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By M. B. C. Brandt

Richter magnitudes for seismic events were calibrated for use as a Local magnitude scale in the West Rand (WR), Far West Rand (FWR), and Klerksdorp–Orkney–Stilfontein–Hartebeesfontein (KOSH) gold mining areas. Richter magnitudes are currently calculated from seismograms recorded by local surface cluster networks using tabulated calibration values for Southern California, published in 1958. The Richter (1958) model is incorrect for distances of less than 30 km and should be applied only to crustal earthquakes in regions with similar attenuation properties to those of Southern California. When compared to the South African National Seismograph Network (SANSN), the cluster networks, on average, overestimate seismic event magnitudes by approximately 0.1 of a magnitude unit. A calibrated Local magnitude scale was derived by means of a multiple regression analysis between the Local magnitudes reported by the SANSN and the largest zero-to-peak trace amplitudes measured on the cluster network horizontal seismograms, after modelling the attenuation of the seismic waves as these progress from the epicentre to the station position. Magnitudes reported by individual stations for the same event show a significant scatter around the average magnitude owing to the near-surface amplifications of the seismic waves at the recordings sites. Average magnitude should be estimated using as many magnitudes of individual stations as possible to ensure an accurate estimate. Larger event magnitudes should be compared with those recorded by the SANSN.

Nov 1, 2021

By Margaret E. Egan

Reliable fire detection is essential for both safe evacuation and containment or extinguishment. In order to increase reliability by reducing the number of nuisance fire alarms in underground mines that use diesel-powered equipment, the U.S. Bureau of Mines has developed a diesel-discriminating fire detector (DDD). It was designed to discriminate between smoke produced by a fire and the smoke-laden exhaust of a diesel engine. Experiments were conducted by the Bureau to compare the smoke detection capabilities of the DDD with those of conventional fire detectors in response to smoldering coal and conveyor belting. A comparison was made among the alarm times of a carbon monoxide (CO) detector with an alarm threshold of 5 ppm, a smoke detector with an optical density alarm threshold of 0.044 of', and the DDD with an alarm threshold of 0.025 V. The results show that the DDD will reliably detect developing coal and conveyor belt fires. The average time delay separating the DDD alarm from the first detector to alarm was 76 s for smoldering conveyor belt and 65 s for smoldering coal. The longest time delay between the response of the DDD and the first detector to alarm was approximately 120 s.

Jan 1, 1993

By H. E. Pawson

Giant Yellowknife is located 600 air miles north of Edmonton on the north shore of Great Slave Lake in the Northwest Territories. In its 24 years of operation some 7,730,000 tons of ore have been treated to yield $175,000,000 worth of gold.The gold ore occurs at irregular intervals throughout a fold-like sericite schist zone cutting Precambrian rocks. The ore is characterized by 40 to 80% quartz - carbonate and about 10% pyrite and arsenopyrite. Considerable amounts of stibnite and antimony sulpho-salts are also present. Gold is finely divided in the native state existing in complex association with the sulphides. In most instances stibnite is barren but minor values are evident on occasion. Visible native Fold, quite prevalent in the early operating years, is, practically non-existent today. It was readily apparent from mineral dressing investigations conducted in .1944 that Giant ore would be difficult to treat. By 1948 a flow sheet had been established and operations began. In the ensuing years, changing ore characteristics necessitated modifications to some process steps and complete abandonment of others. By 1962 the major metallurgical problems were solved and all that remained was the refining of operating performance to its highest level.With one or two exceptions today's operation follows the practice established by 1962 (Fig. 1 - Flowsheet).

