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By Leon D. Keller

Hydraulic concentration of minerals has been practiced for a good many years. Until recently, however, the practice has been limited to a multiplicity of small pockets and relatively low tonnages and flows. The adaptation of the SiphonSizer to the concentration and classification of magnetite has changed this concept. Some fifty commercial units are currently in operation on magnetite, varying in size from 16 ft diameter circular unit to a 25 ft by 100 ft rectangular unit. Additional units up to 38 ft diameter are under construction. Depending upon the application in the flowsheet, upgrading-varies from 0.75% to 14% Fe in a single stage. To those not familiar with taconite processing, the importance of the struggle to economically remove as much silica as possible may not be fully appreciated. These figures pertaining only to transportation may be thought-provoking. If a 10,000,000 ton per year plant could reduce the silica content of their concentrate by 17, a savings in boat freight alone would amount to 100,000 tons at $2.00 per ton annually.

Jan 1, 1963

By Betty L. Gibbs

Microcomputers are becoming more convenient to use at all levels of the business world, including the mining industry and mine offices. The state of the mining industry requires that we become more productive and innovative in our analysis of deposits and operations. With the help of computers, examination of options to increase productivity can be performed quickly and inexpensively. Effective use of the computer for designing underground workings combines the calculation power and speed of a computer with the technical expertise and judgment of the engineer. Computer programs can perform calculations in minutes that could take an engineer several months. The engineer must be on guard when using the computer for any calculation because it is very easy to assume the results produced by a computer program are always correct. The computer is a sophisticated calculator but cannot recognize logical errors nor transposition of numbers. Also some intuitive or obvious decisions made by an engineer are difficult or impossible to program effectively.

Jan 1, 1987

By N. Arbiter

If two fluid phases are brought into contact with a solid, one fluid may completely wet the surface to the exclusion of the other, or both may wet it, forming a three-phase line of contact. These relative wetting tendencies are quantified by the contact angle 0 which is related by Young's equation (1,2) [12 cos? = 13 ? 23] [to the three interfacial tensions (3). No contact angle for the first fluid, indicating that it does not wet the solid in the presence of the second, means that the difference between the two solid-fluid fluid surface tensions, - 8 is greater than (or just 13 -23 equal to) the fluid-fluid tension 12; a finite angle indicates that the difference is less.*]

Jan 1, 1964

By B. F. Dickerson

STRATEGIC METALS! Recently, this money accented cry has been heard in such diverse locales as Mining company boardrooms, Banker's offices, Stockbroker's quarters, Swindler's dens and Congressional committee rooms. (In some cases, these locales are one and the same). Is the strategic metals rush for real? Should it be? Our paper attempts to give a very generalized view of the subject for a few metals, points to a few potential, but generally overlooked sources of these metals, and offers conclusions based on our studies.

Jan 1, 1981

By Irwan Halim, Seung Han Kim

This paper will describe design of precast segmental tunnel lining for the Pawtucket CSO Tunnel Project in Providence, Rhode Island. The tunnel is 11,700 LF long with 30-foot finished diameter to be constructed in complex sedimentary rocks. Special features of the segments include a large keystone and no connector used on radial joints. The typical segments will be steel fiber reinforced, and hybrid segments with additional steel rebars and shear bicones will be used around the adit openings without use of any structural framing. The important design considerations will be discussed, including special 3D segment to adit connection analyses performed.

Dec 1, 2022

By G. Xu, A. R. Kumar, N. A. Amoah

Prolonged exposure to high concentrations of respirable coal mine dust causes coal workers’ pneumoconiosis and silicosis. Underground coal mine roof bolter operators are more prone to elevated exposure to coal and silica dust. The canopy air curtain (CAC) was developed by NIOSH to protect roof bolter operators from the exposure. The CAC supplies filtered air over the breathing zone of the operator. This dilutes the high coal dust concentrations and provides for an impenetrable air curtain. Many studies have been carried out to improve CAC efficiency. However, field test has shown variable dust control efficiencies indicating rooms to further improve due to the nonuniform airflow distribution across the plenum and ineffective perimeter flow. This study therefore redesigns the CAC with optimized flow distribution that effectively protects roof bolters from coal dust exposures. Computational fluid dynamics (CFD) simulations are used to optimize the uniformity of airflow distribution across the plenum to achieve the best possible uniformity. A lab experiment validates the CFD model and confirms the ability of this design to reduce floor dust pickup, prevent external wind infiltration, and offer an improved protection efficiency

