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By Pawan Bharadwaj, Wim Mulder, Thomas Tscharner, Guy Drijkoningen, Rob Jenneskens

"The Earth’s properties, composition and structure ahead of a tunnel boring machine (TBM) should be mapped for hazard assessment during excavation. We study the use of seismic-exploration techniques for this purpose. We focus on a seismic system for soft soils, where shear waves are better and easier to interpret than compressional waves, as has been shown over the last decade. The system is intended to be deployed on the machine’s cutter head, with a few seismic sources and sufficiently many seismic sensors to tackle spatial variability and noise characteristics. An important property of the newly developed system is its ability to process data with very little human interaction. Images need to be available in near real time, without human interactions slowing down the imaging process. This can be achieved by employing Full Waveform Inversion, which minimizes the difference between modeled and observed data. Because this method may suffer from local minima in the cost function if the data lack low-frequency information, we employ a dedicated seismic source that can generate sufficiently low frequencies for the relevant length scales. With data acquired in a number of field settings that mimic realistic TBM configurations, we show that the designed seismic system can successfully look ahead of the TBM and offers a valuable capability to support decision-making during tunnel excavation. INTRODUCTION While excavating a tunnel with a Tunnel Boring Machine (TBM), the geology and the ground conditions along the planned tunnel trajectory need to be investigated in order to safely and efficiently carry out the underground operations. This entails detecting the occurrence of boulders, foundations, pipes and faults, necessary to prevent hazards and time-consuming delays in the tunnel boring operations. In order to facilitate ground prediction ahead of a TBM, techniques as used in seismic exploration can be deployed. Two components common to seismic-exploration techniques are data acquisition and processing, the latter including inversion. We will discuss each of these for the application to tunnel excavation with TBM, in particular for soft soils."

Jan 1, 2016

By C. T. Aimone-Martin, B. M. Meins

This paper compares response of large urban structures to small charge weight, ultra-high frequency rock blast excitation from contiguous excavation to that of houses to more distant, larger charge weight blasts. Time correlated responses were measured for both structures at the corners, top and bottom of the structures as well as in the foundation rock below the bottom. The comparison allowed the following conclusions: Close-in blasting with direct rock to building wave transmission imposes short wave length excitation which fails to excite the large, massive structures synchronously whereas the more distant blasts do synchronously excite houses. The larger urban structures respond predominantly in wave transmission mode where there is a noticeable difference in time, frequency, phase and amplitude of motions measured at the bottom and top corners of the structure. Excitation motions along the base of the larger urban structures also differs in time, frequency, phase and ampli-tude. The short wave length of the excitation motions leads to attenuation of the peak particle veloc-ity along the base. Ultra-high excitation frequencies, which are much higher than the expected struc-tural natural frequencies, lead to deamplification for all events for the large urban structures.

Jan 1, 2018

By J. C. Folinsbee, D. R. Derry

"The Property of Opemiska Copper Mines (Quebec) Ltd. is in Levy Township, Chibougamau district, west of Chibougamau and south of Opemiska Lake. The original find was made in 1929 by the late Leo Springer and associates of Prospectors Airways Ltd., following observation from the air of an area of dark rocks in newly burned-over country. Work on the ground discovered three veins of high-grade chalcopyrite in gabbro (No. l, No. 2, and ""North"") and, after several seasons of trenching and diamond drilling, financed by Ventures Ltd., a shaft was sunk in 1936. This work indicated about 280,000 tons of six per cent copper ore to a depth of 500 feet. During this period, the senior author carried out a reconnaissance geological survey over the whole property and surrounding claims, which showed that the veins were in the gabbro portion of a large composite basic sill that had been folded with the enclosing lavas. Owing to the low price of copper and lack of transport work was suspended and the property remained dormant until 1951.In that year the company was re-financed, the property prepared for production, and further exploratory drilling undertaken. The drilling, based on structural indications, located a new vein of which the only previous evidence had been some irregular stringers. This vein, No. 3, was traced by drilling for a length of 2,000 feet and the indicated reserves were thereby increased to about one million tons. An additional vein, No. 4, was intersected in several holes.With this encouragement, plans for production were confirmed, and operations commenced' at the beginning of 1954 on a scale of about 400 tons a day, concentrates being shipped by truck to St. Felicien and thence by rail to Noranda. In the first year of operation concentrates were re-covered carrying 14,047,210 pounds of copper, 76,714 ounces of silver, and 6,259 ounces of gold. The operation is under the direction of J. P. Millenbach, General Manager, with J. M. Thompson as Assistant General Manager and F. G. Cooke as General Superintendent on the property."