Jan 1, 1973

By Luke Evans

What are Best Practices? What are Bad Practices? Who Uses Best Practices? Why Bother? Acceptability Guidelines Published Best Practices Published Bad Practices Additional Best Practices Some Best Practices for Low Grade Deposits Interpretation Guidelines Big Bear Gold Deposit Example Conclusions Questions

May 1, 2013

By R. Marleau, R. Assad, J. Dugas

"A study of the geological features of known occurrences of mineralization in Gaspe is the basis for a classification. Nickel, chromite, asbestos and some copper are pre-or syn-Taconic, whereas the most important deposits are tied to granitic post-Taconic stocks. Most occurrences are clearly related to igneous rocks: nickel, chromium and asbestos to Ordovician serpentinite; copper to volcanic rocks of different ages; and copper, zinc and lead to acidic intrusions with apparent zoning. Some lead-zinc deposits lying between the Grande Greve and York Lake formations are stratigraphically controlled. Some occurrences are tied to faults; e.g., the nickel-copper mineralization along the North Grand Pabos fault. Northerly-trending transverse structures appear to coincide with the Gaspe Copper, Mount McGerrigle (Tabletop) granite and Lemieux dome areas of mineralization. JEAN DUGAS, after graduating"

Jan 1, 1969

The Objective: To reduce the noise generated by the exhausting air from a pneumatic roof bolting drill to a maximum of 90 decibels. Any attachment used for this purpose must be lightweight and must not cause a significant increase in back pressure. The Approach: Absorb the noise with a properly designed muffler that will permit sufficient airflow without affecting the normal operation of the drill. How It Works: The air exhausted by the drill enters the muffler through perforated disks into a resonator chamber. It then passes through a series of expansion and contraction chambers and is expelled to the atmosphere through another perforated disk. The basic muffler design for the pneumatic drill was established by using both digital computer analysis and experimentally simulated noise tests. The measured parameters used in the computer program consisted of inlet and outlet pressures, temperatures, airflows and exhaust areas. United

By J. W. Hunter, J. H. Jacobs

"Approximately 355 tons of nodules from Chamberlain; S. D., ore were processed in the 1-ton-per-day electrolytic-manganese pilot plant of the Bureau of lanes at Boulder City, Nev., in a continuous 3-month operation. The ore, ground to minus 48-mesh, was found to be amenable to leaching with acid directly or after roasting under reducing conditions in a Skinner muffled multiple-hearth furnace.Unroasted ore gave an acid-leach extraction of 84 to 88 percent of the manganese, which after neutralization showed an over-all extraction of between 81 and 85 percent of the manganese. The amount of iron extracted varied, but it was always,enough to permit the use of ammonia for neutralization.Roasted ore showed an acid-leach extraction of 89 to 91 percent of the manganese. A large amount of iron went-into solution, so that it was not economical to neutralize it entirely with ammonia. By neutralizing with calcine to a pH of 5.0 and completing -neutralization with ammonia to a pH of a.5 an over-all manganese extraction of 84 to 86 percent was obtained. The slight increase in. extraction on roasted ore probably would not justify the cost of roasting.Acid consumption averaged 1.75 pounds per pound of manganese extracted. Settling rates of the residue in leach solution were to slow to permit clarification in thickeners, but a Moore vacuum leaf filter proved to be satisfactory. Purification of raw leach solution was .accomplished readily by hydrogen sulfide with a low gas consumption. Electrolysis was normal, without difficulty, and with -current efficiency ranging between 62 and 66 percent.The use of Chamberlain modules for the production of electrolytic manganese would result in an operating cost of 0.8316 cent per pound higher than the cost of producing electrolytic manganese from Three Wids ore."

Mar 1, 1946

By R. L. Loofbourow

Reasons for reexamining underground mining include: 1. The assurance that more deep deposits of useful minerals will be found. 2. The existence of deeply covered deposits of industrial minerals near large markets where quarries are becoming depleted or are lacking. 3. Surface property values, zoning and other limitations on open pit mining. 4. Expectation that underground space will be increasingly used for transportation, power plants, storage and similar purposes. 5. The improvements which have been made in underground mining. During the last three or four decades many changes and improvements have been made underground. All underground construction and mining has benefitted to some extent but the effect on the productivity of labor employed with some methods- has changed little and the use of these methods has declined. Productivity of labor in other methods has increased substantially. The relative usefulness of mining methods has changed and a vital industry, bituminous coal, has been returned to health. In this paper, consideration is limited to nine methods used with high productivity during the period under review. These methods are not necessarily better than others but they may be considered the prime methods in the sense that, in our economy, many, low grade ores, coal and the principal industrial minerals could hardly be produced by less productive means.2 Although most of the examples cited are from mining as such., the first four methods discussed can be used for the construction of stable excavations of various' shapes in sound rock.