Mar 2, 2022

By Yuting Xue, Alper Kirmaci, Taghi Sherizadeh, Dogukan Guner, Khaled Mohamed

Rib brows present a significant safety hazard in underground coal mines in the United States. To address this issue, researchers at the National Institute for Occupational Safety and Health (NIOSH) and Missouri University of Science and Technology (MST) are developing a practical tool to assess both the potential of rib brow formation and the stability of any formed brows. As part of this effort, a monitoring study was conducted to assess the potential for rib brow formation in coal pillar ribs. This study was conducted in a room-and-pillar coal mine where coal pillar ribs are prone to developing rib brows. Although no rib brows formed in the instrumented pillar, data from monitoring and visual observations provided valuable insights into the loading mechanisms impacting the instrumented pillar. These findings helped identify factors that may reduce rib brow formation, including the cavability of the roof in mined areas, the applied rib support, the strength of rock partings, and the overall integrity of the coal seam. The scientific findings published in the case study aid in assessing the potential of brow formation, offering additional evidence for the need to improve rib control methods in underground coal mines.

Feb 1, 2025

By Vivek Priyadarshi, VIVEK KUMAR HIMANSHU, A. K. Vishwakarma, M. P. Roy, A. K. Mishra, RAVI SHANKAR

The nature and orientation of joints in rock strata affect the damage pattern under explosive loading. Most of the limestone deposits in India are found with severity of joints. Categorically, these joints may have variable orientations such as dipping out of the blast face, inside the face, horizontally or having strike parallel to the face. The damage pattern under the varying category of orientation will be different. Accordingly, a numerical model in Ansys-Explicit Dynamics was prepared to compare the damages of rock mass under different joint orientations. The physical nature of a joint reflects frictional and stiffness behaviour. Accordingly, the damages have been compared under bonded and frictional nature of joints. The output damage pattern from the model has been validated on the basis of blastability index proposed by Lilly. Different limestone mines in India show different nature of jointing in their rock strata. Accordingly, the blasting outputs from three different limestone mines, viz. Rawan limestone mine, Sagmania and Birhauli limestone mine and Injepalli limestone mine, have been compared along with their blast design parameters and the nature of joint. The comparative results show that the closely spaced horizontal joints support maximum in burden movement and rock fragmentation due to blast.

Nov 23, 2023

By Yiming Zhang, Yunpeng Li, Chun Feng, Ruyang Cao

In the past, the selection of the number of empty holes between blast holes heavily relied on the subjective experience of practitioners, leading to unsatisfactory blasting results. The number of empty holes between blast holes is particularly important for the perforation of explosive cracks. In order to determine the optimum number of empty holes for inducing the propagation of explosive cracks, a two-dimensional numerical model of two-hole blasting was established based on the continuous-discontinuous element method (CDEM) using polymethyl methacrylate (PMMA) as the medium, and numerical simulation of various working conditions was conducted; the simulation results are basically consistent with the PMMA model test. Through the analysis of blasting parameters, the optimal number of empty holes with a certain hole spacing is fitted. The following conclusions are drawn: (1) There is a threshold for variable x. When x exceeds 50, the presence of empty holes cannot lead to the perforation of explosive cracks between the blast holes. (2) When x is below 50, the optimal number of empty holes inducing the propagation of explosive cracks can be determined through fitting an empirical formula. By adjusting the number of empty holes between blast holes, a significant spacing between adjacent blast holes was achieved, allowing for effective penetration, so as to effectively “induce” the direction of the fracture zone and make full use of the energy of explosives. The research results of this paper are conducive to the research of directional blasting technology and provide certain references for the optimization of precision blasting parameters.

