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By R. J. Bridges

Mining operations on the Witwatersrand are conducted for the most part in rocks of highly quartzitic character. They comprise the following types: Conglomerates, grits, and quartzites, to which on the Far East Rand must be added fine-grained quartzitic shales and shales. In addition, vein quartz occurring as small veins, veinlets and fissure fillings, and igneous rocks forming dykes, must be mentioned, although they constitute only a small percentage of the rock broken. The following is an account of the character and mineralogical composition of the various types.

Jan 1, 1947

By Mauro Torres, Gabriel Zarate

"AngloAmerican used the extractant M5640 at Mantos Blancos and Mantoverde and uses PT5050MD at Los Bronces Division, which are aldoxime and modifier blends. In the first case, the modifier is the esther TXIB, while in the second case is the tridecanol TDA. It is a well-known fact that the extractant degrades while the modifier does not and with time the oxime/modifier ratio can change significantly, depending on the operating conditions of each plant.In order to evaluate the effect of this varying modifier content in the plant organic, especially in the organic losses, a complete metallurgical test work program was conducted at laboratory and pilot plant scale by Flomin SNF, a new extractant supplier. Results showed that the addition of an aldoxime without the modifier did not affect the chemical performance of the extractant, but there was a significant decrease in the viscosity and density of the organic.Based on the results obtained in the metallurgical program, it was decided to run plant scale tests at the SX plants of Mantos Blancos and Mantoverde. In these tests, instead of adding extractant to maintain the organic inventory, CuPROMEX 3406 which is an unmodified aldoxime was added until the original oxime/modifier ratio was reached. This was obtained after 6 months of operation and since then both plants are running with the extractant CuPROMEX 3302 both supplied by Flomin SNF.In the case of Los Bronces, the pilot plant work was completed and it is programmed to run similar plant scale tests. In this case, the oxime/modifier ratio increased and TDA will be added until reaching the original ratio.The plant results obtained at Mantoverde and Mantos Blancos, together with the pilot plant test results obtained at Los Bronces, are discussed in this paper."

Jan 1, 2016

By F. J. N. Bruwer, T. R. Stacey

The research described considers whether the variability in coal material strength, as derived through a series of uniaxial compressive strength (UCS) tests, could be used to indicate the variability in coal pillar strength. The aim is to be able to use a distribution of UCS tests as input into the coal pillar strength calculation. This will allow the pillar design to be expressed in terms of a probability of failure rather than as the commonly used safety factor. To achieve this, the bulk strength factor associated with commonly used pillar strength formulae was replaced with a distribution of UCS results divided by an adjustment factor. The factor was determined so as to ensure that the resulting bulk strength does not deviate from the statistically determined bulk strength published in the original formulae. This approach enabled pillar strength distributions to be obtained using industry-accepted strength formulae, subsequently allowing for a probability of failure to be calculated for a specific pillar design. Using a regional coal material strength curve as a baseline, coalfields in which the coal is stronger than the regional mean can be identified and the pillar designs optimized. This is based on the stronger coals achieving lower probabilities of failure at similar safety factors. The research has considered actual UCS data from multiple mines in the Mpumalanga coalfields of South Africa, and has proved that the variability in material strength between coalfields could allow for some optimization using the proposed approach. Based on the data used in the study, a 2.78% increase in extraction could be achieved. However, further research will be required to validate the results of the study in an underground environment.

May 3, 2023

By Charles D. Litton

This U.S. Bureau of Mines report describes the results of two large-scale tests conducted to evaluate a prototype nitric oxide (NO)-compensated carbon monoxide (CO) fire sensor, developed by Carnegie Mellon Research Institute (CMRI). In the tests, small coal fires were allowed to develop in the presence of diesel exhaust at relatively low ventilation airflows. These tests compared the response of the CMRI fire sensor with that of other fire sensors, including the Bureau's diesel-discriminating smoke detector. During the tests, CO, NO, and smoke levels were continuously monitored in order to determine the sensor alarm times and gas levels as the fire developed. The data indicated that the NO-compensated CO fire sensor was capable of suppressing the CO produced by a diesel engine and that the sensor responded reliably to the CO produced from the test fires. The tests also showed that the Bureau's diesel-discriminating smoke detector alarmed earlier than the prototype NO-compensated CO fire sensor.

