZ could be a useful tool to generate potentially innovative and sustainable approaches. Its most appropriate position would be as a supplement to current decision-making procedures, and as a validation tool to review existing solutions for possible improvements. Keywords: minerals, environment, TRIZ, contradiction, resources

Sep 1, 2012

By M. Saghaeian, R. Hejazi, L. Hosseini

The specific surface area (Blain value) of iron ore concentrate entering the pelletizing plant is one of the characteristics most effective on the overall performance of the plant such as producing harder pellets, decreasing additives consumption, and decreasing energy consumption. Therefore, preparing the feed entering pelletizing plant is required. The iron concentrate entering Ardakan pelletizing plant located in Yazd province, Iran bears relatively low Blain value (approx. 1600 cm2/g) which necessitates one stage of regrinding so as to increase the Blain value to more than 1800 cm2/g. Studies were conducted and results showed that HPGR is the best regrinding equipment for increasing specific surface area. Conducting pilot plant tests on the concentrate sample revealed that specific throughput is 181 to 263 ts/hm3 and specific energy consumption is 1.6kWh to 2.2 kWh. Pilot tests also showed that one stage of grinding results in 407 cm2/g to 553 cm2/g increase in specific surface area. Based on these results, diameter of rolls, length of rolls, power consumption and grinding force were calculated to be 1.3 m, 0.9 m, 1276 kW and 13800 kN, respectively. Therefore, an HPGR with a roll diameter of 1.52 m, roll width of 1.1 m, power of 1660 kWh and a capacity of 500 t/h has been selected and implemented in Ardakan pelletizing plant. Industrial performance of HPGR and its effects on the plant study results show that limestone and bentonite consumption has reduced about 60% and 30%, respectively. Total Fe of the final pellet has increased from 65.5-65.7% to 66.2%. Cold compressive strength (CCS) and porosity of final pellets are approximately 292 kg/pl and 20.4, which are in the acceptable range.

Jan 1, 2014

By W. Kobal

The extraction of nickel (Ni) and cobalt (Co) from the laterite deposit of Ramu nickel-cobalt Project in Papua New Guinea was performed in this study. Chemical analysis by Inductively Coupled Plasma (ICP-AES) atomic emission spectrometer, SPS-3000 (Seiko Instruments (Inc.), shows the ore contains 48% Fe, 1% Ni, 0.1% Co, 1.8% Al, 0.14% Mg, and 0.8% Mn. Characterization by X-ray diffraction (XRD) analysis of the laterite ore obtained from the mine site shows the ore contains 70 to 80% goethite (FeOOH), assuming Fe content of 48% is mainly from geothite. The main leaching parameters investigated include; slurry temperature, leaching time and sulphuric acid (H2SO4) concentration to evaluate nickel and cobalt extraction. For all experiments, 10g batch samples are put into 300 ml beaker containing 100 ml of sulphuric acid of varying concentrations (1M, 2M, 4M). During the leaching period, 5 ml slurry samples are withdrawn at different times and filtered to obtain filtrate for ICP analysis to monitor nickel and cobalt extraction. Solid samples at the end of all tests are also obtained by filtration and after drying, XRD and ICP tests are performed to monitor nickel and cobalt contents. According to the test results performed at normal atmospheric pressure, over 99% of nickel and over 50% cobalt were extracted into solution within 120 min at 95ºC in 2M H2SO4 solution. Similar results were obtained when only temperature was reduced to 90ºC, but cobalt extraction increased to over 70% when leaching time was increased to 240 min. Further reduction in temperature to 80 and 60ºC resulted in reduction of nickel and cobalt extraction. At the end of each leaching test, magnetite was seen to attach to magnetic stirrer. The study showed nickel can be completely leached into solution but cobalt only up to 70%. Keywords: atmospheric pressure, sulphuric acid leaching, nickel laterite