Dec 19, 2023

By Abhiram Kumar Verma, Soumya Ranjan Mallick

Generally, waste such as soil and sandstone is used in mines for road construction or haul roads. In many such mines, it is challenging to design haul road pavement to match the dumper capacity. This paper investigates overburden soil to find its utility as a pavement material. It is found that overburden soil is unsuitable pavement material without stabilization; hence, nine composite materials are developed using overburden soil and RBI. Physical, mechanical and microstructural properties of unstabilized and stabilized soil are determined. Statistical analysis is carried out to assess the effect of soil type, RBI and curing period of strength characteristics of unstabilized and stabilized soil. ANOVA tests assess the influence of RBI percentage on soil geotechnical properties, and regression relations are developed. Two-way ANOVA shows the effect of RBI and soil type on soil geotechnical properties, whereas one-way ANOVA shows that the influence of soil type is more than the RBI. The regression relation is developed for CBR, UCS, Poisson’s ratio and modulus of elasticity with a good correlation coefficient. The performance of RBI is more with the finer material and reduces with an increase in the size of soil grains. The performance of the developed composite is better than the earlier developed composite based on overburden with fly ash, lime kiln dust, lime or clinker.

Mar 19, 2024

By Kanchan Mondal, Gopi Bylapudi, Anand Bhagwat

Corrosion of steel roof support systems can cause potential premature failure of the support, thus adversely affecting the excavation stability and rock-related safety. An in-house corrosion test system was designed and developed to test full-length roof bolts for material performance based on tensile load capacity and strength under different corrosive conditions found underground. The roof bolts tested are also used to identify the possible corrosion mechanisms that influenced the bolts’ performance over time. Initially, the most commonly used bolt material in the USA, the ASTM A615 grade 60 steel roof bolts, was tested with and without stresses in a simulated underground coal mining environment for approximately 6 months, and the results are discussed. Localized corrosion forms such as crevice and pitting were mainly observed after testing. The stressed and unstressed roof bolts with and without threads that were tested in alkaline coal mine corrosive environment for 6 months passed their load-bearing capacity as per ASTM F432 test standards. From the results, it is concluded that this test protocol could be applicable to test the material performance of different roof bolt metallurgies and coatings with desired modifications to the proposed methodology for the specific underground mine environment. This paper mainly discusses the test system and protocol and shortcomings of the system and makes recommendations based on the observations and results.

By Lei Pan, Venkata Atluri, Xuming Wang, Yuesheng Gao, Jan D. Miller

The wetting characteristics and water film stability at the talc surface have been studied, particularly the effect of polysaccharides such as guar gum, starch, and dextrin. Talc is a gangue mineral in the flotation of base metal sulfide ores, precious metal sulfide ores, and platinum group metal (PGM) sulfide ores. Talc surfaces were investigated using surface analysis techniques including atomic force microscopy, high-speed video bubble attachment measurements, and wetting film stability measurements using a synchronized tri-wavelength reflection interferometry microscope (STRIM). In the presence of polysaccharides, there is a significant increase in bubble attachment time at the talc surface, but only a slight change in contact angle, which suggests that polysaccharide depression of talc is due primarily to the slow rate of bubble attachment and not due to a change in contact angle. The critical rupture thickness (hc) for a hydrophobic talc surface was found to be 56 nm, while the hydrophilic phlogopite surface of similar structure has an equilibrium film thickness (he) of 25 nm. At low polysaccharide concentrations, the wetting films formed on the talc surfaces were unstable, but at high concentrations the wetting films became stable with similar thickness values as the critical rupture thickness, and bubble attachment did not occur. However, it was found that the critical and equilibrium film thickness values do not change significantly with the polysaccharide type or concentration. The results from this research help us understand further details of film rupture and displacement during bubble attachment.

