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By R. Hart

In this paper, problems that have been experienced with the rockpass system at Kloof Mine No. 3 Shaft are described. Actions that have been taken to overcome the problems are also described. These include the use of slugshots to remove hang-ups, the abandonment and waste filling of passes, and design criteria adopted for an alternative pass system.

Jan 1, 2006

By A. El-Midany

Dolomite impurities are increasing in the currently mined phosphate deposits in Florida. Several research efforts have been conducted in various laboratories around the globe to find methods to economically removing the dolomite. However, a universal and cost-effective process is not now in commercial use. In this paper, a new process for dolomite/apatite separation is presented. The differential solubility of dolomite in slightly acidic solution is utilized to generate micro CO2 bubbles at the dolomite/water interface. Particle (dolomite)/bubble aggregates float to the surface leaving phosphate concentrate with low MgO content. Interestingly, up to 6.0 mm particles can be floated by such micro-bubble/particle aggregates. Different surface-active agents were tested to stabilize the bubbles. Results of these tests are presented, and the mechanisms involved are discussed.

Jan 1, 2009

By B. H. Moore

Foundation and excavation problems associated with lock construction projects vary widely. Each lock requires a different foundation to respond to a unique geologic setting. The range of heights and founding materials are illustrated thru description of selected structures encountered in the United States. Examples range from 113-ft high John Day Lock on the Columbia River founded on basalt rock to the 17-ft high Lock No. 5 on the Arkansas River floated on a clay foundation. A description of the basic elements of design and construction is presented. Several case histories involving lock design and construction are assessed to aid in recognition of potential problem areas on forthcoming construction. In the past decade there have been many improvements in construction materials and techniques. The application of these new approaches to lock construction is discussed.

Jan 1, 2010

By A. Azizi, P. Blatter, A. Bouajila

"Due to the high reactivity of sulfide minerals in alkaline cyanide solutions, some parasitic reactions inflict a heavy gold surface passivation and excess cyanide consumption resulting in a dramatic decrease of the gold leaching rate. Atmospheric pre-oxidation was shown to be an effective tool to enhance gold extraction by preventing a passive film from forming on the surface of gold grains. This work aims to highlight efforts undertaken to determine: (1) how gold cyanidation is limited by passivation; (2) what are the reactions and mechanisms involved during gold cyanidation; and (3) how a better understanding of fundamental issues can be used to design a proper pre-oxidation strategy. INTRODUCTION Precious metals (PM), gold in particular, naturally occur in contact within a wide range of sulfide mineral systems. Hence, one of today’s most challenging R&D tasks consists in accounting for the presence of sulfides on the cyanidation behavior of gold. An important body of knowledge reveals that metal sulfides display a range of reactivities in alkaline cyanide solutions (Marsden & House, 2006). Such reactivities are acknowledged to inflict additional utility costs and loss of profits because they are accompanied with higher consumption of cyanide and/or formation of undesirable by-products that are often detrimental to gold leaching rates. Gold recovery in cyanidation is hampered by a multitude of factors, among others: (1) consumption of excess cyanide as a result of the formation of thiocyanate and dissolution of transition (Cu, Fe, Zn, etc.) metals (Habashi, 1967); (2) gold surface passivation by solid reaction products, e.g., Fe(OH)3 (Guo, Deschenes, Pratt, Fulton & Lastra, 2005), sulfur (Dai & Jeffrey, 2006; Jeffrey & Breuer, 2000;) or oxo and thiooxo (SbO33- SbS33-) salts in alkaline solutions (Guo et al., 2005). Because of their energy structure, most of the sulfide minerals exhibit semiconductor properties (Marsden & House, 2006). Therefore, the contact between constitutive sulfide minerals inside complex sulfurous ores entrains electrochemical phenomena in which sulfide dissolution is a genuine corrosion process (Azizi, Petre, Olsen & Larachi, 2010). For instance, galvanic interactions could be initiated between the various constituents within the ore and could substantially increase or decrease the reactivity of some of the associated minerals."

