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By Van E. Shaw

Bastnaesite is a natural rare-earth fluorcarbonate of the cerium group that affords an abundant and high-grade source of the lighter rare-earth elements. A simple and efficient method has been developed by the Bureau of Mines for extracting rare-earth compounds from this mineral. Digesting of a flotation concentrate with sulfuric acid converts the rare-earth compounds from fluorcarbonates to sulfates. Action of the acid releases gaseous com-pounds of fluorine and silicon, leaving the sulfated material free of these elements; carbon dioxide from carbonate decomposition is eliminated at the same time. Calcining the sulfated material at 1,200° F. renders the gangue constituents insoluble, whereas the rare-earth sulfates are left in water-soluble form. Leaching with water yields a solution of pure rare-earth sulfates. Bastnaesite could become prominent as a source of cerium-group rare-earth elements. It is rich in the light rare-earth elements and comparatively easy to process; reserves of the mineral are extensive enough to supply a greatly expanded market for many years.

Jan 1, 1959

Managers are demanding efficient use of their resources and part of this demand is leading to the idea of integrated audits for Occupational Health and Safety (OH&S), quality and the environment. It is possible to construct audits which test the compliance in this area with standards established by management systems and it may be that such an integrated audit of a site could reduce the time of auditing and be equally effective as three separate audits. However, this is only a maybe. To do an audit on all three aspects when they are not fully integrated results in more time wastage than doing three separate audits. But organisations are not structured around the audit process (some financial managers may query this statement). The organisational management systems are put in place to achieve the organisational goals - presumably in an efficient and cost-effective manner.

Jan 1, 1995

By N. A. Warner

Dense cylindrical specimens of artificial hematite were reduced in hydrogen over a range 0-f total pressures between 0.1 and 1.0 atm and temperatures between 650" and 950°C. Hydrogen reduction at a total pressure of 1.0 atm in the presence of a chemically inert diluent and reduction in hydrogen/water mixtures were also studied Znter.face movement during reduction was followed using metallographic techniques. Substantiu1 partial-pressure gradients are shown to exist in both the gas film and the reduced iron layer. The results are consistent with a mixed-control mechanism involving an interaction of gaseous-difusion effects with a first-order reversible chemical reaction at the iron/wüstite interface. Over the hydrogen-pressure range of 0.1 to 1.0 atm, the rate is not directly proportional to the hydrogen pressure in the bulk gas stream. Nitrogen dilution of the reducing gas masks the true effect of hydrogen partial pressure by influencing the effective molecular dif-fusivity and gives an apparent first-order relationship. The transport of hydrogen and water vapor across the iron layer is consistent with molecular gaseous diffusion rather than a Knudsen diffusion mechanism. ALTHOUGH the literature on the reduction of iron oxides is very extensive, it is only comparatively recently that a definite quantitative model for the reduction of hematite has been proposed. This development has been largely due to the work of McKewan. An extensive literature review of previous work has recently been compiled by Themelis and Gauvin. Exclusive control by gaseous diffusion in the reduction of hematite has been recently advocated by Kawasaki and coworkers.' Although the results of the latter workers are of considerable practical significance, the extreme porosity (approximately 30 pct) of their specimens precludes their application to a kinetic evaluation of the reduction of dense polycrystalline hematite. The salient features of the kinetic model used by McKewan for the gaseous reduction of dense hematite at temperatures in excess of 560°C (when FeO is stable) are: 1) The reduction is a topochemical reaction taking place through 'the series FeO/FesO4/FeO/ Fe; 2) The gas-solid type of reaction takes place only at the FeO/Fe interface and the internal reduction: FeO proceeds by solid state diffusion; 3) The iron layer formed is quite porous and offers negligible impedance to gaseous diffusion; 4) The rate-controlling step in the reduction is a chemical process occurring at the Fe/FeO interface. In view of the relatively fast reaction rates involved when hematite is reduced in a stream of hydrogen, it seemed possible that the simplifying assumptions of negligible diffusional resistance in both the bulk gas phase and the reduced iron layer could introduce serious errors in the interpretation of experimental reduction data. The present work was initiated to elucidate the effect of gaseous diffusion on the reduction rate and to determine its possible influence in the formulation of the reaction mechanism at the metal/oxide interface. EXPERIMENTAL Procedure and Apparatus. Dense cylindrical compacts of artificial hematite were prepared by sintering pressed compacts of reagent-grade ferric oxide, containing 99.6 pct FezO, in air at 1200°C for 80 hr. The resulting compacts had a final porosity of less than 2 pct and a height and diameter of approximately 1 cm. Variations in sintering atmosphere from air to pure oxygen, in sintering time from 20 to 80 hr, and temperature from 1150" to 1250°C had no effect on the subsequent reduction behavior. The reduction of the samples took place in a vertical tube furnace in which was placed a 1-in. transparent silica tube. The 24-in. heated length

