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By P. J. Bourassa

Incorporated in 1957 under the laws of the Province of Quebec, Quebec Cartier Mining Co. undertook the development of its low-grade iron ore reserves located at Lac Jeannine in the southwest extremity of the Quebec-Labrador trough. This challenge comprised the construction of a 200-mile access road, two towns, a 191-mile-long railroad from Port Cartier to Lac Jeannine, a hydro-electric generating plant on the Hart Jaune River, and mining, crushing, concentrating and ancillary facilities to support a yearly production of 8.0 million tons of iron ore concentrates at 66% Fe. In order to meet increasing market demands for iron ore concentrates concurrently with the depletion of its Lac Jeannine reserves , Quebec Cartier announced, late in 1969, the first step toward bringing into production a new iron ore deposit, known as Mount Wright, located 70 air miles northeast of Lac Jeannine and 25 miles southwest of Labrador City, Newfoundland. In September 1970, the company announced its decision to develop and bring into production its Mount Wright reserves at an annual rate of 1 8.4 million dry long tons. The scope of this project included the construction of an access road linking the mine, the new town and Labrador City, Newfoundland, the extension of the railroad by some 86 miles, the construction of an ore concentrating plant with all the ancillary facilities, the development: of the mine, the construction of a pourer transmission line and a new town adjacent to Lake Daviault. The Mount Wright story is divided into five individual papers covering: (a) the history and development of the project; (b) the mine; (c) plant control by a process computer; (d) crushing, grinding and concentrating; and (e) the townsite of Fermont.

Jan 1, 1977

By D. A. Rhys

"The Red Bluff porphyry is a tabular 2 km long north-west trending Early Jurassic quartz diorite to monzodiorite body that intrudes a folded Triassic greywacke sequence in the lskut River area, northwestern British Columbia. The porphyry is 500 m to 800 m northeast of the Snip orebody, which is a southwest-dipping shear-vein, termed the Twin zone that contains approximately 35 tonnes of gold.The intrusion associated with the mineralization is characterized by 0.3 cm to 4 cm phenocrysts of K-feldspar in a mediumgrained plagioclase porphyritic matrix. It is overprinted by pervasive sericite + quartz ± K-feldspar ± biotite (potassic) alteration characterized by intense stockworking of quartz veins containing magnetite--hematite bands. This assemblage is cut successively by quartz veins with minor iron-oxides and pyrite, and by younger pyrite veins with phyllic envelopes. The system is gold-rich but copper-poor, with typical grades between 0.25 g/t and 0.6 g/t Au, and 0.1% and 0.2% Cu. All styles of alteration and veining have similar abundances of these metals. Where southwest- and north-east dipping shear zones are developed in the porphyry, veins of all types are sheeted and foliation parallel. These sheeted zones are interpreted to be syntectonic. Asymmetric phenocrysts, folded veins and oblique foliations developed in the 130 haulageway of the Snip mine imply oblique normally-directed shear on the southwest-dipping foliation.The adjacent Twin zone is a high-grade auriferous shear-vein system that is internally banded with: (1) carbonate-chlorite-biotite veins, with textures indicating formation at least partially by wallrock replacement, and (2) dilatant quartz-sulphide veins. Veins commonly have potassic alteration envelopes that contain biotite ± calcite ± K-feldspar. The zone is highly deformed and schistose, with numerous kinematic indicators including shear bands, asymmetric folds, rotated porphyroclasts and oblique foliations that indicate a normally-directed shear sense which is parallel to that indicated by fabrics within the porphyry.Precious and base metal veins within 2 km or 3 km of the Red Bluff porphyry are zoned. Veins and shear-veins proximal to the intrusion, such as the Twin zone, are typically enriched in gold, copper and molybdenum, and have potassic alteration envelopes dominated by biotite. Distal veins usually contain relatively abundant zinc and lead and have sericitic alteration envelopes. Structures of both types have an Early Jurassic galena Pb-Pb isotope signature.The similarities in structural fabrics and alteration histories in both the Twin zone and the porphyry, the zoning of the vein systems in the area, and the apparently concordant Early Jurassic zircon U-Pb age from the porphyry and galena Pb-Pb dates from the Twin zone and surrounding vein systems suggest that intrusion, semi-brittle deformation and a large mineralizing hydrothermal system were closely related temporally and genetically."

