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By H. W. McQuaid

IT IS usually assumed that chemical specifications are sufficient for steel to be used for case carburizing, and if the steel analyzes within the ordinary limits specified for steel for this purpose, no difficulty traceable to the steel used should be encountered in obtaining satisfactory results in the case carburizing and hardening. Much work has been done to determine the effect of various alloying elements on the rate of carbon penetration, etc. but, to our knowledge, little if anything has been published in regard to the effect of the quality of the steel on the final results in the hardening of case-carburized steel parts. The writers believe that the structure of the case both before and after quenching is greatly affected by the actual condition of the steel itself as made, and that for good results in the case-carburizing and hardening departments, the steel should be of the best possible quality as regards non-metallic impurities. It is the purpose of this paper to prove that the presence of excess dissolved oxides in the steel, as made in the melting furnace, affects permanently the results obtained in carburizing and hardening and that it is possible that the presence of dissolved oxide can result in total unfitness of low-carbon steel for, case hardening purposes. When races and rolls for roller bearings are made from a low-carbon steel, case carburized and hardened, it is of primary importance that the results of this treatment be of the highest quality. It is necessary, therefore, that in the case-carburizing work each detail be rigorously checked to avoid any defects which would cause the loss of much time and material. The case carburizing with which this paper deals was done in under-fired oil furnaces. The temperature of each furnace is controlled by means of a platinum platinum-rhodium thermocouple, in connection with a potentiometer indicator and potentiometer recorder. The temperature of each furnace is registered every 15 min. by an operator, who is continually checked by the automatic recorders.

Jan 2, 1922

By Robert S. Nichols

Fording Coal Limited's mine in the Rocky Mountains near Elkford, B.C. has produced 21.8 million clean tonnes of metallurgical coal from 1971 to 1980, inclusive. This production has come from several pit areas and required the removal of 149.1 million bank cubic meters of waste rock and overburden by truck-shovel and dragline operations. Waste dumps from 30m to 200m in height have been successfully constructed on natural slopes, generally between 10° and 26°. Design considerations for the dumps include foundation and soil conditions, natural slope angles and containment of weak overburden or rehandle materials. Dump control is maintained by monitoring the crest and the face of an active dump area. Crest movement is measured by extensometers locally termed "Spoil Monitors". When crest movement rates progressively increase above normal, dumping operations are temporarily relocated. Some unstable conditions and mass failures have occurred as the result of natural foundation slopes being in excess of 26°, failure of weak water saturated foundation soils or weak material being placed on the dump.

Jan 1, 1983

CONTENTS PAGE HESSE, A. W,-Safeguarding Coal-mining Operations against Danger from Oil and Gas Wells. Discussed by A. W. Hesse, T. G. Fear, George H. Ashley, George S. Rice, W. E. Fohl, R. V. Norris, S. A. Taylor, F. B. Tough, C. W. Gibbs, A. Hurlburt, S. W. Meals 1 DAWSON, THOS. W.-Belt Conveying of Coal at H. C. Frick Coke Company Mines. Discussed by F. F. Jorgensen, Thos. W. Dawson, Graham Bright, A. W. Hesse 13 OTTO, HENRY H.-Ultimate Recovery from Anthracite Coal Beds. Discussed by R. V. Norris, S. A. Taylor, Henry H. Otto, Douglas Bunting, Graham Bright, Howard N. Eavenson, J. B. Warriner 15 HOSLER, Rush N.-Schedule Rating Coal Mines in Pennsylvania for Compensation Insurance Rates. Discussed by E. A. Holbrook, W. W. Adams 17 ARCHBALD, HUGH.-Application of Gaussian Curve to Mining Industry. Discussed by Donald A. Laird, T. T. Read 19 ASH, SIMON H.-System of Coal Mining in Western Washington. Discussed by Eli T. Conner, Simon H. Ash 21 MILLER, J. S.-Method of Mining a Steeply Pitching Anthracite Vein by Successive Skips. Discussed by Eli T. Conner, J. S. Miller, J. B. Warriner 22 HARRINGTON, GEORGE B.-New Orient, an Unusual Coal Mine. Discussed" by George S. Rice, Eli T. Conner, John A. Garcia, George B. Harrington, F. F. Jorgensen, Graham Bright, W. M. Hoen, George N. Simpson, W. C. Adams, R. W. McNeill, Chas. C. Whaley, Carl Scholz, E. T. Gott, Andrews Allen 23 PERROTT, G. ST. J.-Properties of Liquid-oxygen Explosives. Discussed by George S. Rice 48 Safeguarding Coal-mining Operations against Danger from Oil and Gas Wells Discussion of the paper of A. W. HESSE, presented at the New York Meeting, Feb-ruary, 1925, and issued, as Paper No. 1412-F, with MINING AND METALLURGY, February, 1925. A. W. HESSE.-The well under investigation, No. 101, Fig. 2, was started about Sept. 5, 1921, and drilled-in in November. The first hole was started with a 13-in. bit and reached the Pittsburgh coal at a depth of 563 ft.; at 602 ft. the 10-in. casing was run in and the well was continued with a 10-in. bit and 1400 ft. of 8-in. casing was put in. It was then continued to a depth of 1770 ft. and 6-in. casing put in; then continued to a depth of 2555 ft. where the gas was struck. As the well produced only about 100,000 cu. ft. per day. 2-in. tubing was used to conduct the

