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By J. Blodget Britton

Six different samples of anthracite, each a firm compact lump, were finely pulverized and immediately put in bottles. Portions of these were weighed and placed upon an ordinary water-bath and dried for one hour; the average loss was 1.24. The same portions were then placed in a hot-air oven, and for two hours kept at a temperature of 285° F., and, after cooling in a dry chamber, were again weighed, when there was found a further average loss of 1.22, making a total so far of 2.46. They were then immediately returned to the oven and for two hours more kept at a temperature of 530° F. and cooled and weighed again, when no further loss was found, but an average gain of .55 upon the previous weighing. The same portions were a third time placed in the oven and for about ten minutes kept at the last-mentioned temperature, and then, while still hot, were poured into one-quarter inch glass tubes, each with a bulb at one end, and heated over a Bunsen burner at a temperature below a red heat, when more water vaporized and condensed in small clear globules on the cold parts of the tubes. Fresh portions of the coals were then taken, and the total amount of water determined, and the average was found to be 3.04, or 1.80 more than was found at the temperature of the water-bath, which was perhaps a little below 212° F., and .58 more than at 285° F. Tests were afterwards made by placing other fresh portions of the

Jan 1, 1877

By Isobel Clark

The increasing complexity of modern mining technology makes it ever more difficult to decide on the 'best* way to solve problems in mine planning. Yet with escalating costs it becomes increasingly more important for the mining engineer to be able to evaluate quantitatively the implications of the 'what happens if' postulation on the efficiency and economics of exploitation. The use of a model of the orebody can yield an estimate, not just of overall expected results, but also of the sensitivity of these results to possible variations in the orebody. Estimation techniques, such as Kriging, will produce the expected value for the grade of ore at any given point, or over any given volume within a deposit. However, the actual grades mined during production will - of necessity - differ from the predicted values. These possible variations, and the sensitivity of the management decisions to them, can be investigated in detail by the use of simulation. An orebody can be simulated which follows the known characteristics of the deposit at any given stage in development. These properties might be the histogram of grade values, the semivariogram from the samples, the actual borehole assays, geological constraints and/or interpretation, topography, lease boundaries etc. This would be one possible 'realisation' of the deposit as dictated by the currently known data. If several of these simulations are carried out, each conditioned to the current knowledge of the orebody, then it is possible to gain an idea of the range of possible outcomes of any mining procedure or decision taken - all of which are equally likely. Not only can the best decision then be taken, but its sensitivity to the inherent variation within the orebody, and to the ever present estimation errors may be thoroughly studied.

Jan 1, 1977

By Waldemar F. Dietrich

Mineral fillers are relatively inert chemically under the conditions of use but have physical properties* that modify those of the materials in which they are incorporated. The mineral fillers considered in this article are asbestos, barite, clays, diatomite, crushed limestone, limestone whiting and lime, mica, silica, talc and soapstone, and pyrophyllite. Slate and stone, other than limestone and its derivatives, are excluded because, even though used in large quantities, they are exceptionally low-cost materials generally produced close to the area where they are used.

