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By T Christie, A Swain

Patterns of quartz veining in epithermal gold-silver deposits at Wharekirauponga, Neavesville and Ohui in the Hauraki Goldfield, have been analysed to determine the effects of different lithologies on vein distributions. At Wharekirauponga, quartz veins are hosted in rhyolite and minor andesite, with the andesite containing slightly higher gold grades. Local basement andesite, rhyolitic tuff and silicified black shale host gold-bearing quartz veins at Neavesville. At Ohui, quartz veins are hosted in rhyolite, rhyolitic tuff and andesite. Fractal analysis was used to quantitatively describe the distribution of veining. The fractal dimension (D) of veining in silicified tuff is 0.25, moderately silicified rhyolite has D = 0.23 - 0.26, clay-altered andesite has D = 0.3, strongly silicified rhyolite has D = 0.3 - 0.39, silicified andesite has D = 0.4, and silicified black shale has D = 0.43. The D values are related to the composition of the host rock, and appear to be controlled by its competency. Hydrothermal silicification results in increased competency and higher D values. Vein thickness frequency plots for different lithologies show that andesite at Ohui, and to a much lesser degree at Wharekirauponga, contains more thick veins than rhyolite and tuff. Gold grades show a strong to fair correlation with higher vein density in three drillholes at Wharekirauponga. The fractal dimension of veining is an important control on fluid flow and gold deposition within an active epithermal system. Vein systems with higher D have a greater density of veining which would have favoured increased fluid-rock interaction. Lower D vein systems have more clustered arrays. The increased fluid-rock interaction induced by a high D vein system, when combined with a reactive host rock, results in an environment which is highly favourable for gold deposition. This situation is seen in the andesite at Wharekirauponga.

Jan 1, 1994

By J J. Hanhiniemi, M S. Powell

A ‘Variable Blend and Rates’ model is developed for SAG mills which extends upon the JKSimMet® Variable Rates Model. Similarly, a ‘Variable Blend Residence Constrained Perfect Mixing’ Ball Mill model is also introduced, also extending upon the existing JKSimMet® model. These models are used in conjunction with JKSimMet® while employing external technical programs. The technical model is then used to inform an economic model described elsewhere in Hanhiniemi and Powell (2022), which calculate operating and unit costs based on operating conditions, design, and ore characterisation. The SAG and ball mill models include constraints beyond those in the JKSimMet® models. The SAG model constraints include Size Specific Energy (SSE) verification, charge weight limit, and assessment of the impact of media to ore composition in the charge using the SAG Charge SSE Model developed in this paper. The ball mill model includes residence time, volumetric capacity, and SSE verification constraints. These models are applied to Cortez Gold Mine in the processing of two very different ore types and their blends; ‘Horse Canyon’ which is softer in coarser sizes and competent is fine sizes, and ‘Wenban’ which is competent at coarser sizes but softer in fine sizes than Horse Canyon. Horse Canyon also has a finer run-of-mine size distribution then Wenban. The application of the model at this site included undertaking five surveys at varying blends. The behaviours of the blends and individual components is then studied in the SABC circuit. A nonlinearity is observed with throughputs increasing with blending. The newly developed modelling approach captures these responses. Controlled blending based on ore competence-by-size and size distribution was implemented by the site, which then realised significant improvements in throughput without any capital cost (Ntiamoah et al, 2020). The modelling developed in this paper is then compared to existing practice, and the new method was found to provide improved fidelity and utility. A three-dimensional surface is then developed using the model describing the SAG mill throughput capacity at varying conditions (speed-filling) versus varying blend. The change in throughput as a function of only the changing charge composition is presented. The result is nonlinear, and explanations are provided to describe this behaviour.

Aug 24, 2022

By Scott Chesman

Increased TBM performance is leading the way for resurgence in tunneling activity in NYC. Tunnels will be excavated in the same geologic formations as previously excavated D&B tunnels whose construction records are providing valuable insight into the prediction of rock mass behavior. This report compares an eight mile stretch of NYC Water Tunnel #2 with the recently excavated eleven mile stretch of the TBM driven Water Tunnel #3. Comparisons of the type and amount of rock support installed as well as water inflows and grout quantities are made. Rock mass characteristics specific to TBM performance are also evaluated.