Jan 6, 1925

By T. M. “Mike” Gurr

"U. S. marketable phosphate rock production for the 2018 crop year (July 1, 2017 to June 30, 2018) showed an increase to 27.7 Mt (30.5 million st) from the 2017 crop year production of 27.1 Mt (29.8 million st), as reported to the U. S. Department of the Interior by the mining companies operating in the United States during crop year 2018 (Table 1). Domestic consumption decreased in the 2018 crop year to 23.9 Mt (26.3 million st), as compared to the 27.2 Mt (30 million st) consumed in crop year 2017. U.S. imports of phosphate rock increased to 3 Mt (3.3 million st) for the 2018 crop year from the 1.81 Mt (1.9 million st) for crop year 2017. Imports of phosphate rock were from Peru and Morocco. There was an increase of 2.85 Mt (3.1 million st) in producers’ stocks from 7.45 Mt (8.2 million st) in crop year 2017 to 10.3 Mt (11.3 million st) in crop year 2018 (Table I).For calendar year 2018, Florida and North Carolina phosphate rock production accounted for 75 percent of the total U.S. production, with the balance being produced in Idaho and Utah. The Florida and North Carolina percent of U.S. production is declining. U.S. production of 25.7 Mt (28.3 million st) in calendar year 2018 was produced by five companies at 10 mines in four states and accounted for approximately 9.6 percent of the world production of 267.7 Mt (295 million st) for calendar year 2018 (Table 2).In calendar year 2018, U.S. phosphate production decreased by 2.2 Mt (2.4 million st), while companies increased stocks of phosphate rock by 1.7 Mt (1.9 million st). The domestic production for calendar year 2018 of 25.7 Mt (28.3 million st) represents 78.4 percent of the domestic production capacity of 32.8 Mt (36.1 million st).At present, China reportedly produces more than 50 percent of the world’s phosphate rock. As a result of planned expansions, Morocco production has increased from 27 Mt (30 million st) in 2017 to 33 Mt/a (36 million stpy), which is approximately 12.3 percent of the world’s production, moving ahead of the U.S. production. In calendar year 2018, the U.S. phosphate rock production was 25.7 Mt (28.3 million st), which is less than 10 percent of the world’s production of phosphate rock (Fig. 1)."

Aug 1, 2019

By S. A., Taylor

IT is very difficult to arrive at exact figures for the cost of maintaining excess capacity of coal mines, but we can approximate the various items. To do this, I will take the Pittsburgh district of Pennsylvania and the other districts can be compared to this one. I believe we can take the depreciation item of plant ac- count as a whole and discount it over a period of 20 years; while this is high for some items it is low for others and I believe it is not far from a safe basis. This equals 5 per cent per year, and this depreciation will take place about as rapidly when not in use as when in operation. A fair value in the Pittsburgh district to- day for plant and houses is close to $4 per ton per annum. At 5 per cent this will equal 20 cents per ton per year. The item of keeping the mine in condition, free from water, etc., will be close to an average of 2y2 cents per ton per annum.