Jan 8, 1959

By J. F. Poland

Location of Basins and Geologic Features of Occurrence: The major ground-water resources of California occur and are stored in the many large alluvium-filled valleys of the state. The deposits of Quaternary age which hold the ground water commonly are called valley fill. Meinzerl has discussed the characteristic features of this fill and showed that for western United States its distribution is concentrated chiefly in western Utah, Nevada, central Oregon, California, southern Arizona, and central New Mexico (see fig. 1). For California the principal ground-water basins are shown on fig. 2. Except for the Mojave Desert and the "Basin and Range" Valleys (fig. 2, Nos. 23 and 23A), which are not shown individually, the basins outlined on fig. 2 contain all the large reservoirs in valley fill within the state. The Sacramento and San Joaquin Valleys (fig. 2) together comprise the Great Central Valley of California, which has an area of about 18,000 square miles. The Sacramento Valley contains about 5000 square miles of valley lands, approxi- mately equal to the area of Connecticut; the San Joaquin Valley embraces about 13,000 square miles, equivalent to the areas of Massachusetts and Connecticut combined. Both the area and the ground-water use in the Central Valley is far greater than for all the other shaded alluvial basins of fig. 2 added together. Except for the Sacramento Valley, all the major ground-water basins of the state are south of Sacramento. The valley fill in these ground-water basins has been transported by streams and most of it has been laid down in alluvial fans, producing the typical alluvial-fan structure of aquifers radiating as tongues from a prismatic pile of coarse, permeable debris at the canyon mouths; these aquifers are encased down slope by poorly sorted materials consisting of a clayey matrix with imbedded pebbles and boulders, interbedded with flood-plain silt. In the deeper inland structural valleys, the alluvial deposits interfinger at depth in the valley bottoms with horizontally bedded lacustrine sand, silt, and clay. The San Joaquin Valley is a good example. In the coastal valleys exposed to the sea, such as the Los Angeles coastal plain, the alluvial fans pass coastward into lagoonal and thence to shallow marine deposits. In all these basins, the gravel is coarsest and most permeable near the apexes of the fans, but tongues or lenses of clean gravel and sand may extend for many miles down the fan. Thus, these water-bearing structures are in a position to absorb stream flow near the canyon mouths and to transmit it through the buried radiating conduits.

Jan 1, 1951

By J. F. Poland

Location of Basins and Geologic Features of Occurrence: The major ground-water resources of California occur and are stored in the many large alluvium-filled valleys of the state. The deposits of Quaternary age which hold the ground water commonly are called valley fill. Meinzerl has discussed the characteristic features of this fill and showed that for western United States its distribution is concentrated chiefly in western Utah, Nevada, central Oregon, California, southern Arizona, and central New Mexico (see fig. 1). For California the principal ground-water basins are shown on fig. 2. Except for the Mojave Desert and the "Basin and Range" Valleys (fig. 2, Nos. 23 and 23A), which are not shown individually, the basins outlined on fig. 2 contain all the large reservoirs in valley fill within the state. The Sacramento and San Joaquin Valleys (fig. 2) together comprise the Great Central Valley of California, which has an area of about 18,000 square miles. The Sacramento Valley contains about 5000 square miles of valley lands, approxi- mately equal to the area of Connecticut; the San Joaquin Valley embraces about 13,000 square miles, equivalent to the areas of Massachusetts and Connecticut combined. Both the area and the ground-water use in the Central Valley is far greater than for all the other shaded alluvial basins of fig. 2 added together. Except for the Sacramento Valley, all the major ground-water basins of the state are south of Sacramento. The valley fill in these ground-water basins has been transported by streams and most of it has been laid down in alluvial fans, producing the typical alluvial-fan structure of aquifers radiating as tongues from a prismatic pile of coarse, permeable debris at the canyon mouths; these aquifers are encased down slope by poorly sorted materials consisting of a clayey matrix with imbedded pebbles and boulders, interbedded with flood-plain silt. In the deeper inland structural valleys, the alluvial deposits interfinger at depth in the valley bottoms with horizontally bedded lacustrine sand, silt, and clay. The San Joaquin Valley is a good example. In the coastal valleys exposed to the sea, such as the Los Angeles coastal plain, the alluvial fans pass coastward into lagoonal and thence to shallow marine deposits. In all these basins, the gravel is coarsest and most permeable near the apexes of the fans, but tongues or lenses of clean gravel and sand may extend for many miles down the fan. Thus, these water-bearing structures are in a position to absorb stream flow near the canyon mouths and to transmit it through the buried radiating conduits.