Jan 1, 1995

The United States is rapidly depleting many of its most important minerals and fuels. The first two Annual Reports by the Secretary of the Interior, under the Mining and Minerals Policy Act of 1970, made us acutely aware that the natural resources that enabled this Nation to attain an unprecedented growth in terms of economic well-being, and to set an example of independent strength through the democratic process, are finite. Once they are depleted, large imports will be required. Simultaneously, competition for available supplies, especially of petroleum, is increasing in the expanding European and Japanese industrial communities and in the underdeveloped nations of the world. Even before the crisis of late 1973, the oil-producing nations of the world, principally in the Middle East, but including Canada and Latin America, were recognizing that the worldwide need for crude oil, petroleum products, and natural gas could be translated into an unprecedented economic bargaining position. Thus, the members of the Organization of Petroleum Exporting Countries (OPEC) raised the price of their crude twice during the first 6 months of 1973. By yearend the energy situation had be-come acute, and it seemed probable that regardless of current political developments, the era of cheap energy was over.

Jan 1, 1973

By R Dimitrakopoulos, K Kawahata, L Montiel

A method that optimises mining complexes that are comprised of multiple processing destinations, open pits and underground operations is presented. Mining, blending, processing and transportation decision variables are simultaneously optimised while accounting for geological uncertainty. The method uses a simulated annealing algorithm at different decision levels to generate a stochastic-based extraction sequence and processing policies. A case study shows its ability to generate a higher net present value while facing a reduced amount of risk when compared to traditional optimisation methods.CITATION:Montiel, L, Dimitrakopoulos, R and Kawahata, K, 2014. Globally optimising open pit and underground mining operations under geological uncertainty, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014, pp 201–212 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By Teixeira

An experimental investigation on the kinetics of oxidation of As(III) with H202 in synthetic effluent solutions followed by precipitation of Fe/As (V) compounds was carried out. The variables investigated were: As concentration (200 -3000 mg/l) , oxidation pH (2.0 -11.0), oxidation temperature (25 -800C) , H202 stoichiometric excess (50% -100%), precipitation pH (5.0 -7.0), precipitation agent (Fe2+ -Fe3+). Fixed conditions were, Fe/As molar ratio (6:1) and stirring speed (560 rpm). The results were empirically modelled. The precipitates obtained were amorphous. The precipitates were checked upon their environmental stability according to the United States Environmental Protection Agency (U.S.E.P.A.) Toxicity Test, and were considered to be adequate for deposition in impermeable waste dumps. The combined Fe/H202 detoxification process, in selected conditions, was able to reduce the As contents of effluents containing 1600 mg/l As to 0.1 mg/l, in about 2 1/2 hours of total processing time.

Jan 1, 1990

By Charles P. Lazzara, Alex C. Smith, Mark W. Ryan

The U.S. Bureau of Mines conducted a study to evaluate the effect of ventilation on the performance of automatic sprinkler systems in extinguishing wood crib fires. Experiments were conducted at airflows of 0, 0.76, 1.5, 2.5, and 4.1 m/s. Two experiments were conducted at each airflow, using 74° C fast response pendent sprinklers in one experiment and 74° C fast response horizontal sidewall sprinklers in the other experiment. In the experiments at airflows of 0 and 0.76 m/s, sprinklers were located directly above the fire and 2.4 m upstream and downstream of the fire. The sprinkler directly above the fire was the only sprinkler to operate with no discernible difference in the suppression capability of the pendent and horizontal sidewall sprinklers. In the experiments at airflows of 1.5 and 2.5 m/s, sprinklers were located directly above the fire and 2.4 and 4.8 m downstream of the fire. The sprinkler located 2.4 m downstream was the only sprinkler to operate with the horizontal sidewall sprinkler being more effective in extinguishing the wood crib fire. The average response times of the sprinklers at airflows of 0.76, 1.5, and 2.5 m/s were 3-1/2 times the average response time of the sprinklers at 0 m/s. The results of this study will help enhance the safety of the nation's miners.