Jan 1, 1949

By J. Brendan Mclaughlin, Casimir J. Koshinski, Michael V. Rose, Wolfgang Baum

Mercury contamination is a worldwide problem in the mining, smelting, and refining of gold, silver, and copper. In these areas, mercury may be found as a naturally-occurring material in ores and concentrates, and/or in secondary feedstocks such as leach residues, pyrometallurgical treatment residues, refinery by­products, electrowinning electrodes, autoclave discharge solids, and waste water and acid plant sludges. The United States Environmental Protection Agency (EPA) has designated mercury one of the most harmful heavy metal contaminant in the environment and has implemented regulations that prohibit land disposal of characteristically hazardous wastes containing greater than 0.20 mg/1 TCLP mercury without prior treatment, thus increasing the cost of managing these materials. The presence of mercury in mine, smelter, and refinery by­products and wastes severely decreases, and in some cases eliminates, the ability to recover residual metal values from the contaminated material. The lost revenue associated with this disposal, combined with the increased direct cost of waste treatment, and/or disposal and protecting workers and the environment, can adversely affect overall profitability. The safe, efficient, and economical removal of mercury from gold, silver, and copper mining by-products requires a treatment process that is capable of liberating the mercury from the wide variety of compounds and matrices in which it may be contained, reducing the mercury content in the matrix to desired levels, and recovering the mercury in pure saleable form, without producing any secondary solid, liquid, or gaseous wastes. This paper reviews results from commercial operations and pilot scale tests using a thermal process owned and operated by Mercury Recovery Services, Inc. (MRS) to remove and recover mercury from copper acid plant blowdown sludge, Merrill­Crowe precipitate from gold/silver mining operations, and Cottrell and salt slag dusts from a precious metals refinery.

Jan 1, 1997

By Karl Fetters

IN the process of making steel in the open-hearth furnace the refining of the metal during the working period of the heat is largely accomplished through the agency of the slag. From the birth of the process until the present day steelmakers have recognized the importance of the slag in determining the composition of the metal and the quality of the product. The general relationships between slag composition and metal analysis have long been known, at least in a qualitative or approximate fashion. For examples, the iron oxide content of the slag is higher on lower carbon heats; the more basic slags are higher in iron oxide for a given carbon content; certain amounts of iron oxide and lime are required for phos-phorus removal and a high lime-silica ratio is needed if the sulphur content of the metal is to be diminished. In recent years a number of quantita-tive relationships involving these and other variables have been developed through plant and laboratory studies by numerous investigators in this country and abroad. The direct comparison of laboratory and open-hearth data involves the question of the degree to which each approaches the conditions of chemical equilibrium, a question which, from the open-hearth standpoint, we are scarcely yet in position to answer. And, although a considerable body of dependable equilibrium data has been obtained in the laboratory, this work has not yet been extended to cover the ranges of slag composi-tion encountered in basic open-hearth practice. In the present study we shall not attempt to draw comparisons between data from the two sources; nor do we attempt to draw conclusions as to the approach to chemical equilibrium in the open-hearth furnace. Many of the operating variables that are likely to be erratic or unrecorded during the earlier stages of the heat become more consistent and are more readily subject to observation and control during later stages. For example, undigested lime or ore gradually goes into solution, the rate of carbon drop levels off, and the temperature of the metal is brought under control. For these and other reasons a greater degree of self-consistency is likely to be found among data obtained during the