Jan 1, 1993

By E. S. Leaver

Experiments dealing with the dissolution of silver by cyanide from various silver minerals were reported several yews ago.4/ This work showed that the silver in some silver minerals is completely and readily soluble in cyanide solution, whereas other silver minerals must be given special treatment before or during cyanidation to obtain much dissolution of the silver by cyanide. Flotation as a method for treating silver ores has not been studied much, except in the case of base-metal ores carrying silver, particularly lead-silver ores. However, many mills now are concentrating gold ores by flotation, and when such ores also contain silver the recovery of the silver by flotation is of considerable importance. Moreover, many mines contain ore in which silver is the principal valuable constituent. Some of these ores are amenable to cyanidation, but the cost of a cyanide plant may be prohibitive because of limited ore bodies or other factors. In such instances the successful application of flotation would mean that the property could be operated.

Jan 1, 1939

By L. E. Schultze

Experiments were conducted by the U.S. Bureau of Mines to verify enhancements due to chloride and surfactant additions in the leaching system of chalcopyrite with ferric sulfate and sulfuric acid. A statistical experimental design was used and equipment was designed to eliminate contributions from changes in solution electrochemical potential during the course of the measurements. Results confirmed that chloride additions increased chalcopyrite leaching by as much as 94 pct over the electrochemical potential versus hydrogen electrode range of 630 to 750 mV at pH 1.7 and 50°C. Total iron concentration had no effect over the range of 1 to 5 g/L. The effect of surfactant addition was less well defined. While additions of LA 790 (a polyoxyethylene lauryl ether) resulted in increased copper leaching in several of the tests, the differences were too small to be statistically significant. No interaction effect could be verified.

Jan 1, 2010

By J. L. Johnson

The U.S. Bureau of Mines investigated the recovery of tin and silver from the Coal Creek deposit in the Talkeetna Mountains, AK. Approximately 5 million st of reserves grading 0.2 pct Sn with silver credits of 0.2 tr oz/st have been delineated by drilling. A 10-to 25-pct Sn gravity concentrate was produced by treating the minus 20-mesh ore with a spiral, then regrinding to minus 65 mesh and tabling. Sulfide contamination in the gravity concentrate was as high as 60 pet. Sulfide flotation of this concentrate produced tailings containing 40 to 50 pet Sn. Overall recovery was 76 pct for tin but only 5 to 10 pct for silver because of losses during sulfide flotation. Other methods tested to clean the concentrate included cassiterite flotation, gangue flotation, nitric acid leaching, and wet and dry magnetic separation. Tin beneficiation tests on the minus 325-mesh fraction included cassiterite flotation, vanning, sulfide flotation, and fuming. The bench-scale and locked-cycle tests were used to estimate the mass flows for a 1,000-st/d plant.

Jan 1, 2010

By D. F. Malan, J. A. L. Napier

This paper describes some important aspects associated with historical underground measurements in South African gold and coal mines. Deformation measurements were used to confirm the use of elastic theory to simulate the rock mass behaviour in the Witwatersrand gold mines in the 1960s. Although a prominent time-dependent component of stope closure was measured as early as the 1930s, it was ignored owing to the benefit of adopting elastic theory. Neglecting the time-dependent response of the rock for many decades resulted in important aspects such as the effect of mining rate, the effect of advance per blast, and the need for enhanced design criteria not being explored. Recent work is only now starting to address this gap in knowledge. In-situ measurements of large coal specimens in the 1960s and 1970s indicated that a linear formula may possibly be a better approximation of coal pillar strengths. This alternative formulation was never adopted, however, as the power law strength formula was already deeply entrenched in the industry at that stage. In spite of these apparent failures to continuously generate and adopt new knowledge, a key lesson learnt is that major advances in rock mechanics will not be possible without careful monitoring of the rock mass behaviour in experimental sites. Areas requiring further research, such as pillar strength formulae for the Bushveld Complex and enhanced design criteria for the gold mines, can only be developed using extensive undergroundmonitoring programmes.

