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By B. Yu, Y. O. Oyediran, M. Robart

"This paper presents the latest flotation development testwork conducted in 2015 on the ‘B Zone’ samples from the Strange Lake Alkalic Complex (SLAC). Since the discovery by Iron Ore Company of Canada (IOC), metallurgical development has been under taken by a number of mining companies targeting various value metals, including yttrium, zirconium, niobium, and rare earths.Most recent, Quest Rare Minerals Ltd. (Quest) completed a Pre-Feasibility Study (PFS) in 2013 where the flowsheet was relatively complex and led Quest to explore alternative options. In 2014, the PFS flowsheet was simplified and one of the features introduced was pre-concentration by rougher flotation. The combined rougher flotation concentrate and slimes successfully recovered >90% TREE in 60% mass thus reducing capital cost and technical risks of the downstream hydrometallurgical processes. The latest flotation development testwork focused on achieving a pre-concentrate in which >80% TREE are recovered in 20% mass. Two separate reagent schemes, based on an ester phosphate collector (Clariant 1682) and a benzoylhydroxamic acid collector (Florrea 7510), were developed. Parameters evaluated in the development testwork included desliming, secondary yttrium and zircon collectors, depressants, temperature, conditioning temperature, time, and density, pH, sodium silicate type, cleaning, and flowsheet configuration. Both developed reagent schemes achieved the targeted metallurgy.INTRODUCTIONThe Strange Lake Alkalic Complex (SLAC) was discovered after geological survey and mapping studies by Geological Survey of Canada and Newfoundland and Labrador Department of Natural Resources between 1967 and 1980. Subsequent exploratory drilling programs by Iron Ore Company (IOC) in the 1980s found that the REE and high field strength element (HFSE) mineralization were within the central region of the SLAC which was named A Zone by IOC and later renamed Main Zone by Quest Rare Minerals Ltd. (Quest). Additional exploratory drilling outside the Main Zone by IOC and later by Quest, led to the discovery of B Zone, which was recognized as the most significant deposit of rare earth elements, yttrium, and zirconium in the SLAC. The B Zone Indicated Resources are estimated at 278.13 Mt at 0.93% total rare earth oxide (TREO) and Inferred Mineral Resources are estimated at 214.35 Mt at 0.85% TREO (Oyediran et al., 2014)."

Jan 1, 2016

By W. J. Tough

THIS paper offers examples of some of the typical calculations which occur in the ventilation of metal mines. The fi.rst section of the paper discusses the problems associated with natural-draft pressure; the second section presents the more common of the calculations concerned with the operation of mine fans; the third section illustrates the integration of the individual problems covered by the preceding sections into the larger problem of determining the operating characteristics of a fan for a particular mine duty. There is a very definite limit to the extent to which pure arithmetic can be successfully applied to the solution of min<; ventilation problems. As mines advance from the exploration, development, and initial production stage to the rime when underground workings become exceedingly complex, there is a considerable increase in the relative importance o theory and judgment in the solution of ventilation problems. These calculations illustrate the application of mathematics to ventilation, but they also in-elude examples of instances where arithmetic cannot be conveniently applied, and important estimates, based on judgment compounded of experience and a knowledge of the theoretical consideration involved, must be made. The inclusion of such estimates is intended as a guide and a warning to the reader; a guide in assisting him to recognize and estimate his own incalculables; and a warning that the solutions must not be blindly applied to his apparently similar problems. These sample calculations are intended to assist the reader in applying the theory contained in the standard texts on metal-mine ventilation. They have been selected from the ventilation experience of a British Columbia mine.