Sep 1, 2012

By Arkady Senchenko, Yevgeny Zhagun, Yury Kulikov, John Starkey

"The paper contains description of a new project in Russia - gold-processing plant at Aleksandrovskoye deposit (start up in September, 2013). The paper includes a brief description of plant flowsheet, data for material composition and technological properties of ore, as well as information about the achieved parameters of ore processing over the first months of plant operation. The project is interesting because a new semiautogenous mill and a ball mill were purchased on the basis of SAGDesign Consulting Group recommendations after the testing of ore samples characterizing the deposit according to specific years of operation. The plant has relatively small design capacity - 750 000 tpa, but nevertheless is the biggest gold-processing plant in the territory of Zabaikalsky region. Major valuable component in the ore is gold, silver is recovered as a by-product. The ores are very hard to grind. The design grinding flowsheet includes a semiautogenous mill operating in closed circuit with a screen, and a ball mill operating in a closed circuit with hydrocyclones (SAB). Process technology includes gravity processing and flotation with subsequent cyanide leaching of concentrates. Mill operation analysis and conclusions about the compliance of the achieved values to target ones are shown, as well as the accuracy of SAGDesign method when applied to very hard ores of Aleksandrovkoye deposit are presented in this paper. Basic directions of technological flowsheet optimization are also given."

Jan 1, 2014

By A. S. Choudhary

Most of the coal reserves in India are of drift origin and have very poor washability characteristics and a high level of near gravity materials. At least 30 new coal wash plants are expected to be set up in the next 5years.In such a scenario, adequate sampling followed by sink float test work for washability analysis becomes very critical for designing these new plants. For coal sampling purpose, stipulations of different standards are sometimes formidable and on the border of ?impracticality?; sometimes are self contradictory in terms of gross sample weight vis-a-vis minimum number of particles required in each size fraction and in each relative density fraction and also the minimum mass in the latter. Validation of the generated data is another important aspect of washability analysis. These issues can easily be addressed by using straight forward mathematical relationships, well known RR plots and by using simple MS Excel tool, etc.

Sep 1, 2012

By S. P. Nagaeva, A. V. Kuptcova, O. Yu. Poperechnikova

"The present paper contains study results of gold morphology and grain size distribution in flotation concentrates produced from original ore samples from deposits of different genesis. Pre-concentration methods were used with selective dissolution of rock minerals and mineral heavy medium separation to obtain statistically valid data on gold grain size and morphology in concentration products. Special attention is given to study of flash flotation concentrates that is mainly used for coarse gold, underextracted in gravity circuit. Analysis of geometrical optics has allowed to establish that during flash flotation gold grains more than 150 µm can be extracted from 10 to 35%, and in some cases single gold grains above 300 µm. INTRODUCTION Distinctive features of gold that have a significant impact, and in some cases, decisive influence on its recovery into saleable products are mineral shape, grain size and morphology of metal particles, paragenetic associations of gold. Peculiar feature of coarse gold is its easy extraction during grinding from associated mineral components like quartz, sulphide and other and almost complete recovery into gravity concentrates (Lodeischikov V.V., 1997). Morphology of native gold is so diverse that different gold grains are better extracted using different methods of concentration. Compacted and rounded particles are easily processed using gravity concentration but low cyanidable and hard to process using flotation. On the contrary, lamellar, flake, dendrite and capillary aggregates of high specific surface are easily cyanidable and under definite conditions it has strong floatability (Lodeischikov V.V., 1997). Flotation of gold-containing sulphide minerals and free gold takes place simultaneously during flotation concentration. In case of low-sulphide ores, native gold takes the basic load, having the high density (15.6 to 18.3 g/cm3, for pure gold – 19.3 g/cm3) it has limited size and morphology for successful flotation. It is known that flake gold and fine-grained gold up to 0.1 mm are easily extracted (Lodeischikov V.V., 1997). Authors of the present paper performed a study of gold granulometry and morphology in flotation concentrates produced from gold-containing ores from two deposits of different types: gold-copper oxidized hematite ores and low-sulphide gold-quartz ores. Ores are different by both host rock composition, mineralogical and petrographic features, gold grade in mineral assemblage and morphology and size of precious metal. Common for both ore types is low-sulphide content and presence of free gold."

Jan 1, 2018