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Development and Validation of Ore Characterisation Test and its Use in Variability Campaigns of Comminution Circuits Impact testing was developed by assessing the fragmentation characteristics of ore samples after controlled impact. Standard methods are, however, limited to relatively large and coarse samples, which thus precludes their use in early stages of projects, as well as where only drill cores are available. The method described in this paper is based on the same concepts of controlled ore breakage, but using relatively smaller samples. It is particularly useful in assessing the variability of ore characteristics in early stages of greenfield projects, as well as in predicting the performance of existing grinding circuits. A validation program was carried out in which a good adherence to the original test results was obtained. The results were used for (a) simulation of a copper comminution circuit as a function of the ore characteristics, and (b) evaluation of sampling protocols used for assessing fragmentation characteristics.

Sep 13, 2010

By J. P. Germiquet

"Rock properties have a material impact on mining processes, including drilling performance. An investigation using point loaded index (PLI) data converted to uniaxial compressive strength (UCS) has revealed that a direct relationship between grain size and UCS exists at Mogalakwena Mine. This correlation is best seen in unaltered rock, with lower correlations for altered rock types. Measurements from the new RockMa system installed on drill rigs can be used to obtain rock strength data to validate the current rock strength domains and create additional data for the next benches below. An investigation of penetration rates in different lithologies shows that rock composition plays an important role in determining drill performance. Additionally, there is an inverse relationship between rock strength and drilling penetration rate – a measure of how efficiently a hole is drilled.The domaining of grain-size-adjusted UCS at Mogalakwena Mine will allow more accurate scheduling of drill rigs through increased knowledge of rock strength in various areas. Successful rock strength domaining has the potential to be incorporated into blast indexing and predicting crushing/milling performance.IntroductionThe optimization of mining and processing through geometallurgical characterization of ore are key drivers of value realization (Deutch, 2013). Rock strength is one such property and is affected by, among other variables, composition, texture, and grain size (Ozturk, Nasuf, and Kahraman, 2014). Mogalakwena Mine is exploiting the intrusive Platreef PGE (platinum group element)-bearing orebody which forms part of the northern limb of the Bushveld Complex. This complex orebody exhibits areas of metasomatic alteration, metamorphism, and sporadic mineralization of the footwall and hangingwall (Nex et al., 2006). Understanding this variability is paramount due to the implications for rock strength and hardness, which in turn affect crushing, milling, and liberation efficiency. These variables must be known prior to blasting in order to optimize mine and plant processes using in-situ variables. This necessitates predictive modelling (Deutch, 2013). Geological and geotechnical data was sourced from the Overysel (OY) exploration database for the study. Point load testing was done for each borehole and the results converted to uniaxial compressive strength (UCS) (Akram and Bakar, 2007). The relationship of lithology, texture, and grain size with UCS revealed an inverse relationship between grain size and UCS in unaltered rock. The relationship was not present in altered rock types. A comparison of mean strength and hardness results indicated that Bond work index and UCS may be related. Drilling performance is affected by UCS (Bourgoyne et al., 1986), and this was proven using recent measurements obtained during drilling. Lastly, grain-sizeadjusted UCS values were applied to a 3D model for the OY property."

Jan 1, 2016

By J. Nakayama

Down-the-hole hammer is commonly recognized as the most powerful drilling equipment for weathered to fresh rock formation including boulders. However, its drilling diameter is restricted by reasons of difficulty to actualize large diameter drillhead and to ensure discharging means of cuttings. Cuttings are usually removed by flushing i.e. uprising return air after compressed air actuates hammer, but in case of large diameter drilling, as the clearance between drill rod and surrounding wall of hole become fairly large, necessary up-hole air velocity to transport cuttings can not be maintained. In case of marine or underwater drilling or high groundwater table, orthodox down-the-hole hammer is obstructed its operation by water. This single head hammer drill combined large diameter drillhead with reverse circulation of drilling fluid enables large diameter drilling extending to 1.5 m, i.e. actualized large diameter mechanical drillhead incorporated with ensured cuttings removal means enabled this range of drilling. This paper introduces its features and actual applications to large diameter bored pile drilling for varied sorts of rocks in maritime construction projects.