Jan 1, 1928

By Galen G. Waddell

Several years of rock-burst research conducted by the U.S. Bureau of Mines in cooperation with the mining companies of the Coeur d'Alene mining district, Idaho, in addition to progress made by others throughout the world, have led to a good understanding of the rock-burst problem. This paper describes conditions which have caused specific bursts, present capabilities of detecting stress buildup and bursts, control methods, and a suggested approach to analyzing any individual mine-burst problem. A rock burst is the sudden, violent release of stored strain energy in rock by some mechanism of rock failure, generally accompanied by expulsion of rock with consequent damage to the mine. A burst may be audible for only a few hundred feet, or on the surface it may sound like a sonic boom miles away. A Dictionary of Mining, Mineral, and Related Terms, U.S. Bureau of Mines (USBM)* 1968yand defines a burst as Bureau "That phenomenon which occurs when a volume of rock is strained beyond the elastic limit and the accompanying failure is of such a nature that accumulated energy

Jan 1, 1971

By Rao S. B, Baafi E. Y

A venturi based multi-scrubber air cleaning system has been developed for dust control along a longwall face in coal mines. The system consists of a number of scrubbers. strategically placed along the wall face which deliver cleaned air at high exhaust velocity into the middle section of the longwall cross-section thus dividing it into two zones. The aim is to maintain the walkway on the powered support side as a zone of relatively clean air. Laboratory studies have shown that the scrubber's average efficiency is 90 per cent. Field trials in three longwall faces have shown that. under normal operating conditions. 40 to 50 per cent average protection efficiency can be achieved within 3 m to 4 m downstream of the scrubber. A three-dimensional finite element computational fluid dynamic model. FIDAP. was used to simulate the airflow patterns the dust concentration and the scrubber dust control technique at a typical longwall face. Results of simulations tally very well with the field results.

Jan 1, 1995

Methods for ore reserve estimation are classified. The amount of information needed to asses ore reserves is analysed. Reference is made to gold sampling. Consideration is given to nugget effects and ore reserve estimation procedures where they are significant. Computer methods are discussed

Jan 1, 1997

By R. L. Nyirenda

An investigation of the reducibility of a cassiterite concentrate with charcoal was made in the temperature range of 1123-1373 K. The course of the reaction was monitored by a combination of sample weight loss measurements, product gas analysis, and chemical analysis of the reaction product. It was found that the cassiterite could be best reduced by a combination? of high temperature, reasonably high charcoal proportions, high charge poroslty, and the addition of a small percentage of lime. Analysis of kinetic data obtained from isothermal experiments using theory from the oxidation of carbon by carbon dioxide gave an activation energy value of 255 lci/mole for the consumption of carbon by reaction with cassiterite.

Jan 1, 1990

By D. Campbell Mackenzie

THIS paper is submitted primarily to put on record the results of a number of experiments carried out at the Wingdam mine of Consolidated Gold Alluvials of B.C., Ltd., with the object of establishing a reliable method of concentration of 'wash' and a maximum recovery of gold from the concentrate. It will be generally admitted that, during the last two decades, a tremendous amount of research work has been carried out, both by private companies and Government departments, with a view to improving the technique of the recovery of gold .from quartz veins or lodes. So thorough have been these investigations that milling practice at a modern quartz gold mine is almost an exact science, carried out with meticulous accuracy. In placer mining, on the other hand, very little departure from old traditional methods can be noted, with the exception perhaps of the more modern gold dredges. This may be due to the fact that the concentration of placer gravels, up to a certain point, is comparatively easy. Only a simple equipment of sluice box and riffies seems necessary where the gold is coarse and the gravel free from clay. In the early days of placer mining, when claims were rich and fairly 5hallow, nobody worried very much about fine gold; and, if clay was present, an enlarged dump box was constructed in which the gravel was subjected to a rather desultory puddling. That large quantities of gold are lost in normal placer practice is generally admitted. Some 26 years ago, I had inspectorial charge of many bucket dredges on the Ovens river, in Australia. Occasionally it was necessary for a dredge to work through its own tailing to reach a new section, and almost without exception enough gold was recovered from these tailings to defray the total cost of moving the dredge. Since those days, the technique of gold recovery in dredging has been considerably improved and it is still receiving close attention. Outside of dredge mining, most placer operations, deep or otherwise, are as they were-notorious gold losers, paying little attention to the recovery of fine gold and taking an absurd amount of time over each clean-up. In the Cariboo district of British Columbia, the alluvial gold is usual y associated with varying quantities of black sand (magnetic) and grey sand (non-magnetic); and it can be taken as axiomatic that, if you save all the black sand and grey sand, you save practically all the gold. It is on this hypothesis that we have carried out our research work and brought our recovery system up to its present highly satisfactory standard.