Jan 1, 2012

The commercial development of the shallow (2200 ft2 400 ft) Windalia sand reservoir at Barrow Island provided the opportunity to conduct an intensive drilling programme using equipment and techniques designed for optimum performance.During the initial exploratory and reservoir delineation phase, 12 specific Windalia test wells were drilled using drilling equipment with an optimum depth range of 6QOO ft - 8000 ft and a 9 5/8 in by 7 in. casing programme was employed. The average time from commencement of move-in to rig release exclusive of coring for five representative wells was 187 hr during this phase.Development drilling commenced December 1966 with one rig, with the second in operation January 1967.As of January 1 1968, 168 development wells had been completed. The two rigs employed are drive-in units equipped with a telescoping .gelf raising doubles mast.Optimum depth range with 4 1/2 in. drill pipe is 2500-4000 ft. Casing programme is 8 5/8 in. by 5 1/2 in. Efficient performance was achieved immediately. The average time from commencement of move-in to rig release for 15 wells drilled early in the development programme was 99 hr.By application of experience and further modification of techniques, performance was improved to an average time of 72 hr per well for 15 wells recently completed.The major drilling problem on Barrow Island is surface hole drilling due to the very hard surface limestone combined with complete loss of circulation at sea level.In this operation, significant improvements have been effected. During the exploratory phase drilling, 12 1/4 in hole to set 9 5/8 in. casing, average penetration rate was 23 ft/hr. At the commencement of the development programme penetration rate, drilling 10 5/8 in. hole to set 8 5/8 in. casing, was 28 ft/hr for the 15 early wells considered, improving to 55 ft/hr for the 15 recent wells considered.This programme is a team effort and much credit must be given to the enthusiastic co-operation of the two drilling contractors.The current field record is 2 days 4 hr with a 4 1/2 hr move including the drilling of mousehole and rathole.

Jan 1, 1968

This Bureau of Mines publication contains five papers pertaining to the effective grounding of mine power systems, as follows: Ground-check monitor types and safety characteristics; ground wire monitors for surface coal mines; ground bed design and measurement; electrical ground rod corrosion; and a continuous ground bed resistance monitor.

Jan 1, 1979

By R. H. T. Garnett

N.B. This paper provoked much (positive!) discussion in later issues, with responses from the author (and thanks also for the many private contributions he had received) - see under Garnett R.H.T. Expanded version of a paper originally presented at the Alluvial mining conference, London, 11-13 November 1991 and published in Alluvial mining, Barking: Elsevier Applied Science for IMM, 1991, p.115-156. The usual measure of performance in gold and tin dredging is the R/E factor. It compares actual production or recovered grade for a given period with that estimated from the original sampling. The factor is a multiple of four component factors, each ideally approaching 1.00. The factors are concerned with estimation, selection, excavation and treatment. The estimation factor reflects the errors involved in determining the grade and depth of single drill-holes or pits. An optimum selection factor is achieved by a higher drilling density. The excavation factor is affected by failure of the dredge to excavate the total volume contained within its course. The required dredge throughput rate influences not only the success in digging recovery but also the treatment factor. No two alluvial deposits are the same, but, in general, the greatest divergence from 1.00 is invariably demonstrated by the estimation factor. A major divergence in one of the other factors may also be the cause of the R/E factor being significantly different from 1.00. The component factors are examined in detail and historical trends in R/E factors are discussed

Sep 1, 1991

By M. Sibanda

The diffusion of carbon in Co-5% Fe alloy was studied in a belt-type pressure system at temperatures of up to 1330°C and press loads or nominal pressures of 7 020 tons or 42±3 kbar. Under these conditions, this alloy is in the solid state. Discs of graphite and prealloyed Co-5%Fe were used to make up the diffusion couple. The diffusion coefficient increased with increasing press load due to the tendency of the low density graphite to dissolve in the metallic phase reducing the overall volume and increasing the density of the system. Furthermore, inhomogeneous plastic deformation may have promoted diffusion by creating defects in the alloy. Diffusion couples treated at atmospheric pressure exhibited graphite particles in the metal, while those treated at high pressures exhibited carbide in the form of Widmanstatten laths. Carbon analyses indicated increased carbon solubility with increasing pressure. This was confirmed from calculated high-pressure phase diagrams.

Jan 1, 2005

A study of drilling data at various stages of development of an orebody show that the semi-variogram, used for calculating the accuracy of block estimates can be ill-defined if too few data are available. The consequencesin this case are to have blocks supposedly more accurately known than is possible at the early drilling stage; such a result being potentially dangerous. However, as the amount of data increases the recalculated, semi-variograms approach the underlying semi-variogram of the deposit and the calculations made using them become more reliable and robust.