Jan 1, 1964

By V. Omaynikova, A. Lossin, H. Salomon-de-Friedberg

In 2009, Aurubis AG and Teck Resources Limited, recognizing a growing industry need, joined together to advance and further develop technology to deal with arsenic-bearing copper concentrates in an effective and environmentally sustainable manner. The work that followed included extensive bench testwork and 3 months of continuous, fully integrated pilot campaigns on high arsenic-bearing copper concentrate as well as environmental testing, market studies and economic assessments. The success of the CESL Process in processing arsenic-bearing copper concentrates, at levels of up to 4.6% arsenic, has been previously presented. The present paper discusses aspects of similar, equally successful trials on copper concentrates with grades of arsenic approaching 12%. Key parameters to the successful processing of these types of concentrates are discussed. In addition, data on subsequent continuous, pilot gold recovery from the leach residues and the longer term stability characteristics of these residues are also included.

Jan 1, 2014

By R. L. Curfman

In May 1960, six months after conversion of one- half of the Uranium Reduction Co. mill from acid to alkaline leach, severe corrosion was encountered in the 112 stainless steel wash baskets in the resin- in-pulp portion of the uranium circuit. Fortunately the corrosion was limited to the stainless steel screen cloth and bolts. The frames were not affected. Each resin-in-pulp wash basket serves as a container and a vehicle for approximately 40 cu ft of ion-exchange resin. Four baskets are installed in each tank through which uranium-rich solution flows as the baskets move up and down mechanically in the tank. The ion-exchange resin has an affinity for the uranium in the solution which causes it to be deposited on the resin in solid form. By reverse action with different chemical solutions, the uranium may be stripped from the resin for further processing and purifying. This section is the first step in the actual recovery of the uranium.

Jan 9, 1962

By G. Yang, M. J. McPherson, P. Mousset-Jones, G. Danko, F. Calizaya

In the last 20 years, studies on controlled flow recirculation in various countries have been carried out in both coal and metal mines. These studies have shown that in addition to economic gains, partial flow recirculation can be used to provide mine workings distant from surface access points with the required volumes of air. These studies have also shown that the operation of fans and regulators, used in a recirculation system, will induce transients in gas flow and gas concentration. Various models have been developed to explain the problem. However, most have failed to incorporate important factors such as diffusion and dispersion in the modeling process. This study examines the theoretical background of gas emission transients from caved areas in coal mines, represents the problem by a "tank-airway" network model, and provides a possible solution. The study also presents the results gained from a laboratory model constructed to evaluate the major factors affecting the shape and duration of gas flow and gas concentration transients in an airflow recirculation system. In this model, the gas injection system was rearranged to simulate the variations in gas emission rates due to changes in air pressure. Within this model, a set of booster fans and regulators were used to generate the changes in air pressure within the model. Finally, the study presents an algorithm and a computer program GASTRAN, developed to analyze the gas concentration transients and calculate the pollutant transport levels in a complex ventilation network. The application of the program is illustrated by means of an example problem.

Jan 1, 1991

By W. C. McBee, B. W. Jong, T. A. Sullivan

A sulfur concrete technology has been developed by the US Bureau of Mines, where chemically modified sulfur is used with suitable mineral aggregates to produce construction materials that are resistant to corrosion by acids and salts. This report presents a summary of the basic technology and results of testing the materials under actual operating conditions in 50 corrosive environments in 40 commercial plants. After four years of testing, there was essentially no evidence of material degradation or loss of strength. Regular concrete materials were attacked and, in some cases, completely destroyed under the same conditions. Testing is continuing to establish ultimate longevity and durability of the sulfur concretes. The materials are finding widespread applications in metallurgical, chemical, and fertilizer processing plants.