Jan 1, 1937

By G. L. Neumann

In October 1949 the College Park Branch of the Mining Division instituted a survey of the New England pegmatites. Many of the New England pegmatite deposits were superficially examined, and the Bumpus quarry in Albany, Oxford County, Maine (see fig. 1), was selected for a diamond-drill exploratory-development project to supply information for developing more economical mining methods and no increasing production of beryl and other scarce minerals associated with pegmatitic intrusives. The Bumpus quarry has been mined intermittently by three operators since it was opened in 1927. At the time of drilling, the vein or dike (see figs. 2 and 3) had been mined to a depth of 60 feet for a strike length of 280 feet. The dike averages 40 feet in thickness and dips 50 degrees southeast. The Bureau of Mines drilled seven diamond-drill holes between September 27 and November 27, 1950. These holes showed that the dike persists for at least 350 feet to the east and probably 200 foot to the west of the present excavation. The drilling also indicated that the dip, as exposed at the surface, continued unchanged at 500 to a depth of at least 50 foot below the pit. The dike was not delineated, although it fingered out as pegmatite interbanded with Granite, diorite, and gneiss in diamond-drill hole B-4, approximately 250 feet west of the pit. Further drilling will be necessary to find the extent of this pegmatite dike and to determine the safest and most economic mining system.

Jan 1, 1952

By L. Yan, N. Damiano, J. Bickson, E. Bauer, D. Yantek, B. Whisner, M. Reyes, J. Srednicki

Built-in-place (BIP) refuge alternatives (RAs) are designed to provide a secure space for miners who cannot escape during a mine emergency. Heat and humidity buildup within RAs may expose miners to physiological hazards such as heat stress. To minimize the risk of heat stress, Title 30 Code of Federal Regulations (CFR), or 30 CFR, mandates a maximum allowable apparent temperature (AT) for an occupied RA of 35°C (95°F) [1]. The National Institute for Occupational Safety and Health (NIOSH) has conducted extensive research on the thermal environment of occupied RAs intended for use in underground coal mines. NIOSH research has demonstrated that a fully occupied BIP RA can exceed the AT limit by >5.6°C (10°F) in mines with elevated mine strata and air temperatures. In this circumstance, an RA cooling system could provide a solution. This paper provides an overview of test methodology and findings as well as guidance on improving the performance of a cryogenic air system prototype by optimizing the flow rate, increasing the tank storage capacity, and improving the efficiency of the heat exchanger of the cryogenic system. This may enable BIP RAs to meet the 35°C (95°F) AT limit in mines with elevated temperatures. The information in this paper is useful for RA manufacturers and mines that may choose to implement a cryogenic air system as a heat mitigation strategy. INTRODUCTION The apparent temperature inside an occupied RA could be significantly affected by the surrounding environment’s thermal conditions, such as mine air temperature and mine strata temperature. Apparent temperature (AT) is a temperature-humidity metric for the perceived temperature caused by the combined effects of air temperature, relative humidity (RH), and air velocity. It is used to assess the perception of indoor temperatures. Depending on factors such as geographic location and season, mine air temperature, relative humidity, and mine strata, temperatures can vary significantly [2]. RAs located in cold mines may pass the 96-hour 35°C (95°F) AT limit test that poses a challenge for RAs located in hot mines. One solution in these cases is that the occupancy of the RA could be derated (i.e., the RA occupancy could be reduced) to ensure the AT limit is not reached. However, this would require mines to purchase additional RAs to accommodate all personnel in the mine. For mines with high temperatures (above 26.7°C or 80°F), the occupancy might have to be reduced so much that the necessary number of additional RAs would be impractical. In these cases, RA cooling systems could provide a solution.

