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By A. Haque

The shear behaviour of infilled joints produced from ordinary gypsum plaster (gyprock) and bentonite was investigated in the laboratory under Constant Normal Stiffness (CNS) conditions. Shear tests were performed on saw-tooth profiles having Joint Roughness Coefficients (JRC) of 4.75 and 9.25 under an initial normal stress (sno) of 0.30 to 1.10 MPa, and at a normal stiffness (kn) of 8.5 kN/mm. Test data under the same sno and infill thickness to asperity height ratio (t/a) were analysed for two different sets of JRC. The peak shear stress plotted against the t/a ratio under constant sno revealed an increase in peak shear stress with the increase in JRC, up to a t/a ratio of about unity. The effect of roughness on the peak shear stress was observed to be minimal when the t/a ratio exceeded 1.40. A mathematical model for the prediction of peak shear stress due to the increased infill thickness has been developed based on a hyperbolic stress-strain relationship and energy balance principles. The model predictions are in good agreement with the laboratory observations. Le comportement de cisaillement des joints remplis produits à partir de plâtre ordinaire et de bentonite a été étudié dans le laboratoire sous des conditions de rigidité normales constantes. Des essais de cisaillement ont été réalisés sur des profils en dents de scie ayant des coefficients de rugosité des joints (CRJ) variant de 4,75 à 9,25 sous un effort normal initial (sno) de 0,30 à 1,10 MPa, et une rigidité normale (kn) de 8,5 kN/mm. Le résultat des essais conduits sous la même contrainte et épaisseur de remplissage au rapport aspérité/hauteur (t/a) ont été analysés pour deux ensembles différents de CRJ. La variation de l'effort de cisaillement maximal contre le rapport t/a sous une contrainte normale constante a indiqué une augmentation de l'effort de cisaillement maximal avec l'augmentation du CRJ, jusqu'à un rapport de t/a proche de l'unité. L'effet de la rugosité sur l'effort de cisaillement maximal a été minimal quand le rapport t/a a excédé 1,40. Un modèle mathématique pour la prévision de l'effort de cisaillement maximal dû à l'épaisseur accrue du remplissage des joints a été développé sur la base de la variation entre contraintes hyperboliques et déformation et sur des principes de bilan énergétique. Les prévisions du modèle sont en bon accord avec les observations de laboratoire. Das Scherverhalten in mit gewöhnlichem Gips und Bentonit gefüllten Klüften wurde im Labor unter Bedingungen konstanter Normalsteifheit (CNS) untersucht. Scherversuche wurden durchgefürt für Sägezahnprofile mit Werten des Fugenrauhigkeitskoeffizienten (JRC) von 4.75 und 9.25 unter Normalspannungs-werten (sno) von 0.30 bis 1.10 MPa, und bei Normalsteifheit (kn) von 8.5 kN/mm. Testresultate für gleiche Werte von sno und Verhältnis Fülldicke zu Rauhigkeit (t/a) wurden untersucht für zwei verschiedene Werte von JRC. Die Beziehung zwischen maximaler Schubspannung und und t/a Verhältnis unter konstantem sno zeigte einen Anstieg der maximalen Schubspannung mit zunehmendem JRC, bis zu einem t/a Verhältnis von etwa 1.0. Der Einfluss der Rauhigkeit auf den Maximalwert der Schubspannung war minimal solange das t/a Verhältnis den Wert von 1.40 überstieg. Ein mathematisches Modell wurde entwickelt für die Vorhersage der Schubspannung die von zusätzlicher Fülldicke erwartet werden kann, ausgehend von einer hyperbolischen Spannungs-Dehnung Beziehung und dem Energiegleichgewichts-prinzip. Die Modellvorhersagen zeigten gute Uebereinstimmung mit den Laborbeobachtungen.

Jan 1, 2003

By William N. Patterson

This report describes the design and testing of an improved quiet hard rock percussion drill. The improved drill incorporates a tappetless design with independent rotation in a hand held drill weighing 50 lbm. Laboratory and field testing in three mines were conducted. The testing showed improved drilling performance with no increase in measured noise levels over the fist design.

