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By John Griffen

The modern anthracite breaker or washery uses almost exclusively a wet method of preparation, which requires, roughly, 1 gal. of water per minute per ton of production per day. The entire anthracite industry uses about 320,000 gal. per min. of water for this purpose or 800,000 tons of water per day. As this water leaves the breakers, it contains fine solids—coal, slate, pyrite, and clay—and is then called silt or slush; as slush is the term most commonly used, it will be employed throughout this paper. The solid content of the slush will be referred to as solids. In the earlier days of anthracite mining, little coal was washed, less crushing was employed, and virgin coal was mined exclusively. As a result, the slush problem was not acute because of the relatively small quantity and the coarseness of the solids. Such slush as was produced could usually be easily impounded and retained or could be discharged into streams without any appreciable pollution being apparent. The character of the fine waste from the breakers changed materially as its quantity increased until now about 40,000 tons of slush solids are produced daily. Second mining and robbing operations materially increased the quantity of fine solids delivered to the breaker in the mine car. The demand for chestnut, stove and egg sizes, to the exclusion of grate, steamboat, and lump sizes, requires finer crushing of the mine-run coal with a consequent increase of fine solids in slush. The use of rice and barley sizes removed a considerable tonnage of coarser solids from the slush but left great quantities of fine solids difficult to retain completely, and to store, and long considered of no possible fuel value. Despite the efforts of the coal operators, the slush solids have found their way into the streams causing, in some cases, serious pollution. The Water Supply Commission of Pennsylvania published, in 1916, a report on Culm in the Streams of the Anthracite Region,' from which the following is taken: About 40,000,000,000 gal. of water carrying 10,000,000 tons of fine culm are discharged into the water-courses direct, flushed into the mines, or disposed of by various means on the surface. The extent to which the very small sizes of anthracite have been deposited in the rivers draining the coal fields is made evident by the fact that over a quarter of a million tons are recovered annually from the river beds by coal-washing operations.

Jan 1, 1922

By R. R. Knuckey

HAVING been associated with the operation of the de Vooys process for coal, which has treated 13,000,000 tons per annum, and recognizing the process as of value in ore sorting, Huntington, Heberlein and Co. Ltd. (Great Britain) in 1936 made an examination of all other existing methods. In none of the pioneer applications had recognition been given to the necessity for maintaining certain conditions that are essential for sorting certain ores if a truly efficient separation by gravity alone is to be assured. Consequently, in 1936-1937 Huntington, Heberlein and Co. Ltd., with Pearson, employing certain ideas connected with the de Vooys application, commenced the development of a separator that would allow conformance with optimum conditions in the zone where separation is effected. Later, Holt and Wade added to the value of the original application by Wuensch, Rakowsky and others, whose conceptions are being successfully operated today. Meantime, Trostler had enhanced the value of the original H-H. process by improvements that are now embodied in operating plants, and today the process incorporates an improved apparatus and a stable medium that produce the optimum conditions for separation. These conditions are: 1. Elimination of disturbing currents in the separating zone; 2. Reduction to a minimum of medium-density differences throughout. the separating zone; 3. Stable medium of minimum viscosity to permit the unretarded fall of mineralized particles; 4. Removal of products of separation with minimum disturbance to the separating zone. DESIGN OF SEPARATOR The H-H. sink-and-float separator consists of a pyramidal tank in which the separation actually takes place, connected at the bottom with an inclined bucket elevator. The tank and the elevator are filled with medium to within a few inches of the top of the tank. Medium is fed into the separator at a variety of points, according to the type of ore being treated, and it is withdrawn from the separator at two points: (1) together with the float product, by means of a variable-speed paddle, at the surface of the medium, and (2) by flowing over an adjustable weir cut in the side of the elevator casing. The prepared ore is fed onto the surface of the medium. The intermediate paddles, which revolve at a slow speed of 2 to 5 r.p.m., move the floating ore across the bath from feed end to float-discharge end. The ore, which is heavier than the medium, sinks below the sweep of the paddles and reaches the boot of the bucket elevator, which discharges it without disturbance of the separating zone. These arrangements for withdrawing medium from the separator allow the use of minimum flows, which connote minimum