Jan 1, 1986

By Pranav Deshpande

The wear behavior of metal matrix composites differs from that of the monolithic metallic counterparts because composite materials have multiple constituents in their structures and these constituents wear at different rates. It was observed that under low wear stresses, abrasive wear prevailed. As the wear stress increases, pullout of reinforcement occurs and both abrasive wear and wear due to pullout contribute to the overall composite wear. A model of wear taking into account both types of wear has been developed. A critical pullout wear stress was suggested for each composite. Below the critical wear stress, no pullout of reinforcement occurs. It turns out that the critical wear stress simply equals to the ratio of the interfacial strength between the matrix and the reinforcement to the friction coefficient between the reinforcement and the wear counter surface. The critical wear stress is independent of the particle size of the reinforcement. From data on wear of 53% WC composites, the equation of wear for 32% WC composites was obtained. Experimental results agreed well with the predicted wear rate of this composites. This provides an excellent verification of the wear model developed by Lin and Deshpande. Wear data from Modi et al. in the literature were also perfectly fitted with the model.

Jan 1, 2006

By Frank Nicholson

Copper ore was first noticed in Ste. Genevieve County in 1563. The diswvery mas made by a German farmer named Simon Grass, who had occasion to make a road from his farm down the hill into the neighboring valley, and while so engaged noticed pieces of a green-colored mineral, some of which he collected. Not knowing the character of the ore he had found, and supposing it to be valua ble for its brilliant green color only, he carried a piece with him into the town of Ste. Genevieve and showed it around the various bar rooms as a curiosity. No special attention was paid to the matter until nine years later, when Mr. 0. D. Harris sent a specimen of the ore to Dr. Theodore Fay, of St. Louis, for analysis. This analysis, which was the first ever made of Ste. Genevieve copper ore, showed the specimen to contain : Copper,. .........17.75 per cent. Zinc,..........3.21 " Iron........... 24.50 " Sulphur ..........1.09 " Organic matter, silica, carbon, and oxygen,. .. 53.45 " 100.00 " From this analysis it is evident that the sample was taken from near the surface, and was probably recognized by its green color. The almost entire absence of sulphur proves it to be an oxidized form. There is on file, at the office of the Ste. Genevieve Copper Works, a paper* giving three arsays of the ore made in 1875 by Henry B.

Jan 1, 1882

Lower the respirable dust exposure of longwall shearer operators with improved water spray systems on the shearer. Approach Orient sprays (rather than relocate them) so that dust is held against the face. How It Works Research by the Bureau has indicated that shearer operator dust levels depend largely on how fast dust from the upwind drum spreads into the walkway. Water sprays on the shearer body can greatly affect the spreading of this dust because each spray moves air like a small fan, generating strong cross-currents of air around the shearer. Poorly designed spray systems, especially those with nozzles pointing upwind, will stir up much more dust than they sup-press. On the other hand, Improved systems may be designed to hold the dust cloud against the face while also suppressing It. In such arrangements the water is sprayed downwind and used with screens made from conveyor belting.

Jan 1, 1981

Don Hausen was a pioneer in the field of quantitative mineralogy. Methodology that he developed at Newmont almost 40 years ago is still employed today, only the technology has advanced. Petrographic methods were stressed with an emphasis on alteration, mineralisation and paragenesis. Methodologies employed by Don on the Carlin deposit were applied to developing the Carlin Trend by helping to work out lithology and structure, which ultimately led to the discovery of deep high-grade deposits. Quantitative methods used by Don on San Manuel, Copper Creek and Superior, Arizona were applied to the development of the Batu Hijau Deposit in Indonesia. Advancements in technology since DonÆs time have made the mineralogist much more efficient. Manual measurement of peak heights off of strip charts for semiquantitative XRD has been replaced by software that does Rietveld refinement and whole pattern fitting. Hand contouring of XRD data has been replaced by digitised data incorporated into geologic models. Optical point counting, which would take a dayÆs work to process 1000 points, has been replaced by automated SEM methods where 20 000 points are possible in an hour. The use of the optical microscope remains relatively unchanged, and still remains as Don emphasised the æeyesÆ of mineral exploration. However, the information can be relayed much more quickly with digital image capture and electronic data transfer. Don insisted on becoming involved in projects at the grassroots level and supporting the project through mine closure. This made the mineralogist a liaison between exploration geologists, mine geologists, metallurgists and mine engineers. The methodology that Don helped develop continues to provide invaluable support to Newmont geologists and metallurgists worldwide today.

