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By Braden T. Lusk, Rex A. Meyr, Kyle A. Perry

Following three major mining accidents in 2006, the MINER Act of 2006 was enacted by MSHA and required every underground coal mine to install refuge alternatives to help prevent future fatalities of trapped miners in the event of a disaster. A polycarbonate safe haven wall for use in underground coal mines was designed and modeled using finite element modeling in ANSYS Explicit Dynamics to withstand the MSHA required 15 psi (103.4 kPa) blast loading spanning 200 milliseconds. The successful design was constructed in both half-scale and small scales in the University of Kentucky Explosives Research Team’s (UKERT) explosives driven shock tube. The constructed polycarbonate walls were tested multiple times to determine the walls resistance to blast pressure. The results for each test were analyzed and averaged to create one pressure versus time waveform which was then imported into the finite element program and modeled to compare deflections of each part to that was measured during testing for model validation. This paper summarizes the results.

Jan 1, 2014

By Woodcock J. T

During the dissolution of gold in fully aerated cyanide solutions the CN ion is the active agent, and consequently the usual method of evaluating the dissolving power of such solutions is to determine the CN- concentration analytically. The presence in the solutions of copper and/or zinc which themselves form complex cyanides, may result in erroneous conclusions as to the free cyanide ion concentration determined by titration.In this paper the theory of titration of such solutions has been developed, and potentiometric methods have been used to follow the behaviour of complex cyanides of copper and zinc. The results for cuprocyanides show Cu (CN)s to be the most important copper complex, and in addition they explain the reported low rates of solution of gold in copperbearing solutions which when titrated in the usual way, appear to have adequate free cyanide. An explanation of the misleading value of the titration is given, and suggestions for recognition of the condition are offered. Preliminary results for zinc-bearing solutions show that there is no satisfactory end-point for the titration of CN- in excess of that in the complex Zn (CN) 4=, which dissociates to CN and Zn(CN)g-.

Jan 1, 1950

By M. Abdellatif

Keywords: Magnesium, pyrometallurgy, Mintek Extensive testwork on atmospheric thermal magnesium production has highlighted certain important fundamental and operational factors that have a major influence on magnesium extraction and its extraction rate, the condensation efficiency of magnesium, as well as on the quality of the condensed metal. The possible impact of these factors on the selection and preparation of raw materials, recipe choice, furnace electrical energy consumption, and on the refining requirements of the crude magnesium is discussed. Selected pilot plant operational and metallurgical data are also presented.

Jan 1, 2006

By Gregory Yates

INTRODUCTION Project Description The Silver Line is a Bus Rapid Transit (BRT) Line and is Boston?s newest transit service. Silver Line Phase I extends along Washington Street entirely on the surface in priority bus lanes from Dudley Station in Roxbury through the South End and Chinatown neighborhoods to downtown Boston. The Phase I opened in July 2002. Silver Line Phase II consists of an underground transit tunnel from South Station to the South Boston Waterfront with underground stations at Courthouse and World Trade Center to Silver Line Way east of D Street. Phase II continues through the Ted Williams Tunnel to all the terminals at Logan Airport, and on the surface to the Boston Marine Industrial Park and City Point. Phase II opened in December 2004. Silver Line Phase III is a one mile tunnel connection to the existing Phase II tunnel in the vicinity of South Station and will eventually portal on Tremont Street just north of Marginal Road. After leaving the portal, the buses will use dedicated bus only lanes on the surface roadway network to connect to the Phase I service. Figure 1 shows the alignment of the Silver Line upon completion of the Phase III project.

By W. Vorster

Bateman Engineering Project's acid-plant track record goes back to 1977. Bateman Engineering can design sulphuric plants based on gas from sulphur burners, metallurgical off gas as well as pyrite roasting systems. Bateman Engineering has a technology marketing agreement with NORAM Engineering Ltd of Canada to provide state-of-the-art, well-proven acid plant technology, and also has access to roaster technology from several sources, including Chinese technology. Utilising the Noram technology agreement, Bateman was awarded the Engineering and Procurement (EP) contract for the Ambatovy Nickel Project, Sulphuric Acid Facilities in 2007. This is the first Greenfield sulphuric acid plant Bateman has designed for many years, producing a combined 5,500tpd, and is one of the largest sulphur burning acid plants in the world. This paper gives an overview of the sulphuric acid plant for the Ambatovy Nickel Project, advantages of Noram?s unique technology on offer, an overview of work conducted on a recent study of an pyrite roasting acid plants as well as a new technology currently being developed by Bateman for the direct combustion of solid sulphur to form sulphur dioxide.