Jan 1, 1985

By Alden H. Emery, J. J. Forbes

The data contained in this paper were collected during the course of an investigation which covered 15 representative coal mines in six coalmining states. The purpose of the investigation was to determine by atmospheric sampling how much dust was raised into the air during the various operations of coal mining, such as undercutting with machines, loading coal by hand and transporting it from the working face to the surface. The data thus obtained were considered from two angles; namely, the possible physiological effect of inhalation and the explosion hazard of the dust. No attempt will be made to discuss the former factor in this paper. ConDitions of Mining The mines in which this investigation was conducted were considered representative, and it is believed that the results obtained will suffice for the average dustiness encountered in most coal mines. All of the coal mined was bituminous, from beds 30 to 120 in. thick. Only the ordinary room-and-pillar system of mining was employed. Daily production ranged from approximately 700 to 1500 tons and the men employed from 150 to 450. Coal was undercut by shortwall mining machines in all mines, with the exception of one in which pick mining was employed. Loading at the face wets done by miners; none of the mines used mechanical loaders. Electric drills, both for brushing roof and for shooting coal were commonly used, although some roof work was done with jack-hammers and a little of both with augers. Coal was hauled by motor, mule, or rope power in end-gate cars with capacities ranging from 1800 to 3600lb. With few exceptions, coal was won at the face by dry methods, that is to say, no water was employed for wetting down the dust either during undercutting, loading or transportation. Observations of Sources of Dust The common sources of coal dust as observed, arranged by decreasing amounts, were as follows: (1) Undercutting with mining machines; (2)

Jan 1, 1927

By K. S. E. Forssberg, J. A. Jirestig

Laboratory investigations on the possibility of using magnetic separation for the recovery of sulfide minerals have been reported. A survey of several sulfide ores and flotation concentrates indicated that, in most cases, magnetic separation is not a suitable primary beneficiation method. However, encouraging results have been obtained in concentrate purification. At the Boliden complex sulfide ore concentrator in Garpenberg, Sweden, an Allis-SALA Mark III carousel High Gradient Magnetic Separator (HGMS) is used with a small flotation circuit to recover sphalerite lost to the galena concentrate during lead flotation. After four years of refining the HGMS process, there has been an increase in zinc recovery and an enhancement in the quality of the lead concentrate.

Jan 1, 1994

By Victor F. Hollister, Robert W. Hodder

"The petrology and mineralogy of porphyry copper deposits are thoroughly described in recent literature and cited as the definitive characteristics for this type of deposit. The magmatic-hydrothermal aspect of genesis is also dealt with in detail. However, descriptions of their internal structure and regional setting are not as rigorous, and the genesis of this structure is simply stated as the release of high fluid pressures in a cooling magma emplaced along large fault zones. Genetic relationships between internal structure, regional setting and the tectonic evolution of continents has been alluded to infrequently in the past, but can now be considered together within the developing concept of orogeny at the margins of drifting crustal plates.Tensional structures, on both local and regional scale, and a Triassic to Tertiary age are described for porphyry copper deposits. We contend that such structure and age are distinct and unifying characteristics for this type of deposit and are genetically related to major crustal movements. British Columbia has porphyry copper deposits contemporaneous with plutons 180 to 200 million years old and 40 to 60 million years old. The former age group correlates with early stages of the continent's westward drift, and the latter group with a change in tectonic style during late development of the Canadian Cordillera. Hence, one can in British Columbia reflect on the genesis of a deposit's structure in the broader context of tectonic evolution. Such consideration should lead to more definitive criteria for area selection in exploration."