May 1, 2021

By M. Kumral, Y. A. Sari

Underground mining operations tend to have higher operating costs than surface mines. When metal prices decrease, profitability is jeopardized due to the high costs. Therefore, mining management harnesses new practices that increase operational efficiency. One way to manage this challenge is to invest in new mine planning practices. Stope layout optimization as a part of underground mine planning aims to identify a portion of the orebody in the form of production volumes (stopes) to maximize profit under roadway and stope dimension constraints. In this paper we propose a novel approach based on identifying ore-rich areas of the deposit and prioritizing their extraction through an iterative heuristic clustering approach. The proposed approach is compared with and validated by an exact method through a small mining example. The heuristics produced nearly identical results in a very short time. Finally, a case study was carried out using a larger data-set. The cluster-based iterative approach generated nearoptimal stope layouts in a computationally effective manner.

Mar 1, 2021

By S. M. H. Haddad, M. Saghaeian, R. Hejazi, V. Sheikhzadeha, A. H. Baladastian, A. Dehghani Ahmadabadi

Sulfide impurities in iron ore concentrates play an important role in designing pelletising and steel making plants. Therefore attempts are made to keep the sulfur content of the final concentrate produced by the plants as low as possible. Generally, in the beneficiation process of iron ore concentrate, the removal of sulfur is performed through magnetic separation systems, followed by reverse flotation. The sulfide content of the iron ore concentrates originated from two main sources, including pyrite and pyrrhotite. In this research, in order to compare the floating capability of these two types of sulfide minerals, two iron ore concentrates with different sulfide constituents, pyrite or pyrrhotite, were selected. Reverse flotation tests were done separately on these samples under similar conditions. Process parameters considered for the tests included pH (2, 4, 6, 8 and 10), collector consumption (150, 200, 250, 300 and 350 g/t) and frother consumption (40, 50, 60, 70 and 80 g/t). Potassium Amyl Xanthate (PAX) and Methyl Isobutyl Carbinol (MIBC) were the collector and frother used in the tests, respectively. For modelling and optimising process parameters, the Central Composite Design (CCD) method was applied to the test results. Empirical coded equations were obtained for responses involving weight recovery, Fe recovery, Fe grade and S grade. Finally, comparison of test results revealed that the elimination recovery of pyrite sulfides was far greater than pyrrhotite sulfides, and it was possible to remove 84% sulfur content of the pyrite sample compared to minus 30% for the pyrrhotite sample. Keywords: Reverse flotation, pyrite and pyrrhotite, sulfur removal, iron ore concentrate, beneficiation plant

Jan 1, 2020

By E. P. Jennings

These unique copper-deposits occur on the top of the Kaibab Plateau, in Cocouino county, Arizona, and extend from the northern edge of the Grand Cañon of the Colorado river to near the Utah State line. The best-developed deposits are near Jacobs Lake, 30 miles south of the Utah line, where they are 16 ft. thick, of unknown width, and are more or less continuous for 5 miles. From Jacobs Lake to the edge of the Grand Cañon, a distance of 40 miles, outcrops of ore have been found, but no explorations have been made except those of wandering cowboys and hunters. The Kaibab Plateau, the highest of the Colorado river plateaus, is a great uplift, about 90 miles long from north to south, and from 10 to 20 miles wide from east to west. Its southern face is the Grand Cañon; its western boundary a N—S. fault plane, which separates it from the Eanab Plateau, lying 1,500 ft. below. Its eastern edge is a monocline which brings the horizontal beds of the high plateau to the level of the plateaucountry of eastern Utah. The elevation of the plateau near the Colorado river is over 8,000 ft., and about 6,000 ft. at the Utah line. Its structure, as shown by the western fault, consists of about 500 ft. of Aubrey limestones underlain by 1,000 ft. of red sandstones. The limestone is the upper member of the Carboniferous, and is overlaid by the marls and shales of the Permian, 25 miles to the north on the Kanab Plateau. At the town of Kanab, near the Utah line, the Permian strata pass under the magnificent redsandstone cliffs of the Triassic, that rise to heights of 1,000 ft. above the desert. The Grand Cañon exposes a section a mile deep at the southern end of the plateau, showing all the formations from the Archean to the top of the Carboniferous.