Jan 1, 1996

By Romano J. Micciche

One of the largest scale uses of a multiple, high-strength steel bar tiedown system is described. Tiedowns were installed to resist hydrostatic uplift forces acting on a section of the Interstate Highway Route I-90 southern approach roadway to the Third Harbor Tunnel, in Boston, Massachusetts. Site specific information is discussed regarding design, testing, and installation of Tiedowns. Conclusions are presented regarding the overall performance of this system and the application of this type of tiedown system on future projects.

Jan 1, 1994

By J. L. Thompson

The U.S. Bureau of Mines conducted a water-jet-studies program using a single-bit, in-seam test unit to determine effects of a moderately high-pressure (up to 10,000 psi) water-jet-assisted cutting system on rock weakening. The in-seam test unit was used to obtain cutting force data in tangential, normal, and side force directions. Conical continuous miner and radial longwall miner bits were used to penetrate test samples of coalcrete, Berea sandstone, and Indiana limestone with unconfined compressive strengths of 4,600, 8,000 and 10,000 psi, respectively. Depth of cut in the coalcrete tests was 1 in, with 2-in cut spacing (2:1 ratio). Because of cutting equipment and instrumentation limitations, the Berea sandstone and Indiana lime-stone were cut using a 0.5-in depth of cut and 2-in spacing (4;1 ratio). Bit velocity was maintained at 25 ft/min for both bits. Each specimen and bit type was tested using 0.3-, 0.6-, 0.8-, and 1.0-mm-diam nozzles and water-jet pressures of 2,500, 5,000, 7,500, and 10,000 psig. Water-jet-assisted cutting decreased average resultant conical and radiallongwall bit cutting forces 6.4 and 8.4 pct in coalcrete, 5.5 and 1.4 pct in Berea sandstone, and 2.0 and 5.5 pct in Indiana limestone. Slight reductions of power requirements resulting from water-jet assist were ascertained during these experiments.

Jan 1, 1989

By T. A. Grammatikopoulos, B. Vasily, A. H. Clark

"The St. Lawrence deposit is a large wollastonite skarn (ca. 9 Mt @ 41.3% wollastonite) adjoining the gabbroic-to-syenitic Leo Lake pluton in the granulite facies Frontenac Terrane of the Grenvillian Central Metasedimentary Belt. It occurs within a horseshoeshaped horizon of quartzite, open to the east. The skarn extends over 1.2 km2, and comprises wollastonite-dominant, wollastonite-clinopyroxene, and diverse quartz-feldspar-sulphide (-titanite) layers, interbanded with, and strongly folded within, the quartzite. As in the world-class wollastonite deposits of the Willsboro district, New York, no carbonate protolith is preserved, and calcite is a negligible constituent of the mineralized zones. Wollastonite development is nonetheless ascribed to metasomatism of a metacarbonate unit by magmatogene, silica-rich, CO2-poor (XCO2 < 0.05) fluids, at P = 350 MPa and ca. 560°C, or, alternatively, 550 MPa and ca. 630°C.Several high-grade zones, averaging >40% but locally exceeding 80%, of translucent, white, tabular wollastonite grains, with lengths of 0.2 cm to 5 cm, have been delimited by drilling. Preliminary beneficiation studies yield high aspect-ratio and high-purity (low Fe and Mn) concentrates.St. Lawrence compares favourably to other known prospects and operating wollastonite deposits: having good chemical and physical properties, low iron content, and high aspect ratios (>20:1). In addition, the deposit has a favourable size and location, and will benefit from a low Canadian dollar. Canada currently has no wollastonite production."

Jan 1, 2003

By Luis Alberto Medina

La característica principal de la composición de un cuerpo mineralizado es la heterogeneidad, dado que sus elementos no son iguales. En ese sentido, la prueba de heterogeneidad en el mineral de Cerro Verde, es una guía para la geología, mina, metalurgia y laboratorio químico, que busca optimizar los protocolos de muestreo y minimizar errores en las muestras tales como: Error Fundamental; Error de Segregación, generado por una muestra o submuestra cuando es cuarteada; Error de Extracción, generado por una muestra pequeña o insignificante colectada o tomada, y Error de Preparación, producido por la pérdida excesiva de finos. De acuerdo al estudio, el presente trabajo señala que la heterogeneidad de cobre total, cobre soluble en ácido y cobre soluble en cianuro, desarrollada para el mineral de Cerro Verde, es baja, lo que permite un manejo operacional sencillo para el muestreo con protocolos más simples, mientras que el parámetro más heterogéneo es el cobre soluble en cianuro y el protocolo podría ser afectado en el error fundamental.