Jan 1, 1967

By L. V. Kin, V. V. Lodeischikov, A. V. Byvaltsev, IRGIREDMET JSC, O. D. Khmelnitskaya, S. V. Petrov

"Irgiredmet Institute carried out the study on the development of gold recovery technology from refractory ore from a Russian deposit. The ore contained 1.1 g/t Au, 1.5% of pyrite and 2.4% of pyrrhotite. The recovery of gold achieved was 84.7% using gravity with generation of high grade recoverable gold concentrate and gravity middling. In the course of lime treatment, cyanidation of the middling followed by tailings detoxification the consumption of reagents was 13.0 kg/t CaO, 95 kg/t NaCN and 72 kg/t Ca(OCl)2 of the concentrate. This was capital intensive.In order to decrease the consumption of reagents, magnetic separation of the middling of the concentrates from gravity separation was added to this flow sheet. Pyrrotite recovered to magnetic fraction, which did not contain gold in accordance to this advanced flow sheet. The mass yield of pyrite goldbearing non-magnetic fraction decreased down to 1.5 times in relative to gravity middling. The slurry filtration prior to and after cyanidation allowed the organization of cyanide solution recycling.The results of pilot plant tests using the developed flow sheet showed that the content of pyrrhotite in the non-magnetic fraction decreased from 59.1% to 11.3%. The reagents consumption was 12 kg/t CaO, 3 kg/t NaCN and 16 kg/t Ca(OCl)2 of the pyrite concentrate. The total gold recovery using this flow sheet was 83.4%. Due to a decreased consumption of reagents, cost efficiency of the process was achieved. Based on the results of this research, a project design criteria was developed. A processing plant with the annual throughput of 2.6 million tonnes of ore is being designed."

Jan 1, 2016

By Donald J. Frendzel

The post-World War II expansion of the Soviet petroleum industry has established the U.S.S.R. as a major oil-producing nation and has led to Russian reentry into the international petroleum trade. The rapid growth of Soviet petroleum production will allow the U.S.S.R. to displace Venezuela as the world's second largest oil-producer in 1960 and to narrow further the gap between Soviet and U.S. crude-oil production. U.S.S.R. crude oil output was only a tenth of U.S. production in 1946, but it will be more than a third at the end of 1960 and more than half in 1965. The Soviet Seven-Year Plan (1959-65) for oil provides for substantial increases in petroleum production, refining, storage, and distribution facilities. Crude oil production and primary distillation capacity are to double, considerable storage capacity is planned, and pipelines for crude oil and petroleum products are to increase threefold. According to the Soviets, the initial phases of this plan (1959 and 1960) have been completed successfully. However, this progress has been achieved with difficulty.

Jan 1, 1961

By M. R. HULL

FOLLOWING the discovery of a body of ore that appears to have commercial possibilities there is a period of development work to determine its extent and grade and the most economical method of mining it. Laboratory tests are made in an effort to determine the most practicable and economical treatment for the extraction of the valuable constituents of the ore and these tests are carried farther and checked in a pilot or test mill. The rate at which the ore is to be mined and the daily capacity of the plants that are to treat it will depend on a number of important factors such as: The size of the orebody; the capital available for building the plants; the market or demand for the final product; the supply of skilled and common labor available for the construction, operation and maintenance of the plants; the quantity and quality of available water, and the amount and cost of power that can be purchased or that can be economically developed. Having decided on the treatment that is to be given to the ore and after full consideration of the above factors the management decides to erect a reduction plant of a given capacity.