Jan 1, 1943

By M. C. Flemings, F. R. Mollard

Conditions necessary for plane front growth of two-piwse solids from a single-phase melt are discussed. Alloys consideved are those from a simple binary system containing a eutectic, but are not, in general, of eutectic cornposition. It is concluded that: 1) plane front solzdification is favored by low growth rate, steep thermal gradient, and essential absence of convection; and 2) for steady-state solidification, the structure should resemble that of directionally solidified eutectics (lamellar, rodlike). Factors affecting THERE are many materials, including metals, available today with strengths in excess of 10' psi when in whisker or fiber form. The challenge facing those interested in practical application of such materials has been, and remains, the economic production and incorporation of the whiskers or fibers into useful engineering composites. solute redistribution along the growth direction are described quantitatively, by numerical solution of the diffusion equation. Effects of variations in growtlz rate on average composition of the solidifying composite are significant. For alloys not too close to a single-phase region, the initial transient at constant gvowth velocity is the order of D/R where D is diffusion coefficient in the liquid and R is interface velocity. Composites consisting of the reinforcing phase within a metallic matrix have excited particular interest in recent years because of their potential for high strength at elevated temperature and for resistance to brittle fracture. Techniques employed to incorporate the whiskers or fibers in the metallic phase have included 1) liquid metal infiltration, 2) solid or liquid phase sintering, and 3) direct growth of composites from the melt, of rodlike or lamellar morphology, by directional solidification of eutectic alloys. Two recent books"2 have reviewed the status of this growing field. Concerning the last method, growth of eutectics, it has been shown that the reinforcing phase (e.g., rods)

Jan 1, 1968

By T. C. King

AT the new Graham-Central Mill of Eagle-Picher, near Galena, Ill., material is simultaneously dewatered and introduced into the ball-mill scoop boxes by the use of variable-speed, 24-in. spiral classifiers. This arrangement has proved satisfactory in that the moisture content of the wet feed is reduced, thus allowing maintenance of density within the mills, and a constant feed at any desired rate to the mills is provided. In this mill the primary feed is wet crushed to minus 1/2 in. and preconcentrated by jigs to produce a bulk lead-zinc-iron concentrate and a waste tailing. The jig concentrate is then dewatered by a conventional dewatering classifier and stored in bins ahead of the ball mills. Even though this material is well dewatered, the discharge at the bin bottom is sloppy because of the gradual drainage of the water from the surface of the particles. Conventional belt feeders with vertical cutoff gates are unsatisfactory because of the flushing characteristic of the wet sand.

Jan 9, 1950

By Charles Pack

DIE castings may be defined as metal castings made by forcing molten metal, under pressure, into a metallic mold or die. It is necessary to keep this definition in mind to avoid confusing this process with other permanent-mold casting processes. The fundamental principles of the process have been known and practised many years. The simplest application is embodied in the modern linotype machine in which molten metal (usually tin-lead alloy) is forced under pressure into a metallic mold. The pressure is derived from a piston and cylinder immersed in the molten metal. Progress in the art of die casting may conveniently be divided into threee groups: Machine for imparting pressure to the metal, material for the die or mold, casting alloys. CASTING MACHINES The problem of delivering molten metal under pressure into a die is comparatively simple, when dealing with low-fusing-point alloys, as the alloys of lead and tin, but it is much more complicated when dealing with metals of higher fusing points, such as the alloys of zinc, aluminum, and copper. Although the art of die casting is comparatively new and, to a large extent, unknown, the records of the patent office are replete with patents on the subject. Fig. 1 shows the Underwood machine patented in 1902; this is probably one of the first machines designed for the production of commercial die castings. The relation of this machine to the linotype casting machine is clearly. apparent. A cylinder and piston are immersed in the molten metal, the application of power to this piston forcing the molten metal, under pressure, into the mold or die. The Doehler machine, Fig. 2, patented in 1907, is based on the same general principles. This machine is used to a large extent at the present time, throughout the United States, for the production of zinc, tin, and lead alloy die castings.