Sep 13, 2001

By P. B. Grote

The report provides a general description of DOM technology, sources for DOM technology, and identifies approaches and requirements for acquisition by the Enterprise of DOM technology by conventional means. The approaches identified assume the Enterprise enters into a contractual/ joint venture arrangement with an uncommitted and competent systems management firm at various stages of the DOM system acquisition process. The approaches provide for training through work/study as well as through direct participation in acquisition programs. The potential success of the alternatives are evaluated in terms of the likelihood of the acquisition of an ongoing Enterprise economic DOM operational capability. The study concludes that sources exist and that the Enterprise should under-take the development of its own technical capability through conceptual design prior to selecting its source for systems management expertise.

Jan 1, 1980

By Q. Cheng

This paper introduces the multi fractal interpolation method (MIM)developed for handling singularities in data analysis and for data interpolation. The MIM is a new moving average model for spatial mapping and interpolation. The model decomposes the raw data into two components: singular and nonsingular components. The former can be characterized by a localized singularity index that quantifies the scaling invariance property of measures from a multifractal point of view. The latter is a smooth component that can be estimated using ordinary kriging or other moving average models. The local singularity index characterizes the concave/convex properties of the neighbourhood values. The paper utilizes a binomial multiplicative cascade model todemonstrate the generation of one- and two-dimensional data with multi-scale singularities which can be modelled by asymmetrical multifractal distribution. It then introduces a generalized moving average mathematical model for analysing and interpolating data with singularities. Finally, it is demonstrated by a one-dimensional case study of de Wijs’ data from a profile in a zinc mine, that incorporation of spatial association and singularity can improve the interpolation result, especially for observed values with significant singularities.

Jan 1, 2015

By Garry M. Johnston, Matthew L. Sutcliffe, Nicholas J. Welham

"The predominant current processes for the treatment of oxidized copper–cobalt ores use a reductive acid leach to bring the desired metals into solution. However, the indiscriminate nature of acid leaching results in a solution, akin to a metal soup, containing not only the Cu and Co but also an extensive suite of other metals. These other metals, notably Fe, Mn, Al, Ca, Mg and Si, all have to be eliminated from solution before the copper and cobalt can be recovered. Generally precipitation processes are used, but these tend to result in significant losses of copper and/or more usually cobalt from solution, leading to reduced recoveries. The AmmLeach® process uses ammonia-based chemistry to selectively leach the target metals, leaving the rest behind in the leach residue. This approach eliminates any need to clean the solution of unwanted metals and the consequent metal losses. After solid–liquid separation, the leach solution is immediately subjected to separation and concentration of the copper and cobalt using solvent extraction and electrowinning. INTRODUCTION The Copper Belt extends through the northern part of Zambia and the southern province of Katanga in the Democratic Republic of Congo (DRC) and contains the richest and highest grade deposits of copper and cobalt remaining in the world. Whilst there are a number of mines that produce sulphide concentrates, using froth flotation, the largest deposits are those where near-surface sulphides have been weathered over time to form oxides. The oxides cannot be concentrated by conventional physical means to give high recoveries. Despite this, a number of dense medium separation plants have been installed and used to produce a higher grade concentrate which is typically exported (while the rejects, typically 2 to 3% Cu are stockpiled for treatment at a later date). These plants generally have low recoveries and can only be used on the dwindling supply of high grade materials. In exporting the concentrate, little value adding is undertaken within the country, thus greatly reducing the economic benefits to the country. Recent changes to the regulations in the DRC will effectively ban the export of low value ores, concentrates and intermediates in favour of high value metals. This will necessitate mines to install new processing circuits in order to comply with these regulations. The head grade of ores currently being treated in the DRC is slowly decreasing as the extremely high grade materials are being selectively mined out. In many cases, the removal of a small volume of high grade materials leaves a much larger volume of economically marginal ore behind. This is due to a desire for short-term profits overtaking long-term prosperity. The remaining ore, which in many cases is still of relatively high value by world class standards, is likely to be only treatable by low cost heap leaching. There are some initial trials of heap leaching within the DRC, but implementation at a large scale has yet to be adopted."