Jan 1, 2005

Researchers from the National Institute for Occupational Safety and Health (NIOSH) are developing a coal pillar rib rating (CPRR) technique to measure the integrity of coal ribs. The CPRR characterizes the rib composition and evaluates its impact on the inherent stability of the coal ribs. The CPRR utilizes four parameters: rib homogeneity, bedding condition, face cleat orientation with respect to entry direction, and rib height. All these parameters are measurable in the field. A rib data collecting procedure and a simple sheet to calculate the CPRR were developed.

Jan 7, 2020

By Holger Witthaus

Various seam conditions had been examined during longwall production at RAG German hard coal mines. Based on the field data a prediction method was developed considering separation planes as influencing factors for roof falls at the face. The characteristics, orientation, and density of separation are important factors on the occurrence of roof falls. In addition to geological influences, the performance parameters and geometry of support must be considered and optimized for the prediction and prevention of roof falls in a longwall face. Based on detailed macro- and microscopic investigations of e coal seams considering various ranks of carbonization, the origin and characteristics of separation planes are determined and a strata-specific influence on roof fall is interpreted. It was assessed that the coal face fracturing and displacement caused by the stress depend on the floor and roof strata conditions due to activation of the existing separation planes. Field studies are shown giving an idea of influences by advance rates of the longwall face, support delay and hydraulic pressure to the roof control in longwall faces in depth of more than 3000 ft. The analysis includes the application of specific software developed for longwall roof fall prediction as a result of a European research project. The software allows a laminar graphic display of roof fall probability, which is used for recognition of risk areas and risk management.

Jan 1, 2009

This paper is in two parts. The first part provides background to coal in New Zealand, information on Solid Energy the Company and details of the resources, mines and products of the company. This part of the paper is intended for people who have limited knowledge of the New Zealand coal scene. The second part of the paper focuses on developments underway in New Zealand and discusses planned or possible changes and opportunities. This paper was first presented at the Coaltrans Asia Conference in June 2000.

Jan 1, 2000

Atlas Copco Construction and Mining Australia identified a number of issues in regard to the skill levels, labour turnover and productivity of our service technicians. In 1994 we were experiencing a labour turnover rate of 42 per cent per annum amongst our technicians. Exit interviews were held with each individual and one of the major areas of dissatisfaction was the degree of product training provided on our equipment, compared to what is required to be competent across the range of our products. These tradespersons were prepared to accept the reduced remuneration that an OEM offers, for the benefit of comprehensive, professional training that, in theory, could be provided. The truth is that we were achieving approximately 40 per cent of our target for training hours because of the demands of field service, pre-deliveries, etc. So, the summary was the same as the industry was experiencing at that time because of skilled labour shortages, production demands, etc people were employed and thrown in at the deep end. A recipe for failure that will be successful every time.

Jan 1, 1998

By David S. Yantek

Miners in underground coal mines experience prolonged exposure to high noise levels, often with A-weighted sound levels in excess of 90 dB. Field tests have shown that the continuous miner conveyor is a dominant noise source. This paper will identify the most significant noise-radiating surfaces on the continuous miner tail section using vibration levels and surface areas to estimate the sound power levels of each surface. In addition, using five test cases, this study will examine the effects of three engineering noise controls on the surface-averaged vibration levels and average sound levels measured with four microphones located two meters from the tail section. The noise-radiating surfaces of the conveyor’s tail section include the top and bottom decks, the sideboards, and the flex plates. Emphasis is placed on the changes in the estimated sound power levels in the 500 – 2500 Hz 1/3-octave bands since this frequency range accounts for 80-85% of the sound energy near the tail section. The results show that the bottom deck is the most significant noise radiator for the untreated miner. Installing a coated bottom deck reduces the estimated sound power level radiated from the bottom deck by 11 dB and the average sound level by 2 dB. Using a coated tail roller results in reductions of the estimated sound power levels for individual components from 1 to 4 dBand reduces the average sound level by 2 dB. Coating the slide plate has little effect on both the estimated radiated sound power levels and the average sound level. The test results indicate that modifications that reduce flex plate vibration and reduce energy transfer from the tail roller into the tail section will be effective in reducing noise when combined with a coated tail roller and coated return deck.