Jan 2, 1919

By M. H. Forester, John D. Cooner

ALTHOUGH the unmined anthracite will last for approximately A 150 years, most of the thicker and cleaner coal beds have been almost entirely first-mined and pretty well robbed, leaving much of the present and future production to come from thin and dirtier beds. Herewith is a section of one of the dirty beds being mined in the Wyoming region This section shows that 45.8 per cent of the bed is made up of impurities and that the 45 in. of coal in the bed is in five benches, the thickest of which is 19 inches. In some localities of the anthracite region there are 14 beds of minable coal. Orderly and proper mining of the coal makes it necessary to rob or second-mine-almost all beds have already been first-mined-in sequence from the top downward. Therefore the robbing of the few remaining portions of the thicker and cleaner beds is in many instances being held up by the mining of the overlying thin and dirtier coal beds. Impurities Impurities consist of fire clay, slate, rock, and bone. The latter, which is black, contains 40 to 60 per cent carbon and often resembles good coal. In some beds there are also bands of "blue" coal, which, as the name implies, is of a bluish slaty color. Although much of this "blue" coal has a carban content almost as high as the good anthracite, it is not

Jan 1, 1943

By D. T. Farnham

The shale used at the Renton plant of the Denny-Renton Clay and Coal Co. for the manufacture of vitrified paving brick occurs in a hill rising from 200 to 300 ft. above the level of the valley in which the plant is situated.

Jan 1, 1915

By M. W. Cox, V. F. Hollister

EXPLORATION for metallic mineral deposits is carried on by those special adaptations of methods which the explorer believes will yield most economically or satisfactorily the particular answer sought. In this project the usual methods of geologic observation, recording, and interpretation, when combined with magnetic geophysical methods and geochemical soil sampling, led to disclosures of appreciable zinc mineralization where none was visible in surface exposure. Since 1945 considerable work has been done with geochemical prospecting methods, chiefly in determining the presence and distribution of various elements existing in minor amounts in rocks, soil, vegetation or waters of mineralized areas. Such work, in which the U. S. Geological Survey has taken the lead, finds a ready place in the field repertoire of the exploration geologist as a supplement, not a substitute, for other methods. The Chollet project was carried out in 1951 by the American Smelting & Refining Co. near its Van Stone mine in northern Stevens County, Wash., in the area shown in Fig. 1. The Van Stone mine is located in the Onion Creek drainage of the Selkirk Mountains, midway between the towns of Colville and Northport, Wash., and some twenty airline miles west of the Metaline mining district. Its zinc-lead orebodies, currently yielding about 1000 tpd of ore, occur as bedding replacement deposits in the middle Cambrian Metaline formation near an intrusive granodiorite contact. The target of exploration at the Chollet prospect was a similar geologic environment along the intrusive contact about 5 miles west of the mine. Geographic Setting The Chollet ground covers a north-facing slope at 3000 to 4000-ft elevation. Second-growth jack pine and tamarack with some hemlock and yellow pine make a thick forest cover. A heavy under-forest of alder, willow, and lesser shrubs occupies the draws, see Fig. 2. Grassy slopes appear at higher elevations. The lower slopes are underlain by a thick blanket of glacial till and alluvium so that outcrops are scarce; however, perhaps 50 pct rock exposure prevails at higher elevations. This part of northern Washington annually receives about 25 in. of precipitation, which largely falls as snow in the winter months. Summers are dry with occasional rainy periods. General Geology The Van Stone mine and the Chollet prospect lie along the southern margin of a westerly extending lobe of the Kaniksu batholith, one of the series of granodioritic masses that are intrusive into Cretaceous and older rocks in northern Washington and southern British Columbia. The margin is composed of complexly deformed Paleozoic sediments ranging in age from the lower Cambrian Maitlen phyllite on the east, through middle Cambrian Metaline formation (limestone and dolomite), to Ordovician Ledbetter slate on the west. In general the formations strike N10 to 50E and dip steeply northwestward, although dip reversals and minor folding occur. This general rock distribution is shown on Fig. 3. In this area the Metaline formation, which is the host rock for mineralization, appears to be of about 4000-ft thickness that can be conveniently divided into the same three units defined by Park and Cannon' for the Metaline area. The basal part consists of 1000 ft of interbedded white limestone, argillaceous limestone, and gray silty argillite. The middle part, approximately 1500 ft thick, consists of fine-grained black, gray, and white dolomite. This unit also contains minor interbedded limestone. The upper part is a gray massive limestone about 1500 ft thick that grades upward into slaty limestone and slate capped locally by a thin black jas-peroidal dolomite which is either the uppermost member of the Metaline formation or the basal member of the overlying Ledbetter (Ordovician)