Jan 1, 2019

By W. A. Klikoff, I. Fatt

The concept of fractional wet wattability is examined. Fractional water wettability of a reservoir rock is defined as the fraction of the internal surface urea that is in contact with water. Capillary pressure and relalive permeability of unconsolidated sand are shown to be functions of fractional wettability. INTRODUCTION The petroleum industry has long recognized that wettability of reservoir rock has an important effect on multiphase flow of oil, water and gas through reservoirs. As early as 1928 the American Petroleum Institute sponsored a study of wettability as part of API Project 27 at the U. of Michigan.' Despite 30 years of research, there is still little exact knowledge of the wettability of reservoir rocks. There are two parts to the wettability problem. After agreeing to a uniform nomenclature in regard to wettability,' the first question to be answered is, "What is the in situ wettability of a given reservoir rock?" If this can he answered the next question is, "What part does wettability play in determining the characteristics of multiphase fluid flow through the rock?" This paper represents an oblique attack on the problem of wettability. No attempt is made here to answer the basic question of wettability in situ. instead the consequences of the concept of fractional wettability are examined. Multiphase flow in sandpacks is shown to he highly influenced by fractional wettability. Jennings' has given 3 definition of wettability and the other terms used in discussing wettability. These terms must be applied to the physical situation existing In reservoir rock. A survey of the pertinent literature from 1928 to 1956 indicates that the concept of a contact angle was applied to reservoir rock in the same way it would be applied to a flat, homogeneous surface. Attempts were made to state quantitatively the wettability of a reservoir rock in terms of a contact angle which was presumably constant at all points on the very rough and heterogeneous interior surface of a porous rock. Calhoun, et al,3-6 prepared synthetic consolidated and un-consolidated porous media in which they claimed there was a known uniform contact angle. They then showed the effects on the capillary pressure and relative permeability characteristics of varying this angle. The API Project 47 at the U. of Texas' and others' have made extensive studies of an indirect approach to the contact angle through the use of heat of wetting data. Even if successful. however, this approach also states the wettability of porous rock in terms of a contact angle which is uniform over the entirc surface. If the angle varies from one part to another on the internal surface, there is no way of determining from the measurements the area distribution of contact angles. In 1956 Brown and Fatt5 suggested that the concept of a contact angle, as applied to reservoir rock, be abandoned. This suggestion was made because it is known that the internal surface of most reservoir rocks is composed of many different minerals, cach with a different surface chemistry and a different capacity to adsorh surface active materials from reservoir fluids. Furthermore, the operation of a contact angle in determining the form of a fluid-fluid interface is difficult to picture in the very complex geometry of a pore. Brown and Fatt proposed that the wettability of reservoir rock be stated in terms of the fractional internal surface area that is in contact with water or oil. All surfaces on which there is water are called water-wet; surfaces on which there is oil are called oil-wet. The fractional water wettability is then stated as a number which represents the fraction of the internal surface that is in contact with water. A symmetrical statement can be made for the fractional oil wettability. The concept of a fractional wettability as previously stated has in its favor the recognition of the heterogeneous mineral composition of most reservoir rocks. Another point in its favor is that fractional wettability can be measured quantitatively with relative ease. Hol-brook and Bernard10 se a simple dye adsorption test to obtain fractional wettability of reservoir rocks. Amott11 uses a combination of imbibition and displacement to arrive at a wettability index of reservoir rocks which seems related to fractional wettability in the range 0.25 to 0.75 fractional water wettability. Jennings" has shown the changes in relative permeability that take place when a porous material is changed from unity to zero fractional water wettability. He also shows that reservoir rocks in their natural state, but at room temperature and atmospheric pressure, have relative permeability characteristics which would indi-