Jan 1, 1951

Jan 1, 1944

By Foster J. Witthauer

First mining operations in the Tyrone District, located just north of the Burro Mountains in Grant County, New Mexico, commenced in the 1870's. A major operation was undertaken by Phelps Dodge Corporation in the early 1900's when a 2,000 ton per day underground mine was developed and a gravity concentrator was built east of the mine and across the Continental Divide. It was during this time that the picturesque Tyrone townsite was built and occupied. In 1921, however, the underground operation was closed because of high operating costs and low demand for copper. The area was drilled extensively during the 1950's and in October 1966 Phelps Dodge announced the pending development of the new Tyrone with a large open-pit mine, a modern concentrator, suitable support facilities, and a new townsite to be located between the mine and Silver City. Stripping for the pit and construction of shop and milling facilities began in 1967. By the spring of 1969, ore was being stockpiled near the primary crusher. Operation of the concentrator on a 3-shift per day basis commenced on July 17, 1969. The concentrator as initially built had one primary, two secondary, and five tertiary cone crushers, two grinding sections of six ball mills each, two flotation sections, four filters, and four tailing thickeners. The capacity was about 30,000 tons per day. In 1971 and 1972, the capacity was increased to 48,000 tons per day by the addition of one secondary and two tertiary crushers, one section of eight ball mills, one flotation section, two filters, and four more tailing thickeners. Centralized automatic control was built into the original and expanded facilities to the greatest extent possible, considering the state of the art at that time. Installation of additional control

Jan 1, 1976

By J Price, M. R. Geer, H. F. Yancey

COAL mine operators recognize coal as an abrasive material, because the wear of drilling, cutting, and conveying equipment is reflected as a cost item for replacement of parts. Similarly, industrial consumers of coal experience abrasive wear on all coal-handling equipment. Operators of pulverized fuel plants are doubtless most keenly aware of the abrasiveness of coal, because under the high contact pressures developed between coal and metal in pulverizers, abrasive wear is increased many fold. Moreover, experience in operating pulverized fuel plants has demonstrated that some coals are much more abrasive than others. Hardgrove' stated that maintenance costs entailed by the wear of grinding elements is often a more important variable than the cost of the power required to pulverize different coals. Craig2 also reports that one coal may cause pulverizer parts to wear several times faster than another. It is apparent, therefore, that those concerned with pulverizing coal could profitably employ a method for estimating the abrasiveness of different coals, just as they utilize standard tests for thermal value, grindability, and ash-fusion temperature to assist in selecting the most suitable and economical coal to use in a particular plant. The objective of this investigation was to develop a test procedure that would be suitable for general use in estimating the abrasiveness of coals. However, few, if any, of the standard tests now used for evaluating the properties of coal are the product of a single investigation or the result of a single investigator's efforts. Rather, in each case, a testing procedure was devised by one investigator, used by others on a wider variety of coals, and finally refined completely as the result of the joint efforts of a number of interested people. Thus, the test procedure for estimating abrasiveness developed in the course of this work may not be refined sufficiently in its present form for general use, but it may serve as the starting point from which an acceptable test procedure can be developed. The method has been used thus far on only about a dozen coals, and there has been no opportunity to attempt a correlation between experimental results and actual plant experience. Only wider use of the procedure by other investigators and correlation with plant experience can determine to what extent the method will have to be modified to render it suitable for general application. Test Method Although the literature contains no record of an attempt to devise a method for estimating the abrasiveness of coal that could be used industrially, several investigators have tested properties of coal that are closely related to its abrasiveness. The abrasiveness of a material generally is considered to be related to its hardness, and hardness tests for coal have been employed by Heywood,' O'Neill," and Mathes. Also, the resistance of coal to abrasion, a property that presumably is related to the abrasiveness of coal, was measured by Heywooda and by Simek, Pulkrabek, and Coufalik.2 11 these investigators tested only individual pieces of coal. Since coal is a heterogeneous material having components of varying properties, tests of this type can yield results having little more than academic interest. Only a test method that utilizes a representative sample of coal can give results that are useful industrially. The abrasion tests used for various other materials have been considered for adaptation to testing the abrasiveness of coal. The tests used for metals,7-9 paving and flooring,'" and rubber," cannot be used because coal is not sufficiently abrasive.~ The present experimental work was begun before World War II and was conducted by three research fellows"'" working under a joint agreement between the University of Washington and the Bureau of Mines. After a great deal of preliminary work with a variety of apparatus and materials, a test procedure was developed which consisted of rotating a test disk 2Yz in. diam in a steel mortar containing the coal sample. The shaft carrying the test disk at the lower end and a 100-lb load on the upper end was free to move vertically. The bed of coal in the mortar was kept fluid by low-pressure air admitted through a port near the bottom of the mortar. Measurable wear on an Armco iron disk could be obtained in this test procedure, but, despite extensive efforts to eliminate them, several major disadvantages remained in this test method. First, with most coals the amount of wear on the iron disk did not exceed a few milligrams. Second, a single type of disk was not applicable for all coals. A smooth iron disk gave satisfactory results with both bituminous and sub-bituminous coals, but hardly any wear with anthracite or coke. A disk having studs or projections gave more satisfactory abrasion losses with anthracite and coke and presented no operating difficulties with free-burning bituminous and sub-bituminous coals. It could not, however, be used with caking coals because these coals formed a