Jan 1, 1942

By R. E. Johnson

Seventy years after the start of the Industrial Revolution in Great Britain, as reckoned from Arkwright&apos;s water frame patented in 1769, there was a significant development of the metallurgical industry in Virginia. In Britain, crucible steel had been rediscovered by Benjamin Huntsman in 17~0, and this made spring and tool steel more generally available. The metal-turning, screw-cutting lathe, including the basic principles recognized in today&apos;s engine lathe, was developed by Henry Maudslay about 1797. Wrought iron, as manufactured by Henry Cort&apos;s process patented in 1784, was readily available. Richard Trevithick&apos;s highpressure steam locomotive had met its test on the Pennydarren tramroad in 1804, and George Stephenson had built his famous Rocket, along with several other locomotives, at Newcastle around 1828. Puddling furnaces and a rolling mill had been placed in operation at the Tredegar Iron Works in Glyn Sirhowy, Monmouthshire, Wales, in 1807. In the United States, expanding commerce and a growing population resulted in continuing development from the Chesapeake to Virginia&apos;s Blue Ridge, and this demanded improved means of transportation. Ore deposits rich in hematite had been found in Virginia&apos;s Piedmont during the Colonial period, and a number of blast furnaces now dotted that area. The products of these operations were mostly pots, kettles, stove parts and like items for local trade. The James River and Kanawha Canal was incorporated in January 1785. Its eastern leg, winding along the slope of the high bluffs overlooking the river, was completed about 1800. About two dozen railroads were chartered in Virginia between 1830 and 1837. With expanding population and steady industrial development came a need for metallurgical products. Throughout the eastern United States, numerous metallurgical enterprises sprang up, and many of these flourished. The purpose of this article is to outline the development of one Southern metallurgical company, the Tredegar Iron Works, which was to have a significant impact on the industrial development of Virginia and the fighting of the American Civil War. Although the Tredegar Iron Works no longer exists, remnants of the early operations have been restored, and the current status of the site is also presented.

Jan 1, 1999

By Jiuhua Xu, Shuiku Jia, Weiren Sun

"Abstract -The Jinqingding gold deposit, situated in the east Jiaodong Peninsula of Shandong province, is typical of the pyrite-quartz vein gold deposits in the Muping-Rushan gold belt of China . The gold deposit is controlled by a great NNE fracture zone and is composed of several lenticular orebodies within the fracture zone occurring in the Kunyushan granite massif. The Kunyushan granite massif was formed by the replacement of the Archean Jiaodong group.The main minerals associated with gold are pyrite, chalcopyrite, galena and sphalerite; the gangue minerals are dominated by quartz, sericite, microcline and calcite. The mineralizing event can be divided into four stages: (1) pyrite-quartz; (2) quartz-pyrite; (3) siderite-polymetallic sulfides; and (4) calcite-quartz. Gold occurs mainly as native gold and electrum in stage 1 and stage II. There are some evident differences between pyrite from major stages of gold mineralization and that from minor stages; these include differences in crystal forms, size and composition of fluid inclusions.Wallrock alterations consist of sericitization, silicification, pyritization and potash-feldspar alteration. Five alteration zones can be distinguished from unaltered granite (zone 0) to vein lodes (zone IV). Au and Ag increase rapidly from zone 0 to zone IV, Cu increases continuously, while Pb and Zn increase slowly. R-type geological factor analysis indicates that the Au, Ag, Cu, Pb and Zn bear a close relationship to wallrock alteration."

Jan 1, 1994

By J. Peterson, D. D. Tannant, J. Todd

"A review of blast designs and improved blasting practices at the EkatiTM diamond mine is presented along with the results of three blast-monitoring experiments. Blast monitoring was undertaken to investigate blast damage mechanisms in the mine’s well jointed rock mass. Rock mass damage caused by production, pre-shear and wall control blasts was measured. EkatiTM uses 270 mm holes for production blasting, and 165 mm holes loaded with a decoupled charge for pre-shearing. The production blasts are loaded with bulk emulsion/ANFO blends. The mine plan involves using 30 m double benches. A 30 m high pre-shear is drilled and blasted prior to the production blasting that is done with sequential 15 m benches. This paper summarizes the monitoring equipment and data gathered to date. IntroductionThe EkatiTM diamond mine is located about 300 km northeast of Yellowknife, Northwest Territories, Canada. The mine is a joint venture of BHP Diamonds Inc. (80%) and geologists Charles Fipke and Stewart Blusson (10% each). The EkatiTM mine is Canada’s first diamond mine and BHP is the operator. The mine is accessed by air and by a winter ice road.The first kimberlite pipe mined at EkatiTM is known as the Panda pipe. The Panda open pit mine will have a total depth of 315 m (Fig. 1), a width of about 600 m, and a 50° overall slope. Initial ore production is 9000 tonnes per day.This paper summarizes the pre-strip blasting and the evolution of the production and wall control blast designs from 1997 to 2000. The initial blast designs and the rationale behind subsequent changes that took place are presented along with the techniques currently in use.The paper also briefly presents an experiment done to measure the rock mass response to blasting. Three blasts were instrumented with geophones, gas pressure sensors and time domain reflectometry cables. A brief summary of the instrumentation and data gathered is included."