By Andre C. Zingano

It is a very difficult task to estimate the immediate roof and support behavior in a room-and-pillar mining section in the initial phase of the mining project. There is little information available at this phase, and it is restricted to geomechanic characterization of the rock layers from cores samples, and the in-situ instrumentation of experimental entries and intersections. Even being a pilot excavation for roof support test a good indicator for the behavior of the immediate roof, its behavior for a full excavation mining section is different from a single intersection of two entries, mainly because the stress redistribution caused by the multiple entries excavation and face advance for a full excavation section. The objective of this paper was to calibrate a 3-D numerical model of an experimental intersection, based on the in-situ instrumentation of an experimental intersection excavation, and the geomechanic description of the rock layers. The numerical model was built with the same specifications as the excavation test, including the entry geometry and roof support. The numerical model calibration was based on wire extensometers that were installed at different positions in the roof of the pilot excavation, and on the geomechanic characterization of the rock layers that form the roof, coal seam, and floor. Therefore, it is possible to estimate whether the roof support specification adopted in the test phase will be good enough for the development of the entire mining section.

Jan 1, 2009

By Purnima A. Shivdasan

The fluorspar deposits at Okorusu, Namibia are closely related to an alkaline igneous ring complex of late Cretaceous age (125±7 Ma). The fluorite ores consist of relatively fine-grained purple replacement fluorite and subsequent coarser grained purple and green vug-filling fluorite crystals. Homogenization temperature measurements for 38 primary fluid inclusions shows that main stage purple to green fluorite crystals were deposited over a temperature range from 166°C to 144°C, and minor late yellow fluorite was deposited at lower temperatures from 132°C to 128'C. Homogenization and freezing temperatures measured for 18 primary fluid inclusions shows that the fluorite-depositing fluids were less saline than MVT ore fluids and overlap the lower temperature range of fluids that deposited epithermal ore deposits. Mining in two open pits (A and B) at Okorusu has gradually provided exposures which reveal that the fluorite orebodies have been emplaced primarily by the preferential replacement of carbonatites. Evidence for the replacement of carbonatite includes: 1) replacement remnants of carbonatite within the fluorite ores, 2) goethite pseudomorphs after the carbonatite minerals, pyroxene, pyrrhotite, and magnetite that are disseminated in the fluorite ores, 3) partial replacement by fluorite of a titaniferous magnetite rimmed carbonatite dike in the A pit, and 4) partial replacement by fluorite of a large sill-like carbonatite body in the B pit. Electron microprobe analyses of minerals in unreplaced portions of the carbonatites show that their mineralogy consists of titaniferous magnetite, diopside pyroxene, apatite, biotite, and calcite. Magnetite contains 6.97% to 10.46% Ti02, averages 8.44% Ti02, and has an average V203 content of 0.35%. At high magnifications under the SEM, the magnetite shows abundant fine ulvöspinel exsolution lamellae arranged in a cloth texture. Apatite contains moderately high fluorine contents that range 3.21 to 5.0% and average 4.2%, and apatite crystals range in total rare earth oxides from 1.7% to 2.61%. Pyroxenes in the carbonatites are iron-rich diopside, and they contrast to pyroxenes in the fenites that are aegirine-augite. All of the microprobe analyses for mica crystals in the carbonatites give biotite compositions. The fluorite ores also have replaced marble locally in the A pit, especially along the A band in the B pit, and dominantly in the orebody proposed for the new C pit. Carbonatite and marble were preferentially replaced by fluorite because the calcite was readily soluble in the presence of the fluorite-depositing fluids and the dissolution of calcite provided calcium for the formation of fluorite.

Jan 1, 2005

By Richard W. Kimball, Fred B. Estep, Dwayne E. Easterling

This paper discusses the overall challenges to construct a 15,125.7 m (49,625 LF),wastewater drainage tunnel in Cobb County, Georgia by a joint venture of Gilbert Southern Corp. and S.A. Healy Co. and a construction manager Parsons, with Jacobs Associates as a subcontractor. The goal of the project is to provide wastewater retention during peak usage and is connected to a treatment facility near the Chattahoochee River. The primary component of the project is the TBM-driven hard rock tunnel. Additional works include drill and blast areas; four intake interceptors, two construction shafts and a 33.5 m (110 ft), diameter pump station shaft.