Jan 1, 1952

By M. M. Fine

In a laboratory study of grinding and classification of silica sand, a satisfactory means of producing the medium-fine specification sand desired by producers of flint-glass containers was developed. The best procedure consisted of ball-mill grinding and double classification, which gave a properly sized sand containing less iron than the feed.

Jan 3, 1950

By Benjamin B. Lawrence

Arthur Launcelot Collins was born at Truro in Cornmall, England, July 8, 1868. His father, J. H. Collins, is well kuown as an engineer, and his books have been widely read in this country: Arthur was the third son. Three of his brothers are engaged, as is his father, in the profession of mining engineering. His education, gained partly at St. Austell, partly at Falmouth, and partly at Nuttall's Collegiate School in Truro, England, was supervised by his father, who was then Lecturer on the Mining Sciences to the Miners' Association of Cornwall and Devon. In 1881, J. H. Collins went to Rio Tinto, in Spain, as chief chemist and metallurgist, and it was there that Arthur began his practical work in the laboratory and continued his studies in chenlistry and mineralogy. To the latter science he was deeply attached; and he never lost an opportunity of adding to his cabinet of minerals, of which he was an ardent collector. In 1883, he became assayer and general assistant to Mr. Nicol, Manager of the Peña del Hierro copper-mines, ncar Rio Tinto. Until 1885 he was associated with his father in the study of the geology of the Rio Tinto belt. In 1885 he retuined

Jan 1, 1904

By A. F. Frederickson

A MINERAL can best be defined as a phase,' where the term "phase" is described as a homogeneous,* physically distinct, and mechanically sep- arable portion of a system. If one phase develops from another, certain nuclei must first be available.2.394 The manner in which new material is added to these nuclei, and the subsequent structural and other characteristics of the phase, is often markedly influenced by factors other than its temperature, pressure, and gross compositional environment. Rates of growth, presence of impurities, the availability or lack of oxygen, the pH of the system, and percentage of completion of the often determine which modification will develop. Many transitional phases develop when a relatively insoluble precipitate is formed from solution. Different modifications are formed, depending on the speed and percentage of reacting solution added. Some of these "forms" are stable and do not "age" or transform into the so-called stable modifications. These modifications are difficult to treat in terms of equilibrium diagrams for the simple reason that these minerals do not represent an equilibrium situation described by only two (temperature and composition) or three terms (when pressure is considered). Many crystals exist as stable or meta- stable phases in nature in environments much different from those indicated by certain equilibrium diagrams. Cristobalite octahedra grow on zeolite needles in vugs, diaspore develops from a medium that does not appear to have been subjected to high pressures and temperatures, authigenic feld-

Jan 1, 1952

By Raymond B. Ladoo, C. A. Stokes

This paper summarizes the economic problems of the industrial mineral industries which are essentially different from those of the metals and the fuels. Failure to understand and evaluate such factors as markets, place value, and substitutions of one mineral for another may be disastrous. The engineer should be as responsible for profitable operation as he is for technical efficiency. The Raw Materials Survey of Portland, Oregon, is described.