By Ljiljana Solujic

The need for the removal of mercury from the precious metals extraction circuits may be influenced by process, environmental, as well as by occupational hazard reasons. In these circuits mercury is mainly present as cyanide complexes. The effectiveness of any stabilization method will be influenced by the high thermodynamic stability mercury-cyano species exhibit in an aqueous solution. In this study, we have investigated the utility of the trisodium salt of trimmercapto-s-triazine (TMT) for precipitation of mercury from the corresponding cyano-complexes. The influence of pH molar ratio of TMT to Hg, coagulant and flocculant additions, excess of free cyanide, as well as the presence of other metal-cyano species on the effectiveness of mercury precipitation were investigated in detail. Also, a "teal world" precious metals mill effluent initially containing ~7 ug/mL (ppm) of Hg was treated and A was found that greater than 99.8% of the mercury was removed from the solution as am insoluble Hg/TMT complex.

Jan 1, 1996

By R. J. Pine, J. S. Coggan

Distinct-element modelling has been used to study the mechanisms associated with observed deformation of the western face of the quarry. A complex failure mechanism involving distinct planar surfaces that was proposed for a slope failure in 1967 has been modelled and shown to be plausible. In addition, deep-seated flexural toppling may contribute to the slope instability. Modelling has confirmed the detrimental influence of a raised water-table on the stability of the slope and also indicates that the observed cyclic opening and closing of tension cracks may be attributed to seasonal rise and fall of the groundwater level

Apr 1, 1996

By George K. Burke

Jet grouting was first introduced into North America in the late 1970's, soon after the conception of the system in Japan. However, it was not until the mid-1980's that the technique began to gain acceptance through the renewed interest and efforts of specialist U.S. geotechnical contractors. Since this time, innovations by both American users and other users worldwide have further advanced the technology, with a corresponding increase in the range of practical applications. This paper discusses the evolution of jet grouting in North America, from simple single-fluid methods to more complex triple-fluid methods, to the energy-intensive double-fluid and SuperJet methods. Case histories, illustrating a variety of jet grouting methods and applications, are cited to support the newest United States applications.

Jan 1, 2002

The Effects of Collector and Grinding Environment on the Flotation Selectivity of Rosh Pinah Pb/Zn Ore

Sep 13, 2010

By F. J. Chernosky

Most previous studies of coal flotation utilized chemically pure reagents. Since such reagents are not available in quantity, a study of various wmmercially available reagents as frothers was undertaken. Flotation procedures similar to those used in a large number of commercial coal flotation plants were employed. The reagents used were compared on yield-selectivity-wst basis. The selectivity was found to be relatively constant with yields above 70% but the reagent cost varied greatly. The types of reagents available were compared. In the past, a number of papers have been written on the use of various reagents as coal flotation frothers. For the most part, these have been an attempt to correlate the intrinsic chemical and physical proper- ties of the reagents or reagent groups to the floata-bility of various fine coals. Because of the type or nature of evaluations made, chemically pure reagents were normally used. Generally, these reagents are unavailable in commercial quantities. Therefore, the results obtained with these reagents were usually limited in usefulness to the plant operator or metallurgist. This paper presents the results of a study in which commercially available forms of various reagents were used as flotation frothers. Flotation procedures which would conform in general to those employed in a large number of commercial coal flotation plants were utilized. The objective of the test was to compare these reagents on yield-selectivity-cost basis, that is, 1) the yields obtained, 2) the ash levels obtained and 3) the reagent cost relating to these results. REAGENTS The reagents employed have been grouped into the following chemical classes: 1) aliphatic alcohols, 2) terpines, 3) glycols (synthetic water-soluble

Jan 1, 1963

Surface Plasmon Resonance (SPR) spectroscopy, combined with cyclovoltammetry, has been successfully used to study the interactions between ethyl xanthate, heptyl xanthate, dithio-phosphate and propyl trithiocarbonate flotation collectors and a gold surface. Large, easily measurable responses have been obtained in the potential areas where the thiol collectors are known to interact with gold. The four collector types lead to differing SPR maximum values, with longer alkyl chains resulting in higher SPR responses, and the trithiocarbonate leading to the highest response values. The SPR responses differ considerably from the current density response at very anodic and cathodic potentials. There are indications that thiols might still be adsorbed at potentials as low as-300 mV (vs SHE). Keywords: flotation collectors; thiol collectors; cyclovoltammetry; surface plasmon resonance spectroscopy.