Jan 1, 2008

By John M. Bostwick

Bitumen is a general term for a group of materials composed of mixtures of hydrocarbons that are fusible and soluble in carbon disulfide. Included in the group are petroleum, asphalts, asphaltites, and mineral waxes. Asphalt is a dark-colored, cementitious solid or semisolid, which generally softens on heating and resumes a more viscous or solid state when cooled (personal communication). It is found in native form in fissures and pore spaces in rocks and as lakes. It is also obtained from the residues produced in petroleum refining. Asphaltites are black, naturally occurring solid bitumens. They are generally shiny and break with a conchoidal fracture. Common asphaltites are gilsonite (uintahite), grahamite, and glance pitch. Mineral waxes are solid or semisolid, relatively nonvolatile bitumens of various colors, having an unctuous feel and waxy luster. Of the native waxes, ozokerite is the best known. Montan wax is also classed as a natural wax, although it never occurs in the pure state and must be extracted from lignite or cannel coal (Ladoo, 1920). Mineral waxes may also be obtained by pyroprocessing of petroleum, lignite, and peat. Pyrobitumens are dark-colored, solid hydro- carbons that are infusible and relatively insoluble in carbon disulfide. They are so-called because they will yield liquid and gaseous hydrocarbons only when heated. Asphaltic pyrobitumens are defined as "substantially free of oxygenated bodies" and include wurtzilite (elaterite), albertite, and impsonite (Thrush, 1968). Nonasphaltic pyrobitumens contain oxygenated bodies; examples are coal and peat. The nonasphaltic type will not be discussed further. Petroleum Asphalts Asphalts refined from crude petroleum have almost completely replaced the native types. Refineries can produce asphalts in every desirable grade more economically and in greater quantity than the native types and with a variety of properties that meet the requirements of the various manufacturers using them. For all practical purposes, it is estimated that more than 95% of the asphalts consumed in the United States are refined from crude petroleum (private communication).

Jan 1, 1975

By Christopher W. Schram, Allan B. Tanner, Frank E. Senftle, George R. Boynton, Philip W. Philbin

A borehole sonde using a 252Cf neutron source and a Ge(Li) gamma-ray detector was field tested in a coal bed in Belmont County, Ohio, to ascertain whether such a device could be useful as a coal-exploration tool. As the sonde was lowered into the borehole, successive spectra were accumulated over short time intervals. The intensities of the capture gamma rays from hydrogen and of decay gamma rays from aluminum were determined simultaneously in each spectrum. A log of the intensities versus depth shows the depth and thickness of the coal bed. With the sonde stationary at points above, in, and below the coal bed, capture gamma rays were measured to show the variation in concentration of certain elements. From the spectrum recorded in the bed, a complete ultimate analysis, the percent ash content, and the heat content were determined without recourse to an external standard. Delayed gamma-ray analyses of the core were also made on the surface in the vicinity of the borehole in a fixed-geometry irradiation facility wing the detector in the borehole sonde. The concentrations of 10 elements were determined by this method on a coal split from the drill core. These experiments show that it is feasible to use a 252Cf- Ge(Li) borehole sonde as an aid in coal exploration.

Jan 1, 1979

Provide the technology to remotely control a thin¬-seam continuous mining machine from a safe location hundreds of feet outby the working face in an underground room-and-pillar mine. Background and Approach Hard-wired or radio remote control of continuous mining machine has been commercially available since the early 1970's. This type of remote control, in low and high coal seams, situates the machine operator offboard, but within direct view of the underground coal face, Although positioned under supported roof, the operator can still be exposed to face area hazards that include roof-rib falls, dust, methane explosions, and equipment congestion. The U.S. Bureau of Mines approach has been to put the operator into a protected compartment at a location away from the working face. Since 1979, the Bureau has investigated innovative methods to better protect face area workers in under¬ground room-and-pillar mines. In 1989, the Bureau demonstrated an offboard, computer-based remote con¬trol system in a West Virginia highwall mining operation that stationed the operator hundreds of feet away from the working face. In late 1992, much of this technology, plus improvements, Was used to demonstrate, on the surface, how a thin-scam continuous mining machine could be remotely controlled 200 feet from the machine in a 36-inch working height.

Jan 1, 1992

By Victor Bredykhin

The report is devoted to the investigation and improvement of processes taking place at contact of large quantities of water insoluble liquid and particles of solid phase in a pulp. Theoretical analysis and simulation of acting conditions have allowed to determine that after attaching of oleophilic particles on the «water-reagent» separation surface the break of a formed complex is taking place according to the reagent volume and for oleophobic minerals along the «solid-reagent» separation surface. As a result particles are selectively treated if the magnitude of the reagent adhesion to the surface of solid phase in water is great. The results of dispersion are influenced significantly by availability of sharp edges on the surface of real particles. They keep tree phase perimeter of moistening. It is possible to fix reagent in the form of lens whose contact angle is significantly smaller in comparison to the thermodynamic angle. In adhesion dispersion the reduction of reagent volume, covering the equal area of particles surface is possible when the reagent is in a pulp in the form of thin films on the «water-gas» separation border. The process is tested in laboratory conditions as well as at pilot concentrating mills in flotation of sulfide ores, non-ferrous metals (copper-molybdenum ore), native sulfur and coal.

