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By B. W. Clyburn

"Coals from the Corporation's Lingan and No. 26 mines are classified as high-volatile A bituminous, with a very low inherent ash and containing all essential properties to provide metallurgical coal, with the exception of a high sulphur content. Only through proper cleaning at low specific gravity can the pyritic sulphur fraction of the coal be liberated to an extent where final sulphur meets coking standards. This first section of the paper deals with the operation of a Dutch State Mines heavy-media cyclone circuit to achieve an actual separation in the region of 1.30 specific gravity. A discussion of the parameter of control which must be applied along with an appraisal of the results obtained is included in the paper.Introduction Very high fluidity and unusually low ash are the outstanding characteristics of coal from Devco's mines in the Harbour seam of the Sydney coal field. However, sulphur content, mainly pyritic, ranges from 1 to 2.50Jo. To obtain the low and consistent sulphur level required in metallurgical coking coals, preparation at low specific gravity is required. Metallurgical coke is used as the fuel in an iron blast furnace. Its sulphur content largely determines the quantity of slag required to remove it and therefore influences furnace productivity and unit costs. Typical data on the various coal properties of importance in the production of coke are included in Table 1."

Jan 1, 1985

This paper investigates the effects of solids concentration and the addition of Dispersant S40 on the flowability of original and ground limestone slurries. A rotational viscometer with a concentric cylinder geometry and a controlled-stress rheometer with a cone-and-plate geometry were used to characterize the rheological behaviors of limestone slurries. The rheological behavior of original limestone slurries (<100 µm) is transformed through different types of flows with increasing solids concentration. The use of Dispersant S40 can improve the slurry flowability by decreasing viscosity and eliminating Casson yield stress. It is therefore used as a grinding aid for the wet ultrafine grinding of limestone. The rheological behaviors of ground limestone slurries vary with grinding from a starting dilatant flow-ability to a resulting pseudoplastic one with an evident Casson yield stress in combination with a thixotropic character. The appearance of pseudoplastic flowability combining thixotropy is related to the fineness of a ground product and its specific surface area, which are both correlated to solids concentration and the additive amount of Dispersant S40. In addition, the accurate rheological characterization of time-dependent fluids is dependent on the instruments used and operation conditions.

Jan 1, 2007

By Pollard P. J

Australia is well endowed with both tin and tungsten resources, and is currently a significant producer of both commodities for the international market. The intensity of exploration activity for both metals has been rather sporadic, reflecting the changing market situation. Thus tin has experienced three major boom periods around 1880, 1907 and 1983, while tungsten prices peaked around 1917, 1953, 1970 and 1977. During the earlier periods, the major discoveries were located utilising simple prospecting techniques involving creek travers- ing and stream sediment panning. The resulting location of tin alluvials quickly led to the discovery of adjacent primary deposits. The major tungsten deposits were composed of quartz- wolframite, which was readily visible as mineralised float both within the drainage systems and on scree slopes. Thus by the early 1900s most of the currently significant deposits had been located. More recent exploration approaches have combined these tradi- tional methods with the development of exploration models based on evolving genetic concepts. Within tin systems the emergence of province styles of clas- sification combined with enhanced perceptions of tonnage-grade characteristics and improved geological models has enabled more effective exploration strategies. Province classification at the inter- national scale demonstrated a clear relationship between deposit type and geological environment and thus considerable attention was given to the range of provinces present within Australia. Tonnage-grade diagrams enabled the refinement of economic per- spectives, while detailed models provided the basis for localised search parameters.

Jan 1, 1988

By John Neale, Robert Huberts, Tony Pinches

A major R&D programme for the application of bacterial oxidation to the pretreatment of refractory sulphide gold ores was started at Mintek in the early 1980s. This arose from an established expertise base in the bacterial leaching of base-metal sulphide ores. The refractory gold programme has been supported by a number of South African gold-mining companies, but major support has been provided by the Anglo American Corporation of South Africa (AAC) and the AAC Vaal Reefs Exploration and Mining Company Limited · (Vaal Reefs). The Mintek-AAC collaboration has been formalized as a joint-venture technology agreement for the comme;cialization, as well as continued development and improvement, of the bacterial oxidation process (MINBAC). From a process standpoint, bacterial oxidation involves the contacting of slurries of finely ground sulphide concentrate with suitable strains of iron-sulphur oxidizing bacteria, which act as the catalyst to promote sulphide·· oxidation by oxygen from air. Process engineering is simplified in that this reaction is carried out at low temperatures and ambient pressures. The view was taken that the successful development and implementation of the MINBAC technology should be based on parallel R&D aimed at an understanding of the process fundamentals, the process engineering and scale-up requirements, as well as the ancillary requirements for the gold recovery-processes and environmental management. This has represented a major R&D effort at a total cost to date of around US $10 million.