Jan 1, 1977

By Robert C. Bates

Variations in water percolation rates through saturated cohesionless hydraulic backfill (mill tailings) have been studied in relation to the many physical aspects of the system to determine the most important factors in causing these variations. A multivariable least-squares regression analysis of 135 separate tests shows that a reliable estimate of the water percolation rate through typical hydraulic backfill can be made if the bulk density (unit weight), specific gravity, and grain-size distribution are known or can be estimated. Equations for predicting percolation rate, coefficient of permeability, and seepage velocity are developed both for the range of data analyzed and for extrapolation. The prediction equations for use within the range of data studied are quite accurate, while the ones developed for extrapolation are less accurate but still give reasonable approximations of flow rates. The equations given are valid for cohesionless materials that are free of clays and micas, exemplified by classified mill tailings. The equation developed for predicting percolation rates is as follows: 1nP20 = 11.39147 + 2.853422 1n(VR X D10) + 0.1747436 VR X Cu -178.8039 D10 X D50 + 311.7034 (DSO )3, (1) where P20 = percolation rate, inches per hour at 20° C; correction factors for other temperatures are given in the text, VR = void ratio, dimensionless, D10 = effective size (diameter in millimeters of the 10-percent-finer grain size), Cu = coefficient of uniformity (ratio of the diameter of the 60-percent-finer grain size over D10), D50 = average size (diameter in millimeters of the 50-percent-finer grain size), and In = natural logarithm (log to the base e). The prediction equation for percolation rate is rather complicated, so for practical use a nomograph that simplifies the solution of the prediction equation was developed.

Jan 1, 1967

By C. Sawmliana

Deep-hole blasting operations in opencast mines are always associated with some annoyance to the surrounding areas in terms of ground vibration, noise, flyrock, etc. These become more severe when underground mines run parallel to them. Blasting in opencast mines may pose danger to the underground mines in terms of roof/side failures, damage of water dams, isolation/ventilation stoppings and other underground installations. The paper discusses a case study in India on the impact of deep-hole blasting in Ramagundam Opencast Project ? III on the stability of various water dams of GDK-6B Incline coal mine operating in close proximity. The stability of underground water dams of GDK-6B Incline mine was endangered due to deep-hole blasting at OCP-III. There were 15 water dams in seam 3 and 16 dams in seam 4 of the underground mine. The physical strength tests using a Schmidt Hammer instrument were carried out in all the 15 water dams of No. 3 seam and 16 water dams of No. 4 seam. The test revealed that there is a decrease in compressive strength values of three dams of seam 3, namely 6A, 6B and 7. Theose three dams were also directly connected to the water source. Water seepage was also observed from the surfaces of the three dams. However, they were found to be stable in accordance with their design parameters and damage point of view while considering a threshold value of ground vibration as 25 mm/s. It was found that the value of tensile stress generated by a vibration of 25 mm/s was much lower (i.e. 0.171N/mm2) than the tensile strength of the two weakest concrete dams (1.85 N/mm2). Ten experimental blasts were conducted at different working benches of the opencast mine and the ground vibration data were recorded in roof and pillars near various underground water dams. The maximum value of vibration data recorded was 5.9 mm/s in roof near dam no. 1 in seam 3 with the dominant peak frequency of 22 Hz. No adverse effect on either of the dams was observed after that blast. During the period of study, no deterioration/adverse impact was found in any dam of the mine. Based on the results of the study and the analyses of the data, optimized blast design parameters and explosives weight per delay were suggested for the opencast mine to maintain the safety of the underground water dams. Keywords: Opencast blasting, damage, water dams, underground mine, ground vibration

Jan 1, 2009

This report, the third in an annual series, outlines recent trends and developments in the minerals industry. Discussed are new methods, equipment, techniques, and systems used to more, effectively extract and process minerals and fuels. Environmental considerations, reduced ore grades, and the related increased quantities of material handled were the dominent concerns of the minerals industry in 1972. Productivity increased in most mineral commodities as equipment became more mobile, versatile, and sophisticated. Increasingly, equipment designs incorporated health and safety features. There was considerable interest in the field of energy and in pollution-free metallurgy processes.