Jan 1, 2006

By J. Siege1, R. S. Popielak

A computer model was used to simulate the effect of leakage through confining beds on a hypothetical in situ leach operation in an aquifer with a thin mineralized section. The simulations were used to assess economic and potential environmental implications of leakage on an in situ leach operation. Four scenarios were modeled - three representing cases with different degrees of confinement, and the fourth representing a stratified ore zone under a low degree of confinement. The model simulated the travel path and travel time of lixiviant given the hydraulic conditions prescribed in each scenario. The results show that the travel path and travel times vary by about 10% for confinement ranging from nearly impermeable (essentially no leakage) to an extremely low level (thin confinement with a permeability about equal to that of the aquifer) for isotropic aquifer conditions. The aquifer thickness contacted by the lixiviant varied from 85% to 90%. Horizontally, 55% to 60% of the aquifer was contacted. The flow paths in the stratified aquifer were reduced in the vertical direction and expanded horizontally. Forty- five percent of the aquifer thickness was contacted vertically with 88% contacted horizontally. Break- through time for lixiviant traveling at mid-depth of the aquifer increased two times when the leakage was increased from nearly zero to a value representative of thin and highly permeable confinement. Leakage affects the economics of in situ mining by (1) increasing the time required to leach out the ore, and (2) increasing the thickness of the ore zone aquifer to be restored. The potential for environmental impacts appears to be minor. In all four simulations, the lixiviant did not contact the confining strata. Restoration would be limited to cleanup of the ore zone aquifer within the thickness contacted by lixiviant and within the radius of the lixiviant that traveled farthest away from the production cell.

Jan 1, 1988

[Separates of all the Technical Publications published in 1928 are available at Institute headquarters. All the papers are on file in public, university and technical libraries, and when so indicated in the list, may be found either in the TRANSACTIONS or in the special volumes issued by the Institute.; METAL MINING TECH- NICAL TRANS. PUBLI- TITLE AUTHOR MEETING VOLUME CATION AND PAGE* No. 50 The Eötvös Torsion Balance D. C. Barton New York Method of Mapping Geologic Feb., 1928 Structure 52 A Cartographic Correction for the C. A. Heiland New York Eötvös Torsion Balance Feb., 1928 61 Liquid-oxygen Blasting at Chuqui- H. C. Schultz, New York camata, Chile F. K. Middleton Hunter Feb., 1928 76, 108, 123 64 Working Methods of Practical Geo- Hans Haalck New York physics Feb., 1928 65 Experiments with Eötvös Torsion P. W. George New York Balance in the Tri-State Zinc and Feb., 1928 Lead District 74 Gravity Surveying in Great Britain H. Shaw New York Feb., 1928 75 The Computation of Eötvös Gravity E. Lancaster-Jones New York Effects Feb., 1928 82 Earth-resistivity Measurements in W. O. Hotchkiss, New York the Lake Superior Copper Country W. J. Rooney, Feb., 1928 James Fisher 83 Mining Methods and Records at the Roy W. Moore New York 76, 56, 90 United Eastern Mine Feb., 1928 98 Recent Results in Electrical Pros- Hans Lundberg New York specting for Ore Feb., 1928 101 Relation between the Oxygen Bal- G. St. J. Perrott, New York ance and Propulsive Strength of N. A. Tolch, Feb., 1928 Eight Gelatin Dynamites J. E. Crawshaw 102 Effect of Oxygen Balance of Gelatin G. W. Jones, New York Dynamites on the Gaseous Prod- G. St. J. Perrott Feb., 1928 ucts of Detonation 108 The Financial Report of a Min- Henry B. Fernald New York ing Company-Its Content and Feb., 1928 Meaning 116 What Duty to Support the Surface R. G. Bosworth New York Does a Subsurface Owner Owe? Feb., 1927 136 Comparison of Branch Raise and C. A. Mitke Los Angeles 76, 93, 103 Combined Shrinkage and Caving Sept., 1928 Methods 141 A Mining Company Balance Sheet G. F. Wolff New York Feb., 1928