Jan 1, 1904

By Saul Hissaci de Souza

A liga de alumínio AA 7075 recebida no estado T6 (conformada e envelhecida artificialmente) sofreu tratamento térmico a 300°C com o objetivo de causar o engrossamento das partículas de MgZn2, intermetálico responsável pelo endurecimento do material. As amostras foram então deformadas 45% em redução de espessura por laminação e recozidas isotermicamente a 200°C e a 250°C por tempos variados para estudar a cinética de amolecimento por meio de medidas de dureza Vickers. Os resultados indicam que a cinética de amolecimento em ambas as temperaturas de recozimento aproxima-se do comportamento previsto pelo modelo Johnson-Mehl-Avrami-Kolmogorov (JMAK) com boa concordância (coeficientes de correlação de 0,9725 e 0,9140 a 200°C e a 250°C, respectivamente), ainda que as micrografias ópticas da amostra recozida a 300°C por 4 horas não evidenciem a ocorrência de recristalização.

Oct 30, 2017

By Siddhartha Roy, Hemant Agrawal, Ram Madhab Bhattacharjee, Devi Prasad Mishra

Heat stress in underground coal mines is a major threat to the health and safety of the miners. Hence, managing heat and prediction of heat stress in advance is essential for maintaining a safe, healthy, and productive underground mine environment. In this study, an extensive ventilation survey has been carried out in three different deep and mechanized underground coal mines. The ventilation survey data are used to develop 3D simulation models with the VentSim™ software to predict the conditions that could cause heat stress in underground mine workings. The developed 3D models predicted well the wet-bulb globe temperature (WBGT), a recognized indicator of potential heat stress, with a coefficient of determination (R2) of 0.986, 0.994, and 0.993 for Mine-A, Mine-B, and Mine-C, respectively. Moreover, through 3D modelling, the applications of auxiliary ventilation and spot coolers to reduce the wet-bulb globe temperature (WBGT) for improving the underground workplace environment have been explored. The study demonstrated that auxiliary ventilation and spot coolers can help in significant reduction of heat stress conditions in an underground mine environment. By application of auxiliary ventilation, to increase air volumes, and spot coolers, the WBGT index in mining faces is reduced by 1.2–1.4 °C and 3.9–5.4 °C, respectively. Therefore, it is concluded that the spot coolers are more effective in reducing the heat stress conditions in hot and humid underground mine environments in comparison with auxiliary fan that is used to increase the air volume and velocity. This study opens up a new horizon of 3D simulations for heat stress management in underground mines. The outcome of this study will be useful for the researchers, mine operators, and environmentalists understanding the heat stress contributors and their control in underground mine environment.

May 10, 2023

By Weibai Hu

Four methods to assess the relative flotability of fine coal have been tested: flotation with frother only, flotation with frother and collector, salt flotation, and timed-release analysis. A practical and simple criterion which combines the separation efficiency (capacity factor and kinetic rate constant (intensity factor) has been suggested. Five coal samples are chosen and tested. Based on test results, it is concluded that the flotability test with collector and frother is closer to practice, and, according to the suggested flotability criterion, coal fines can be classified into four categories of relative flotability: very easy, easy, moderate, and difficult.