Jan 1, 2005

By Joe B. Rosenbaum

Fine-sized mineral wastes discarded by ore milling plants require stabilization to prevent air and water pollution. Methods devised for achieving this stabilization include physical, chemical vegetative, and combination procedures. Although vegetative reclamation is preferred to physical and chemical stabilization, it is difficult to achieve because the wastes are sterile, contain deleterious inorganic salts, and lack the essential nutrients and physical characteristics required for sustaining vegetative growth. Nevertheless, recent research has developed methods for producing vegetative growth on all but excessively acidic, basic, or saline tailings at costs ranging from $100 to $650 per acre. This report summarizes effective procedures developed for vegetating average tailings, the cost differential between the various methods, and suggests procedures that may be applicable for achieving stabilization of pyrite-containing wastes that may oxidize and become excessively acidic. The use of buried layers of sewage sludge to prevent this acidification is discussed.

Jan 1, 1972

By M. A. Trevits, I. R. Houlison, A. C. Smith, T. P. Mucho

Timely and rapid intervention to underground combustion events (fires, explosions, and spontaneous combustion) is the key to the successful control of the mine atmosphere and restoring of a coal mine to production. The focus of this paper is the utilization of a GAG 3A jet engine system to combat either large out-of-control fires or to render an entire mine inert when access to problem areas is difficult or impossible. This system is based upon a Soviet designed agricultural jet engine which consumes aviation fuel with oxygen (O2) from the intake air and exhausts combustion gases, primarily carbon dioxide (CO2) and water (H2O), along with the nitrogen (N2) from the air and small amounts of carbon monoxide (CO) and hydrogen (H2). The system is designed to approach stoichiometric combustion (ideally, pure burning that scavenges all the oxygen from the intake air). Therefore, these exhaust gases are almost entirely “inert gases”- i.e., gases which do not contribute to, and in fact, can suppress the combustion process due to the lack of oxygen. Other methods to inert mine areas have been used in the US and internationally, but these methods usually use low flow inertisation equipment or methods. Use of these low-flow inertisation equipment and methods has been successful in proactively rendering gob areas inert and has the ability to inert the entire mine workings. Due to the low flow rate, however, a substantial period of

By A. Takala, B Nielson, J. Schunicht

"Pre-concentration in minerals processing presents clear advantages in energy efficiency, water efficiency, reduction of consumables and minimization of capital and operating costs. Outotec’s sorting solutions are powered by Tomra Sorting in order to achieve pre-concentration of concentrator feed in a variety of mineral processing applications. Sensor based sorting combines advanced sensors with rapid computational evaluation and mechanical separation of valuable material from waste and/or gangue. Modern sensor based sorting machines typically use fine air jets to propel individual rocks, thus optimizing recovery and minimizing “mis-sorting”.Gold is generally present in such low concentrations that sensors suitable for ore sorting cannot directly detect it. Therefore, in order to sort gold ore, properties of associated host rock are used. Free and sulphidic gold is often hosted on the quartz-host rock contact zone. Laser scattering effect can be used to detect the surfaces of quartz and composite quartz-host rock particles for subsequent sorting with very high recovery of 95 to 99%. In addition, ore often preferentially fractures along the quartz-host rock contact zone in the crushing circuit. This behavior helps because it liberates more quartz for detection.The feasibility of sorting is investigated for four gold projects in Northern Europe with similar mineralogy. This includes geometallurgical evaluation, amenability testing, small scale “mini-bulk” factory testing in full scale sensor based sorting. The results of the various tests are presented and basic feasibility demonstrated with information on flow sheet development. In addition, the amenability process is evaluated and recommendations made for future projects."