Jan 1, 2003

As the surface reserves are being depleted, more and more stone operators are seeking underground mining options. Stability of underground openings is a major concern for the safety and productivity. This paper relates to a field study conducted at a large underground limestone mine in Central Pennsylvania. Identification of hazards leading to ground failures and assessment of roof fall risks are important in mitigating injuries. Field observations at this mine were integrated with Roof Fall Risk Index (RFRI) mapping software recently developed by West Virginia University. The system is designed to combine field study data related to geologic factors, mining-induced damages, roof profile, and ground water influx to generate RFRI maps. The mine has adopted a proactive ground control program consisting of comprehensive examination of drilling and bolting logs; precision surveying of roof and rib; accurate mapping of cutters, falls, and geologic structures; and installation of extensometers and microseismic monitoring systems. Investment of time and resources has eliminated fatalities and lost-time injuries due to ground fall. This paper presents the geologic settings, mining conditions, ground control issues along with risk management and control techniques adopted at the study mine.

Jan 1, 2009

By Mark Board

INTRODUCTION As the world's supply of near-surface metalliferous ore bodies is depleted, more emphasis must be placed upon mechanized bulk systems of underground mining. In particular, block caving is becoming increasingly important as a method of mining low to moderate grade deposits at depths of somewhat less than 1219 m (4000 ft). 00 ft). The block caving method requires that the ore body be completely undercut, thereby removing its means of support and inducing failure which progresses from the undercut to the ground surface. As the span of the under- cut increases and the weight of the overlying crushed ore body becomes greater, large stresses are induced on slusher and haulage drifts. Stability of these drifts is critical in block caving operations and often proves to be an extremely difficult task (Kendorski, 1976; McWilliams, 1975). Slusher drift maintenance can be costly, often exceeding that of the original support costs. This chapter analyzes the ground support problems of an Arizona block caving mine. The mine presently uses monolithic concrete liners as a support method. Failure of the liners occurs as the undercut approaches, thus initiating a maintenance problem which will continue until the ore body is depleted in that block or panel. To examine this problem, a simple analysis of the stresses induced by the advancing undercut was per- formed. Utilizing a design method developed by Dixon ( 1973, 1974), the calculated stresses were used to deter- mine the minimum thickness required for varying section shapes of unreinforced concrete liners. It is found that the thicknesses required for stable linings are not economic. Recently developed empirical methods of support de- sign are utilized (Barton, 1974; Bieniawski, 1973) and compared to the analytical method. A final discussion of alternative methods of support is given with recommendations for the use of passive or "yielding" support methods. LAKESHORE MINE (GENERAL GEOLOGY) The Lakeshore copper property is located in Pinal County, AZ, approximately 45 km (28 miles) south of Casa Grande. The Lakeshore deposit is a porphyry cop- per similar to others in Arizona. The ore body consists of disseminated chalcopyrite and fracture fillings in quartz monzonite porphyry (QMP), Cretaceous volcanic (KVS), Precambrian diabase, and Mescal limestone. The ore body has been divided into three distinct zones of mineralization which have been termed (South, 1972) the oxide zone, the sulfide zone, and the tactite zone. The oxide zone occurs in the upper portions of the ore body and consists primarily of leached and oxidized quartz monzonite porphyry and Cretaceous sedimentary and volcanic rocks. The sulfide zone underlies the oxide zone and includes all quartz monzonite porphyry and Cretaceous rocks which have not been oxidized. The thickness of the sulfide zone is variable and ranges from about 61 to 122 m (200 to 400 ft). The tactite zone occurs in a series of Paleozoic metasediments consisting of tactite, quartzite, diabase, hornfels, and dikes of quartz monzonite porphyry. The tactite zone is highly variable in thickness and underlies the Cretaceous volcanic and sediments throughout the mine. Together, the tactite and sulfide zones are known as the thick or tall sulfides. The greatest support stability problems occur in mining of the tactite zone and are therefore the subject of the remainder of this chapter. MINING METHOD The Lakeshore mine is a block caving mine utilizing a panel caving method. The present mine consists of two