Jan 1, 1940

By Peter Scales, Ricardo Jeldres, Fernando Concha, Pedro Toledo, Shane Usher, Anthony Stickland

The impact of several electrolytes present in seawater on the rheological properties of flocculated mineral suspensions was assessed using the creep test. Flocculated suspensions were obtained by adding polymer flocculant to a cylinder of mineral suspension and aggregating the suspension using the plunger method. The suspension was allowed to sediment and the supernatant liquid decanted prior to tests for the viscoelastic properties of the resulting sediment. The solid used was alumina AKP-30 both, below and above the isoelectric point. The polymer used was AN934SH, an anionic flocculant with high molecular weight. Salts analyzed were MgCl2, CaCl2 and NaCl, known as water structure makers, and KI and KCl, known as water structure breakers. A high salt concentration of 0.5 M was used to approach the ionic strength of seawater. For both pH’s studied, the sediments demonstrated a viscoelastic non-linear behavior observed as a non-linear relationship between yield strain and applied stress. In the absence of flocculant, it was observed that the viscosity and yield stress of a suspension increase in the presence of structure maker salts for the case of both silica suspensions and alumina suspensions. These results were explained using hypernetted chain statistical mechanics models describing the interaction of ions with solvated surfaces. In contrast, with the presence of flocculant, the shear yield strain of alumina suspensions increases with the breaker character of the salts, however, this result has been explained by an extension of the results from the models. The work has significant implications for the flocculation of mineral suspensions in the presence of seawater.

Jan 1, 2014

By W. Zhang

"Western China has many shallow coal seams. Mining of these shallow seams contributes to environmental deterioration in part due to disruption of groundwater sources. The lowering of the phreatic surface is attributed to the instability of the impermeable rock groups as a result of mining leading to an increase in permeability and drop in phreatic surface. Underground mining with partial backfilling is one of the fundamental methods of controlling the lowering of the water table in sensitive cases. At present, although significant research has been done in shallow seam mining, there has been no research on the laws governing the movement of impermeable rock groups in partial backfill mining using backfill materials of lower strength. this research, conducted in the Yu Shen-fu region of Western China, developed similar material of sand-based paste filling materials, tested the mechanical parameters of similar material of sand-based paste filling materials, researched on long wall partial backfill mining through similar simulation experiments, obtained the development of “upward fractures” and “downward fracture” under different gap-filling widths and body-filling widths and the movement law of impermeable rock groups under different gap-filling widths and body-filling widths. INTRODUCTION Jurassic coalfield is in the North of Shaanxi province in China, located in border areas of the Maowusu Desert and the Loess Plateau, water resources of Jurassic coalfield in the North of Shaanxi province is meager, ecological environment is fragile (Wang, 2010). With the large-scale development of the mining area, permeable fracture zone will directly affect and spread to the aquifer, causing direct damage to water sources, and lead to the dried up of reservoir, river, wellspring which is recharged by the aquifer(Qian, 2003). There are many researches on aquiclude or impermeable rock groups of shallow coal seam in china, but researches are mainly based on the key strata theory characterized by hard rock as skeleton, without considering the flexibility of impermeable rock groups which is important to reduce the cost of control (Huang, 2010). There are some researches on the stability of impermeable rock groups, but the researches are mainly on permeable fracture zone, which is also called the ""upward crack"" (Wang, 2010), ignoring the influence of the ""downward crack"" on the edge of subsidence basin of impermeable rock groups (Huang, 2010). Previous researches showed that pillar-and-room mining can control the rock crack and surface subsidence (Qiu, 2013), but with the loss of coal resources, and existing disaster a threat of a large scale roof falling. Partial backfill mining mainly by eolian sand bring hope to water-preserved-mining (Fan, 2000), successful practice of paste material backfill mining under buildings and water(Song, 2010)showed its feasibility. Through useing the filling materials with low strength, flexibility and small ratio of height to width, eliminated the threat of a large scale of roof falling, the quantity of partial backfill materials relative to full backfilling are little, the price of sand paste backfilling material is low(Huang, 2011), through designing rational parameters of partial backfill mining, we can achieve the purpose of protecting the phreatic. In this paper, based on the similar simulation experiments, researched on development of the ""upward crack"" , ""downward crack"" and subsidence of impermeable rock groups, researching results can provides the rational parameters to partial backfill mining, and can reduce the cost of filling mining."