Jan 1, 1993

By Lv Guozhi, Ren Xiaodong, Liu Yan, Dou Zhihe

"This paper investigated a new desulfurizer, dolomite and ferrosilicon. Magnesium vapor produced by silicothermic reduction of dolomite and ferrosilicon in an immersion tube of molten iron was injected into the molten iron by carrier gas through the underpunch of the tube and desulfurization reaction occurred. In order to explore the desulfurization process of molten iron by the new desulfurizer, the thermodynamics, and experiments of magnesium vapor production and desulfurization have been studied. Through thermodynamic calculation, the reaction temperature of magnesium vapor production by 75ferrosilicon and light-burned dolomite is 1838K in the standard state and decreased with the decreasing partial pressure of magnesium vapor, PMg· When PMg=25kPa, the reaction happens at 1673K. From experiments of magnesium vapor production, reduction efficiency of Mg vapor is about 60 % in 15 minutes at 1673K. From hot metal experiments, the desulfurization efficiency is 89.35%, and the lowest sulfur concentration after desulfurization is 46ppm.IntroductionPretreatment desulfurization of hot metal has become a necessary step in modem optimizing steelmaking process for its cheap cost, which can not only liberate of blast furnace productivity and reduce the burden of produce steel, but also effectively improve overall economic efficiency of the iron and steel system[l-ZJ_ At present, injection magnesium particle is one of the two main methods of desulphurization in hot metal owing to its strong affinity for sulphur, low amount of slag produced, low iron loss in slag skimming and low equipment investment[3l. However, there are still some insufficiencies on the hot iron pretreatment with magnesium particles at present[4-5l"

Jan 1, 2013

By IPMI Educational and Scientific Foundation

It is with great pleasure that we announce the availability of this fourth issue of the IPMI Journal, a publication of the International Precious Metals Educational and Scientific Foundation. This digital peer reviewed publication has been created as a vehicle for the sharing of technical information related to the science and technology of precious metals. Since 1976, the International Precious Metals Institute has championed the exchange of information of critical importance to the precious metals scientific and commercial communities through its various communications vehicles. This has included instructional videos, annual conference symposia, special topic committee meetings, regional seminars, and professional and student achievement awards. Due to the breadth of important topics related to all aspects of precious metals, it has been the vision of the IPMI to provide a publication available to the general public that would become a key source of pertinent topics containing high quality publications by experts in their fields of study. Historically, the IPMI has attracted world renowned experts in many fields (including Nobel Laureates Henry Taube, Ei-ishi Negishi, Robert Grubs, Professor Ben Feringa, and David MacMillan) in the dissemination of discoveries, inventions, and industry proven practices. Such information has a total value greater than the sum of its parts as seemingly unrelated innovations from distinct focus areas can be adapted to solve problems. Because of this important characteristic of information exchange, we have decided to create a digital journal, available to the general public, that will not only communicate state of the art discoveries and sound practices, but will also review historical communications from the IPMI’s archives that have value and use even in today’s environment. On behalf of the members and leaders of the IPMI, we hope you will find value in this new publication.

Dec 1, 2020

The Comstock Lode, a world-class precious metal vein district near Virginia City in western Nevada, U.S.A. (Fig. 1), produced 8.3 million ounces (0.28 X 106 kg) of gold and 193 million ounces (6.56 X 106 kg) of silver during the period 1859 to present (Bonham and Papke, 1969). More than 95% of production was from the Comstock fault, while the adjacent Silver City, Occidental and Flowery vein systems produced about $10 million (U.S.). Within the Comstock fault high-grade ore bodies, or bonanzas, were distributed over 2.3 miles (3.8 km) along strike and persisted to >3000 feet (>900 m) below the surface (Fig. 2). Bonanzas consisted of as much as 1.4 million tons (1.3 million tonnes) of ore grading up to 1.9 oz./ton (65 gm/ton) Au and 30 oz./ton (1020 gm/ton) Ag (Table 1). Some bonanzas occurred in the main Comstock fault plane while others, including the highest grade bonanzas, formed in hangingwall frac- tures. After 1880 most ore consisted of lower-grade vein material surrounding mined- out bonanzas and large volumes of mineralized vein and wall rock in the Comstock hanging- wall that were mined from open cuts. Deep mining was hindered by large quantities of hot water and bad ground which ultimately defined the limits of underground production. The widths and richness of Comstock bonanzas strongly influenced U.S. mining law, milling and underground mining methods, and securi- ties regulations that are in practice today. Within the district Mesozoic metasedimentary rocks, metavolcanic rocks, and granitic in- trusions are overlain by Miocene volcanic rocks (Thompson and White, 1964). Veins cut all lithologies. Miocene volcanic rocks and their K-Ar ages (Vikre, McKee and Silberman, 1987) include Santiago Canyon rhyolite (22