Jan 1, 2009

By D. J. Duck

INTRODUCTION Construction of the 3,600,000 kilowatt Third Powerplant at Grand Coulee Dam started in late summer 1967 approximately one year after authorization by Congress. The project was made possible by a treaty with Canada providing for cooperative development of the Columbia River which was signed in 1961 and ratified in 1964. Description of the Work The existing Grand Coulee power complex consisted of a dam and two powerplants with a switchyard serving each plant, one on each bank of the river. See Fig. 1. The switching facilities were connected to transformers at the powerplants by overhead 230-kilovolt and 115-kilovolt tie circuit conductors. [ ]

Jan 1, 1997

By Jerry D. Pfarr, Gary Loving, David G. McDowall

Introduction The Open Cut is one of the best known landmarks in South Dakota's Black Hills. It is the site of the original discovery of the Homestake ledge, or lead, in 1876. Between that time and 1945, the Open Cut produced about 36 Mt (40 million st) of gold ore, the majority of which was drawn from underground operations. In 1981, a drilling program was undertaken to determine how much ore the old timers left behind. The results of this study indicated an ore body made up of broken and caved ground, and solid blocks in pillars and crowns. Reserves are estimated at about 6.8 Mt (7.5 million st) of gold ore, grading at 4 g/t (0.116 oz per st). Total tonnage of material, including waste, is estimated at more than 60 Mt (66 million st). The mining plan is a combination open pit and underground operations. The bottom 78 m (255 ft) will be mined by the underground panel-caving method. The open pit was designed as a contractor operation up to the expected milling stage or the point of sustained ore production. The pit was designed to avoid disturbance of US Highway 85 near Lead, SD. In 1983, the South Dakota Board of Minerals and Environment approved the mining and reclamation plan. Test mining began in the north of the Open Cut using open pit methods. Upon completion of the test pit, Homestake Mining's board of directors approved an expanded mine plan. They committed an additional $27.1 million to prestrip the ore body that is expected to yield 23 t (750,000 oz) of gold. Project life is estimated at 15 years. Exploration program In early 1980, 10 diamond drill holes were drilled from the surface in the vicinity of the east side of the Open Cut. The reserves delineated by that drilling were too small to justify their development. A continuation of this study attempted to quantify the tonnage remaining in the bottom of the Open Cut in the crushed remnants of old stope-and-crown pillars. This was originally thought to be minable by improved drawhole methods using highly mechanized procedures. By early 1981, however, thinking turned toward surface mining methods. The effort to quantify minable ore tonnage ultimately involved drilling 385 reverse-circulation rotary drill holes. These were drilled from August 1981 to March 1983 in several groups of holes. Each group, or drilling program, had a slightly different immediate goal or purpose. The holes were drilled to various depths using truck-mounted Drill Tech 40 drills with doublewalled 76 mm (3 in.) pipe with 134 mm (5.25 in.) three-cone rotary bits. Initially, wet drilling was employed using a cyclone collection system. Since cutting recovery was not as high as it should have been, all subsequent drilling was dry. The cuttings were collected and deposited by way of a cyclone into the sample bag. The pickup for the cuttings using the three-cone bits was about 50 mm (2 in.) above the bottom of the hole. Overall cutting recovery for the drilling program was estimated at 75%. Samples were taken on each 1.5 m (5 ft) of hole drilled. Each sample was split into three 48-g (1-2/3 assay ton) charges. The accepted value was the straight average of the three charges. Because of the known "nugget effect," assays were nearly impossible to duplicate. Therefore, to validate the regular assays, a series of screen fire assays were run. Based on this method of assays and checks, it was concluded that 10% more ounces would be produced than indicated by mine grade. Test pit The northernmost portion of the mine as planned is known as the Terraville test pit. This portion was mined ahead of the rest and separately. It provided answers to questions on slope stability, reserves correlation, mill recoveries, mining costs, and surface mining conditions in various weather and ground conditions since many boulders and much timber were expected. The mining plan for this portion of the pit was successful. More ore was mined than was expected. Mixing of Open Cut ore with underground ore in the mill feed was successful. Impact on the surrounding communities