Jan 1, 2015

By Steven G. Jansto

Nearly one third of the globally produced structural flat and long structural products are in the 0.11 to 0.16% carbon range. By definition, numerous steelmakers globally define this approximate carbon range as peritectic in their melting grade family within their organization. The metallurgical consequence is the result of numerous global structural specifications which allow carbon to wide carbon ranges resulting in quality issues. For example, such specifications as ASTM A588 set no minimum carbon and a 0.15 to 0.19%C maximum depending on the specific grade designated within the specification. This peritectic region is specifically challenging in production compared to less than 0.10%C because of solidification issues and a higher propensity for slab or billet cracking during continuous casting. During hot rolling, rejects and/or deviates are increased as well. The relative steelmaking operational cost of production is compared between peritectic and non-peritectic carbon compositions for a given specification.

Aug 17, 2017

By Jochen Petersen, David G. Dixon

"Although heap leaching may be perceived as a somewhat low-tech route for the extraction of low-grade minerals, the underlying physical, chemical and biological processes are in fact extremely complex. There has been increased interest in heap leaching of sulphide minerals in recent years with the advent of controlled bio-heap leaching, and the need to mine more marginal ore deposits.A detailed investigation into the dynamics of heap leach processes has provided much insight into the underlying complexities, and has led to the development of a sophisticated modelling tool. Some of the features include mineral kinetics, particle level effects, bacterial growth, oxidation and adsorption, gas adsorption, pore diffusion, bulk advection, gas balance and heat conservation.Two case studies are presented which illustrate specific features of the model for different applications and how these have helped to identify key areas of concern. In each case the model has proved as an invaluable tool either for the improvement of existing heap leach practice or for the development and assessment of novel applications."

Jan 1, 2003

By C MacRae, N Wilson

CSIRO Minerals has recently developed an electron microprobe (EMP) based imaging (or mapping) method for characterising ilmenite concentrates. The method requires an electron microprobe analyser to collect elemental X-ray maps which are then processed via an in-house developed software module (CHIMAGE). The type of information readily available from EMP mapping includes; primary phase identification, modal analysis of phases, chemical analysis of individual phases, textural information (eg the alteration stages in the formation of leucoxene or pseudorutile from primary ilmenite and the development of macro-porosity), and the identification of coatings or pore-fill material. All of these parameters will impact on the choice of future downstream processing options considered for any particular ilmenite concentrate. The method has been demonstrated to be a sensitive analytical tool for assessing the distribution of aluminosilicate minor impurities in ilmenite feedstocks from the West Coast of Australia and also for characterising the complex chrome-spinel gangue phases common in East Coast ilmenite concentrates from the Murray Basin.