Jan 1, 1987

PROF RICHARD ÅKERMAN Stockholm, Sweden PROF RICHARD BECK Friberg, Germany ANDREW CARNEGIR New York, N.Y. DR. JAMES DOUGLAS New York, N.Y. PROF HATON DE LA GOUPILLIERE Paris, France SIR ROBERT A. HADFEILD London, England PROF HANS HOFFER Leoben, Austria PROF HENRI LOUIS LE CHATELIER Paris France M FLORIS OSMOND Paris, France ALEXANDRE POURCEL Paris, France JOHN E. STEAD Middlesborugh, England DR. ING H. C. EMIL SCHROEDTER Dusseldorf, Germany JAMES M. SWANK (Associate) Philadelphia, Pa. PROF DIMITRY CONSTANTIN TSCHERNOFF St Petersburg, Russia PROF TSUNASHIRO WADA Tokyo, Japan CHARLES D WALCOT Washingtion D.C.

Jan 1, 1917

By Thomas F. Anderson

(Measurements of stable isotopic variations (sulfur, carbon, and oxygen), supplemented by chemical, mineralogical, and petrographic analyses have been used to investigate the processes responsible for : (1) the incorporation of sulfur in coal, and (2) the (development of permineralized peat zones ("coal balls"). Sulfur isotopic results indicate that there are two principal sources of sulfur in the Pennsylvanian coals from the Illinois Basin: (1) "primary" sulfur assimilated by plants (low-sulfur coals), and (2) "secondary" sulfur produced by reactions involving H2S that was produced by the anaerobic reduction of sulfate in seawater which permeated the peat during post-depositional marine transgressions (the dominant source of sulfur in high-sulfur coals). Sulfur isotopic compositions of low-sulfur coals in Several Tertiary basins of Wyoming are consistent with a plant sulfur source. However, the inverse correlation between content and isotopic composition of sulfur observed in coals from the Powder River Basin suggest some "secondary" additions to these low-sulfur coals. Seveeral Quaternary (freshwater pears which were submerged by sea-Level rises during deglaciation over the past 30 ka have sulfur contents and isotopic compositions similar to high-sulfur coals. Carbon and oxygen isotopic compositions of calcareous coal balls from North America and Europe suggest that (1) the carbonate was derived from variable proportions of oxidized plant matter (typically predominant) and inorganic carbonate, and (2) the carbonate minerals were precipitated from fresh-to-brackish waters. Local geochemical and hydrological conditions were apparently more important than regional depositional environments in controlling the source of carbonate and the development of coal balls.

Jan 1, 1983

By E. E. Maillot

In 1943, diamond drilling by the Bureau of Mines, comprising 11 holes which totaled 1,295.6 feet, showed that the pegmatite at Black Mountain consisted of shallow lenses in interbedded biotite-quartz-schist and impure quartzite. The average thickness of the pegmatite was 9.7 feet. Mineralization had a zonal arrangement. Beryl was most abundant near the footwall contact of the pegmatite. The average estimated beryl content of the pegmatite exposed at the surface was 0.81 percent, and the highest content of any pegmatite area was 1.75 percent. Other economic minerals were scrap mica, feldspar, spodumene, and lepidolite. Representative samples of the Black Mountain deposit failed to yield high-grade boryl concentrates by straight flotation owing to the presence of considerable spodumene. By employing heavy medium separation to remove the spodumene, 75.4 percent of the. BeO wan recovered in a flotation concentrate assaying 10.4 percent BeO.