Jan 1, 1993

By Sunfangze Liu, Xumeng Chen, Yongjun Peng

Efficient separation of naturally hydrophobic gangue, such as talc and carbonaceous materials, from sulphide minerals in flotation is becoming a significant challenge in many processing plants due to the need to process lower grade and more complex ores. Considering the hydrophobic nature of these gangue minerals, prefloating them at the beginning of the flotation circuit in the absence of collectors and rejecting the concentrate is a common practice to remove these gangue minerals. However, sulphide minerals, such as chalcopyrite, can become naturally floatable due to surface oxidation and therefore may float together with naturally hydrophobic gangue. In this study, a new approach was developed to maximize the prefloat of hydrophobic gangue while minimizing the loss of sulphide minerals. The new approach introduced a prefloat cleaner stage where sulphide minerals recovered to the prefloat concentrate was depressed and separated from other hydrophobic gangue minerals at a low pulp potential with the prefloat cleaner tailing fed back to the main sulphide flotation circuit. Flotation tests were conducted using chalcopyrite and organic carbon. The results show that the proposed approach can significantly reduce the loss of valuable minerals in the prefloat flotation without affecting the reject of naturally hydrophobic gangue. Applying pulp potential control at the prefloat cleaner flotation stage also reduces the consumption of reducing agents while minimizing the effect of reducing agents on downstream rougher flotation.

Nov 23, 2020

By Jr. Sillers

To prove to .the satisfaction of all concerned that electrolytic manganese from our low-grade domestic ores could be substituted satisfactorily for ferro-manganese made from high-grade foreign fires, an extensive series of tests was conducted in cooperation with industry, in which electrolytic manganese pro-duced by, the Bureau of Mines at its Boulder City, Nev., Station was substituted for the ordinary ferro grades in the production of ferrous and nonferrous metals and alloys and welding-rod coatings. Over 1,200,000 pounds of manganese was given out for this purpose. The objectives of the tests were accomplished, and for some purposes electrolytic manganese was shown to be superior to other grades because of its high purity. The only serious objection that can be raised against electrolytic manganese is its price, which puts it out of reach for most purposes. Even if the price were to be lowered to a point where it would be in line with ferro grades, it is questionable whether electrolytic manganese from domestic ores could supply more than a small part of the needs of American industry because of the large volume of domestic ore that would have to be processed to supply a satisfactory feed for the electrolytic process. Thus, although electrolytic manganese is highly desirable from a metallurgical standpoint, it could not be expected to substitute for more than a fraction of our domestic manganese requirements.

Jan 1, 1952

By Phil Jones, Ben Johnson

During a period of six months in FY2018, a series of trials were conducted to compare drilling accuracy using two different methodologies and the subsequent impact this had on ore dilution. Testing was conducted at Cracow underground gold mine in Queensland, Australia. The drill rig’s existing alignment process was compared to a new technology system with the following observations:

Jan 1, 2019

By Floyd Smith

Based on underground observations made in .the coal mines of the Dominion Coal Company Ltd., this paper deals with the stress phenomena in the approach roads and headways and in the gob areas associated with the longwall method of total extraction. The deformation of roadways during development and the deformation of roadways during the total extraction period is delineated and presented in graphical form .. Conclusions are made as to the feasibility of the introduction of the retreat method of longwall extraction in one of the colhenes. The importance of future studies are enumerated, especially. those pertaining to the determination .of the opti.m.um sizes of protective pillars and to increasing the efficiency of the current methods of artificial roadway support.