Jan 1, 2001

By K. Hawboldt, J. E. Halfyard, C. Bottaro, I. A. Harrison

"The removal of elemental sulfur from leach residues derived from massive sulfide concentrates via hydrometallurgical routes has been demonstrated in a laboratory setting by converting water-insoluble sulfur to water-soluble polysulfides. The approach was applied to leach residue from Vale's nickel hydromet demonstration plant in Argentia, Newfoundland, which contained significant amounts of elemental sulfur. This technique offers an alternative treatment protocol for residues with a sulfur component not amenable to standard flotation/hot filtration processes. The practical considerations of a proposed flow sheet will be discussed including the impact of other sulfur species (e.g. thiosulfate and sulfides) and key process variables. INTRODUCTIONPresently, large scale elemental sulfur extraction from hydrometallurgical leach residue is performed by Teck Resources using a process of sulfur flotation followed by hot filtration (Chalkley et al., 1993). As mentioned, the technique proves viable for residues derived from specific concentrations - in this case zinc - whose residues constituency is primarily elemental sulfur itself. However, problems arise when this constituency is altered as happens when, for example, a mine containing one particular concentrate is mixed or replaced with a differing concentrate from a second mine. Such cases can often strain the effectiveness of current sulfur removal processes (D'Odorico, 2004). If hydrometallurgical residue containing elemental sulfur cannot be effectively treatment by flotation, the residue is stored subaqueously as is the case in some 'grass roots' hydrometallurgical plants (those not coupled with smelting operations). Hydrometallurgical processing of concentrates involving pressure leaching is becoming increasingly common throughout the mining world, the genesis of which can be found in research performed by Sherritt in Fort Saskatchewan since the 1950’s (Ozberk et al., 1995).The investigation of elemental sulfur removal by means other than flotation includes the uses of sulfide salts (NH3S or Na2S) effecting the conversion of hydrophobic elemental sulfur to hydrophilic polysulfides. The work of Kunda et al. (1974) and Olper et al. (2007) shows that elemental sulfur can be quantitatively removed from hydrometallurgical leach residue via the formation of a mixture of polysulfides."

Jan 1, 2012

Provide the U.S. mining industry with the means to measure and control exhaust emissions of diesel engines used in underground mines. Approach Diesel research is divided into four primary areas: exhaust aerosol measurement, particulate control, gaseous emission control, and chemical and biological characterizition of particulate matter. Diesel research is frequently cosponsored by industry; collaborative research ventures between industry, academia, other government agencies, and the Bureau arc common. Diesel research at the Bureau is conducted in the diesel engine research facility at the Bureau?s Twin Cities Research Center (TCRC). This facility is a state-of-the-art laboratory capable of performing emissions testing, exhaust control evaluations, and safety tests. Background Exposure of mine workers to airborne contaminants from diesel engine exhaust is potentially harmful. The National Institute for Occupational Safety and Health has recommended that whole diesel exhaust be regarded as "a potential occupational carcinogen" and that ?reductions in exposure to diesel exhaust in the workplace would reduce the risk." The U.S. Mine Safely and Health Administration (MSHA) convened an Advisory Committee on Standards and Regulations for Diesel-Powered Equipment and is beginning to implement its recommendations, which cover health, safety, and certification and approval issues surrounding the use of diesels underground. In January 1992, MSHA published an advance notice of proposed rulemaking to regulate diesel particulate matter in underground mines.

Jan 1, 1992

By B. Caro Vargas

The Toulon Tunnel project is a key component of the highway corridor on the French Riviera between Marseille and Nice and is a fundamental transportation infrastructure for the region. The first design studies started in the 1960s. The tunnel project is comprised of two separate tunnels: south and north. The north tunnel was built between 1992 and 2002 after 10 years of difficult construction. On March 15, 1996, for example, a collapse of the tunnel in the Marchand area generated a sinkhole in the city center, causing a 20-month delay. The south tunnel alignment runs parallel to the north tunnel below Toulon?s historical downtown at a depth of 20 to 40 m (65 to 131 ft) with some areas with less than 10 m (32 ft) of cover. The risk management program was studied to be a state of the art program in urban tunneling construction.