Jan 1, 2001

By P. Cain, B. Martens

"Grande Cache Coal (GCC), an investor-owned Alberta company, is in the final stages of the regulatory process leading to the resumption of coal mining in the Smoky River Coal Field of Alberta. Although many opportunities for low-cost, high-yield mining remained on the property, GCC opted for a long-term production plan that ensures stability for the local economy, sustainable use of the resources in the area, environmental responsibility and a satisfactory return for its investors.GCC entered the Alberta coal approval process in late 2000 with a public disclosure document. In October 2001, GCC formally submitted an application for mining approval and an environmental impact assessment (EIA) to the government and the public. The application covered the proposed Grande Cache Coal project, which includes the No. 7 underground mine, No. 8 surface mine and coal processing operations. The EIA provided a comprehensive investigation of environmental sensitivities in the project area, matched with environmental protection programs. The project is based on commencement of operations in late 2002. GCC’s plans are founded on a commitment to sustainable development and has framed this commitment in the context of a long-range mine development plan that will sustain the community of Grande Cache over the next 25 years. The Grande Cache coalfields offer extensive coal reserves and opportunities, for both surface and underground mining. Combining highly productive U.S.-style room and- pillar underground mining methods and conventional truck-and-shovel open pit mining, GCC’s approach to sustainable development encompasses community involvement and reclamation of mine sites to productive land uses after mining."

Jan 1, 2002

By A. J. Makoka, B. C. Qi

Reliable monitoring of corrosion is vitally important in the combat against corrosion and over the last two decades the interpretation of electrochemical noise has received considerable attention as a means to discriminate between different types of corrosion. To this end, many different analytical methods have been proposed, such as power spectral density analysis and analysis via various other stochastic criteria. However, although many corrosion systems are nonlinear and therefore not readily interpretable by the abovementioned analytical approaches, few studies in the analysis of electrochemical noise to date have exploited advances made in the analysis of nonlinear systems. In this paper, the use of phase space methods to analyze and detect change in corrosion systems via electrochemical noise is considered. In particular, the electrochemical noise data are used to reconstruct trajectories in the so-called phase space of the system and changes in the topology of these trajectories or attractors as represented by correlation dimension curves are consequently interpreted as an indication of change in the dynamics of the system.

Jan 1, 2005

By C. H. Hopper

DIAMOND drills have played an important part in the development of mines for many years. Recently. they have also entered the production field arid the use of diamond drills m the primary breaking of ores has become a big branch of the industry. The writer has estimated roughly that the total diamond drilling in Canada during 1942 was 5,625,000 feet, of which 2,250,000 feet, or 40 per cent, was for blast-holes. This accounts for 6,750,000 tons of ore broken, using the conservative factor of 3 tons per foot of hole. Many consider that the use of diamond drills for blast-holes is the most important advance in mine practice of the past decade, and the industry owes a great deal to the staff of Noranda Mines, Limited, for the pioneering they have done in the development of long-hole mining methods and for publishing their results. A great many mines have followed Noranda&apos;s lead. At the Waite-Amulet, Aldermac, Flin Flon, Canadian Malartic, Hoyle, and Matachewan Consolidated mines, most of the ore is broken by long-hole blasting. While the mines were developing new methods, the diamond-drill industry was developing mechanically-set bits and better machines. Through the effective use o smaller, cheaper diamonds, as well as more efficient setting, bit costs per foot are only one-half what they were ten years ago. Few people realize that a diamond bit is relatively inexpensive. The common EXT coring bit, for example, contains some 200 small diamonds, weighing altogether about 2.70 carats which, at $3.40 per carat, cost $9.20. After use, the equivalent of about 100 of these diamonds may be recovered. Therefore the true cost of the bit is only $7.00, made up of $4.60, the cost of the diamonds lost, $2.00 for setting, and $0.40 tax. The trend in machines has been toward specialization for the different classes of rock in blast-hole work. Light, high-speed machines have been developed for soft ores and higher powered machines for hard ores.