Jan 1, 1967

By Martin Langenderfer, Sergii Chertopalov, Catherine Johnson, Vadym Mochalin, William Fahrenholtz

The high temperature and high pressure of an explosive detonation can be used for the production of nanomaterials. The controlled detonation of explosive compositions along with the collection and characterization of reaction products encompasses a process known as detonation synthesis. The primary advantage of the method of detonation synthesis is the possibility for producing monocrystalline nanoparticles with diameters of less than 10 nm. In order to successfully synthesize nanomaterials via the detonation process, it is necessary that the explosive detonation is conducted in a sealed environment. This environment when pulled to a vacuum or purged with inert gas such as argon will reduce the oxidation of detonation reaction products. Detonation synthesis testing is currently being conducted in a 1.8 cubic meters (m3) (64.3 cubic feet (ft3)) ellipsoidal pressure vessel consisting of two interlocking half shells. The testing involves the controlled detonation of cast mixtures of Cyclotrimethylene-trinitramine (RDX) and 2,4,6-Trinitrotoluene (TNT) in conjunction with siliceous compounds to produce nanocrystalline diamond and silicon carbide. Alternative detonation environments including the presence of a cooling medium such as water or dry ice to absorb residual, post detonation, thermal energy and enhance the stability of the materials being produced have improved yield. Modifications to the explosive charge composition have an effect on the type and quantity of materials that can be produced. Doping of explosive charges with various organic and inorganic compounds has shown promise in the synthesis of materials that are difficult or uneconomical to produce through other methods. This paper outlines the process development of detonation synthesis facilities. Preparation of the pressure vessel to create a suitable detonation environment for the production of nanomaterials is examined. Formulation of explosive charge compositions and considerations involving test charge initiation are discussed in detail. Experimental results and analysis from initial testing as well as plans for future research are also evaluated.

Jan 1, 2018

By Frederick Laist

While remodeling No. 1 section of the concentrator at the Washoe Reduction Works of the Anaconda Copper Mining Co. during the summer of 1912, for the purpose of ascertaining what additional metal recoveries could be made by improvements in concentration practice which had been developed by the staff of the Boston & Montana Reduction Department, at Great Falls, it was deemed advisable to carry on some experiments on the treatment of the regular mill tailings by roasting and leaching, to see whether the losses of metal values might not be still further decreased. In the course of these experiments about 5,000 tons of tailings were roasted, and of the resulting calcine about 200 tons were leached. The results were so satisfactory that it was decided to continue the work on a larger scale, particularly as regards the leaching end of the process, and construction work on an 80-ton roasting and leaching plant was accordingly commenced during the latter part of February, 1913, and is being pushed as rapidly as possible. 80-Ton Leaching Plant. This plant will consist of one 20-ft. roasting furnace of the Mac-Dougall type, specially adapted to the work of roasting for leaching; two leaching tanks, 32 ft. in diameter by 12 ft. deep, together with the necessary solution tanks, air lifts, precipitating launders, etc. It has been decided to precipitate the copper from solution on scrap iron, so as not to hamper the roasting and leaching departments by any weakness that might develop in the precipitating department. It is, however, the intention to experiment with a number of different methods of precipitation; for example, by electrolysis and by hydrogen sulphide. The acid required for the operation of this plant will be purchased, ad the quantity required is not sufficient to justify the installation of an acid plant. An acid plant will, however, be established in con-

Jan 1, 1914

By W. R. Shimer

In his valuable report on Finishing Temperatures and Properties of Rails,l Dr. G. X. Burgess, Chief of the Division of Metallurgy, U. S. Bureau of Standards, has begun a line of investigation which should be continued by those interested in the subject, and who have proper facilities for carrying out the work. For the past year or more the Bethlehem Steel Co. has been conducting experiments to learn the effect of rail finishing temperatures on their physical properties and microstructure and the results are here given for the consideration of those interested in the rail situation. Considerable differences of opinion have been expressed by various authorities, in the past, as to the effect of large or small grain size and high or low finishing temperatures of steel rails on their physical properties and wearing qualities. Low finishing temperatures and, therefore, low shrinkage, have been advocated on the theory that the wearing qualities would be improved. Others have recommended high finishing temperatures. The generally accepted cause for rail failures, due to the development of transverse fissures, is excessive wheel pressure on hard rails. One of the causes advanced for hard rails has been that they contain too high percentages of carbon and manganese; another that the rails were finished at too low a temperature, i.e., at or near the critical point. In the experiments herein described the rails were rolled from reheated blooms. All the rail blooms were charged hot in a reheating furnace and brought up to about the original ingot-rolling temperature before rolling into rails. These rails gave better results in deflection, withstood a greater number of drops before breaking, and showed greater ductility than rails of identically the same composition and section which were rolled direct from the ingot. Rails rolled from reheated blooms, finished at somewhat higher temperatures than when rolled direct from the ingot, have a different microstructure, which the writer does not believe is due so much to the difference in finishing temperatures, as to the difference in