Jan 1, 1949

By Raymond D. Sloan

Retaining third place in crude-oil production among the nation's oil-producing states, Oklahoma's output in 1942 totaled 137,792,000 bbl., a decline of 9.4 per cent from the previous year's total of 152,117,000 bbl. Production declined from an average of 403,000 bbl. daily in January 1942 to an average of 355,000 bbl. during December, a reduction of 48,000 bbl. daily (11.9 per cent) during the year. At the end of 1942 it would appear inevitable that the downward trend in production will continue in 1953 unless halted in the immediate future by greater than normal discoveries and development. To Jan. I, 1943, Oklahoma has produced 5,067,013,000 bbl. oil crude oil. Development and Exploration Development dropped abruptly in 1942, reflecting the lack of any sizable discoveries and the effect of the provisions of Federal Well Spacing Order M-68, which became effective in December 1941. In all, 1210 wells were drilled in 1942. This represents a decrease of 42.7 per cent from the 1941 total of 2110. Of the total wells completed, 553 (45.7 per cent) were oil wells with an average initial production of 443 bbl.; 102 (8.4 per cent) were gas wells with an average initial of 3,359,000 cu. ft.; and 555 (45.9 per cent) were dry. Although the number of completions declined sharply, the total of 320 wildcats completed (26.4 per cent of all wells) repre-sents a decrease of only 2.7 per cent from the previous year's figure of 329. Of the wildcats drilled, 44 (13.8 per cent) were oil wells, 13 (4.0 per cent) were gas wells, and 263 (82.2 per cent) were recorded as failures. Reconditioning of wells throughout the state resulted in a total recompletion of 355 wells. Of these, 234 were oil wells with a combined initial production of 96,808 bbl., 32 were gas wells with a total initial of 381,488,000 cu. ft., and 89 were abandoned. None of the 26 pools found in 1942 has developed into a major discovery. The Pauls Valley pool, Garvin County, is the most outstanding. Since its discovery in April, 14 wells with an average initial of 1898 bbl. have produced 803,000 bbl. of 42' gravity oil from the Bromide zone. Development in this pool is believed to be almost completed. Other of the more important discoveries are the East Watchorn pool, Pawnee County; Guthrie Townsite and West Navina, Logan County; Brooksville and Macomb, Pottawatomie County, and the Liberty and Northeast Lucien discoveries in Noble county. The East Watchorn pool, at the close of the year, had 14 completed oil wells with an average initial of 989 bbl. from the Wilcox sand at 3930 it.; Guthrie Townsite, one well with an initial of 840 bbl. from dolomite at 5600 It.; West Navina, six wells with an average initial of 284 bbl. in the Lay ton sand at 5050 ft., Brooksville, eight wells in the Hunton at 4800 ft. with an average initial 01 355 bbl.; Macomb, one well with an initial of 160 bbl. in the IIunton at 4700 ft.; the Liberty pool, one well with an initial of 1268 bbl. in the second Wilcox at 4500 ft., and two wells in the Tonkawa sand at 2500 ft., with an average initial of 230 bbl. In the Northeast Lucien pool, four wells were completed in the Wilcox at 5380 ft. for an average initial of 1164 bbl., and one well was completed in the Viola lime at 5255 ft. for an initial of 55 barrels.

Jan 1, 1943

By Raymond D. Sloan

Retaining third place in crude-oil production among the nation's oil-producing states, Oklahoma's output in 1942 totaled 137,792,000 bbl., a decline of 9.4 per cent from the previous year's total of 152,117,000 bbl. Production declined from an average of 403,000 bbl. daily in January 1942 to an average of 355,000 bbl. during December, a reduction of 48,000 bbl. daily (11.9 per cent) during the year. At the end of 1942 it would appear inevitable that the downward trend in production will continue in 1953 unless halted in the immediate future by greater than normal discoveries and development. To Jan. I, 1943, Oklahoma has produced 5,067,013,000 bbl. oil crude oil. Development and Exploration Development dropped abruptly in 1942, reflecting the lack of any sizable discoveries and the effect of the provisions of Federal Well Spacing Order M-68, which became effective in December 1941. In all, 1210 wells were drilled in 1942. This represents a decrease of 42.7 per cent from the 1941 total of 2110. Of the total wells completed, 553 (45.7 per cent) were oil wells with an average initial production of 443 bbl.; 102 (8.4 per cent) were gas wells with an average initial of 3,359,000 cu. ft.; and 555 (45.9 per cent) were dry. Although the number of completions declined sharply, the total of 320 wildcats completed (26.4 per cent of all wells) repre-sents a decrease of only 2.7 per cent from the previous year's figure of 329. Of the wildcats drilled, 44 (13.8 per cent) were oil wells, 13 (4.0 per cent) were gas wells, and 263 (82.2 per cent) were recorded as failures. Reconditioning of wells throughout the state resulted in a total recompletion of 355 wells. Of these, 234 were oil wells with a combined initial production of 96,808 bbl., 32 were gas wells with a total initial of 381,488,000 cu. ft., and 89 were abandoned. None of the 26 pools found in 1942 has developed into a major discovery. The Pauls Valley pool, Garvin County, is the most outstanding. Since its discovery in April, 14 wells with an average initial of 1898 bbl. have produced 803,000 bbl. of 42' gravity oil from the Bromide zone. Development in this pool is believed to be almost completed. Other of the more important discoveries are the East Watchorn pool, Pawnee County; Guthrie Townsite and West Navina, Logan County; Brooksville and Macomb, Pottawatomie County, and the Liberty and Northeast Lucien discoveries in Noble county. The East Watchorn pool, at the close of the year, had 14 completed oil wells with an average initial of 989 bbl. from the Wilcox sand at 3930 it.; Guthrie Townsite, one well with an initial of 840 bbl. from dolomite at 5600 It.; West Navina, six wells with an average initial of 284 bbl. in the Lay ton sand at 5050 ft., Brooksville, eight wells in the Hunton at 4800 ft. with an average initial 01 355 bbl.; Macomb, one well with an initial of 160 bbl. in the IIunton at 4700 ft.; the Liberty pool, one well with an initial of 1268 bbl. in the second Wilcox at 4500 ft., and two wells in the Tonkawa sand at 2500 ft., with an average initial of 230 bbl. In the Northeast Lucien pool, four wells were completed in the Wilcox at 5380 ft. for an average initial of 1164 bbl., and one well was completed in the Viola lime at 5255 ft. for an initial of 55 barrels.