Jan 1, 1982

By P. B. Queneau, J. E. Litz, T. P. McNulty

I. INTRODUCTION Modern hydrometallurgy has its roots in such notable successes as heap leaching for recovery of copper, cyanidation of gold ores, the Bayer process, the Oxland process for tungsten, electrorefining of copper, roast/ leach/electrowin process for zinc, and production of yellowcake from lowgrade uranium ores. Metallurgical testing techniques, sampling and analytical procedures, operating and maintenance practices, and improved methods and materials of construction which were pioneered in these processes have promoted the extension of hydrometallurgy into other applications. Periodically, new tools such as solvent extraction, resin ion exchange, and flocculants have opened new avenues to hydrometallurgists. Conversely, pursuit of more complex mineralization, the rising costs of energy and environmental quality preservation, and declining ore grades continue to create new challenges. For much of this century, it can be fairly said that practically any hydrometallurgical development moved the frontier of technology. The 1970's and 1980fs, however, have seen a significant maturing of hydrometallurgy's role in process metallurgy. Simplistically, this maturing seems to derive from a growing awareness of the strengths and weaknesses of hydrometallurgy and a determined effort to capitalize on the strengths. For example, many of us were among those revolutionaries of the 1960's and 1970's who taught that "chemical smelting" was the answer to the treatment of all sulfides. We now recognize, however, that only in very special cases can hydrometallurgy offer economic advantage over the generally less energy-intensive pyrometallurgical systems. The maturing of hydrometallurgy does not, however, signal stagnation. Important innovations are being studied and developed in most extractive areas, and a number are approaching or have achieved commercialization. From our company's perspective, that of an organization dealing with the development of the most economic solutions to metallurgical problems, innovation must be defined as the commercially successful reduction of an idea to practice. There appears to be no shortage of ideas, nor has there ever been a shortage. Many ideas now being implemented were conceived decades ago, but reduction to practice was foiled by the lack of such technology as responsive process control and economical materials of construction capable of withstanding highly corrosive or erosive environments. Commercialization of a new process is a particularly challenging undertaking. Even if technical risks are reduced to a minimum through careful and thoughtful process development, there are inevitable uncertainties in feed characteristics, variable costs, and product prices. Commercialization takes courage, both on the part of innovators who may be staking their careers or reputations and of investors who may face financial disaster in the event of project failure. This paper discusses innovative programs and recently commercialized processes which either have been discussed in the literature or disclosed to Hazen Research staff in private nonconfidential conversations with contacts in industry. Regarding this latter category of information, relative ease of communication has resulted in many of our observations being of North American origin.