Jan 1, 1956

By J. H. Wright

Longhole sublevel stopes excavate ore with which the production geologist has only remote contact; therefore, predicting grade and tonnage from such a stope can be a problem. However, the longholes themselves yield data that can be used to improve those predictions. Here, a radial distribution method of weighting sample data is discussed, which is useful in forecasting grade and tonnage from certain longhole sublevel stopes.

Jan 1, 1985

By Charles M. Rolker

THIS remarkable and well-known district lies about 320 miles south of Salt Lake City, in Washington County, near the Arizona border of the territory. It is now reached by the Utah Southern Railroad and its extension, and the last 100 miles are run by stages. These vehicles are called "jerkies" in the West, which name conveys a good idea of the comfort they afford, and the relief experienced when you alight. Arriving at Silver Reef, the main camp of the district, one sees at once that he stands where once a surging sea had its domain, marked now by heavy sandstone deposits of a red and white color. The town itself, a neat, clean, and orderly mining town, is encircled on the north by traohyte and granite mountains, skirting to the west. They are cut through in places by deep gorges, left us as the only trace of the force of former currents, which drained the adjoining territory to the north; and which when swelled and infuriated by tempests and cloud-bursts, took in their grasp the huge blocks of

Jan 1, 1881

By R. G. Stickney

INTRODUCTION The Basalt Waste Isolation Project, conducted by Rockwell Hanford Operations under contract to the U.S. Department of Energy, is assessing the feasibility of the disposal of commercial radioactive spent fuel/high-level waste in deep geologic formations in basalts beneath and within the Hanford Site in southeastern Washington State. The Basalt Waste Isolation Project mission is to identify and characterize a potential geologic repository site in basalt and to develop associated facilities and technology required for the potential permanent isolation of radioactive wastes in basalt formations. In support of the Basalt Waste Isolation Project, a laboratory testing program was conducted to evaluate the performance of the Council for Scientific and Industrial Research's "Doorstopper" biaxial strain cell. To support site characterization studies and the design of repository openings, in situ stress measurements will be conducted within the reference repository horizon (~970 m). The Doorstopper is one of the instruments being considered for use in these measurements. It was selected because it requires only a small volume of work to achieve stress relief, which is important in a closely jointed basalt. Also, test durations are short, permitting a large number of measurements to be made within a given time to increase confidence in the results. Within the reference repository horizon, temperatures are expected in the range of 40º to 60°C with a humidity of up to 100%. For this testing program, test conditions were selected to closely resemble those expected within the repository horizon. The Doorstopper test, mainly developed by Leeman (1964), is a strain rosette relief method of measuring rock stress in situ. The Doorstopper consists of a four element, 45º strain gage rosette