Jan 1, 1972

By J Coombes

"In today’s challenging climate of reduced staffing, limited funding and uncertain markets, we are called on to operate more productively and ‘be more innovative’. As an industry, we are quick to identify our practice areas as a mark of our role in the machinery of the mine value chain. We proudly note our profession – ‘geologist’, ‘mining engineer’ or ‘accountant’ – and demarcate our responsibilities and even our physical space. We even subdivide our disciplines into sacred entities such as ‘logging geologist’, ‘resource geologist’ or ‘structural geologist’ to prevent any blurring as though somehow the confusion will cost valuable disciplinary ground. How can we function professionally to heed the call to be more productive and more innovative?The purpose of this paper is to underscore what is expected from project evaluation, examine the ways in which we work as an industry and explore alternatives used in other industries and environments.The paper begins with a summary of project evaluation expectations and the ways in which disciplines typically interconnect when conducting project evaluations. Next, the paper examines alternative work frameworks and making a distinction between multidisciplinary, interdisciplinary and transdisciplinary frameworks. In-practice examples of these frameworks in alternative industries and contexts provide evidence for application as well as an opportunity to examine their pros and cons.The paper closes with a call to re-examine working practices in the mining industry, with a view to enhancing productivity and heeding the call for greater innovation.CITATION:Coombes, J, 2016. Transcending the mining discipline divide – multidisciplinary, interdisciplinary or transdisciplinary?, in Proceedings Project Evaluation 2016, pp 2–10 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

By D. L. Wood

INTERNAL oxidation of alloys has been investigated by Rhinesl,2 and by Meijering and Druy-vesteyn. Rhines showed that dilute Cu-A1 alloys can be internally oxidized without forming an external scale by annealing in an oxygen partial pressure equal to the decomposition pressure of Cu2O. The oxygen is supplied at the outside surface at a rate sufficient to maintain saturation of the surface with respect to oxygen. Oxygen diffuses inward and, at the interface between the subscale and the alloy, oxygen meets the solute and reacts to precipitate its

Jan 1, 1957

By R. E. Cech

Particles -3 to 30 µ diam of a 29.5 pet Ni, 70.5 pet Fe alloy after being melted and solidified while falling through a hydrogen atmosphere were found to contain a distortion-free body-centered-cubic phase. In most particles, the amount of body-centered-cubic phase approaches or equals 100 pet. It was shown by a series of experiments that this phase forms directly from the liquid. It is pointed out that a mechanism previously suggested in recent papers on the theory of the liquid-solid transformation can account for the solidification of body-centered-cubic phase in a temperature range where face-centered-cubic is the stable phase. IN the course of an operation to produce powders for a study of the martensitic transformation in Fe-Ni alloys, an unexpected phenomenon was observed. Powders of a 29.5 pet Ni alloy, which has a subzero M, temperature, were found to contain considerable amounts of a body-centered-cubic phase at room temperature. The experiments to be described were designed to elucidate the mode of formation of this unexpected phase. Experiments and Discussion An alloy containing 29.5 wt pet Ni, balance iron, was vacuum melted from high purity electrolytic iron and carbonyl nickel shot and solidified in the crucible. The metal was converted to oxide, ground to 100 pet <37µ, pressed to a cake, and homogenized 20 hr at 1350°C. To insure homogeneity the grinding, pressing, and homogenizing heat treatment was repeated a second time. The oxide was then ground to 100 pct <37µ and hydrogen reduced at 500°C. The reduced powder was given a spheroidizing treatment to produce spherical cast particles. The treatment consisted of dispersing the particles in hydrogen and allowing them to drop through a vertical hydrogen furnace set to a temperature higher than the liquidus of the alloy. This operation, commonly known as shotting, has been described more fully elsewhere.&apos; The powder produced by this method was found to contain approximately equal parts of body-centered-cubic and face-centered-cubic phases. A magnetic separation technique, previously described,&apos; was applied, and it was found that particles were either completely face-centered-cubic or nearly completely body-centered-cubic. The microstruc-

Jan 1, 1957

By R. K. Komarek, F. E. Jr. Briber, G. M. Hanson, Fred D. DeVaney, J. H. Blake, C. L. Matson, T. E. Ban, N. E. Shields, R. D. Frans, R. B. Greenwalt