By Michel Chouteau

"A very conductive zone was revealed in 1977 and 1978 by magnetotelluric (MT) measurements carried out near Ste-Mathilde, 6 km northeast of La Malbaie . In order to identify the structure causing the anomaly, thirty-five MT soundings were recorded in 1980 and 1981 on and around the conductor within a radius of4 km. Results confirmed that the conductor is of limited extent (less than 2 km by 0.4 km). The proposed model is a highly conductive vertical slab, the top of which is within 200 m from the surface. At a depth of approximately 825 m this structure joins a conductive layer which extends to the northwest but not to the southeast. The large conductivities and the depths involved can only be explain ed by a fractured zone flooded with electrolytic solutions, by graphite veins or by metallic mineralization (sulphides). The former seems to be the most likely hypothesis because an EW fault running across this zone could have allowed percolation of water and the leaching of disseminated pyrite out of a mylolisthenite filling the fault.IntroductionLa Malbaie is located 130 km northeast of Quebec City on th e North Shore o f the St. Lawrence River (Fig. I). Four major groups o f rocks have been mapped in this area: charnockitic rocks to the west , granitic rocks in the north east and southeast, gneiss and pegmatites northwest and south of La Malbaie , and Paleozoic sediments in the Clermont-La Malbaie Valley and along the shore of the St. Lawrence River (Rondot, 1966). Two major features dominate the structure of the region: Logan ' s line , a major thrust fault beneath the St. Lawrence which separates the Grenville Province to the north from the Appalachian regime to the south, and the Charlevoix Crater , a large Paleozoic impact crater that created an almost perfect annula r structure centred on Mont des Eboulements (Rondot, 1970). Ste-Mathilde is a village lying 6 km northeast of La Malbaie, just outside the ring-like graben zone caused by readjustments after meteorite impact. The survey area spreads over a granite body which is more than 2 km long and 0.6 km wide, surrounded by a wide migmatite zone which is injected by many bodies of pegmatite, the latter likely related to the granite body (Fig. 2). A zone of leptynites lies west of the area. An east-west trending fault (FA1) related to the Charlevoix Crater runs mid -way across the survey area; a second parallel fault (FA2) south of FAI separates the gneissic rocks from the Paleozoic sediments. The overburden is usually thin with outcrops frequently encountered except for the centre of the survey are a where 10 m of glacial sediments are expected (E. Gaucher, 1982, personal communication)."

Jan 1, 1985

By Joseph Chalmers

Stimulative methods of production, whereby the total recovery of oil from natural reservoirs is increased, have come into considerable prominence during the past 15 years. In many oil-producing areas properties considered ready for abandonment by ordinary producing methods have responded to some form of stimulation, and their economic lives have been extended. The stimulative method having widest application is the injection of air or gas into the reservoir formations through selected input wells and is commonly referred to as the "gas drive." As a result of the many successful "gas-drive" operations operators are depending more and more upon this method for increasing the ultimate recovery of oil from their properties. A number of factors influence the efficacy of different gases as propulsive agents in recovering oil from sands. Gases of high density and viscosity show a tendency toward a slightly higher efficiency than those of lower density and viscosity. The solubility of the gas in the oil also affects the efficiency of oil recovery. Not only does dissolved gas decrease the viscosity of the oil, but dissolved gas that expands from solution in the oil tends to increase the effectiveness of a "gas drive." Interfacial tension between the oil and the gas and its effect upon the recovery of oil by gas injection are factors of which little is known. Dr. A. G. Loomis expressed the opinion that interfacial tension probably plays a minor role in the recovery of oil, except under conditions that produce a gas-oil foam. In connection with the above physical properties that influence the action of a pressure medium, control of the injected volume of the pressure medium is perhaps the major factor. The rate of gas injection determines to a great extent the amount of slippage and the resulting efficiency of the operation. The importance of volume control is realized when one considers that frequently it is the only factor that is under complete control of the operator.