Jan 1, 1915

Those who have had an occasion to apply geostatistics to the estimation of ore reserves are familiar with the conventional approaches of estimating average grade of quality values for arrays of regular grid squares or blocks. Further, the technology to perform geostatistical analysis and prediction for irregular two-dimensional areas has been available in a practical, readily useable form for some time. However, the generalization of this technology into three dimensions has been hampered by lack of a suitable geometrical characterization for realistic, three dimensional shapes and volumes. The extension of these estimation techniques into three dimensions has now been made possible by a successful integration of the volume modelling capabilities of 3D Component Modelling with proven 3D Geostatistical Techniques. The result is a powerful new technique for mineral ore reserves estimation in a practical, useable form. The technique allows direct geostatistical estimation of grade and quality values for precisely defined, irregular, realistic, geological, and mining shapes or volumes. This paper describes the two technologies, their integration and their application in practice to the estimation of mineral ore reserves. The paper closes with a discussion of the benefits provided by the new approach, in terms of accuracy, efficiency and practicality.

Jan 1, 1991

By A. L. Holley

THERE is a growing demand for pure and cheap material for fine open-hearth steel ; a material not only very free from phosphorus, but from carbon and silicon; so that it may he rapidly converted into steel. Iron and steel scrap are not trustworthy as to quality, and they are often dear. There are three methods of purifying cheap materials for the open hearth. 1. Mechanical puddling, as done at Creusot, which removes 90&apos; per cent. of the phosphorus from the pig iron. 2. Krupp&apos;s washing process (the conduct and results of which I fully described in a former paper*), which eliminates 70 to 80 per cent. of the phosphorus and most of the sulphur and silicon from pig iron. Neither of these processes would sufficiently purify, for very fine steel, those very impure pigs which are cheapest in many parts of the United States: 3. The process of producing directly from the ore an iron which is practically pure chemically, although mechanically mixed with the impurities of the ore. This is the oldest of iron processes ; one form of it, the Catalan forge, employed to produce charcoal blooms, is still in use, but its great cost is rapidly throwing it out of competition. Among the modern attempts to produce iron direct from the one, on a large scale and at a cheap rate, several have been in various respects successful. Dr. Siemens&apos;s process of treating a ton and a half or more of ore and the coal to deoxidize it, in a rotating gas furnace, and bringing out, in some four hours, a ball of chemically pure iron so soft that the fluid and impure slag may be squeezed out of it, is the most attractive and the most highly developed of all the modern direct processes. I have watched it, from time to time, since 1874, and have noted a steady improvement. It may now be said to have passed the experimental stage, although, like older processes, it must be adapted by practice to special materials. The cause which has been more potent than all others, including the defects of the best direct processes, to bring these processes into disrepute, is the waste-ful treatment of the direct product. With one or two exceptions (when failure was due to other and obvious causes), the direct product has been made into wrought iron (weld iron). Even Dr. Siemens has, at Towcester, in England, and at Park, Bro. & Co.&apos;s, in Pittsburg, set up his apparatus for this purpose. Is it likely that