Jan 1, 1943

By Noris Del Be1 Belluz

Drilling underground in the Grasberg dewatering drifts has routinely hit water aquifers with high flow rates and pressures. Two types of holes are used. Pilot holes probe ahead of the tunnel development to intersect aquifers ahead of the face. And dewatering holes dewater rock formations that will drain water from the Grasberg pit and allow tunnel development to proceed safely. Recently, static pressures of >8.3 MPa (> 1,200 psi) have been recorded with flows from a 100 mm (4 in.) HQ core hole measured at 5,700 L/min (1,500 gpm). The waterflows can be slightly acidic, necessitating the use of stainless-steel collar gear to resist corrosion. These rates were anticipated and contingencies were planned early on to deal with these conditions. PT Freeport Indonesia (PTFI) established procedures to maintain the safety of the drill crews, to enable coring of the rock, and to maintain the safety of the miners driving the drifts. The collar gear controls the waterflows because these drill holes are a vital source of water for the concentrator.

Jan 1, 1998

Organization Place Date 1919 National Drainage Congress St. Louis, Mo. Nov. 11-13 American Mining Congress St. Louis, Mo. Nov. 1.7-21 Canadian Mining Institute Vancouver, B. C. Nov.. 26-28 American Society of Mechanical Engineers:.... New York, N. Y. Dec. 2-5 American Institute of Chemical Engineers Savannah, Ga. Dec. 3-6 Geological Society of America...; Boston, Mass. Dec. 29-31. American Society of Heating and Ventilating 1920 Engineers New York, N. Y. Jan. Mining and Metallurgical Society of America ... New York, N. Y. Jan. 13. American Institute of Min. and Met. Engineers... New York, N. Y. Feb. 16-19 American Ceramic Society Philadelphia, Pa. Feb. 23-26

Jan 11, 1919

By L B. Zhou, S Li, B L. Wang, S B. Li, Q Wang

The rapid development in ChinaÆs metal mine resources has caused a series of mine environment problems such as serious ecological damage and environment pollution, and secondary geological disasters. The paper has reviewed ChinaÆs metal mine development, including current status and environmental situation, analysed existing problems in mine development and environmental management, and proposed corresponding countermeasures and suggestions.CITATION:Wang, B L, Li, S B, Li, S, Zhou, L B and Wang, Q, 2012. Current situations, problems, countermeasures and suggestions for ChinaÆs metal mine development, in Proceedings Life-of-Mine 2012 , pp 353-356 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By R. F. Shurtz