Jan 10, 1987

By Milner A, Brockway D, Hodges S

The combustion of brown coals in Latrobe Valley power stations produces approximately 500 000 tonnes of solid wastes each year. This material, which includes precipitator ash, char and furnace ash, is hydraulically sluiced to large ashing ponds and the supernatant solution is ultimately discharged to the sea. There are significant operational and capital costs associated with the current ashing system. The ash produced from the Latrobe Valley coals is unique and has a wide variety of potential applications including soil conditioning, concrete and cement extenders, fillers in non-metallic materials, components of building products. In addition, with the application of appropriate technology, it is possible to extract char, sodium sulphate, calcium carbonate and magnesium metal (as the chloride) in substantial quantities from the ash. Research has been carried out to explore the prospects of these various options for ash utilisation. The research has focused on detailed characterisation of the ash material and the potential extraction efficiency for various species under various conditions. From this work a conceptual process has been developed and subsequent studies have been directed towards understanding variables and optimising operating regimes for product extraction. Currently, the work is concentrating on the separation of char, the development of high-grade carbon products and the extraction of sodium sulphate.

Jan 1, 1992

By Stephen R. Iverson, Bill M. Stewart, Michael J. Beus

The U.S. Mine Safety and Health Administration (MSHA) has identified ore pass hazards as a significant safety problem in underground metal mines in the United States injury and fatality data show that many injuries are related to pulling or freeing ore pass chutes and structural failures of control gates and ore pass walls. Researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health are investigating these hazards and developing methods to improve safety during transport of ore and waste. Particle flow analysis methods were used to simulate chute and control gate response to various material loading scenarios. Results from computer models indicate that dynamic impacts from ore and waste rock might be considerably greater than theory predicts. Static and dynamic loads were measured in a laboratory setting using scaled ore (sass mock-ups. Field tests were initiated in an active ore pass to determine actual static and dynamic loads. Field data were compared to computer results and indicated that impact and total static loads were substantially less than the computer model results suggested. Damping factors, normal and shear stiffness, and mass frictional characteristics have a significant effect on particle flow and resulting impact loads.

By K. K. Kelley

The collection and correlation of thermodynamic data concerning substances of metallurgical interest have constituted one of the major activities of the Pacific Experiment Station of the Bureau of Mines, at Berkeley, Calif., for the past several years. Earlier bulletins (32, 33, 34, 36, 36, 37, 38) s in this series are entitled: (1) Contributions to the Data on Theoretical Metallurgy. I. The Entropies of Inorganic Substances; (2) Contributions to the Data on Theoretical Metallurgy. II. High-Temperature Specific-Heat Equations for Inorganic Substances; (3) Contributions to the Data on Theoretical Metallurgy. III. The Free Energies of Vaporization and Vapor Pressures of In¬ organic Substances; (4) Contributions to the Data on Theoretical Metallurgy. IV. Metal Carbonates--Correlations and Applications of Thermodynamic Properties; (5) Contributions to the Data on Theoretical Metallurgy. V. Heats of Fusion of Inorganic Substances; (6) Contributions to the Data on Theoretical Metallurgy. VI. A Revision of the Entropies of Inorganic Substances-1935; and (7) Contributions to the Data on Theoretical Metallurgy. VII. The Thermodynamic Properties of Sulphur and its Inorganic Compounds. The present paper collects and discusses thermodynamic data relating to metal carbides and nitrides, with the view of obtaining usable heat and free energy of formation relationships. Pertinent data on both classes of substances are difficult to obtain experimentally and consequently are extremely rare; it is therefore necessary in many cases, if equations are to be derived, to introduce certain approximations and assumptions. Lack of adequate means of checking results by utilizing data of different types, such as was done frequently in the bulletins dealing with carbonates and sulphates, are readily apparent to anyone who has made even a cursory examination of the available information. Consequently, some of the relationships derived undoubtedly will be found to be inaccurate when more or better data become available. Nevertheless, in view of the importance of some of these substances, it appears worth while to consider the information available at present and to attempt the formulation of as complete a

Jan 1, 1937

Measurement of densities, susceptibilities, permanent magnetization, and calculation of demagnetization factors has allowed computer modelling of gravity and magnetic data over the Middleback Range iron formations of South Australia. As well as providing structural information, the study emphasizes the effects of weathering on the interpretation of magnetic data.