Jan 1, 1973

By A. M. Gaudin

THE purpose of ore dressing is to separate the rough ore into one or several valuable concentrates and a discarded tailing. The first step is to crush the ore so that the resulting particles may be individually valuable or worthless. The next step generally has to be a sizing operation, because the property by which concentration is effected depends on the size of the in-dividual mineral particles as well as on their physical properties. These two effects may cancel each other if a preliminary sizing is not resorted to. Sizing is accomplished by screening or classifying. Screening depends almost solely on the dimensions of the particles; classifying depends also on the specific gravity of the particles and the viscosity of the settling medium in which the classifying operation is conducted. Classification, therefore, is to a certain extent a con-centrating operation as well as a sizing operation. Before the days of concentration by flotation, the available screens were mechanically poor. As a result classification was employed for sizing in the range. of comparatively coarse sands (table feeds). In recent years, the advent of stage-grinding to flotation size has brought about the development of good screens, which are more economical than classifiers down to about 20, -mesh. With decreasing size at which separation is to be made, screens become increasingly uneconomical, while classifiers become increasingly economical. The line of demarcation between the respective fields of screening .and classification is, therefore, fairly sharp. With the development of processes of concentrating finely comminuted ore, the need for classifiers or other sizing devices operating so as to make efficiently a split at a very fine size has become increasingly apparent. Such classifiers might be termed de-slimers, from the fact that they separate a material having a slimy ap-pearance from one having the characteristics of a sand. Sizing-tests are carried on by means of testing sieves, the finest of which have apertures of about 1/500 of an inch. The 200-mesh sieve, which has an average open-ing of 0.0029 linear inches is generally considered the limit of practical test-sizing. As a result, little is known of minus 200-mesh material and the advantages of classifying concentrator feeds within the minus 200-mesh range has been overlooked. An extension of the -present sieve scale beyond the 200-mesh screen is given in Table 1.

Jan 2, 1927

This report is the 26th in a series summarizing Bureau of Mines research and technologic work on coal and related investigations and the 8th of these reports to be issued on a calendar-year basis.1 It reviews briefly work in progress during 1961, and it provides references to publications by Bureau personnel during 1961 and also to a few older papers that were not cited in prior reports of this series. Details about some of the researches mentioned may be obtained by referring to the publications cited in the footnotes or in the further list in the Bibliography; other phases of work are reported here for the first time and will be covered in more detail by later publications. The coal program of the Bureau of Mines extends over the wide range of applied and theoretical studies indicated by the table of contents of this report. Applied studies are conducted in connection with the development and evaluation of new mining techniques, and the effective processing and utilization of coal and coal products. Analyses of coal, technical advice, and other assistance to Federal agencies in connection with fuel and boiler-water problems, and health and safety activities are among the practical services handled by the Bureau, Fundamental research such as that on coal structure and on the properties of coal is conducted because it will, over a period of the, furnish an increasing general knowledge about coal; scientists and engineers may use this knowledge in solving problems in mining and utilization of

Jan 1, 1963

By Ross Byron, Ken Roberts

"During the fall of 2001 a program was initiated to determine the feasibility of improving the metallurgy in the flotation circuit at the Penhorwood Talc Concentrator located near Timmins, Ontario. Bench scale testwork led Plant staff to believe that opportunities existed to improve the flotation performance. Pilot scale testing was then conducted using two vendors and their respective cylindrical type flotation cells to indicate where these opportunities existed.The results of the test program determined that the replacement of the existing flotation circuit (roughers, scavengers and cleaners) with new flotation cells could be economically viable. Justification was due to a reduction in installed horsepower, maintenance costs and a subsequent increase in recovery and throughput while maintaining product quality. Unforeseen benefits included reagent and air reduction, accurate level control as well as improved working conditions due to the removal of the antiquated equipment and ancillaries.This paper will detail the justification, installation and implementation of the new flotation circuit. A special emphasis will explain the hurdles encountered while trying to install and commission the circuit in an operating Concentrator with minimal interruptions to production.INTRODUCTIONThe Penhorwood mine and Concentrator is 28 yrs old and has gone through many ups and downs with different owners, Johns Manville, Steetley Talc and now Luzenac. It has also been expanded twice, with flotation and grinding capacity being added in recent years.All of the concentration is completed at the mine site while the fine grinding takes place in the Timmins micronizing plant.Luzenac’s Philosophy is to be the world leader in Talc production, technology and sales, having about 70% of the current world High Grade talc market."

Jan 1, 2004

By D. M. Avant, S. M. Pickering

A variety of grades of very white muscovite mica are now being produced from sedimentary sands and clays in Central Georgia. The mica is naturally concentrated near the base of the lens-shaped kaolin deposits and also disseminated in associated quartz sands. The same weathering and bacterial alteration processes which have transformed the kaolins from dark organic muds to white pigment-grade industrial clays have also removed discoloring iron from the micas and developed unusually white muscovite. Further, chemical alteration has removed some potassium from the muscovite atomic structure, resulting in an easily delaminated mica which can be cleaved to unusually fine, high bulking, high aspect ratio products. The peculiar alteration history of these sedimentary micas enables production of some of the whitest, finest particle size, and thinnest aspect ratio muscovite mica products on the world market today. Raw mica feed is obtained from kaolin and sand processing by-products, and also from beneath the useful base of abandoned kaolin mines. The processed ultrafine and filler grade muscovite mica products are used for paint, plastics, cosmetics, mold release, thermal and electrical insulation, epoxy, and dry wall joint cement markets.