R. Duval (Mining Engineer, Ancien eleve de PEcole Polytechnique, Paris, France) I do not agree with the Eq. 3, reading: m =1/100- [(0.214x30.4) + (0.7B6 x0.00)] =6.5pct CaO If 0.214 and0.786 were proportions by weight, the equation would represent the well known mixtures law of the conventional arithmetics and 6. 5 pct CaO would be the correct average content. But it is not the case as the author states: "In samples consisting of single grains of mineral, those grains must, as already mentioned, be either of dolomite or magnesite. Since 78.6 pct of the deposit consists of magnesite and 21.4 pct of dolomite (excluding for present purpose the presence of other minerals), for any single grains picked at random the probability will be 0.214 that is it dolomite and0.786 that is it magnesite. In 1000 such samples the expected numbers of dolomite and mapesite grains will be 214 and 786 respectively." 0.214 and 0.786 would be proportions by weigbt under the necessary condition that all grains of dole mite and magnesite should have an identical weight. Obviously it is not the case, as the specific gravities are not the same for mapesite and dolomite and the volumes of the grains are different. Furthermore, because of these differences the conditions for a random sampling are not fulfilled and we are not authorized to state that the probabilities are, respectively, 0.214 and 0.786. The author however makes a simple application of Eq. 1: M = 1/n— ? fi x i . n Should we deduce that this relation is wrohg? Not at all, but when applying Eq. 1 you must not overlook what it actually. means. Eq. 1 gives a definition of the arithmetic mean of a total of n observed values Xi and nothing else. But the average conteht of a deposit has not the same significance. It is the ratio between the weight of concerned mineral in the deposit and the total weight of the deposit. As from 1000 particles the 214 of dolomite and the 786 of magnesite have not the same weight, the two definitions do not concur, and when applying Eq. 1 the result is an arithmetic mean of figures which has no connection with what is named average contentof a deposit. The situation is similar to the calculation of an average velocity. If a car travels a first mile over at 30 miles per hr and a second mile over at 60 miles per hr, when applying formula 1 you find as average velocity for the 2 miles: 30+60 ------- - 45 miles per hour. Many people calculate in this way and they do not realize that a mistake is involved. In fact the definition of he average velocity for the 2 miles is the quotient of the distance of 2 miles by the time (in hours) necessary for 2 miles travel, i.e.: 2 ---------- = 40 miles per hr. 1 + 1 30 60 In other words, the average volocity wanted is not the arithmetic but the harmonic average of the two velocities. The above mentioned bias in the calculation of the average contents of deposits is frequent, even in the assessments made by experienced engineers and is independant of what is named the sampling error. In order to supress the bias and to be able to use Eq. 1, you must apply a correction. An example on the subject can be found in an article by Duval et al. in the January 1955 issue of the ''Annales des Mines" (French), page 19. R. F. Schurtz (Author's Reply) Mr. Duval's position is quite correct. The proportions shown for dolomite and magnesite., respectively, of 0.214 and 0.786 are, in fact, proportions by weight uncorrected for specific gravity. In our day to day operation of producing magnesite from these mines at a very substantial rate, we do not normally make corrections for the difference between the specific gravity of dolomite and that of magnesite. If these corrections are made in Eq. 3 as shown in my article, then the numbers of grains turn out to be in proportions of 0.226 dolomite and 0.774 mapesite instead of the values actually shown in the equation. For the purposes of our work, and in view of the inherently low accuracy of the data, this correction was not deemed worthwhile making.

Jan 1, 1961

A dinner was given to Ambrose Swasey by the United Engineering Society, at the Engineers' Club, on November 14. Those present -included -twenty-one presidents and past presidents of the Founder Societies. Charles F. Rand, President of United Engineering Society, presided. President Robert S. Woodward, of the Carnegie Institution of Washington, and Dr. Robert W. Hunt, of Chicago, made addresses to which Mr. Swasey responded. Dr. Michael I. Pupin, Chairman of Engineering Foundation, made the closing address. The evening was marked by the high character of the addresses, inspiration for grave duties lying before the engineering profession, and by the spirit of good fellowship. Among the seventy-two persons present were the following members of the Institute: E. E. Bartlett, William N. Best, J. Parke, Channing, C. R. Corning, F. C. Cottrell, J. V. Davies, J. V. N. Dorr, H. S. Drinker, Karl Eilers, H. M. Howe, A. C. Humphreys, Robert W. Hunt, Wm.. B. Jackson, D. S. Jacobus, J. H. Janeway, J. E. Johnson, Jr., John Johnston, George F. Kunz, Edwin Ludlow, Philip N. Moore, Fred'k. H. Newell; Wm. H. Nichols, H. Hobart Porter, Charles F. Rand, R. M. Raymond, .Jesse M. Smith, E. Gybbon Spilsbury, Bradley Stoughton, . Joseph Struthers, Benj. B. Thayer, Wm. H. Wiley, S. T. Wellman.

Jan 1, 1919

By NIOSH Publications

In 2004, 14,478 mining operations reported employment statistics to the Mine Safety and Health Administration (MSHA). Almost half (48.9%) were sand and gravel mines, followed by stone mines (30.4%), coal mines (13.9%), nonmetal mines (5.1%), and metal mines (1.7%).

Sep 1, 2007