Metallurgically, the term agglomeration is used to describe processes whose goal is to form balls, briquettes, nodules, flakes, or other sized shaped particles from loose, usually fine, incoherent particles. In practice it includes such varying processes as the briquetting of coal dust and other substances, the balling and induration (heating) of such nonmetallics as cement, fluorspar, lightweight aggregates, etc. It includes such widely used processes as the sintering of nonferrous concentrates, such as those copper, lead, zinc, etc. The agglomeration of specific nonferrous metal concentrates is discussed in detail in the section of this handbook devoted to that particular metal. Agglomeration processes are of particular value to the iron and steel industry where the nature of the primary reduction process, the blast furnace, requires for best results a burden essentially free of fines. This is a change that has taken place since about 1960. Prior to that time many fine unsized ores were fed to the furnace. The development of the pelletizing process gave to the industry a chemically controlled closely sized product that increased the produc¬tion rate and reduced the costs so much that unsized fines are seldom used in modem furnaces. Steel plants produce many fine sized waste products such as fine dust (fine ore coke and gangue) and mill scale. These products, which have a valuable iron content, are usually sin¬tered directly at the plant for reuse. Fine sized ore concentrates are usually pelletized at the mine and shipped as pellets to the steel plant. Common practice in some areas producing natural high grade ores is to screen the ore at the mine to about 3/8 in. The oversize is shipped "as is" and constitutes blast furnace feed. The / in. may be shipped to the steel plant where it may be sintered or otherwise agglomerated. At some mines the fines may be pelletizied prior to shipment. With the development of large ocean ore carriers, and with the transportation of slurried concentrates or fines, a trend has developed of constructing large pelletizing plants or other types of agglomeration plants near large consumption centers (i.e., in the Netherlands or Japan) where ores of many types are brought together, ground if necessary, blended, and agglomerated. As an indication of tonnages of agglomerated materials produced, for iron materials alone (the largest share of the total) production in 1970 in the U.S. was Million gross ton Sinter 40.7 Pellets 43.1 Briquettes, nodules, & others 0.1 Total 83.9 During the 1960s, U.S. production of sinter rose from 40.3 million gross tons in 1961 to a high of 48.7 million in 1964, then settled back to almost the 1961 figure in 1970. Pellet production rose steadily from 14.4 million gross tons in 1961 to the 59.9 figure for 1975. Worldwide, sinter production in 1966 was estimated at 340 million mt (mainly in Europe, Russia, Japan, and the U.S.) and pellet produc¬tion the same year at 64 mt (primarily Canada and the U.S.). World pellet production capacity rose to 200 million tons in 1976.

Jan 1, 1985

By O. Guyot, A. Broussaud, J. Björkman, P. Söderman, P. O. Samskog

Model-Based Expert Control systems (MBEC) are on-line supervisory dynamic optimization systems which combine the ability of a phenomenological model to generate a large amount of information about the state of the process and predict its evolution, with the flexibility of a rules-based approach to take plant constraints into account and apply a complex control strategy. For its new concentrator started in 1995 in Kiruna (Sweden), LKAB has implemented a progressive grinding flowsheet with closed-circuit autogenous grinding followed by closed-circuit pebble grinding with ore pebbles. The standard for instrumentation in this new plant is very high. The control hardware consists of a Distributed Control System (DCS) through which the operators interact with the plant, supplemented by a site-level Management Information System (MIS). A state-of-the-art MBEC system was imbedded in the MIS by the authors before plant start-up. It consists of several modeling and expertise software modules: a phenomenological process model and a Kalman filter estimate continuously the state of the process, an optimizer calculates an optimum feedrate, while rules-based modules establish production targets and key process set-points. The decision to install the MBEC system as an integral part of the new plant before start-up illustrates the current maturity of the technology, i.e., enough know-how was accumulated through former projects to design and develop the system to a large extent without accessing the plant. The feasibility and the power of dynamic optimization systems were previously demonstrated in Kiruna pre-existing concentrator by the authors. First, a MBEC system was installed on the three existing pebble mill circuits, providing both an increase in quality (stabilised size distribution) and a 10% increase in capacity. An on-line expert control system with limited modeling capabilities was also installed in the existing flotation plant, with the aim of stabilizing phosphorous content in the concentrate and optimizing collector additions. Both objectives have been achieved.