Jan 2, 1950

By E. J. Quinn, M. F. Fogler

In a recent paper, Rawdon and Mutchlerl gave some exceptionally interesting results on the Brinell and scratch hardness of severely cold-worked metals. In their work, they found that, on continued cold rolling, the metal hardened up to a particular point and then reversed and became softer; this was true for both Brinell and scratch hardness values. The generally reported behavior2 of metals, with respect to Brinell tests on cold-worked material, is that the metals harden up to a certain point and then, on further cold rolling, no change in Brinell hardness occurs. Jeffries and Archer3 state that there is little difference between the scratch hardness of annealed and cold-worked metals; the work of Faust and Tammann4 also indicated no difference between the hardness of annealed and cold-worked copper. Rawdon and Mutchler found, when they plotted the reduction ratio (initial thickness divided by thickness after rolling) against the hardness value for the cold-rolled material, that the hardness number increased up to a reduction ratio of about 3 and then decreased and became even smaller than that for the annealed metal. This behavior was reported for both scratch and Brinell hardness; Figs. 1 and 2 show their results for Brinell hardness on the metals for which they published data. This is an exceptionally interesting phenomenon, if it occurs under all conditions of rolling, and would have an important bearing on the practice of cold

Jan 1, 1925

By B. F. Oliver

A levitation zone melter is described which has the necessary characteristics for processing metals of controlled purity. No crucible is required; control of the solidification variables is stable; the environment of the charge is chenzically controlled. Rotation of the solidifying interface and mixing in the liquid by the magnetohydrodynamic stirring produce an eight-fold increase in freezing velocity over former melting units with better resulting solute redistributions. The smooth appearance of processed specimens, resistivity ratios as a hnction of position, as well as a segregation curve, are presented as evidence of smooth continuous solute fransport over distances in excess of ten zone lengths. THE difficulties of the floating zone-purification of higher density metals in large quantities under conditions of lowered surface tension are well known and have hindered fundamental research programs for some time. The inordinate amount of time required to obtain a small reproducible yield of high-quality metal has excluded the use of such material for many important material research programs. However, with the use of controllable induction levitation forces' to accomplish stable liquid zones with nearly flat solidifying interfaces, and with good physical and chemical control of the processes involved, these difficulties can be overcome. A zone melter that is to be used for both high-purity and controlled composition work in metal systems must have the following three characteristics: 1) The process must avoid the use of containers. 2) Physical control of the solid-liquid interface and of the mixing within the liquid phase must be stable. 3) The chemical environment of the melt chamber must be controllable. A description of an apparatus that accomplishes these objectives follows.* APPARATUS One of the basic features that is necessary for good process control of large sections is that the charge, the coil, and the motion mechanisms be within the same chamber. This arrangement permits a close coupling between the work coil and the load, which then provides a good flexibility for adjustments of coil dimensions, for controlling the amount of levitation needed for stable operation at a given power level. An overall view of the melter is shown, with the melt-chamber door open, in Fig. 1. The radiation shields surrounding the single-turn induction coil are of water-cooled copper. The chamber is stainless steel, as are most of the components within the chamber. The control panel for the scanner is located at the immediate lower right of the melt chamber. This panel controls the operation of the scanner. The operations controlled are the interface rotation rate, the stretch-squeeze or diameter control, the up and down scanning speeds, and the induction power. All of the drive motors are constant-torque variable-speed motors. The scanning speeds are set with precision helipots and continuously observed with the voltmeter on the control panel and checked with a mechanical indicator within the melt chamber. The rotation rate is also set with a precision helipot. The up-scanning speeds are 2 to 300 in. per hr.