Jan 1, 2015

In the interest of safety in underground coal mining, the Bureau of Mines recommends: 1. That doors used to control ventilation (a) Shall be installed in pairs to form air locks, (b) Shall be self-closing, (c) Shall not have latches or other devices for holding them open, (d) Shall be constructed and maintained to prevent excessive air leakage through or around them, (e) Shall be fire resistant. 2. That wherever practicable the use of doors shall be limited to development openings. The Mine Safety Board is of the opinion that the best practice in coal-mine ventilation makes use of a split system employing overcasts or undercasts with doors limited as far as feasible to development openings. The distance between air-lock doors on haulageways should be sufficient to accommodate a trip or train of maximum length. Where auxiliary doors are installed to control ventilation during emergencies, they should be so placed that they can be utilized readily in case of damage to the air-lock doors.

Jan 1, 1938

By S F. Simmons, J Fleming

Alteration and mineralisation at the Island Copper deposit is related to the intrusion of Early Jurassic quartz feldspar porphyry dykes into surrounding comagmatic Bonanza volcanic rocks. The pyrophyilite alteration zone forms an upward flaring cone, largely hosted within a breccia body that cross-cuts the Co, Mo, and Au-rich ore shell. This alteration zone contains pyrophyllite, dumortierite and diaspore and resembles alteration occurring in some high-sulfidation deposits, but which is barren. Fluid-mineral equilibria and fluid inclusion studies indicate formation at approximately 300 ¦C from fluids dominated by steam and gases. These fluids appear highly acidic, but sulfur poor, leading to extreme base leaching within the breccia body and surrounding rocks.

Jan 1, 1995

By Steve Kral

After years of cutbacks, closures and layoffs, the mining industry is beginning to expand again. Metals prices are up and so is investor interest and confidence in the industry. Gold prices began to slowly move up in January2003 and finally cracked the $12.86/g ($400/oz) mark in early December. Silver, too, is up, as is copper. So the mining industry is feeling good about itself again and many companies are expanding existing mines and developing new ones. One side benefit to mining’s improved outlook is that companies are beginning to send more of their employees to industry conferences. Such was the case at the109th Northwest Mining Association meeting in Spokane, WA. The meeting was held in early December and attracted 1,100 attendees and 84 exhibiting companies. That is up from 2002’s attendance of about 900 people and 65 exhibitors. The theme was “A Partnership into the Future.”

Jan 1, 2004

This report presents information developed during Bureau of Mines contract H0242016, "Mine Shaft Fire and Smoke Protection Systems" from May, 1974 through June, 1975. Purpose of the metal and nonmetal health and safety project was to evaluate mine shaft fire and smoke hazard problems, and to develop and demonstrate a low-cost, reliable mine shaft fire protection system that would protect against such hazards and would be applicable to a majority of metal and nonmetal mine shafts, including raises and winzes, especially in deep mines. Program effort proceeded through five phases, culminating in the successful in-mine fire demonstration of a prototype system. In addition to this final report, a film is available which depicts components of the system and its successful shaft fire testing at an underground mine.

Jan 1, 1975

By Ian Orford, Peter Radziszewski, Lud Strah

"An autogenous grinding circuit was commissioned at the Brunswick concentrator in October 1998. The AG mill was subsequently converted to SAG operation in May 1999 for a number of reasons. The mill had 48 rows of the NORCAST top-hat integral lifter/liners configured in Hi-Lo mode. A charge motion simulation study, the results of which are the subject of this presentation, was initiated to develop a better understanding of SAG mill behaviour. Using a design of experiments approach, a lifter face angle was determined that would increase mill power draw. Once determined, lifter profiles were modified and installed in July 2001, and a second set installed in February 2002. Resulting changes in mill power consumption are presented.INTRODUCTIONThe Noranda Inc. Brunswick Mine, located near Bathurst, New Brunswick, is a large lead/zinc mine and began milling ore in 1964. The ore is massive sulphide with approximately 20% valuable minerals, 60% pyrite and 20% silicates. In October 1998, an autogenous grinding circuit was commissioned at the Brunswick concentrator (Cooper, Orford, Larsen, 2001).At the time, the autogenous grinding circuit replaced existing surface crushing plants, fine ore storage, rod mills and primary ball mills. The 8.54 m diameter x 4.27 m long (EGL) ANI mill was subsequently converted to SAG operation in May 1999.The mill had 48 rows of the NORCAST top-hat integral lifter/liners and was operated initially with all shell lifters at the same height. Following problems with packing and abnormal wear pattern, the profile was changed to a high-low configuration.Further, it was found that over the life of the lifters, mill power draw and throughput varied considerably. Although a change in mill power draw was expected following lifter replacement (predicted during mill design to be in the order of 300-400 kW), the replacement of the worn lifters with new high lifters resulted in mill power draw decreased by some 1000 kW."