Jan 1, 1987

By C. Garcia, J. J. Opazo, A. Potulsha, T. Comi

"Sierra Gorda SCM is a joint venture partnership of KGHM International (owned by KGHM SA, Poland), Sumitomo Metal Mining and Sumitomo Corp. (Japan) operating in northern Chile. The Sierra Gorda openpit mine and coppermolybdenum processing plant will become one of the largest mines in the world. The need for optimum production efficiency and sustainability has driven the creation of the most modern, wellinstrumented mine in Chile. This article contains a general review of the project including geology and history.This was a fast-track project going from greenfield site acquisition to mill startup in 10 years. Highly experienced and motivated engineers and technical staff have overcome many significant challenges resulting in a rapid ramp-up of production capacity. A potential expansion to double the production rate in the fourth year of operation has also been intensely studied.The Sierra Gorda property is located in the Atacama Desert of northern Chile, in the District of Sierra Gorda, Region II of Antofagasta, Chile (Fig. 1). There is almost no precipitation in this area. The mine site is generally flat with some rolling hills. The project is located about 5 km (3 miles) from the village of Sierra Gorda at an elevation of approximately 1,700 m (5,600 ft) above mean sea level. The village is near a highway and railway line. The city of Calama, home of the famous Chuquicamata Mine, is located about 60 km (37 miles) northeast of Sierra Gorda. In addition, the SG mine is in the midst of numerous other mines including Spence, Esperanza, Mantos Blancos, El Tesoro, Lomas Bayas, Gabriela Mistral, El Abra, Radomiro Tomic and Escondida, to name a few.The primary organizational value at Sierra Gorda is "Zero Harm." This includes employees, contractors, the environment, the community, plant facilities and mine equipment. A cornerstone of this program is called 5X5S (five by five S), which combines the lean principles of 5S with the safety model of taking five steps back and thinking about the task at hand for five seconds, five minutes, the time it takes to assess and manage the risk. "People caring about people" promotes proactive engagement in the safety of coworkers and others at work and at home."

Jan 1, 2014

By David Mast, Irwan Halim, Brian Hagan, Kaveh Talebi, Jason Edberg, Amanda Foote

On June 14, 2023 Jay Dee Contractors’ Tunnel Boring Machine (TBM) “Phoenix” holed through and completed mining the second drive of the I-75 Segment 3 Storage and Drainage Tunnel. Completion of the tunnel came only after overcoming several challenges, including a groundwater intrusion event which deposited thousands of cubic yards of wet ground material into the tunnel. This paper will discuss the events which delayed completion of the tunnel by over nine months, the risk management and construction approaches assumed by the Design-Build team during bid, several challenges faced by Design-Build teams when building stormwater resilience tunnels using traditional Department of Transportation standards, and recommendations for improving risk allocation and proposal documents for future similar Design-Build tunnel projects.

Jun 23, 2024

By Amado Yataco Medina

Año a año el incremento de muertes por ignición del gas metano o carbón en concentraciones mayores a las soportable, se hace cada vez mayor. Por tal motivo, el presente texto refiere la importancia de las normas de control y seguridad, como las factores sobre la explosividad del polvo del carbon. Entre estos tenemos: la distribución de partículas, composición de polvo, el gas inflamable en el aire, cantidad de polvo, distribución de polvo en la mina, fuentes de ignición, rugosidades de la labor y cambio de sección. Existen dos formas de prevenir dichas explosiones: la primera, es a través de la prevención de acumulación de gas por medio de la ventilación y la segunda, es por medio de la eliminación de las posibles causas de la ignición. Asimismo, se sugiere una serie de recomendaciones de prevención de explosión, como se describe los reglamentos del Código de Minería.