Jan 1, 1943

By W. E. MacDonald

This paper relates the story of 100 years of mining in the Harbour Seam at the Princess Colliery, Sydney Mines, Nova Scotia. Several interesting anecdotes are included along with the discussion of the evolution of coal mining methods in the area. Finally, some of the recently introduced equipment at Princess Colliery is described, and prospects for the future of the industry are outlined.

Jan 1, 1968

By Bennett McLaughlin

AGNICO-EAGLE started sinking the Penna Shaft in 1995 with a hoisting plant capable of hoisting 1,800 tonnes per day from a 2,240 metre deep shaft. Exploration success lead to the installation of a hoisting plant capable of extracting 4,500 tonnes of ore and 1,800 tonnes of waste per day from a depth of 2,210 metres. The introduction of a new rope selection factor, permitting a safety factor of 4.0, represented the breakthrough required for a cost-effective project. This paper describes the process taken to introduce the new rope selection factor and its impact on the original plant.

May 1, 2001

By Paul Armstrong

THE first discovery of lead and zinc ore on Calumet island was made in 1893 by John Lawn, who then staked a portion of the property now owned by Calumet Mines, Limited. His discovery was developed by James and Calvin Russell, who are said to have shipped a few tons of sorted ore, averaging 39 per cent zinc, 13 per cent lead, and 11 oz. silver per ton. In 1898, the property was being operated by the Grand Calumet Mining Company, who mined and shipped, for treatment in a Belgian smelter, 1,100 tons of ore averaging 32 per cent zinc, 9 per cent lead, and an unreported content of gold and silver. After some indecisive exploration by an American syndicate in 1907, the property lay idle until1910, when the Calumet Metals Company-later reorganized as the Calumet Zinc and Lead Company-re-commenced exploration. After sinking an 85-foot shaft-the McDonald shaft-and doing a few hundred feet of drifting and cross-cutting, this Company, in 1912, erected a 150-ton daily capacity gravity-concentration plant, in which some 800 tons of ore, mined from the McDonald shaft and Bowie pit, were milled. Owing to very disappointing mill recoveries, the property was shut clown and-after several years of idleness-in? 1916 the mill and mining plant were destroyed by fire and the Company went into bankruptcy. In 1918, an unknown operator shipped to an Omaha, Nebraska, smelter 22 tons of ore, probably sorted from the dumps of the Ste. Anne shaft and Galena pits, averaging 44 percent lead, and 0.26 oz. gold and 61 oz. silver per ton. The British Metals Corporation (Canada), Limited, in 1926, optioned the property. They unwatered the McDonald shaft and, after doing an additional 300 feet of cross-cutting and drifting on the 85-ft. level, estimated there were some 33,000 tons of ore between this level and the surface. Surface exploration, including trenching, on other showings on the property gave discouraging results and the option was dropped.

Jan 1, 1941

By L. H. Van Loon, E. G. Crayston, A. F. Heather

"IntroductionTHE PROPERTY of Madsen Red Lake Gold Mines. Limited. comprises fifty-eight claims located between Russet and Faulkenham lakes in Baird and Heyson townships of the Patricia portion of the District of Kenora. The mine is seven miles •by road from the hamlet of Red Lake. This latter centre is .connected to the Trans-Canada Highway at Vermillion Bay, Ontario, by provincial highway No. 105 which has a total length of one hundred and thirteen miles.The Madsen property went into production on August 11th, 1938, with a milling plant rated at 300 tons per twenty-four hours. Changes made in the crushing plant during October, 1938, allowed a •finer feed to be delivered to the mill and increased the milling •capacity to 400 tons per twenty-four hours. During 1948, steps were taken to add an additional 400-ton capacity unit to the milling plant. This latter work was completed by May, 1949, giving the present total milling .capacity of 800 tons per twenty-four hours.It was realized in the early 1940's that, eventually, considerable material suitable for backfilling in the mine would be required. As there were no large deposits of gravel or sand anywhere near the mine, officials of the Company considered it advisable to investigate the feasibility of using mill tailings for mine •backfill. Since Madsen mill tailings contain approximately 80 per •cent of minus-200-mesh material, it was not considered practical to use them for underground backfill without first removing the finer material. as the slimes present in a product of this fineness would without doubt preclude any drainage whatsoever. Table I gives a sizing analysis of Madsen mill tailings and Table II a quantitative chemical analysis of the ore."