Jan 1, 1963

By L. J. Erck

H EAVY-MEDIA separation continues to be the favored process for concentrating the coarser fractions by elimination of undesirable tailing and middling fractions. The first vessel used for heavy-media separation was the closed-top cone. Further developments then led to the Akins spiral separator which fulfilled the requirements for improving metallurgica1 separation as well as gaining mechanical advantages. During the last season there has been a substantial influx of separator designs for further improvements of metallurgical separation based on the heavy- media method as well as attempting to garner further mechanical advantages with reduction in power consumption to boot. The newest of these designs was the Hardinge counter-current separator which was introduced into the field last spring in two plants. Both Hardinge separators proved satisfactory in operation and substantiat-

Jan 1, 1950

By E. H. Denny

IN the past few years many men, including technically trained engi-neers, have been asphyxiated in metal mines, coal mines, tunnels and surface wells where a few relatively simple precautions with regard to ventilation and air testing would have saved them. Death from mine gases is analogous in some respects to death from poison and from drowning. The respiratory passages of a victim who has breathed oxides of nitrogen from burning explosives are badly irritated and a few hours or even a day after exposure he may develop a quick and fatal pneumonia; if, however, he enters without respiratory protective apparatus an atmosphere deficient in oxygen (a condition that may occur in unventilated or poorly ventilated parts of all underground mines) he collapses and if not rescued dies more quickly and surely than a lone nonswimmer who falls suddenly into deep water. An example of an atmosphere virtually without oxygen was demonstrated by an air sample taken by a Bureau of Mines engineer wearing oxygen breathing apparatus in a Cripple Creek shaft some years ago, during the recovery of the bodies of two victims of asphyxiation; analysis of the sample by the Pittsburgh laboratory of the Bureau showed the presence of 18.40 per cent of carbon dioxide, 0.27 per cent of oxygen, and 81.33 per cent of nitrogen, although the atmosphere apparently was clear and normal. In a mine one can pass from good, breathable air to an atmosphere that will kill as quickly as one can dive from a board to deep water below.

Jan 1, 1938

By V. F. Marsters

SEEPAGES Of oil in Ecuador have been known for many years. The locality first to receive attention, and still worked in a modest way, lies on the north shore of the Santa Elena peninsula, between La Puntilla and Salinas. Operations were first conducted largely by local capital. Later, foreign companies acquired large blocks of land, where they have done considerable drilling. For details concerning present drilling activities in Ecuador, we are indebted to Leon Price, an American resident engineer of Ecuador. The information solicited, came to the author through the office of the American Consulate,' with permission to use it. The coastal plain bordering the Province of Tumbes, Peru, continues to the northeast, but narrows on passing the Zarumilla River. From this, point northward it widens toward Santa Rosa. In fact, the pampas, as shown on the official Wolf map, correspond fairly well to the areal extent of the coastal plain as far as Guayaquil. This is shown in a general way on the accompanying map. The author understands that the Guayaquil embayment is bordered on all sides by the coastal plain, as recognized at Tumbes and farther southwest, and that it can be followed without a break as far north as Palmar. This view is supported by the mapped area regarded by Mr. Price as favorable or possible oil territory. Moreover the islands in the Gulf of Guayaquil are the same geologically as the coastal edge, being composed of Tertiary sediments. The author understands also that Tertiary formations occur north of Palmar. According to a report by Mr. Cardon, of Guayaquil, Tertiary sediments are exposed in the region of San Francisco and extend to and beyond Pta. Calera. There is also reason to believe that at least the lower part of the valley of the Santiago River is occupied by Tertiary sediments, which probably border the coast line and extend into the River Mira basin, and into Colombia.