Jan 1, 1995

By A. J. Duncan, Bath M. D., E. R. Rudolph

Some factors influencing gold recovery by gravity concentration by M. D. BATH,. M.A.Se. (Met.) British Columbia (Visitor) A. J. DUNCAN,. B.Sc. (Hons.) Rhodes, M.S.A.C.I. (Visitor) E. R. RUDOLPH,* M.Se. (Eng.) Rand (Member) Recent studies have shown that the overall extraction of gold from Witwatersrand ores is increased as the proportion of gold reporting to the amalgamation circuit is increased. Testwork has therefore been carried out with a view to improving recovery by gravity concentration. In this paper, the history of gold recovery by gravity concentration is reviewed, and methods and machines at present in use are briefly described. The results of plant and laboratory tests are presented, and the limitation of existing concentrators is discussed. A pilot plant is being built for the testing of improvements to the existing concentrators and of several new devices, particularly the Reichert-cone concentrator.

By Jue Kou, Fazhao Sun, Jiang Liu, Cuili Gui, Baoqiang Yu, Chunbao Sun

A novel special magnetic separator was developed based on the special properties of precious metal-bearing alloy in highgrade nickel matte. The recovery of Au, Pt, and Pd was 77.79%, 84.79%, and 81.79% respectively at optimum operation conditions of magnetic separator feed of 2.5t/h, pulp density of 45%, and flush water of 1.5t/h, and the recovery significantly improved comparing with normal magnetic separator. Magnetic field simulation of the special magnetic separator indicates that magnetic intensity of 0.6 T can be generated on the surface of magnetic drum, which can strengthen the recovery of heavy alloy that contains precious metals. The alternate strong and weak magnetic field can also make magnetic particles rolling on the surface of drum, which will reduce the generation of magnetic agglomeration to a large extent and decrease the content of impurities in magnetic concentrate.

Jun 16, 2022

By W. Murray Small

Nickel plays an important role in determining the properties of many stainless steels and superalloys. Cobalt also contributes significantly to the performance of certain grades of superalloys. A major technical aspect, in which both of these metallic elements are involved, concerns the solubility of nitrogen in these classes of alloys. Beyond certain content limits, dissolved nitrogen may contribute to the deleterious mechanical behavior by these alloys. It is therefore essential to control the level of this element during alloy processing. In this paper, results from several experimental studies have been assembled and are analyzed to describe phenomena related to the individual effects of nickel and cobalt on the solution of nitrogen in several groups of alloys. Both solid and liquid alloy systems are considered. This information may be used as a guide to limit or control the presence of this interstitial element in alloys.

Jan 1, 1993

By Kevin Landey, Eric Gerst

Expanding blast patterns to near the limit of an explosives’ ability to do the necessary amount of work is a common practice to reduce drilling and blasting costs. Choosing less expensive explosives such as ANFO vs. emulsion, bulk product versus packaged product, etc. are also common cost savers. Both practices are only effective as long as the pattern geometries are accurately drilled. However, will pushing the limits on pattern sizes and explosive products produce consistent results at the face, minimize oversize, produce superior fragmentation, and improve crusher throughput? Sometimes, but no amount of explosives can overcome a poorly drilled pattern. Knowing the probable outcome of any changes in drilling and blasting is valuable in achieving success.