Aug 20, 1965

By M McGrory, A Rodolfo, J Paredes, L E. Manguba, K A Villaspir, G Webb, R Setiagani, H Cardenas

"OceanaGold’s Didipio operation has been in operation for three years. Integral to the flow sheet design is a flash flotation circuit treating a portion of cyclone underflow, consisting of an Outotec SK-500 flash rougher and an Outotec TC10 flash cleaner and a SB-2500 falcon treating flash rougher concentrate to recover fine free gold.Flash copper recovery has been holding steady at 60 per cent, while flash gold recovery at 50 per cent. Gold recovery from the gravity circuit is 22 per cent, bringing the overall flash plus gravity gold recovery to 72 per cent.Operation of the flash rougher is mainly by pulp level control. Control of copper grade in the flash cleaner is mainly controlled by air inflow and flash cleaner pulp level control drives copper recovery. Gold recovery around the circuit is mainly driven by gold head grade.SB-2500 concentrate is scalped with a 250 micron screen with the coarse fraction reporting to a SB-250 falcon, concentrate of which combines with the screen fine fraction to a Gemini table.Citation:Cardenas, H, McGrory, M, Webb, G, Paredes, J, Setiagani, R, Villaspir, K A, Manguba, L E and Rodolfo, A, 2016. Didipio Flash Flotation and Gravity Recovery Circuit, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 123–126 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By M. Westerstrand

The processes involved in the concentration of magnetite ore with process water as the aqueous medium can have a strong influence on the surface properties of the magnetite particles. In this study, different leaching methods, as well as zeta potential measurements, were used to examine the major easily accessible ions on the particle surfaces and their effect on the surface charge. The results show that the enrichment of elements on the surface of the particles appears early in the refinement process. Ca was enriched up to 15 times and Si up to 50 times compared to what pore water alone would have given. The leaching experiments also showed that the addition of water glass increased the surface enrichment of Si and that the collector might hinder desorption of Ca. An alkali leaching method was evaluated, which showed that Si was much more enriched than S and Cl. Zeta potential measurements on synthetic magnetite particles showed that process water resulted in zeta potentials different from the potentials measured for these particles in aqueous calcium and silicate solutions. Therefore, it is important to consider the complexity of the process water when making predictions about the properties of the particle surfaces in the final magnetite concentrate, which most studies do not. Zeta potential measurements were also used to rule out a strong influence from organic matter in the process water on the magnetite zeta potential.

By L W. Palmer

"Evaluating the geological risk associated with ore deposits is becoming common practice in the mining industry. While geostatistical simulation is a useful tool for evaluating this risk, the effect of applying different types of simulation is less understood. For simulation of categorical variables like rock types, available methods perform simulation in fundamentally different ways. In this study, the geological risk relevant for informed mine planning is studied with two categorical simulation methods, PluriGaussian Simulation (PGS) and Sequential Indicator Simulation (SIS). Risk is expressed as a probability of repeated occurrence of lithological units in the same location across simulations. Significant differences are observed between the methods in terms of spatial distribution of risk. To identify the most plausible risk model, the input parameters at every step of both techniques are scrutinised. PGS and SIS inputs are classified as four parameters that are: fundamental to implementation of the methodfixed to enable comparison of PGS and SISdetermined by user interpretation, hence variablenormally optimised during application of PGS and SIS. The effect of parameter selection from categories 1 and 4 on the risk model is investigated using drill core data from a leucogranite deposit. A corresponding block model is created for assigning outputs from PGS and SIS. Risk models produced by either method are illustrated in a cut-out from the block model to enable bench-by-bench comparison. For PGS, risk associated with relatively rare lithologies is relatively sensitive to variation of parameters. Independent of the abundance of lithology, a location-dependent effect of variogram and vertical proportion curve parameter selection is observed, with risk increasing towards the deposit edge. Although SIS requires fewer inputs, single lithologies must be modelled in turn. Using small numbers of samples in the search neighbourhood, all risk models differ substantially. For larger numbers of samples, the risk models are similar. Overall it appears that the risk model produced using SIS is less sensitive to changes than PGS but further work is required to confirm this.CITATION:Palmer, L W and Glass, H J, 2014. Risk associated with rock type prediction using simulation techniques, in Proceedings Ninth International Mining Geology Conference 2014 , pp 217–228 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 18, 2014