Jan 1, 1984

By Mario L. Villa

Oil activities and the petroleum industry in general have suffered severely in this country as a result of present war conditions. War has imposed a very heavy and unpleasant burden on the shoulders of those whose duty it is to keep .Argentina supplied with the necessary oil to meet industry's growing demands. Since 1940, imports of manufactured products from Europe and the United States have fallen to a minimum, making it necessary to manufacture as many of them as possible locally. This has brought about the establishment of many new industries and the enlargement of already existing plants, creating new demands for fuel that drain heavily the country's stocks, which already were overtaxed because of the diminished supply imported. To cope with this problem, a plan for an intensification of oil-field activities was drawn up by Yacimientos Petroliferos Fiscales (Argentine Government Oil Fields) which included the drilling of many new

Jan 1, 1943

By Mario L. Villa

Oil activities and the petroleum industry in general have suffered severely in this country as a result of present war conditions. War has imposed a very heavy and unpleasant burden on the shoulders of those whose duty it is to keep .Argentina supplied with the necessary oil to meet industry's growing demands. Since 1940, imports of manufactured products from Europe and the United States have fallen to a minimum, making it necessary to manufacture as many of them as possible locally. This has brought about the establishment of many new industries and the enlargement of already existing plants, creating new demands for fuel that drain heavily the country's stocks, which already were overtaxed because of the diminished supply imported. To cope with this problem, a plan for an intensification of oil-field activities was drawn up by Yacimientos Petroliferos Fiscales (Argentine Government Oil Fields) which included the drilling of many new

Jan 1, 1943

WHAT DOES "MAGNETIC" MEAN? The word magnetic has several meanings. When used, as it usually is, without qualification one is often unable to tell which meaning is intended. 1. A body is magnetic which has power to attract iron magnetically. Such is a lodestone or magnet, either permanent or not. This is an active sense or meaning in that the body itself does the attracting or is .magnetic. 2. A body is magnetic which may be made to attract iron magnetically, as the iron core of an electro-magnet when not magnetized by the current. This is a potentially active meaning, the body being capable of becoming a magnet. 3. A body is magnetic which has the property of being. attracted by a magnet magnetically. Such are iron, cobalt, nickel, magnetic oxide of iron, magnetic alloys, etc. This is a passive meaning, the attracting being done by the actively magnetic body. With these three meanings to choose from, one must usually make a guess based on previous knowledge as to which is the right one. Would it

Jan 5, 1914

By Eugene Coste

In a recent paper' I took exception to the opening paragraph of Mr. Hill's paper, in which he says:— " In endeavoring to interpret the geological occurrence of oil, the geologist is confronted by the fact that science has not yet solved the problem of its origin, which lies at the root of the subject.... For the present we must consider oil as a material in the rocks, the origin of which is still unexplained." I take this occasion to repeat my objection to the above statement, as well as to the similar statement of Mr. C. W. Hayes and William Kennedy in their recent bulletin2 on the same oilfields :—" The origin of petroleum is one of the most obscure problems by which geologists are confronted." I do not hesitate to say that these statements, which claim we know so little to-day of the origin of petroleum, are not warranted in the present state of geological science, and that, on the contrary, geology can to-day most clearly prove the origin of oil to be inorganic and the result of solfataric volcanic emanations. It has been so long assumed that oil or bitumen is due to the decomposition of the organic remains of the sedimentary rocks, that the words organic and bituminous are used synonymously and, accordingly, without attempt at explanation, the origin of oil is in every case ascribed to some bituminous-shale horizon, more or less full of organic matter. Such falla