Jan 1, 2003

By C. H. Fisher, M. L. Fein, A. Eisner, G. C. Sprunk, Loyal Clarke, H. H. Storch

"The large reserves of low-rank coals in the western United States are at a disadvantage in competing with the more mature but less plentiful eastern coals, which are nearer important markets and are more suitable for combustion and coke production. However, low-rank coals generally are amenable to hydrogenation, and the western coals might become an important source of liquid fuels and organic chemicals when petroleum is less plentiful.In view of these facts an the tremendous quantities available, further information on the western coals clearly desirable. The purpose of the work described in this paper was to study the hydrogenation characteristics of some of the low-rank western coals in discontinuous converters. The data obtained in this manner, which are inadequate for predicting the suitability of coals for large-scale continuous hydrogenation, were used as a basis for selecting samples for further study in the Bureau's experimental coal-hydrogenation plant (26, 35). 8/ Because of the general importance of the western coals and recently demonstrated relation between coal hydrogenation and petrograghy (14, 15, 16), the proportions of anthraxylon, (vitrain), translucent attritus, and opaque matter were determined. In some instances samples of anthraxylon were isolated and hydrogenated separately so that their properties might be compared with those of the entire coal. The samples studied include peat, brown coal, lignite, sub-bituminous coals, and low-rank bituminous coals."

Mar 1, 1940

By H. Preßlinger, H. Hiebler, K. Klepp, W. Posch, M. Mayr

It was investigated in which form sulphur is bonded in ladle slags. For this purpose, the mineralogical phases of the ladle slags were qualitatively and quantitatively evaluated by means of a microprobe. This slag characterization allowed reconstructing the bonding of sulphur into the phases of the ladle slag. Moreover, the reaction process with regard to the ionic theory as well as the structural formula for the mechanism of sulphur bonding were discussed. The bonding of sulphur into calcium aluminate slags is determined by the sulphide ion content in the slag as well as by the ratio of (CaO)/(Al2O3). Calcium sulphide separates only if the slag contains a large number of sulphide ions. When Ca12Al14O33is separated, the sulphide ion is successively integrated into the lattice. The crystal lattice of Ca12Al14O33is characterized by an open, three-dimensional anionic network composed of aluminium-oxygen tetrahedrons linking the edges. In this network, large interstitial spaces are formed, which may be filled with calcium ions on the one hand and statistically with a free oxygen or sulphide ion on the other hand. Key Words: ladle slag, structure, phases, calcium sulphide, calcium aluminate, desulphurization