Jan 7, 1922

By J. R. Hassemer, T. T. Chao, University of Georgia, K. C. Watts, R. F. Sanzolone

Secondary oxides of Fe-Mn have been used in mineral exploration from the time gossans were first recognized Since gossans are conspicuous features and are largely explored, it is necessary to look for more subtle indication of blind mineralization. Sampling materials used in these geochemical studies consist of secondary Fe-Mn oxide-rich products of hydrothermal mineralization, and "in situ" weathering found in fracture fillings-as selvages along joints and disseminations in host rock. These materials were selectively collected and studied in the Silver City mining region. Two independent sampling methods were compared. The difference in the sampling methods was mainly in the ways samples were obtained and processed. One method involved systematic sampling of fracture fillings and coatings from which secondary Fe and Mn oxides and associated trace elements were then selectively extracted by chemical methods. The second approach involved collection of composite stream sediments and physical extraction of Fe-Mn oxide materials by gold panning, bromoform concentration, and electromagnetic separation. The source of the Fe-Mn-rich materials in the stream sediments is considered to be fracture fillings and coatings that mechanically entered the drainage basins. Map distributions of the two-sample types were compared. Both methods showed generally supportive patterns of anomalous metal dispersion, although anomaly-to-background contrast seems better in joint coatings. Both were useful in distinguishing geochemical differences between mining districts in the region. For example, the Pinos Altos district may contain more hydrothermally-introduced iron than the Central district, whereas the Central district has lead and zinc enrichments that are less on the amount of iron enrichment than is the case in the Pinos Altos district. The methods were qualitatively compared relative to time, expense, and other advantages and disadvantages.

Jan 1, 1984

By Paul D. Merica

DURING the Dark Ages, when metallurgy was practiced by the alchemists, any unusual or disturbing variation in metallurgical operations was ascribed to the, presence, in the metals or ores, of an evil spirit, and it was necessary to exorcise and drive it out "by suitable incantations. In this day of science and of engineering, things still incomprehensibly go wrong in the metallurgist's work shop. The metallurgist is even now not unwilling to lay the blame for many such experiences at the door of something which intellectually- much resembles an evil spirit, "gas in the metal." The presence of gases in his metal, he knows, occasions him many very definite troubles which he can clearly distinguish and diagnose-why may it not be also responsible for those which he cannot so well understand?

Jan 1, 1931

By Ellsworth Daggett

The ore smelted in the Winnamuck furnace during the year 1872 consisted, for the most part, of oxidized ores from the Winnamuck mine, only sixty tons of outside ore (from the Spanish mine) having been smelted. The latter, like the principal Winnamuck ore, was oxidized or so-called carbonate ore. There was mixed with these oxidized ores three hundred to four hundred tons, or 7 to 10 per cent. of galena, some of which was mined with the oxidized ore, while a part was mined separately from the lower portion of the mine, and afterwards mixed with the ore, with a view of preventing the formation of deposits of metallic iron in the furnaces. The average assay in silver of all the ore handled was 51.46 oz. per ton, most of it existing as chloride of silver. The lead contents were 34.98 per cent,, all, or nearly all, in the form of carbonate of lead. The relative amount of silver is not at all constant, the best silver ore often being poorest in lead. The predominant gangue was silica, several determinations of which have been made on representative samples, yielding in three such samples 26, 38, and 58 per cent. silica, the latter test being ore containing but little lead. The average contents in silica are about 35 per cent., with 6 to 7 per cent. sesquioxide of iron, and small quantities of alumina and lime. Mechanically, the ore was very fine, and so thoroughly disintegrated that it presented few distinguishing characteristics, rendering sorting or separating of ore from waste difficult, and often impracticable. Experiments on a small scale have been tried, with a view to separate the silica by washing; but these were unsuccessful, as the finest slime, requiring a long time to settle in still water, contained a large amount of silver; and on a careful sizing and washing of the sands and coarser parts, the silver contents were found to be less dependent upon specific gravity