Jan 1, 1880

By A. L. Holley

There is a growing demand for pure and cheap material for fine open-hearth steel; a material not only very free from phosphorus, but from carbon and silicon; so that it may he rapidly converted into steel. Iron and steel scrap are not trustworthy as to quality, and they are often dear. There are three methods of purifying cheap materials for the open hearth. 1. Mechanical puddling, as done at Creusot, which removes 90&apos; per cent. of the phosphorus from the pig iron. 2. Krupp&apos;s washing process (the conduct and results of which 1 fully described in a former paper*), which eliminates 70 to 80 per cent. of the phosphorus and most of the sulphur and silicon from pig iron. Neither of these processes would sufficiently purify, for very fine steel, those very impure pigs which are cheapest in many parts of the United States. 3. The process of producing directly from the ore an iron which is practically pure chemically, although mechanically mixed with the impurities of the ore. This is the oldest of iron processes ; one form of it, the CataIan forge, employed to produce charcoal blooms, is still in use, but its great cost is rapidly throwing it out of competition. Among the modern attempts to produce iron direct from the one, on a large scale and at a cheap rate, several have been in various respects successful. Dr. Siemens&apos;s process of treating a ton and a half or more of ore and the coal to deoxidize it, in a rotating gas furnace, and bringing out, in some four hours, a ball of chemically pure iron so soft that the fluid and impure slag may be sqneezed out of it, is the most attractive and the most highly developed of all the modern direct processes. I hare watched it, from time to time, since 1874, and have noted a steady improvement. It may now be said to have passed the experimental stage, although, like older processes, it must be adapted by practice to special materials. The cause which has been more potent than all others, including the defects of the best direct processes, to bring these processes into disrepute, is the wasteful treatment of the direct product. With one or two exceptions (when failure mas due to other and obvious causes), the direct product has been made into wrought iron (weld iron). Even Dr. Siemens has, at Towcester, in England, and at Park, Bro. & Co.&apos;s, in Pittsburg, set up his apparatus for this purpose. Is it likely that

Jan 1, 1880

Book Review MAN-TO-MAN: THE STORY OF INDUSTRIAL DEMOCRACY. By John Leitch, Phila¬delphia, Pa. The B. C. Forbes Publishing Co., New York, 1919, 2.19 pp., 7 1/2 X 5 in. $2.00. "Man to Man" is a short, well-written, well-printed, easy to read and very interesting hook. It is an account of a method introduced into more than twenty industrial plants to give the workers a share in managing their own troubles. It is not a panacea for labor troubles and strikes, but neither have existed where the new method has been tried. The scheme is, in a word, to organize the working force like the government, having a cabinet composed of the executives, a senate composed of foremen, and a house composed of men elected by fellow workers from all departments. This governing machinery takes up all complaints of workers, investigates, reports, and settles. The increased profits due to economy and increased production from this cooperation are divided 50-50 between the company and the men. Experience has shown that, since inattention, tardiness, irregularity, and inefficiency tend to reduce their profits, all men very quickly, after once convinced of the sincerity of the management in their scheme of cooperation, eliminate them because it is for their personal profit. Astonishing results have been attained, including higher wages, greater output, lower unit costs, great reduction in labor turnover, elimination of waste, an increased loyalty and a waiting list of employees even in periods of labor shortage. Profit sharing as such and stock ownership as a benefit to industrial relations are discussed briefly and illuminatingly, although they are not believed by the author to he the best way to bring about the human relation between those who work,for and those who work with money. The author is not against unions but does not believe the union is the best medium for improving industrial relationship. The look is nowhere dogmatic but is always forceful and convincing and, being well written, is very entertaining. It is doubtful if "Industrial Democracy" is the right expression for the solution of the problem but certainly anything that will place on the shoulders of labor some of the responsibility of industry and will increase production is tine much-to-be-desired desideratum. It is a. contribution to the solution of our biggest problem and should be read by everyone who employs men and who has been worried by the labor turnover. P. E. B.