Jan 1, 2004

By H. A. Bilgin, A. Özgenog?lu, G. Kaçar

In this study, the influences of rock mass properties on the blasting performance in open cast mines are investigated. To this end, discontinuity spacings and discontinuity orientations are measured and full scale blasts with various designs are observed in open cast mines of Aegean Lignite (ELI) and Bursa Lignite (BLI) Establishments belonging to Turkish Coal Enterprises (TKI). For each blast, blasting cost is calculated, and particle size distribution representing the fragmentation of muckpile is determined by means of Split-Desktop software using image processing. 50%(K50), 80%(K80) passing sizes and topsize values are used in the determination of blasting performance according to rock mass properties. The relationships between orientation angle, which is the acute angle between the strikes of slope face and major discontinuity, and 50%(K50) and 80%(K80) passing sizes and topsize values and also blasting cost are investigated in order to analyse the influences of major discontinuity orientation on fragmentation and blasting cost. Furthermore, the relationships between discontinuity modal spacing (or block size index) and 50%(K50) and 80%(K80) passing sizes and topsize values and also blasting cost are investigated in order to analyse the influences of discontinuity spacing on fragmentation and blasting cost. In this paper, the trends observed in these relationships are discussed and the importance of it in mining is commented. Dans ce travail, Il a été traite les influences des qualites des rocheux massif sur les performances des abattages de l’excavation a ciel ouvert. Dans ce cas, les excavations a ciel ouvert dans les Entreprises Lignite d’Aegean et de Bursa qui appartient a La Societe Charbon de la Turquie; Il a été mesuré le trou du discontinuite et l’orientation du discontinuite et aussi, Il a été observé les abattages qui sont pareilles aux critaires exactes. Pour chaque abattages, Il a été fait le control des expences et la distribution du particle au dimension du pile qui a été deja abatté, a été trouve en utilisant le Software du Split-Desktop. Pour determiner les influences des qualites des rocheux massif sur les performances des abattages, Il a été utilisé K50, K80, et le plus grand valeurs des dimensions. Aussi pour determiner l’influence sur l’orientation du discontinuite majeur de la fragmentation et les expences de l’abattage, Il a été observé les relations entre l’angle de l’orientation ( C’est l’acutage entre la direction du banquette front et la direction du discontinuite majeur ) et les plus grand valeurs des dimensions et les expences de l’abattage. Plus, pour determiner des influences du trou du discontinuite sur l’abattage et la fragmentation; Il a été observé la relation entre l’index de la dimension du block et K50, K80 et les plus grand valeurs des dimensions et aussi les expences de l’abattage. Pour conclure; on peut dire que dans cette presentation, apres la discusssion des sujets consideres ces relations, Il a été souligné l’importances de ces relations dans la domain de la Minéralogie. In dieser Studie wurden die Einflüsse von Gesteinsmasse Eigenschaften auf die Sprengleistung in Tagebau Bergwerken untersucht. Zu diesem Zweck wurden Diskontinuität Abstände und Diskontinuität Orientierungen gemessen und Sprengungen im Originalmaßstab mit verschiedenen Anordnungen in Tagebau Bergwerken der Ägäischen Braunkohle (ELI) und Bursa Braunkohle (BLI) Betrieben, die zu der Türkischen Kohlegesellschaft (TKI) zugehörig sind, beobachtet. Für jede Sprengung wurden die Sprengkosten berechnet und die Teilchengrößenverteilung zur Darstellung der Aufteilung von Haufwerk ist durch Mittel von Teilbelegungssoftware, das Bildverarbeitung verwendet, bestimmt worden. 50% (K50), 80% (K80) durchlaufende Größen und Spitzengröße Werte wurden zur Bestimmung von Sprengleistung geordnet nach Gesteinsmasse Eigenschaften benutzt. Die Beziehungen zwischen Orientierungswinkel, welches der scharfe Winkel zwischen den Streichen der Hangfläche und Hauptdiskontinuität ist, und 50% (K50) und 80% (K80) durchlaufende Größen und Spitzengröße Werte sowie Sprengkosten wurden untersucht, um die Einflüsse von Hauptdiskontinuität Orientierung auf Aufteilung und Sprengkosten zu analysieren. Außerdem, wurden die Beziehungen zwischen Diskontinuität modal

Jan 1, 2003

By R. L. Grayson

In 2010, MSHA began holding hearings on a new coal mine respirable dust rule, which proposes a 1.0 mg/m3 standard, a separate 0.1 mg/m3 quartz standard, and the use of single-shift samples for compliance. Small mines largely comprise the ?hot spots? where dust diseases of the lungs increased dramatically over the past decade. This paper presents findings on the feasibility of small mines? compliance with the proposed new 1.0 mg/m3 standard. It gives probabilities of noncompliance by MSHA district, seam height, and selected ?hot spot? counties. Because silicosis and respirable quartz dust appear to be the primary issues related to a recent doubling of the prevalence of dust diseases of the lungs, multiple regression models for prediction of the average total quartz content of compliance samples are given. These findings have significant implications on the need for better dust control methods.

Jan 1, 2012

THE object that the writer has mainly in view in presenting this paper is to draw the attention of those connected with the technical side of the industry to the unsatisfactory and by no means up-to-date methods employed in estimating the tin contents of an ore. At the same time, what is regarded, from the writer&apos;s personal experience, as a satisfactory and reliable method is explained in detail. It is a curious fact that for the last 25 years tin&#183;assay methods have made little or no advance, while those now in general use ill connection with copper and lead ores can scarcely be compared with those then obtaining, so greatly have they been improved upon. Though it. is not altogether expected that the method herein advocated will at once meet with general approval, the writer hopes the resultant discussion may bring out points that have hitherto escaped detection.FIRE METHODSThe old Cornish method of smelting with anthracite is now obsolete. The cyanide assay, although unreliable, is still much used because of its simplicity. In the Malaya many buyers of tin ores use the cyanide assay, the smelting being carried out generally in a benzine furnace. It is essential that the smelting with cyanide be performed at a low temperature. Even then, impurities, such as Sb2S3 and...

Jan 1, 1912