Jan 1, 1905

By Adrien Berton

FOR nearly a century, the Corocoro deposit has been renowned among geologists from the fact that it shares with the Lake Superior deposits of the United States the distinction of being the only important copper districts where native copper is worked commercially. The Corocoro district, named after the city of Corocoro, the capital of the Province of Pacajes (Department of La Paz, Bolivia) is situated towards the western edge of the Bolivian high plateau, at an altitude of a little over 13,000 ft. The most interesting part of the district is that immediately surrounding the city of Corocoro, at a distance, by railway, of 65 miles from La Paz and 210 miles to the Chilean port of Arica on the Pacific Coast. The climate of the region is that of the semi-desert, dry and relatively cold, with big differences of temperature between day and night. The rainy season begins in December and ends in March. The cupriferous lodes of Corocoro have not attracted as much interest as the silver mines of Potosi but they have been known for a long time. In the precolonial period the Indians were using the charquis, or natural native copper sheets, to make small brass objects, and the beautiful pale green brochantite of the outcrops as a source of green pigments. During the colonial period, the oxidized ores of the outcrops were worked for copper, which was used by the mint at Potosi for making currency. The native copper ores were neglected because the Spanish miners were at a loss how to concentrate and smelt them. About 1830, work by rudimentary processes, which were improved little by little, was begun on the native copper ores. The total production of native copper in the following hundred years amounted to 100,000 tons. This native copper, which was remarkably pure, was much appreciated on the European markets before the introduction of electrolytic copper. It was useful for making special ornamental brass or bronze and the granular concentrates of native copper, called barrilla, containing 80 to 85 per cent copper were suitable for making copper sulfate by direct oxidation and subsequent leaching with sulfuric acid.

Jan 1, 1936

By H. M. Bannerman

IN the past few years the mineral raw materials problem has risen from comparatively obscurity to great national significance. The transition has come so rapidly that the nature of the problem and what it portends have not yet been clearly defined. Consequently there are wide differences of opinion among the experts as to what can, or should be done to insure a continuing, adequate supply. On one hand, it is said that depletion of known domestic deposits and lagging discovery of new ones will bring about an imminent decline in mineral production and that in future U. S. mineral-using industries will have to depend on foreign sources for more and more of the major mineral raw materials. On the other hand, it is argued that domestic mineral resources are virtually inexhaustible if there were only legislation against competition from low-cost foreign producers. Still another school of thought contends that within the past decade the country has entered a period of unprecedented mineral discovery that is rapidly solving the problem of depletion. Only time will tell which of these widely divergent views is nearer the truth, for mineral resources are, after all, the result of research and adaptation, and resources of the future, as of the past, will depend largely on human response to circumstances. Of 18 substances now termed reactive metals, only 8 (boron, thorium, potassium, sodium, lithium, uranium, molybdenum, and tungsten) were considered of commercial significance at the turn of the century. Except for hafnium and rhenium, the other ten were well known to chemists and mineralogists before this, but none had found use commercially, whereas some, like titanium, were looked upon as nuisances in the ores of other metals. Of these ten elements, several were considered of minor commercial significance, and others were of little more than academic interest as recently as 15 years ago. Before World War II only a few of the better informed spoke of uranium or thorium as possible sources of power. Still fewer talked of converting boron into a super- fuel, and the time had not yet arrived when hafnium, rhenium and even zirconium were thought of as critical to U. S. welfare and safety.