Jan 7, 1919

By Robert B. McCormick

World War II has developed a use for the nonmetal mineral quartz crystal that was unknown in World War I. During the interim period of peace, experimental work in the radio field with the piezoelectric properties of quartz crystal resulted in the almost universal adoption of quartz-crystal radio oscillator plates to control frequency in radio broadcasting, police, commercial and amateur communications equipment. Telephone resonators and filters made from quartz crystal also were developed, which vastly improved the frequency control of long distance telephone circuits. Expansion of the Industry The sudden war demands of the armed services for radio equipment using quartz crystal for frequency control led to an unprecedented expansion of the manufacturing industry. It is estimated that the 1940 peacetime volume amounted to approximately $1,500,000, while today a vast new quartz-crystal industry supplies more than $150,000,000 worth of quartz oscillator plates to the Army and Navy each year. This demand has caused an enormous expansion not only of American manufacturing facilities but also of Brazilian mining output, virtually our only source of raw quartz crystal. Actual figures of imports and consumption cannot be cited, for security reasons, but certain comparisons have been made, which indicate the transformation of quartz crystal from a minor to a major nonmetal. Lundl has shown that the value of quartz-crystal exports from Brazil is now about equal to that of phosphate rock produced domestically in 1941 and actually exceeds the combined value of crude feldspar, gypsum and fluorspar production in the United States in the same year. This great expansion under wartime pressure was not accomplished without some anxious moments, but all the demands of industry have been met and the Government has been able also to accumulate a substantial stock pile of material against future contingencies. Inspection and Grading of Quartz Crystal The swift growth of the quartz-oscillator industry necessitated the simultaneous evolution of methods and criteria for inspecting and grading quartz crystal. It has been found that, generally speaking, it is economically feasible to cut only crystals that are at least 30 per cent by volume free from major defects such as optical and electrical twinning, cracks and fractures. Blue needles, bubbles, "chuva" and other minor imperfections can be tolerated in the usable portion unless present in great excess. The present marketing system in use in both Brazil and the United States, as far as quality is concerned, depends solely on the "usability" of a crystal, which is defined in the Brazilian-American agreement2

Jan 1, 1948

By L. Marais, S. Denoon-Stevens, J. Cloete

"Historically, mining companies worldwide provided housing and developed towns to accommodate their employees. At the end of the 1980s this approach became less prevalent and attempts were made to mitigate the effects of mine development and mine closure on communities living near the mines. Permanent settlement in mining towns urgently needed to be minimized. Since the advent of democracy, South African policy has moved in the opposite direction, shifting the emphasis to creating integrated communities and encouraging home ownership. Despite this policy shift, however, mines continue to influence local housing conditions. One direct outcome has been the development of informal settlements. We surveyed 260 informal settlement households in Postmasburg, a small and remotely located town in the Northern Cape Province of South Africa. We found that because they employ contract workers and thus arouse expectations of employment, the mines here contribute extensively to the development of informal settlements. But local factors also contribute, and the functional role of informal settlements as a form of housing that supports mobility should not be underestimated. We also found that both municipal and mining company policies for informal settlements were inadequate. Finally, we found that low-income informal settlers not associated with mine employment suffered the highest levels of social disruption.IntroductionA mine generates demand for labour, which in turn generates demand for housing. When settlements spring up near a mine this often means poor housing conditions. In South Africa in the 1960s and 1970s mining companies invested heavily in company towns or mining settlements, but they have become increasingly hesitant to do so, for three reasons. First, declining resource prices in the mid-1980s and the 1990s compelled them to focus on core business interests and reduce the costs of peripheral activities such as housing (Bryceson and MacKinnon, 2013); second, at the turn of the 20th century they were often accused of taking over the role of local government (IIED, 2002) and consequently became hesitant to invest in developing mining towns; and third, changing labour regimes also curbed their investment in such towns (Haslam McKenzie, 2010). Increasingly, the companies began to endorse block-roster shifts, and outsourcing also became more common in the early 1990s. Block-roster shifts in Australia (together with improved technology) have meant that miners do not need to settle near the mines but can fly in and fly out and have their urban houses as their stable homes. This has had serious negative implications for housing in remote towns in Australia, particularly worker camps, large-scale renting out of available accommodation, and ‘hot-bedding’."