Jan 1, 2018

By J. N. Ong, J. P. Ratledge, J. H. Boyce

SINCE German operators opened the Tsumeb mine in the early 1900&apos;s, continuous operation has been interrupted only by enforced shutdowns during two world wars and the depression of the 1930&apos;s. Original metallurgical practice was blast furnace smelting. This was applicable only to low zinc ore, leaving large tonnages of high zinc ore to be stockpiled on the surface. A gravity concentrator using tables, buddles, and jigs operated for several years, but differential flotation of the ore did not get beyond the experimental stage. When the property was put up for sale by the South African Custodian of Enemy Property there was an estimated 434,000 tons of ore on surface dumps. The dump material, assaying 4.48 pct Cu, 15.8 pct Pb, and 10.9 pct Zn, had become highly oxidized during a stay of many years on the surface. But these dump ores had to be used in evaluating possible metallurgy because the shaft became flooded after the 1940 shutdown and underground ore was unavailable. Many companies examined Tsumeb but quickly lost enthusiasm because of the formidable metallurgical problems presented by the dump ore. However, on the basis of extensive test work, the present company decided that differential flotation would be successful and purchased the property after competitive bidding. Geology and Mineral Association is Complex The Tsumeb mine lies near the northern boundary of South West Africa at an altitude of 4200 ft. The village of Tsumeb is 335 air miles northeast of Wal-vis Bay, territorial port of entry. The orebody is a hydrothermal replacement deposit associated with an irregular intrusion of aplite cutting folded pre-Cambrian dolomite beds. In plan the deposit is a lens of 250x600 ft maximum dimensions. In section the orebody dips 55" south from the surface to 2000 ft, below which there is a reversal in dip to 75" north. Mineralization is localized in the aplite and in the adjoining brecciated dolomite. In the upper levels the ore is largely confined to a single lens, but below the 1890 level massive sulphide ore forms north and south lenses that partially enclose a pipelike body of medium to low grade disseminated ore, part of which is of too poor a grade to mine. Drilling below the 24th, or bottom level, has disclosed that a high percentage of the mineralization from the 3000 to 3300-ft horizons is comprised of copper and lead oxides. The deep oxidation may be local, since it appears due to circulating waters in a major fault cutting the orebody. Tsumeb ranks as one of the highest grade base metal deposits in the world. It is geologically and mineralogically famous for 41 copper, lead, zinc, vanadium, and germanium ore minerals, but its complex mineral assemblage is not attractive to metallurgists. In addition, there is a gradual change in oxidation intensity from the upper levels to the lowest level now operating, which is the 24th. This is well illustrated by the copper minerals. In the upper levels malachite and azurite are predominant, in the intermediate levels chalcocite, and in the lower levels tennantite. Throughout the mine there are sufficient heavy metal soluble salts to activate zinc, and large amounts of depressants are required even for so-called clean sulphide ores. When the same sulphide ore is exposed to prolonged oxidation aboveground, as was the case with the dump ores, reagent requirements become fantastic. Plant Construction First staff members arrived at Tsumeb in March 1947, and by May essential services had been restored and mine unwatering began. In 2 1/2 months company employees built a temporary jig and sorting plant for treating existing dumps to provide a saleable product during high metal prices. Meanwhile, concentrator design and construction was contracted to a South African firm, with subcon-

Jan 1, 1956

By P. Bonadia, A. Tabereaux

Nearly all aluminium smelters are increasing the potline amperage to achieve higher aluminium production. In some instances the higher amperage operation has a significant negative impact on shortening the lifetime of aluminum electrolysis cell cathodes due to loss of the protective sidewall cryolite ledge freeze and too rapid penetration of the cell bottom refractory lining by cryolitic bath components due to the higher temperature isotherms. Thus Cathodes require careful thermal modeling of the cathode relining designs and improved refractory materials to allow greater heat loss from the sidewall to preserve a stable sidewall ledge freeze at higher amperages, and the selection of optimum refractory barrier materials to control the penetration and reaction of bath into the cathode bottom refractory and insulation lining. This requires an understanding of the reaction mechanisms and product formation for molten NaF enriched bath and alumino-silicate refractories. It is desirable to use dense, low porosity refractory fireclay firebricks, or similar materials with a sufficiently high silica content to promote the formation the mineralogical phase albite, NaAlSi3O8, that significantly increases the viscosity of the melt which slows the diffusion of reactive species in the melt and thereby retards further bath penetration.

Jan 1, 2004

By C. P. Sandberg

INTRODUCTION. NOTWITHSTANDING the growing importance of this subject, no work specially devoted to it has hitherto been published. Having had to inspect during the last twenty years nearly a million tons of iron and steel rails for various countries, I have obtained experience of what rail manufacturers can practically execute, as well as of what railway engineers practically require. Bearing these two points in mind, I have from time to time published observations with a view to unite both interests, -that of the producer and that of the consumer,-and to reduce the specifications and the forms of sections to standards, or types, in order to facilitate the execution of the works and to improve the construction of permanent way. The Swedish government railways, as well as private companies owning railways in Sweden, Norway, and Denmark, have during the time above mentioned consulted with me and intrusted to me their rail inspection. I therefore owe to these countries much of the opportunity which I have enjoyed of gaining experience and position. Next to Sweden, America is the country which has most liberally favored me with its confidence in placing these matters in my hands. Through circumstances not under my control there has been little exportation to, and less work done by Europe for, America during the last six years ; but the recent revival of the rail trade has been the more gratifying to me, seeing that almost all the importers of American rails are still specifying for the Sandberg rail sections and inspection. It is therefore with .feelings of gratitude that I now beg to lay before the American Institute of Mining Engineers, and I hope, through that body, before the American railway world, the results of some experience which I have gained in the execution of work for their country, and which therefore belongs rightfully to