Jan 10, 1957

By A. Rosenzweig, M. M. Karnowsky

The generalized binary diagram of the Au-Sn-Pb system is presented. The chief characteristic is the pseudobinary between lead and AuSn. On the high-gold side of the pseudobinary, four reaction isotherms were found at 363°, 274°, 225°, and 204°C. On the low-gold side of the pseudobinary, three reaction isotherms at 277°, 205°, and 176°C were found. A vertical section from the eutectic solder composition to gold was developed from the isothermal sections generated. METALLURGICAL problems arising from the intentional or accidental formation of Au-Sn-Pb alloys in soldering applications have indicated a need for information on the phase equilibria in this ternary system. The literature indicates that a complete diagram presenting this information has not been prepared. Even the recent excellent work by prince' entitled "The Au-Pb-Sn Ternary System" actually extends only to the AuSn or 50 at. pct Au range. There are more events in the 50 to 100 at. pct Au than in the less than 50 at. pct range. This article by Prince furnished much guidance in preparing this report. Initial efforts with the isopleth from the eutectic solder composition 61.9 wt pct Sn-38.1 wt pct Pb and 0 to 90 wt pct Au indicated that extensions of the work to the whole of the diagram (even if in less detail) were necessary to understand this system. In undertaking the construction of such a diagram, this study used differential thermal analyses (DTA) and metallography with verification and identification of phases by electron microprobe analyses. EXPERIMENTAL PROCEDURE The procedure began with the development of a cell which would be unreactive with lead, tin, and gold, retain its strength to 1100°C, exclude oxygen, and also furnish a suitable well for insertion and protection of a thermocouple to monitor temperature changes in the material. Such a cell would make it possible to reuse the sample should a repetition of determination be desired. Fig. 1 is a photograph of two such quartz cells as finally developed. The specimens have been run many times. The cell is made up of an inner sample bucket and an outer capsule with a thermocouple well which the sample surrounds. The DTA unit was an assembly devised from available instrumentation. The sample holder was a 3-in.-long cylinder of nickel, 2 1/2 in. in diam, fitted securely in a vertical tube furnace. Two holes 7/8 in. in diam were symmetrically located to receive the quartz cells. A dummy cell with nickel powder was used as the reference. The absolute temperature was recorded with a Pt/Pt 10-pct Rh thermocouple with an automatic Kaye ice bath compensator. (Calibration indicated the compensator to be accurate to better than ±0.5° over the 100° to 1000°C range.) The absolute temperature was measured in the sample and recorded on an L&N mul-tirange recorder with a full-scale display of 1 mv and automatic ranging of 99 mv. The differential signal between the sample temperature and the reference temperature was amplified with an L&N microvolt amplifier and recorded on an L&N Speedomax G recorder. Since two charts were obtained, the chart speeds were equalized and each event was noted on the differential chart, and the temperature at that time was obtained from the temperature record.

Jan 1, 1969

By Jose Luis de Valle Alonso

Although present electrolytic zinc manufacturing processes are aimed at the direct wet process recovery of the metal, and, with this end in view, several industrial scale patents have been applied for during the last few years, the object of this paper is to enhance the possible metallurgical interest in the conventional recovery of zinc and other metals from leaching residues. Therefore, its main end is the description and discussion of the recovery process of zinc, lead and cadmium from leaching residues. Fundamentally, the process consists of the following: Flotation processing to recover the non-roasted blende still contained in the residues. Pyrometallurgical processing of flotation tails in low-shaft furnaces (kilns) and open-flame rotating furnaces and the ensuing recovery of zinc, lead and cadmium as a mixture of their oxides through volatilization.

Jan 1, 1970

THE compiler, or author, of the Probierbücblein is not known, and the date of its first printing is uncertain. It was obviously not written by an assayer who wished to give a coherent description of his craft for the instruction of others; this was left for Biringuccio first to do. It is easy to believe that originally the Probierbücblein was a random collection from various sources of information useful to an assayer, probably gathered by one of the profession for his own use. It must remain a matter of speculation whether this was shown to a printer, who recognized the opportunity to turn an honest penny and made an inept attempt to give the manuscript the appearance of a coherent account by writing a preface and arranging the various items in somewhat logical sequence, or whether the assayer him- self started this job and was prevented from finishing it. That some sections of the book, especially near the be ginning, present an almost continuous story, while others are chaotic in their arrangement; that several paragraphs are printed more than once in different places; that there are paragraph headings, for which the text was never written, or lost, followed by irrelevant information-all this seems evidence of a job unfinished and points to a publisher's offering for the public's quick money. The demand must have been brisk, for metal working was a profitable profession, and the jeweler who was working with metals but did not care to become completely trained in assay methods would jump at the chance of acquiring easy knowledge. Even the great Agricola has whole sections obviously plagiarized from the Probierbücblein. Neither Biringuccio nor Ercker shows any direct influence, though they and all subsequent metallurgists will in some degree be affected by

Jan 1, 1949