Oct 1, 2018

By Robert B. McCormick

World War II has developed a use for the nonmetal mineral quartz crystal that was unknown in World War I. During the interim period of peace, experimental work in the radio field with the piezoelectric properties of quartz crystal resulted in the almost universal adoption of quartz-crystal radio oscillator plates to control frequency in radio broadcasting, police, commercial and amateur communications equipment. Telephone resonators and filters made from quartz crystal also were developed, which vastly improved the frequency control of long distance telephone circuits. Expansion of the Industry The sudden war demands of the armed services for radio equipment using quartz crystal for frequency control led to an unprecedented expansion of the manufacturing industry. It is estimated that the 1940 peacetime volume amounted to approximately $1,500,000, while today a vast new quartz-crystal industry supplies more than $150,000,000 worth of quartz oscillator plates to the Army and Navy each year. This demand has caused an enormous expansion not only of American manufacturing facilities but also of Brazilian mining output, virtually our only source of raw quartz crystal. Actual figures of imports and consumption cannot be cited, for security reasons, but certain comparisons have been made, which indicate the transformation of quartz crystal from a minor to a major nonmetal. Lundl has shown that the value of quartz-crystal exports from Brazil is now about equal to that of phosphate rock produced domestically in 1941 and actually exceeds the combined value of crude feldspar, gypsum and fluorspar production in the United States in the same year. This great expansion under wartime pressure was not accomplished without some anxious moments, but all the demands of industry have been met and the Government has been able also to accumulate a substantial stock pile of material against future contingencies. Inspection and Grading of Quartz Crystal The swift growth of the quartz-oscillator industry necessitated the simultaneous evolution of methods and criteria for inspecting and grading quartz crystal. It has been found that, generally speaking, it is economically feasible to cut only crystals that are at least 30 per cent by volume free from major defects such as optical and electrical twinning, cracks and fractures. Blue needles, bubbles, "chuva" and other minor imperfections can be tolerated in the usable portion unless present in great excess. The present marketing system in use in both Brazil and the United States, as far as quality is concerned, depends solely on the "usability" of a crystal, which is defined in the Brazilian-American agreement2

Jan 1, 1948

By S. J. Swainson

PHOSPHATE ROCK is a low- priced commodity. This fact has influenced the choice of mining and beneficiating methods to a greater degree, perhaps, than in most other low-grade mining operations. The fact that many yards of everburden and matrix must be stripped and mined per ton of salable "rock" produced and sold has necessitated he development of relatively simple btneficiating plants having high capacity and low capital and operating costs. The law of diminishing returns must always be reckoned with in phosphate mining and washing, and often recovery must be sacrificed in favor of costs in order to achieve the highest over-all economic efficiency. The phosphate-bearing formation, known as "matrix," is composed of (1) phosphate pebbles, which are somewhat rounded in shape and which vary in size from 1-in, to micron sizes, (2) rounded quartz grains usually smaller than 10 mesh, and (3) clay, of varying "stiffness," which is the binder of the matrix. The phosphate pebbles vary in hardness. Their color, which varies from white to black, is not a reliable indicator of the Bone Phosphate of Lime (B.P.L.) content of the

Jan 1, 1944

By J B Tucker, A T. McGrath

Situated in north-west Queensland, Australia, the Ernest Henry Mine (EHM) has been producing copper and gold since 1996. Owned and operated by Glencore Xstrata, ore is currently sourced from a newly developed underground sublevel cave (SLC) mine below the old EHM open pit (the pit). Ore feed to the concentrator is supplemented by satellite open pits comprising the Mount Margaret operation.The transition from open pit to a producing underground mine involved a complex extraction sequence for the first two production sublevels on RL1650 and RL1625. Underground mining during cave initiation was further complicated when south wall instability prevented completion of the final open pit shell. The transition mining phase included mass firing of an inclined crown pillar between the initial SLC void and the pit followed by a combination of transverse and longitudinal SLC mining.The inclined crown pillar mass firing was the first significant milestone in the extraction of the transition ore block. Comprising approximately 890 000 t of in situ material; 70 000 m of drilling was charged with 351 t of emulsion and 6026 electronic detonators to initiate the single mass firing. The firing contained five direction changes over 19 seconds making it one of the largest and most complex underground blasts ever conducted in Australia.Risk management was integrated into every facet of the technical and operational planning and execution of the transition mining phase, whilst maintaining daily mine construction and production commitments. This paper provides a detailed overview of the transition objectives and constraints, mining method selection, post mass blast outcomes and the journey ahead.CITATION:McGrath, A T, Campbell, A D and Tucker, J B, 2014. Transition of the Ernest Henry Mine from open pit to an underground sublevel cave, in Proceedings 12th AusIMM Underground Operators’ Conference 2014 , pp 297–308 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 24, 2014