Jan 1, 1975

By Bern Klein, Malcolm Scoble, Justin Widdifield, Andrew Bamber

"It has been suggested that the pre-concentration of ore underground can bring positive economic and environmental benefits to underground mining, particularly at extreme depth. The integration of mineral processing systems for coarse waste rejection and disposal into the underground mining environment has a substantial impact on the economics and operation of the mine. A case study for the integration of underground pre-concentration at Falconbridge’s Thayer Lindsley and Fraser Copper operations in Sudbury, Ontario is discussed, with particular focus on ore evaluation, system design, integration, and impacts on the operation. Conclusions as to the overall feasibility and potential impacts of underground pre-concentration are presented.INTRODUCTIONObjectivesA scoping investigation has been conducted for Falconbridge Ltd on the Fraser Copper Zone and Thayer Lindsley mines in order to develop a better understanding of the operations, and to do a preliminary evaluation of the potential for pre-concentration of the ore underground. The objective was to develop a conceptual design and evaluation of a pre-concentration system for each site. The results are to be used as the basis for a more detailed future study.Underground Pre-ConcentrationThe pre-concentration of ore to reduce the quantity and improve the quality of material transported to the processing plant is not a new concept and has been in practise at several mines including the American Zinc Company in Mascot Tennessee (Munro et al, 1982), the Sullivan Mine in British Columbia and presently at Xstrata’s Mt Isa lead-zinc mine in Australia, as well as at several PGM mines operating in the South African Bushveld. For each of these mines, a high degree of waste rejection was achieved at a coarse particle size with good metallurgical recoveries. The benefits arising from the surface pre-concentration of ore are well documented in the literature (McCullough et al, 1999; Miller et al, 1978; Munro et al, 1982; Schena et al, 1990; Sivamohan & Forssberg, 1991)."

Jan 1, 2006

By C. M. Clapperton, K. E. Darke, A. J. Boyce, C. M. Rice, S. D. Redwood

"Abstract - The Kori Kollo gold deposit is hosted by a c.15 Ma sericitized dacite stock in the La Joya district on the Bolivian Altiplano. The mineralization is of the Bolivian polymetallic vein (BPV) type, with a significant amount of the gold reserves contained in the oxide cap. Field and microscopic studies, K-Ar dating, ??34S values of pyrite, alunite and jarosite, and ??18O values of alunite and jarosite demonstrate that some of this gold is supergene. Two types of supergene gold are present: minute gold grains, 1 to 10 microns across, of high fineness and associated with jarosite and iron oxy-hydroxides; and ‘invisible’ gold, which is probably sorbed onto minerals such as jarosite and iron oxy-hydroxides.Pyrite ??34S values fall in the limited range -3.5 ± 0.6‰, consistent with a magmatic origin. Sulfate ??34S values are homogeneous and overlap closely with those of pyrite (-1.2 ± 2.1‰), which supports petrographic evidence that sulfates replaced pyrite. By contrast, sulfate ??18O values are inhomogeneous with a large range (alunite +2 to 26‰, jarosite -5 to +18‰). These data are interpreted as reflecting kinetically controlled reactions involving various proportions of atmospheric oxygen and local meteoric water. This is typical of supergene alteration and is due to the seasonally dry climate of the Altiplano.The oxide-zone mineralogy is dominated by sulfates and iron oxy-hydroxide minerals with some phosphates and halides, which indicates that the groundwaters were acidic, oxidizing and relatively saline. Under these conditions the most likely complexes responsible for gold mobilization are halides.Geological data and K-Ar ages indicate that oxidation of the BPV deposits began at least around 11 Ma and possibly up to 15 Ma ago, and that supergene alteration lasted until around 4 Ma. During this period, erosion was minimal. Although supergene processes have been active on the Bolivian Altiplano since the Middle Miocene, in contrast to Northern Chile, enrichment of gold has not occurred."