Jan 1, 1926

By A. T. Adema

The cohesive zone, where the ore fed into the blast furnace softens and melts, is critical to the blast furnace performance and stability due to its influence on the gas and solid flow. This paper de-scribes a project for the development of a process model to predict the cohesive zone properties and the results of its first step; the solid flow model. The process model is expected to describe a realistic solid burden flow and the formation of the cohesive zone, its shape, location, structure, permeability, and in particular the mineralogical changes within the cohesive zone. This will be achieved using various simulation and computing tools: a combination of the Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD), the DEM?CFD hybrid approach, together with models for the thermodynamics and reaction kinetics. The key benefits of the hybrid approach lie in the coupling of the continuous phase and the discrete particles, and the possibility of introducing thermodynamics and reaction kinetics into the system in a more realistic manner. Two DEM simulations are presented for a small scale blast furnace to investigate the influence of non-spherical particles on the solid flow. This influence can be observed from a more even solid flow pattern and a reduced deadman size. The results indicate the requirement to include non- spherical particles in a blast furnace simulation to achieve a realistic solid flow.

Jan 1, 2014

By M. D. Gibbs, T. N. Smith, B. Verbaan

When heated in the absence of oxygen, pyrite from refractory gold concentrates decomposes endothermically to pyrrhotite, releasing sulphur. The decomposition starts at the particle surface and progresses inwards, leaving an adhering layer of porous pyrrhotite. Use of the conventional shrinking-core model implicitly assumes a negligible partial pressure of sulphur in the bed, but this pressure is in fact at least equal to the equilibrium vapour pressure of sulphur over pyrite, constituting the principal control of the rate of decomposition. Further experiments showed a decrease in reaction rate as the conversion increased. Both phenomena are attributed to the persistence of non-isothermal conditions in the fluidised bed during pyrolysis, caused by the endothermic nature of the reaction and the relatively slow rates of heat transfer to particles and vapour removal from the bed. Equipment must be developed to maximise these two parameters

Jun 19, 1905

By Briggs H.

The illustrated device uses the principle that the lamp can burn with a smaller inlet passage if the air is rich in O2 and that the size of the inlet can be made a measure of O2 percentage. The appliance consists of an adjustable cut-off applied to the inlet of a safety lamp of the improved Gray pattern. Precision is assessed from tables of calibration tests in air contaminated with blackdamp of CO2:N2 composiiton 1:5.67 at temperatures of 40-70 degrees F. Results are presented of tests at St. Germain's colliery, of tests in air contaminated with pure CO2 and of air contaminated with both blackdamp and inflammable gas; published ranges in mine-air blackdamp compositions are tabulated as ranging from 90.06% N2 to 43.90% CO2. When firedamp is present at 1.25-2.5%, its content must first be estimated by means of the cap and a fifth of its value then deducted from the lamp reading for O2

Dec 1, 1916

By John Newby, Edward Kennedy, Ulf Gwildis

Alluvial deposits of major rivers often provide relatively uniform tunneling conditions. However, these conditions pose specific challenges due to the tunneling behavior of the granular soils as flowing ground, if unsupported. This paper describes the design considerations and construction experiences gained during the Tunnel Boring Machine (TBM) drives for the Annacis Island WWTP New Outfall System in the Vancouver, B.C. metropolitan area. Meeting the design criteria for connecting two (2) deep on-land shafts with an in-river riser manifold required advancing a 5-meter-diameter slurry TBM through the Fraser Rivers sands and at a tunnel invert elevation with a baseline hydrostatic head of 3.4 bar.

Dec 1, 2022

By M. S. Badollet, N. W. Edgerton

"A study of the physical properties of long grades of asbestos fibers imported into the United States during the past eight years has disclosed information that will contribute materially to effective selection and use of fibers for electrical products. The study embraced fiber lengths, volume resistivity under three different conditions, total iron by chemical analysis, magnetic rating, conductivity of an aqueous ex-tract and its sodium chloride equivalent.The fibers examined included chrysotiles from Rhodesia, British Columbia, and Barberton area; marlime from Bechuanaland and Province of Quebec; amosite and crocidolites from Africa and Australia; and anthophyllites from Mozambique and from Georgia in the United States. Volume resistivity values provide a relative basis for estimating the electrical performance of end products; magnetic rating -an estimate of the quantity of iron compounds present in excess of those in the asbestos structure; conductivity of an aqueous extract; and an estimate of the ionizable impurities in fibers.Tests of these factors yield in-formation, not heretofore generally known, which may serve as a guide in the evaluation of asbestos fibers for electrical products."