Jan 1, 1954

By Angus D. Campbell

Introduction In the Twentieth Annual Report of the Mcintyre Porcupine Mines, Limited, for the year ending March 31st, 1932, the General Manager, Mr. R. J. Ennis, said: "During the period under review, the plans outlined in last year&apos;s report have been completed, and all operations have been centralized in the new plant adjacent to No. 11 shaft. The new mill went into operation on May 27th and attained its rated capacity of 2,000 tons per day on November 15th. The new shops, warehouse, change-house, and general offices were occupied on December 1st, consummating the change from the old to the new plant ... "Silicosis is now definitely recognized as an industrial disease, and progresses rapidly when associated with tuberculosis. In an effort to combat its prevalence and progress, the new change-house was designed to build up the men&apos;s resistance to this and other forms of disease. It provides for a complete change from underground to street clothing, with a shower bath and solarium treatment in the interval. &apos;Unfortunately, in almost every goldmine, a very small percentage of the work-men are not adverse to taking some of the high-grade ore for their own purpose. This, in turn, tends to cast suspicion upon the honourable as well as the dishonorable employees. The new change-house routine discourages this practice and eliminates unjust suspicion, to the satisfaction of all concerned with the Company&apos;s operations".

Jan 1, 1933

By Clifford S. Gibson

A year ago a paper (1) was presented at the Annual Western Meeting of the Institute regarding silicosis in Ontario mines. It described the whole problem as we see it and discussed the means of prevention. The work and aims of the Technical Silicosis Research Committee of the Ontario Mining Association, and of the Committee&apos;s field engineer, were fully described also and it is suggested that reference be made to this paper in order to have a better understanding of the observations which are presented now. These observations enlarge upon parts of the dust control measures already discussed and tell of general progress in the past year. They concern fifty properties, the majority of the operating mines, which vary in size from the hopeful prospect to established producers yielding 11,000 tons of ore daily. Most of these are gold mines; a few copper-nickel. The ores range from heavy sulphides to siliceous materials and they are mined by many methods from varying types of deposits. The majority of the latter are steeply dipping and all are found in Precambrian host-rocks. Up to the present, die greatest depth to which mining has penetrated is 6,400 feet.

Jan 1, 1939

By B. S. A. Tatone

The surface roughness of unfilled rock discontinuities has a major influence on the deformational and hydraulic behaviour of discontinuous rock masses. Although it is widely recognized that surface roughness is comprised of a large-scale (waviness) and small-scale (unevenness) components, most investigations of surface roughness have been restricted to small fracture surfaces (< 1m2). Hence, the influences of the large-scale components of roughness are often neglected. Furthermore, these investigations typically focus on analyzing roughness in terms of two-dimensional profiles rather than the complete three-dimensional geometry, which can lead to potentially biased estimates of roughness. This contribution demonstrates the use of a new optical digital measurement system, based on the principle of triangulation, to digitize a large-scale natural rock discontinuity surface at both outcrop-scale (~6m x 2m) and lab-scale (~100mm x 100mm). Subsequently, the digitized surfaces are systematically analyzed using the three-dimensional roughness methodology proposed by Grasselli to investigate the dependency of roughness on sample window size and measurement resolution.

May 1, 2009

By Peter Moser, Thoma Oberndorfer

"Within the research project “Mine Development” (Fettweis and Moser, 1990) a PC-based mine database has been built up since 1991 and so far includes detailed technical and economic data of about 150 under-ground hardrock mines in industrialized countries worldwide. These data represent about 50% of the underground hardrock mines in west and central Europe, Scandinavia, United States, Canada and Australia (Fig. 1). The mining operations included in the database have been visited directly and analyzed with respect to their deposit conditions, their general design and layout and also their operational and economic performance.The main aim of the Mine Database is to make a contribution to an improved planning of new underground hardrock mines. An analysis of current mine planning practices shows, that both personnel and company experience is still a dominant factor in planning new underground hardrock operations. Through the information included in the Mine Database the experience of a single per-son or company is supplemented by the experience of a wider group of people. The Mine Database makes the huge amount of experience that is available worldwide in the field of under-ground mining accessible for new mining projects. From that a contribution to a more reliable mine planning procedure based on the performance of existing mining operations is expected.In addition to its use in planning new mining operations, the Mine Database can con-tribute to the exchange of technical data among different mining operations, especially on equipment performance, etc. Such an information service is offered by the Department of Mining Engineering & Mineral Economics in Leoben and is already being used by different mining companies. To respect proprietory information, company specific information is not released under any circumstances.The cost of building up the Mine Database, so far, is about US$500.000 — two thirds of which is labour, and one third, travel."