Jan 1, 1927

By John B. Ackerman, John G. Mansanti

INTRODUCTION Placer Dome's Turquoise Ridge Joint Venture operation is located some 75 km northeast of Winnemucca, a community in north central Nevada. Formerly known as the Getchell Gold Corporation and First Miss Gold, the operation mines refractory ore from the Getchell and Turquoise Ridge gold deposits located on the east flank of the Osgood Mountain Range above the Kelly Creek Basin in the Potosi Mining District. Mining has been ongoing at Getchell since shortly after its discovery in 1934, and was the nation's second leading producer of gold after Homestake in the early 1940s. Over its history the Getchell property has been mined for gold, tungsten, molybdenum and arsenic; mining methods varied from open pit mining to underground mining; processing options included conventional milling, flotation, roasting, heap leaching, and most recently pressure oxidation followed by CIL (carbon-in-leach). As an historical note, the US Bureau of Mines developed the use of carbon for gold recovery at Getchell during the 1940s (Horton 1999). Placer Dome acquired the property in May 1999. The pressure oxidation plant was mothballed in July 1999 and the property was placed on care and maintenance in February 2002 pending further exploration results. The property is currently ramping up to full production status. A joint venture agreement (75% Placer Dome, 25% Newmont) was established with Newmont Mining in 2003 and ore is processed at their nearby Twin Creeks autoclave plant. Mine dewatering is a key element to success. Arsenic is a ubiquitous mineral in many of the mineralized areas of northern Nevada, necessitating treatment of water prior to re-infiltration.

Jan 1, 2005

By E. T. Dumble

PROF. EDWARD ORTON, in his Report on the Occurrence of Petroleum, Natural Gas and Asphalt Rock in Western Kentucky, thus clearly states his ideas of the universal dissemination and rare accumulations of the bitumens:1 " We need to bear in mind that the various members of the bituminous series are abundantly and almost universally distributed among the unaltered sedimentary rocks of the earth's crust. The valuable accumulations of these substances are rare, it is true, but one can scarcely go amiss of petroleum, asphalt or gas, at least in small quantities, among the stratified rocks that retain their original structure." Speaking of the Ohio valley, he adds: "A fifth of one per cent. of petroleum, if distributed through a, thousand feet of rock, would make a total to the acre, or square mile far , beyond any production that has ever been realized from the richest oil field, and percentages of this amount are not only not rare to find, but are even hard to miss." Dr. F. W. Clarke in his Data of Geochemistry (Bulletin No. 491, U. S. Geological Survey, 1911), discussing these views of Orton with similar views of T. Sterry Hunt and Szajnocha, says that they "lead to the conviction that the formation of bitumens is a general process and by no means exceptional. Wherever sediments are laid down, inclosing either animal or vegetable matter, there bitumens may be produced."2 The organic origin of the bitumens, including petroleum, has long been an accepted fact with nearly all geologists, but the method, place, and time of the transformation into petroleum or other bitumen is still under discussion.

Jan 3, 1914

By C. W. Tomlinson

INTRODUCTORY THE analyses which have been made by the writer according to the method described below were made as part of Professor Withey's investigation of the concrete aggregates' of Wisconsin, in the hope of throwing light on the extent and nature of the influence of the mineralogical constitution of aggregates upon the properties of the concrete, and mortar made from them. This method was found most satisfactory after four weeks of experiment and modification. It attains an accuracy quite sufficient for the purpose of the analysis, and is fairly rapid. Mineralogical analyses may be thus made at a cost considerably less than that of chemical analyses of a similar degree of completeness. The results obtained by this method should not vary in any item by more than 1 per cent. of the total weight of the sample, and may be made very much better than this by the exercise of greater care in the microscopic counting (see below). The accuracy of the hand sorting 'is of course dependent upon the experience and carefulness of the analyst. . After a month's practice, the writer was enabled to turn out these analyses at the rate of four in 33 hr. of working time. It was found most economical to handle four samples at once. The samples analyzed weighed froth 290 to 340 g. each. The same method could be applied to larger or to smaller samples, within reason able limits. The following list covers the necessary apparatus and equipment: 1 good balance capable of weighing accurately to tenths (or, better, hundredths) of a gram, and of handling quantities up to 200 g. in weight. 1 Westphal balance, registering densities to two or three decimal places. 1 Meker or Bunsen burner, and gas supply. 1 nest of sieves, 10, 20, 40, and 100 meshes to the inch.

Jan 5, 1915