Jan 1, 1930

By M. Smutz, C. J. Baroch, E. H. Olson

IN 1949 an orebody containing some 10 billion lb of recoverable rare earth metals was discovered in the Mountain Pass district of San Bernardino County, California.' The following year Molybdenum Corp. of America purchased a number of claims at the deposit and a mill on the property which had been constructed to process the district's gold ores. Average composition of ore from the San Bernardino deposit is less than 0.1 pct Tho2, 25 to 35 pct calcite, 10 pct rare earth oxides, 15 to 20 pct silica, and 30 to 40 pct barite.' Rare earth content of the ore analyzes 50.7 pct CeO2, 4.2 pct Pr6O11, 11.7 pct Nd2O3;, 1.3 pct Sm2O3,, and 34.3 pct La2O3 and others.' By floating the barite and depressing the bastna-site, Molybdenum Corp. of America produced a concentrate that contained 60 to 70 pct rare earth oxides. More than 25 pct of the rare earths, however, was lost in flotation. It seemed likely that a more economical method could be found. At the present time most of the rare earths in the concentrates are converted to rare earth chlorides, which are either fed to ion exchange columns for separation of the individual rare earths or reduced to misch metal. Current investigation shows that solvent extraction may achieve this separation more economically than ion exchange. The study reported here was undertaken to develop an economical method of preparing a pure rare earth nitrate mixture from California bastnasite ore. Results indicated that more than 98 pct of the rare earths could be recovered. Several possibilities were considered for processing bastnasite ore, but only the method outlined in Fig. 1 was investigated. This involved leaching the calcined ore with nitric acid. The nitric acid process is discussed under the following headings: 1) calcination of the ore, 2) leaching of calcine, 3) filtration studies, 4) solvent extraction, and 5) nitric acid recovery. Calcination: Since California bastnasite ore contains 25 to 35 pct calcite and about 10 pct bastnasite, calcination was needed to reduce the violence of reaction with nitric acid. Weight losses of 26 to 30 pct were obtained by calcining the ore at 900°C for I hr or at 800°C for 4 hr. Longer periods resulted in no further weight loss. Leaching the Calcine: When the bastnasite calcine was leached with 30 pct nitric acid for 8 to 10 days, rare earth recoveries of only 45 to 50 pct were

Jan 1, 1960

By M. P. Brandt, T. P. Knoetze, I. I. M. Kessler

It has generally been accepted that the volatile mater in a coal is the factor that determines whether or not a specific coal dust is an explosion risk. This paper presents the results of an attempt to relate the explosibility index (Kex) of South African coals, as determined in a AD-litre explosion vessel, to the volatile mater content of the coal and the calorific value of the volatiles. A good relationship between the calorific value of the volatiles and the explosibility index was established, which makes it possible to calculate the violence of an explosion, as expressed by Kex, for South African coals. The Kex value is but one of a number of parameters that influence the explosion hazard in a specific colliery and cannot be used as the sole predictor of the propagation of an explosion underground. Other parameters include the ignitability of the coal, temperature, humidity, dispersibility of the dust, methane concentration, amount of incombustibles present, and ventilation.