Jan 1, 2002

By K. K. Kelley

"INTRODUCTION The Bureau of Mines nitrogen peroxide process (2) 3/ for extracting manganese from low-grade ores is essentially a two-stage process involving the reversible reactionMnO2 + 2NO2 + 6H2O = Mn (NO3)2 . 6H2O (1).At lower temperatures this reaction proceeds to the rigth and affords a means of dissolving manganece and separating it from unreacted ore. At higher temperatures the reaction proceeds to the left and manganese dioxide is recovered and nitrogen peroxide regenerated for recycling. Evidently, therefore, the energy required for decomposition of manganous nitrate is a matter of practical importance. Similar information for certain other nitrates also is desirable beceuse the nitration step of the process produces appreciable amounts of nitrates of other metals, such as iron, aluminum, magnesium, calcium, and barium, some of which are not broken down in the evaporation and decomposition steps. Thus, a portion of the nitrogen peroxide is not directly available for recycling. Whether or not it is feasible to recover nitrogen peroxide locked in the more-stable nitrates depends partly on the energy required and the conditions necessary for their decomposition.To supply information bearing directly on these subjects, several researches were undertaken at the Pacific Experiment Station: (a) Heats of formation (24, 25, 26) of nitrates of manganese, magnesium, calcium, barium, and aluminum were measured at 298.2° K:; (b) low-temperature specific heats (23), in the range 51° to 298.2° K,, and entropies of nitrates of magnesium, calcium, barium, and aluminumm were determined; and (c) heat contents (21) above 298.2° K. of the nitrates of manganese, magnesium, calcium., and barium were measured. The results of these studies, when correlated by thermodymamic methods, permit evaluation, at any temperature of interest, of the energies required to decomposethe nitrates and furnish information concerning the equilibrium pressure temperature relationships."

Sep 1, 1944

By Goldney L. H

The authors review the literature and discuss the application of methods to the design of thickeners for ilocculated metallurgical pulps. The use and evaluation of flocculents is described. Experimental data show that design based upon laboratory settlingdata is acceptable. The economic aspect of design is also discussed.INTRODUCTIONFor many years there has been little change in the methods for the design of thickener installations. While modifications have been made in the method of applying the data all methods have been based on the observee settling rate of the solids. The development of a theoretical approach based on physical data would involve so many variables which affect the settling rate that the more practical approach of direct observation seems unlikely to be replaced as the basis of design.The advent of synthetic fiocculents has introduced a modification in operation which affects design and should be considered. The authors review the subject and attempt to bring it up to date with present day procedure. Until recently the original work of Coe and Clevenger (1916) remained the basis of thickener design. They described their observation of the different zones encountered in settling, namely clarification, feed, transition, and compression or thickening- zones. The solids pass through the transition zone in settling from feed density to some higher density where settling ceases and ·some compression or compaction effect controls. the density obtained. The point at which the settling zone ceases to exist is known as the critical point.

Jan 1, 1959

By Martti Hagfors

UNDERWATER EXPLOSIONS - Part 6 - EFFCTS OF CYLINDERICAL SHAPE OF CHARGE TO THE RESULTS OF ENERGY MEASUREMENTS OF EXPLOSIVES

Jan 1, 2008

By J. M. Garcia

This paper highlights several management practices from the oil and gas industry to support the proposition that financial performance in the finite, non-renewable resource business relates more to upstream rather than downstream activities. Based on the analysis of nine oil and gas companies, this study supports a previous study involving fourteen mining companies that showed reserves growth is one of the main levers of value creation in mining. Interestingly, this study also finds that the oil and gas industry has been historically more profitable than mining. The reason, it is argued, is that oil and gas companies count on management practices that focus primarily on the upstream segments of the business, compared to the traditional downstream focus of mining. This paper delves into these ideas to conclude that what mining may need to improve its competitive advantage is a new organizational framework. Another conclusion is that the upstream management focus is vital not only for strategy formulation in the resource business, but also for policy formulation in economies based on the export of finite, non-renewable resources.

Jan 1, 2011