Jan 1, 2012

By G. Armand, G. Arnold, A. Giraud, C. Auvray

The knowledge and understanding of the mechanical behavior of claystone is of critical importance in the aim of nuclear wastes storage. In this study, specimens of Callovo-Oxfordian claystone (COx) have been obtained from the ANDRA underground research laboratory in Meuse/Haute-Marne (France). This claystone is composed of carbonate inclusions (10-50µm) embedded in an argillaceous matrix (representing expanding clay minerals, such as smectites). The matrix itself is also multiphase and composed of clay aggregates of 1µm-size carbonate and quartz inclusions. This multiphase microstructure leads to a high heterogeneity witch was analysed through nanoindentation test grids. Moreover, the mechanical behavior of the claystone matrix is highly sensitive to humidity and temperature. The nanoindentation tests were performed in a climatic (i.e. temperature and humidity controlled) chamber at relative humidity levels from 50% to 98% and at two temperatures: 20°C and 60°C. In a first step, the curves of indentation were analysed using the commonly used Oliver and Pharr’s approach. Other wellknown parameters as the creep factor were also extracted. In a second step, Fisher-Cripps model (Fischer- Cripps, 2004) and Vandamme and Ulm model (Vandamme & Ulm, 2006) were used to identify viscoelastic properties. A statistical analysis is used in order to extract mechanical characteristics of the different phases. Hardness and elastic modulus decrease drastically with saturation (above 80% humidity) and to a lesser extend with temperature.

Jan 1, 2015

By See G. T

Bentonites and fuller's earths from seven localities in N.S.W. have been analysed with respect to occurrence, mineralogy and physical properties and areas for future prospecting have been indicated.INTRODUCTIONThe rapid expansion of Australian industry in the postwar years has been accompanied by an ever increasing demand for fuller's earth and bentonite, but in New South Wales at least the demand has been met principally by imports. However, some local and generally inferior active earths have been won to blend with imported materials to reduce costs. The important discovery of the widespread distribution of bentonite clays in the Northern Coal Measures, made recently by Grim (Booker, 1956), has givenimpetus to the further search for material comparable in quality to the imported active earths.Bentonite may be defined as a highly plastic clay, generally possessing swelling properties, composed essentially of montmorillonite and derived from the alteration of volcanic ash. Fuller's earth refers to any clay which, with or without chemical treatment, is capable of decolourizing mineral or vegetable oils and is, therefore of economic value. Montmorillonite is the active component of most fuller's earths, though palygorskite-, halloysite- and even kaolinite-rich clays have been used.Previous literature related to the New South Wales deposits has been confined to general descriptions and little technical data beyond an occasional chemical analysIs have been available. Bentonites and fuller's earths from seven...

Jan 1, 1959

By R Baumgartner

The Canahuire deposit is a recently discovered Au-Cu-Ag epithermal deposit in Southern Peru. A geometallurgy program is a key study element of the project Feasibility study. Metallurgical, mineralogical, and comminution studies have been completed over a suite of samples, spatially distributed among the various geological/ore domains. The early stage of Canahuire presents challenges as there is a lack of metallurgical information to guide geometallurgical sampling, in contrast with an established deposit at a more advanced stage of development or mining. Nevertheless, the available information will assist in the development of geometallurgical domains for Canahuire in order to ensure that future metallurgical, mineralogical, and comminution test work is representative of the deposit variability. This supplementary knowledge will be able to predict important metallurgical parameters which will be incorporated into a geometallurgical model to spatial predict material types, metallurgical recovery and through put. The information obtained will be a valuable addition to the future mine plan, influencing process design, engineering design, plant operation, operating and capital costs, and ultimately will reduce project development risk.

Sep 5, 2011

By C Vejrazka1

The occurrence of airblasts is one of the principal mining hazards in caving operations between the time of cave establishment and breakthrough of the cave to surface. As such, it needs to be managed continuously and risk assessments need to be reviewed on a regular basis for applicability to changing conditions. The likelihood of an airblast occurring is based on a range of geotechnical factors over some of which engineers on-site only have limited control. However, the impact of an airblast to the underground mine, if it does occur, can be managed by following established safety guidelines for the production from the cave.This paper outlines how the Caving Airblast Simulation Tool in Ventsim was used to determine a risk management strategy for a sublevel and a block cave at a mining operation in Australia. The block cave has a footprint of 14 500 m2 with the extraction level located 1250 m below surface while the sublevel cave currently has a footprint of around 18 000 m2 operating between 660 m and 800 m below surface. Both caves are currently in their early operational periods. The risk analysis provided valuable information for the production planning of the caves including confirmation of extraction ratios for the block cave undercut, locations of airblast walls and maximum allowable air gaps for different muck pile heights to ensure safe operation is achieved.