Jan 1, 1997

By C. M. Clapperton, K. E. Darke, A. J. Boyce, C. M. Rice, S. D. Redwood

"The Kori Kollo gold deposit is hosted by a c.15 Ma sericitized dacite stock in the LaJoya district on the Bolivian Altiplano. The mineralization is of the Bolivian polymetallic vein(BPV) type, with a signi?cant amount of the gold reserves contained in the oxide cap.Field and microscopic studies, K-Ar dating, ??34S values of pyrite, alunite and jarosite, and ??18O values of alunite and jarosite demonstrate that some of this gold is supergene. Two types of supergene gold are present: minute gold grains, 1 to 10 microns across, of high fineness and associated with jarosite and iron oxy-hydroxides; and ‘invisible’ gold, which is probably sorbed onto minerals such as jarosite and iron oxy-hydroxides.Pyrite ??34S values fall in the limited range -3.5 ± 0.6‰, consistent with a magmatic origin. Sulfate ??34S values are homogeneous and overlap closely with those of pyrite (-1.2 ± 2.1‰), which supports petrographic evidence that sulfates replaced pyrite. By contrast, sulfate ??18O values are inhomogeneous with a large range (alunite +2 to 26‰, jarosite -5 to +18‰). These data are interpreted as reflecting kinetically controlled reactions involving various proportions of atmospheric oxygen and local meteoric water. This is typical of supergene alteration and is due to the seasonally dry climate of the Altiplano.The oxide-zone mineralogy is dominated by sulfates and iron oxy-hydroxide minerals with some phosphates and halides, which indicates that the groundwaters were acidic, oxidizing and relatively saline. Under these conditions the most likely complexes responsible for gold mobilization are halides.Geological data and K-Ar ages indicate that oxidation of the BPV deposits began at least around 11 Ma and possibly up to 15 Ma ago, and that supergene alteration lasted until around 4 Ma. During this period, erosion was minimal. Although supergene processes have been active on the Bolivian Altiplano since the Middle Miocene, in contrast to Northern Chile, enrichment of gold has not occurred."

Jan 1, 1997

By Qingming Feng, Bo Huang, Dongbo An, Jinhong Zhang

A study of the application of mine tailings as precast construction materials through alkali activation has been carried out, focusing on efficiently activating mine tailings, reducing alkali consumption, decreasing curing time and improving compressive strength. Firstly, the effect of temperature on the alkali activation of mine tailings was studied. Secondly, the impact of additives, i.e., calcium hydroxide and aluminum oxide, on the compressive strength of samples was investigated. Thirdly, the impact of forming pressure on sample strength was studied. Test results showed that unconfined compressive strength (UCS) of 40 MPa was achieved with the geopolymerization products through optimization. Finally, to elucidate the geopolymerization mechanism of mine tailings, microscopic and spectroscopic techniques including SEM/EDX, XRD, and FTIR spectroscopy were used to investigate the microstructure and the elemental and phase composition of the geopolymerization products. The findings of the present work provide a practical method for applying mine tailings as precast construction materials through alkali activation.

By Qingming Feng, Bo Huang, Dongbo An, Jinhong Zhang

A study of the application of mine tailings as precast construction materials through alkali activation has been carried out, focusing on efficiently activating mine tailings, reducing alkali consumption, decreasing curing time and improving compressive strength. Firstly, the effect of temperature on the alkali activation of mine tailings was studied. Secondly, the impact of additives, i.e., calcium hydroxide and aluminum oxide, on the compressive strength of samples was investigated. Thirdly, the impact of forming pressure on sample strength was studied. Test results showed that unconfined compressive strength (UCS) of 40 MPa was achieved with the geopolymerization products through optimization. Finally, to elucidate the geopolymerization mechanism of mine tailings, microscopic and spectroscopic techniques including SEM/EDX, XRD, and FTIR spectroscopy were used to investigate the microstructure and the elemental and phase composition of the geopolymerization products. The findings of the present work provide a practical method for applying mine tailings as precast construction materials through alkali activation.

In spite of a global economy that continues to seesaw and a U.S. Congress that is at odds with the president and themselves, cities around the world are still spending billions on their infrastructure. And that bodes well for the underground construction and tunneling industry and the professionals who work in it. In June, 1,405 of those professionals gathered in San Francisco, CA for the Rapid Excavation and Tunneling Conference (RETC). In addition to the first rate technical programming, attendees were able to see first-hand the latest in tunneling technology from 127 exhibitors who occupied 152 booths. Two short courses preceded the conference and two field trips were offered following the conference.