Jan 1, 1993

By Arthur. H. Winckers, Stephan L. Chryssoulis

"The deportment of gold in residue samples of cyanide leach tests of David Bell ore from level 6A block 13 was established using a comprehensive quantitative mineralogical approach. In every test the feed was first pre-aerated for 4 hours, followed by 48h cyanidation. Test no. 2 was done without lead nitrate and yielded a residue assaying 3.03g Au/t. In test nos. 4 and 9 lead nitrate was added before pre-aeration at 0.03kg/t and 0.3kg/t respectively yielding residues of 1.04 and 0.81 g Au/t.The mineralogical approach employed to establish the deportment of gold involved superpanning, to preconcentrate the free gold and assaying of the tailing fraction to determine the gold associated with quartz. It was thus determined that without lead nitrate added 47.2% of the lost gold is in the form of residual free gold particles less than 20 µm in size. It is this form of gold which is under represented in the residues of leach tests with lead nitrate added.Having eliminated coarseness of gold particles as a factor for lower recovery, it was determined that the residual gold particles have extensively contaminated surfaces. Amongst the deleterious surface contaminants identified: S, As, Ag, Sb and Hg, the two most harmful are S and Hg because of their concentration on the surface and rate of accumulation.Mercury and Ag are minor constituents of native gold at David Bell (average composition Au: 78.9 wt%, Hg: 18.5 wt% and Ag: 2.6 wt%) and they become enriched on the surface of residual gold particles because of their slower rate of dissolution in cyanide. The other elements absorb onto the gold particles from solution.The beneficial effect of lead nitrate was documented by comparative surface analysis of gold from residue samples of 48 hour leach testing with and without lead nitrate added and from time dependent (0-2 hour) leach tests in the presence and absence of lead nitrate. Lead nitrate accelerates the dissolution of gold by performing the following functions: (i) catalytic effect on the cyanidation of gold by accepting electrons; (ii) reaction with surface sulphur to form PbS which is then removed by oxidation; (iii) catalytic reaction on amalgam and Ag facilitating the cyanidation of Hg and Ag thus slowing down their build up onto the dissolving gold particles and (iv) the precipitation of sulphide sulphur from solution thus minimizing its build up on the surface of dissolving gold particles which is believed to facilitate the access of cyanide ions."

Jan 1, 1996

By Joseph Chalmers

[Stimulative methods of production, whereby the total recovery of oil from natural reservoirs is increased, have come into considerable prominence during the past 15 years. In many oil-producing areas properties considered ready for abandonment by ordinary producing methods have responded to some form of stimulation, and their economic lives have been extended. The stimulative method having widest application is the injection of air or gas into the reservoir formations through selected input wells and is commonly referred to as the ?gas drive." As a result of the many successful "gas-drive" operations operators are depending more and more upon this method for increasing the ulti¬mate recovery of oil from their properties. A number of factors influence the efficiency of different gases as propulsive agents in recovering oil from sands. Gases of high density and viscosity shrew a tendency toward a slightly higher efficiency than those of lower density and viscosity. The solubility of the gas in the oil also affects the efficiency of oil recovery. Not only does dissolved gas decrease the viscosity of the oil, but dissolved gas that expands from solution in the oil tends to increase the effectiveness of a "gas drive." Interfacial tension between the oil and the gas and its effect upon the recovery of oil by gas injection are factors of which little is known. Dr. A. G. Loomis5 expressed the opinion that interfacial tension probably plays a minor role in the recovery of oil, except under conditions that produce a gas-oil foam. In connection with the above physical properties that influence the action of a pressure medium, control of the injected volume of the pressure medium is perhaps the major factor. The rate ofg;as injection determines to a great extent the amount of slippage and the resulting efficiency of the operation. The importance of volume control is realized when one considers that frequently it is the only factor that is under complete control of the operator.]

Jan 1, 1930

FOR some time past keen interest has been shown in both America and South Africa in the mining drill-steel problem. This interest has extended to Australian mining fields, and Australian drill users, ever desirous of increasing efficiency, are vigorously attacking the problem. The writer has recently been engaged in the investigation of the problem on two of ,the biggest mining fields in Australia, and has formed very definite conclusions concerning the causes of many drill-steel casualties. He puts these views forward in the hope that they may be of interest to, both drill manufacturers and drill users. The subject is here dealt with mainly from the aspect of the properties of the steel and the modifications of these properties whensubjected to various manipulations. It is generally admitted that the drilling machine has greatly increased in power and efficiency during recent years, and the consequence is that the machine is demanding better service from the steel. This is being impressed on the drill users by an increase in steel casualties. This fact has led many mining people to the view that the machine has developed so rapidly that the steel maker has not been able to keep pace, and that consequently the steel isfailing by fatigue 0:1; so-called crystallization. This view is rather depressing. The writer, on the other hand, is inclined to discountenance fatigue as a serious factor under good normal working conditions where the steel is carefully manufactured and supplied to the user under suitable structural and sound conditions, and has subsequently received kind treatment at the hands of the drill sharpener and the drill user.It is not reasonable to attribute failures to fatigue until it has definitely been proved that the steel is fundamentally sound and is in the best structural condition to resist the stresses it is called upon to withstand, and, this being so, that all fundamental principles of...

Jan 1, 1923