Oct 12, 2022

By Karoly (Charles) Kocsis, Jeff Johnson, Felipe Calizaya, Tulio Dias, Natanna Nunes

Two pressure balancing chambers were constructed at a Colorado coal mine to reduce the risk of spontaneous combustion. Each chamber was established by installing a Kennedy stopping at about 10 ft (3 m) in front of an isolation seal, and equipped with two safety doors, a nitrogen injection system, and a set of environmental monitors. Several pressure balancing tests for different ventilation conditions were conducted in these chambers. During each test, pressurized nitrogen was injected into the chamber and the pressure differentials across the stoppings and seals monitored. This study presents a summary of the results achieved, lessons learned, and the basic requirements to operate a pressure chamber effectively.

Feb 1, 2024

By L Soebari, W Sunyoto

The Wabu Ridge Gold Skarn deposit is located at elevations of up to 3100 metres above sea level, in the Central Highlands of Irian Jaya, Indonesia, 35 km NNW of the Grasberg porphyry deposit. Wabu is a grass-roots discovery in an area with no previous gold mining history or record of gold mineralisation. A geological resource of 117.26 million tonnes at an average grade of 2.16 g/t Au (1.0 g/t Au cut-off) has been defined to-date. Mineralisation is hosted within a skarn occurring along the southern boundaries of the Late-Miocene age monzonite-diorite Pagane intrusive complex. The intrusive complex occurs in the footwall of a major EW structure, the Derewo fault, which displays sinistral strike-slip and reverse fault movement. The Derewo fault separates Derewo metamorphic units to the north from platform sediments of the Australian craton to the south. The skarn has a strike length of 6 km and is up to 1.5 km wide. It is developed within calcareous shelf sediments of the Tertiary New Guinea limestone group and is dominated by prograde garnet development. Gold mineralisation was deposited during retrograde alteration and is directly associated with arsenophyrite and bismuth minerals. Retrograde alteration is distinguished by a sequence of clinopyroxene , magnetite, epidote and hornblende, biotite and chlorite and lastly carbonate. Gold is associated with the biotite/ chlorite phase together with sulphides and precipitated as the result of fluid mixing. The Wabu Ridge Gold Skarn deposit was identified in April 1990 during a regional program of helicopter assisted stream sediment sampling of -80 mesh (180 microns) fraction and panned concentrate sampling. The initial discovery sample site was situated 15 km down stream from the deposit and returned 1.49 ppm Au for the stream sediment sample and 138 ppm Au for the panned concentrate sample. A regional airborne helicopter magnetics survey, conducted in early-1992, helped defined the main magnetite associated skarn zone and the extent of associated igneous rocks. Detailed follow-up commenced in May 1992 and consisted of detailed mapping, soil sampling and ground magnetics prior to drilling the first hole in October 1992. Drilling to-date has delineated a contained geologic resource of 8.1 million ounces of gold and potential exists for a larger resource.

Jan 1, 1999

By M. L. Harris

Coal dust produced during the mining process is a prime explosion hazard in underground coal mines. To inert the coal dust and prevent a catastrophic propagating dust explosion, rock dust is applied to the roof, ribs, and floor surfaces of mine entries. Currently, one determination of whether a mine is adequately protected from the coal dust explosion hazard is made by analyzing collected mine dust samples for percent total incombustible content (% TIC). A minimum of 80% TIC is required per 30 CFR 75.403. The as-received moisture of the dust sample is included in the % TIC. Moisture and humidity within a coal mine vary greatly with the seasons, with explosions occurring more frequently during dry winter months. This paper will discuss the fluctuations of the as-received moisture content of the mine dust samples collected by U.S. Mine Safety and Health Administration inspectors in 2010 and the observed fluctuations of the moisture content of rock dust within the U.S. National Institute for Occupational Safety and Health Office of Mining Safety and Health Research Bruceton Experimental Mine and the Safety Research Coal Mine over a one-year period.