Jan 1, 1881

Jan 1, 1947

By A. D. Hughes

A relatively small area in Malaya, about 200 miles long by 40 miles wide, is the most important source of tin in the world. Some tin is recovered in other parts of the peninsula. Of the tin mined, 98 pct is recovered from alluvial deposits. From 1935 to 1941 the average annual world production of tin was 190,000 tons. The average annual production from Malaya during the same period was 62,000 tons or about one third of the total. Other producing countries, in order of importance, were the Netherlands East Indies 34,000 tons, Bolivia 30,000, Belgian Congo, Nigeria, Siam, Burma, China, and a few others with smaller amounts. The serious shortage of tin during the war period was due to the fact that the Japanese were occupying Malaya, Netherlands East Indies, Siam, Burma, and China which, together, formerly were producing 65 pct of the world supply. Because of the importance of tin in the world economy, and because of the fact that little is generally known in this country regarding the methods of recovering the tin in Malaya, it is believed that a short description of the industry, as carried on there, may be of interest to many of the readers. In addition you may be interested in the effect of the Japanese occupation, subsequent recovery of the properties and conditions existing at that time. The Malay Peninsula lies at the southeast tip of Asia. Singapore, a British colony, is situated on a small island at the southern end of the peninsula. It is a city of nearly a million population, an important world port, the site of a large British naval base and of one of the tin smelters. The Federation of Malaya consists of nine states, plus Penang, Malacca, and other small areas formerly part of the Straits Settlements, and it now covers the entire peninsula. The civil administration is controlled by the British. A constitution was adopted recently after reaching agreement with the Malay Sultans of the various states, who retain control of religious matters. The Capital is at Kuala Lumpur, a city of about 200,000 population, 250 miles north of Singapore and about half way to Penang. The country covers an area of 51,000 square miles, an area about equal to that of Florida and about one third that of California. It has a population of about seven million consisting of Malays, Chinese, East Indians, and a relatively small number of Europeans. The principal products are tin and rubber. There are over three million acres of planted rubber. The country is not self-supporting agriculturally as about one third of the necessary food supplies is imported. Rice is the principal food of the Asiatic population and some of the recent unrest is caused by a shortage of rice and the consequent high price. Good highways have been built through the settled part of the country. A railway, Government owned, extends from Singapore northward through the entire peninsula. The climate is tropical but health conditions are good for a tropical country. I was in Malaya from 1939 until January 1942, during the time of the simultaneous air attacks on Pearl Harbor, Manila, Hongkong, and Singa-

Jan 1, 1950

By George Holderer

THE Enos Coal Mining Co. owns an area underlaid by coal, of approximately 5000 acres. This property is situated 9 miles from Oakland City, in the southern part of Indiana. The mine has been in operation 5 years, during which time some 350 acres have been stripped, and stripping is now proceeding at the rate of about 100 acres per year. TOPOGRAPHY These coal lands consist of gently-rolling agricultural fields which in times past were farmed for wheat. There is no timber and but very little brush to contend with. The overburden varies from 10 to 60 ft. in depth. A thin bed of slate overlies the coal, followed by limestone, which varies from 3 to 15 ft.; this, in turn, is followed by sandstone, slate, shale and clay. There is a very wide variation in the thickness of all of these beds. The coal has an average thickness of 5 ft., and is a good grade of high-volatile bituminous. MINING OPERATIONS Briefly, the sequence of operations is: drilling holes with churn drills; blasting with L. 0. X.; stripping overburden to, uncover coal and, finally taking up the coal, which is sent to a tipple for cleaning and sizing. In order to show what is being accomplished by the use of L. 0. X., results will be shown from May to November, 1926, inclusive, and compared to the same period in 1925. No work was done in No. 1 pit during May, 1925, hence all figures are unduly low for this month.

Jan 2, 1927