Jan 1, 2017

By C. R. Edwards

"Equity Silver Mines Limited, Canada's largest silver mine, has designed, built and operated a leach plant to reduce the levels of antimony and arsenic in its silver-gold-copper flotation concentrate. The orebody contained deleterious antimony and arsenic minerals in such proportions that the economic long-term sales contracts necessary to obtain project financing could not be procured. Construction of the leach plant therefore allowed development of the mine to proceed. Although the plant took some time to reach design throughput and product specifications, due to the complex and unique nature of the operation, these goals were successfully met and surpassed. This paper describes the physical plant and/or process technology modifications made to mold the main processes-concentrate leaching and filtering, autoclaving and filtration of by-products, and crystallization of salt cake-into an effective, economic operation.IntroductionEquity Silver Mines Limited, a member of the Placer Development Group, owns and operates an open-pit silver mine and related facilities located 37 kilometres southeast of Houston in north-central British Columbia. The mine occupies a 44 I-hectare (1089 acre) site at an elevation of 1300 metres (4265 feet) on the Nechako Plateau. Producing a copper concentrate containing high values of silver and gold, it is the largest silver mine in Canada and one of the largest in the western world. Equity stresses open communications, positive motivation, and production with safety, and achieved the best mine safety record in western Canada in 1984."

Jan 1, 1985

By NRMR Bhargava

With the increasing use of lead-free solder alloys, low melting point alloy is often required due to the heat- sensitive parts or substrates in modern electronic devices. For such demand of low melting point, the nanostructure lead- free solder alloy, having excellent metallurgical characteristics and a melting point of <215oC, were developed by mechanical attrition of conventional lead free solder alloys (Sn-Ag-Cu, Sn-Ag and Sn-Cu). The decrease in melting point due to nanosize effect was calculated theoretically as function of particle size and the theoretical results were compared with experimental values measured by differential scanning calorimetry. The newly developed alloys have eutectic composition of Sn-3.5Ag-0.7Cu, Sn-3.5Ag and Sn-0.7Cu and the melting point depression found to be 5.10C, 4.10C and 6.20C when the bulk alloys reduced to 80 nm, 92nm and 96nm sizes respectively.

Jan 1, 2009

By John G. Payne

The Pebble deposit contains three contiguous zones. In the Pebble West zone, granodiorite stocks intrude gently warped volcanosedimentary rocks that had been intruded by diorite sills and two felsic intrusion breccias. In the Central zone, volcanosedimentary rocks are cut by diorite and granodiorite sills; the latter are genetically associated with the granodiorite stocks. In these zones, widespread potassic alteration consists of brown biotite and K-feldspar, with abundant quartz-carbonate-sulphide vein stockworks. Chalcopyrite/pyrite ratios range from 2/1 to 1/20. Diorite hosts the highest-grade mineralization, with much of it being disseminated. Patchy, later phyllic alteration is moderate and commonly depleted in copper. The Pebble East zone occupies a granodiorite stock and intruded host rocks below an eastwardly thickening wedge of barren Tertiary volcanic and sedimentary rocks up to 600 m thick. Brown biotite alteration and copper mineralization are strong, with chalcopyrite/pyrite ratios commonly over 1/1. The zone extends to a depth of at least 1200 m below surface; some drill holes bottomed in strong mineralization. Later, weak to moderate sericitic alteration removed some chalcopyrite and locally remobilized gold. The Pebble deposit has a Measured/Indicated resource of 3 billion tonnes grading 0.28% Cu, 0.32 g/t Au and 0.015% Mo (= 0.5% copper-equivalent) and an Inferred resource of 1.13 billion tonnes grading 0.30 g/t Au, 0.27% Cu and 0.015% Mo (0.55% copper-equivalent). The Pebble East zone has an Inferred resource of 2.13 billion tonnes grading 0.55% Cu, 0.34 g/t Au, and 0.037% Mo (0.97% copper-equivalent). The Pebble East zone is open to the east and to a lesser extent to the north, south, and to depth.

May 1, 2006