Jan 1, 1960

By David A. Hart, Barry P. Osborn, Richard J. Totty, Ana T. Carvalho, Max B. Elliott

This paper addresses the experience designing and installing bored piles for the King’s Cross area. This includes continuous flight auger and rotary bored piles, with a range of diameters between 600 mm and 1200 mm, reaching a maximum depth of 56 m below ground level. Existing Network Rail Thameslink twin bored running tunnels are located directly beneath the subject plots. These tunnels have an external diameter of 6.6 m and the crowns of the tunnels are very shallow, in some cases just 10 m below the existing ground level. Some plots needed piles to be installed in close proximity to the tunnels, which required additional control measures and contingency plans. Pile verticality was monitored as the tip of each pile advanced and in-tunnel monitoring readings were verified and are presented. Lessons learned from designing, installing and testing the piles and monitoring the tunnels are addressed in this paper.

May 1, 2022

By J. W. Cash

The mineralogy and textures of cyclone dust, sludge, and occasional build-ups in the American Iron and Steel Institute (AISI) direct iron making pilot plant at Universal, Pennsylvania have been studied by reflected light, transmitted light, and cathodoluminescence microscopy, and phase compositions have been determined by SEM-EDS. The cyclone dust consists of particles of carbon, metallic iron, sulfur-bearing iron, and wustite. Measurements of particles in the sludge indicate that 69% are less than 2.5 µm across, 21 % are 2.5-5 µm, and 10% are larger than 5 µm. Mineralogically the sludge particles are mainly carbon and metallic iron, with minor wustite and sulfur-bearing iron. Build-ups that sporadically develop in the furnace consist of olivine, hercynite spinel, metallic iron, wustite, pyrrhotite, pseudobrookite, akermanite-ferroakermanite and gehlenite. The microtextures shown by the build-ups indicate that much of that material has precipitated at the build-up loci. This study has been supported by AISI and the U.S. Department of Energy.

Jan 1, 1995

By R. W. Smith

It is well known that certain silicates such as the feldspars and beryl can be readily floated from quartz at a low pH value using a long chain cationic collector in the presence of a fluoride.1-3 However, the mechanism whereby the fluoride activates feldspars and beryl is not known. Indeed, only a few authors have even speculated about possible mechanisms.1,3,4 As a first approach to the problem, it is perhaps best to look closely at the interesting character of hydrofluoric acid and how it dissolves silica and silicic acid. Hydrofluoric acid, unlike hydrochloric acid, is a weak acid with a dissociation constant of about 3.53 x 10-4 at 25°C.5 The reason for the weak acidic character of HF lies in the very small size of the fluoride ion.6 The pKa value is 3.45 which means that at pH 3.45 half the HF is present in molecular form and half in ionic form. The anion present is probably HF2.-6 At pH values below the pKa value, molecular concentration increases rapidly at the expense of the HF2- anion. It is known that HF readily attacks glass, silicates, quartz and silicic acid. The equation usually cited pertaining to the first step in HF attack of silica is6-'

Jan 1, 1965

By Clyde E. Williams, JAMES L. GREGG

THIS review of the past year's progress in iron and steel metallurgy presents examples of only a few of the interesting or important accomplishments made in the United States. In the field of iron ore concentration increased attention was given to the study of the more difficultly separated wash ores and some progress was made in tabling. One difficulty with the table, in concentrating iron ore where the percentage of concentrate in the feed is large, has been the removal of fine silica from the thick layer .of concentrates in the cleaning zone. One company has -Made an important contribution toward the solution of this problem by an extension of the well-known plateau principle. By a special riffling of the plateau section of the table, the concentrates are crowded together. This action forces the fine silica to the top of the bed in the cleaning zone, whence the cross-flowing currents of water -can wash it into the middling product. Some work has been done on the application of froth flotation to the concentration of iron ores. Laboratory experiments were made at the Colorado School of Mines in which hematite was, successfully floated. Using oleic acid as a frothing and collecting agent and sodium carbonate as the conditioning agent, a high recovery of rich ,concentrate was obtained. A laboratory flotation unit is in use at Taconite, on the Mesabi range, and a commer-

Jan 1, 1932