Jan 1, 2011

By I M. Platten, C J. S Sangster, Y Xie

The Cononish gold-silver deposit is a steep, relatively narrow quartz-vein system, with a current total mineral resource of 154 000 oz Au and 589 000 oz Ag. The northeast-southwest trending system was emplaced into late Proterozoic metasediments, and postdates metamorphism and associated Caledonian Orogenic foliations. Assay and mineralogical data show that gold and silver is spatially associated with sulfides in quartz. The main sulfide is pyrite, but galena, chalcopyrite and sphalerite occur in small amounts. Gold occurs as electrum, with minor native gold, and silver occurs additionally as tellurides and native metal. The gold/electrum is fine-grained, generally less than 100 microns in size. The main ore shoots plunge 45¦ south-west, have a 40 m to 80 m intersection with the existing underground development and extend between 40 m and 260 m down plunge. Small-scale sulfide-bearing domains within the vein carry the highest gold grades. They collectively define the ore shoots, where one or two, and rarely three, of the domains are present at an individual site in the vein. Discontinuity of individual domains, variation in domain thickness and internal heterogeneity results in short scale variation in grade across the structure. Geological mapping along a 1.2 km exploration adit has provided critical æconditioningÆ data to support resource evaluation based on development and relatively wide spaced drilling. In addition, it has provided an indication of potential challenges that could be encountered during production.

Jan 1, 2009

By John Chipman, Wayne L. Worrell

Using recent thermodynamic data for the carbides and oxides of tantalum, columbium, and vanadium, the stable solid phases aboue 1300°K and at 1 atm CO(g) pressure in each M-C-O system have been determined. Pourbaix-Ellingham diagrams have been constructed and are used to estimate the minimum temperatures necessary to obtain these metals by carbothermic reduction under reduced pressures. TANTALUM, columbium, and vanadium react with carbon to form the M,C and MC carbide phases. The M,C carbides have narrow homogeneity ranges, but the MC phases possess considerable ranges of homogeneity.' The free energies of formation of the MC carbides were recently measured, and those of MC and M2Ccarbides have been estimated., (The notations MC and MC denote, respectively, the carbide compositions at the carbon-rich and at the metal-rich boundaries of the homogeneous MC phase.) In this paper, these carbide data are combined with thermodynamic data for the oxides to predict the stable phases in the Ta-C-O, Cb-C-O, and V-C-O systems at specified temperatures and oxygen pressures. M-C-O PHASE DIAGRAMS The solid phases in equilibrium above 1300°K for each M-C-0 system are shown in Figs. 1, 2, and 3. Above 1300°K, the vapor would consist entirely of carbon monoxide; and these phase diagrams were obtained by specifying the vapor pressure of CO(g) to be 1 atm. The temperature at which any two solid phases become unstable is specified along the two-phase equilibrium lines in each diagram. To simplify the diagrams, all solid phases in the Ta-C-O and Cb-C-O systems are represented as stoichiometric compounds. However, the homogeneity ranges of VO and VC are indicated, because they form a complete series of solid solutions.3 It also should be noted that the homogeneity range of

Jan 1, 1964

By Taylor G. H

The Triassic Ipswich (SE. Queensland) coals are of bituminous rank. The more exact rank of individual samples was determined by measuring the reflectance of the vitrinite. While in general the rank of the coals increases with stratigraphic depth, minor reversals, probably related to igneous intrusions, occur.The Ipswich coals form a coherent group so far as petrographic type is concerned. All are comparatively rich in vitrite and clarite, cutinite being the common maceral of the exinite group. The mineral contents of all the coals are comparatively high, clay and quartz being most abundant. The coals appear to be of essentially autochthonous origin, and to have been formed under conditions of fairly rapid subsidence.While the use of the coals is at present restricted to combustion, most have pronounced coking properties, as would be predicted from their petrographic composition and reflectance. However, the high mineral content of the coals would be a limiting factor in their use for coke-making.INTRODUCTIONDuring the last ten years, the Division of Coal Research, Commonwealth Scientific and Industrial Research Organization has carried out an extensive investigation of Australian coals, providing a wide range of analyses of most of the important of them. Special attention has been given in recent years to Queensland coals.Most seams were sampled as a number of subsections, enabling the internal variations, as well as the overall properties, to be assessed. The lenticularity of many of the mineralrich layers may tend to limit the significance of the samples, particularly in respect of ash yield, but although the vertical distribution of mineral matter may vary considerably from one sampling position to another, the lateral variation of the total mineral matter in the whole seam may not be great.Apart from extensive chemical analyses and utilization...

Jan 1, 1963