Jan 1, 1996

By Jr. Arcand

Canadian Economy ? Getting Results ???? A stronger Canadian economy ???? National debt cut ???? Taxes reduced, tax-free savings account, support for manufacturing sector ???? Assisting with infrastructure Aboriginal issues affect all Canadians ???? Aboriginal prosperity is in everyone?s interest ???? Conditions for Aboriginal success include: - Indian residential school settlement - resolving outstanding specific claims

May 1, 2008

By L. M. Pidgeon

MAGNESIUM metal, with a specific gravity of 1.73, is two-thirds the weight of aluminium and one-quarter that of steel. It is the lightest metal which is stable in the atmosphere. Before the war it had begun, though somewhat slowly, to take a place among the established metals. In 1939, magnesium production on this continent amounted to some 3,000 tons per annum and was confined to one company. At that time, Germany produced perhaps 20,000 tons. The advent of war, however, increased the demand to fantastic heights and introduced production problems of unprecedented magnitude. By the end of 1943, North American production is expected to reach 300,000 tons per annum (1), an increase of one hundredfold. Such a rate of expansion has not been witnessed previously in the history of metallurgy. It has given the metallurgist an opportunity to try new production methods and to learn in a short time what might otherwise have taken many years. The metallurgy of magnesium is still in its formative years and at this time widely different production methods are in operation side by side. This paper will discuss these methods in so far as information is available for publication at this time. A general description of the new Canadian industry will be included.

Jan 1, 1944

By O. A. Bascur

Several new hydrometallurgical plants have been built in the past years, new processes and equipment as well as advanced process control systems are being used to deal with the increasing requirements of safety, quality and production. Plant Information Management Systems are now being recognized as a key infrastructure component of the plant, giving the management, the operators, process engineers, finance, maintenance, and regulatory agencies an integrated view of the operation and providing the links for the (increasingly) multidisciplinary organization. This paper reviews several implementations of Plant Information Systems; real time performance management infrastructure examples are reviewed as a key component of business strategies, such as Mine to Port Planning and Supervision, Metallurgical Mass Balances, Solvent Extraction Composition Statistical Process Control, methods to minimize organic losses, reduce variable costs and to improve metal extraction. Several examples are provided to illustrate how companies are using the real time and historical information from assets and metallurgical processes to enable and empower people to improve the operations quality, safety and throughput, as well as continuous improvement and innovation initiatives.

Jan 1, 2007

By J. H. H. Chamberlin

"In the Introduction the author briefly discusses the company history as it relates to the development of its contracts with the Japanese steel mills. The main part of the text describes how Coleman Collieries Limited approached the problem of mining coal profitably in thick, steeply inclined seams. For many years a basic room-andpillar system was worked by conventional methods. Main roadways were driven on strike across the mineable area. These roadways acted as haulage routes for coal, materials and men. Rooms were developed to the rise of the main haulage route by pairs of men using air-operated hand picks. As these rooms advanced the miners would lay and extend a sheetiron chute down which mined coal would gravitate to a controlled loading point, where it was loaded into trains of mine cars. Connecting roadways or ""OFFS"" were driven at predetermined intervals between adjacent rooms, forming pil1ars or blocks. Extraction of the blocks followed on a line conducive to good strata control some distance behind the developing rooms. A need for higher productivity, expansion of the operations and a scarcity of qualified miners resulted in the company deciding to mechanize its underground mines. Joy 6 CM continuous miners and 10 SC shuttle cars were selected as being machines that could reasonably negotiate the problems associated with the pitching seam. The equipment, nonetheless, has definite limitations and Coleman therefore developed a modified version of the room-and-pi11ar system such that the miners and cars could work on cross pitch. In the area described, main roadways were driven to the rise on an average gradient of 12 degrees. Panels, which consisted of two parallel roads with interconnecting cross-cuts, were then developed on strike to a boundary point. Blocks formed in the development of the panels were subsequently extracted on retreat. Problems associated with each phase of the operation are thoroughly discussed, together with roadway support methods and equipment used for the conveyance of coal and materials."

Jan 1, 1972