Jan 1, 1985

By K. J. Reid, I. Iwasaki, T. Sabelin

Introduction Occurrences of platinum group minerals (PGM) in mafic and ultramafic rocks in association with Cu-Ni mineralization are well known. Yet for the Duluth Complex, a large body of dominantly mafic igneous rocks in northeastern Minnesota with significant Cu-Ni mineralization (Bonnichsen, 1972; Boucher, 1975; Watowich, 1978; Weiblen and Morey, 1980), little has been published concerning its platinum group element (PGE) contents and mineralogy. In a previous study of massive sulfide rock, sperrylite (PtAs2) was found in nickel arsenide and recovery of arsenide minerals by flotation has been investigated (Iwasaki et al., 1986; Ryan and Weiblen, 1984). Recently, an announcement was made of the discovery of significant quantities of platinum and palladium [peak assay values of 9 g/t (0.27 oz per st)] in an interval of a drill core with disseminated sulfide mineralization 16 km (10 miles) southeast of Ely, MN (Anon, 1985; Sabelin, 1985). This paper describes PGM from the Pt-Pd-enriched zone and evaluates their potential for concentration. Geologic setting The Pt-Pd zone occurs in the South Kawishiwi in¬trusion near its basal contact at 734 to 737 m (2408 to 2418 ft) depth. The South Kawishiwi is one of several minor mafic intrusions that constitute the western margin of the Duluth Complex near Ely, MN (Fig. 1). It is com¬prised of a 70.1- to 350.5-m (230- to 1150-ft) thick sul¬fide-bearing basal unit of troctolite with minor amounts of anorthosite, norite, picrite, and oxide layers overlain by a troctolite unit with interlayered anorthosite (Bonnichsen et al., 1980; Foose, 1984; and Foose and Weiblen, 1986). The basal unit, in which the Pt-Pd zone is found, is markedly heterogeneous in rock type, lacking any coherent internal stratigraphy, and shows evidence of both pre- and post-consolidation faulting (Foose and Weiblen, 1986). Geochemistry Chemical analyses were made on 0.3-m (1-ft) intervals of crushed drill core material (1/4 core, BX size) at 731.5 to 740.7 m (2400 to 2430 ft) depth and the results are presented in Fig. 2. The analytical techniques used were atomic absorption spectrometry for silver, chromium, copper, and nickel; a coulometric titration method for sulfur; and a combined fire assay-DC plasma technique for gold, palladium, and platinum. Figure 2 shows the significant enrichment of platinum and palladium at 734 to 737 m (2408 to 2418 ft) depth; it corresponds to a stratigraphic interval rich in oxide minerals. Average values for platinum and palladium contents over the 3-m (10-ft) interval are 2520 and 2580 ppb, respectively, or 5.1 g/t (0.15 oz per st) platinum plus palladium. Platinum plus palladium contents from individual 0.3-m (1-ft) intervals are as high as 9120 ppb or 9.1 g/t (0.27 oz per st) and average 7.4 g/t (0.22 oz per st) in a 1.5-m (5-ft) interval in the richest part of the zone. The Pt-to-Pd ratio is nearly 1:1 over the entire 9.1-m (30-ft) interval and the platinum and palladium correlate closely with chromium, which ranges from 1.9% to 5.3%. Copper, nickel, and sulfur contents for the drill core interval are also given in Fig. 2. In¬terestingly, the Pt-Pd high corresponds to a depletion in copper, nickel, and sulfur. Mineralogy of the Pt-Pd zone The Pt-Pd zone occurs within an oxide-rich zone or layer that consists essentially of oxide minerals, plagioclase, and olivine. The oxides may constitute as

Jan 1, 1987

By Jed H. Mosgrove

One of the most interesting of all the subjects required of persons studying the different facets of coal mining is coal mine gases. Some mine gases have been a real problem since the very beginning of underground mining, and in the early days there was insufficient knowledge to cope with them. The history of mining shows that until about the last 50 years, much work was done primarily by the hand methods which are primitive by today's standards. Miners had to contend with gases without the aid of enclosed lighting, permissible mine machinery, sophisticated testing devices, and high-pressure ventilating fans. In early days the miners were not educated about the different mine gases nor did they have the technical equipment to determine the actual composition of the deadly atmospheres they encountered. They simply applied a descriptive term to each gas or mixture of gases depending on its effect on a person or the surrounding atmosphere. The gases or mixtures of gases were then referred to as "damps," a term which was probably derived from the German word "dampf," meaning vapors or gases. The more common damps encountered were : Blackdamp A condition of the atmosphere in which a miner's light would be extinguished and in which breathing would be difficult, sometimes even resulting in suffocation. An atmosphere deficient in oxygen which could contain a combination of any of the mine gases Firedamp A flammable mixture of methane and air which would either burn or explode when ignited. White Damp A mixture of gases containing carbon monoxide, most often found in mines during fires or after explosions.

Jan 1, 1981