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By C. M. Signer, W. P. Hewitt

THIS is a story of a mine discovered in the days of the Conquistadores but that remained unimportant until the second decade of this century. Without the usual legendary history of romance and fabulous riches it has become famous for the development of unexpected metals and unusual problems. These developments and experiences, exciting and interesting as any legend, are the substance of the San Antonio mine of the Santa Eulalia district in northern Mexico. Originally opened for its silver-lead content, it developed a tin deposit of singular economic importance and unique geologic interest, a vanadium orebody that for a few years placed it among the leading vanadium producers of the world, and now lead and zinc sulphide ores. It has been the seem of a disastrous flood that brought deep-sea divers into Mexico's desert mountains and raised important problems regarding ground water, demanding unusual measures. Geology and operating questions relating to the above matters will be discussed and much of it is recent history which has become a part of Mexican mining lore. History Dates Back to 1325 Santa Eulalia is the oldest of American cities, founded in 1325 by the Aztecs under the name of Tenochtitlan and devastated in 1521 by Cortes and his rapacious band of iron-willed adventurers. Their lust for gold burned through the Aztec empire and onward into most of North America. Santa Eulalia was in the path of conquest. In 1591 the district's first ore discovery was made near what is now the San Antonio mine. The ores carried no gold and the silver-lead content was unattractive to the early pioneers. Not until 1700 was real mining activity undertaken.

Jan 1, 1952

By C. H. North, L. E. Lynd, W. W. Anderson, H. Sicurdson

Since the composition and structure of the beach sand concentrates correspond so closely to what would be expected of ilmenites that have been altered by oxidation and leaching, there is no reason to postulate the existence of the hypothetical compound, arizonite, to account for the composition of titaniferous beach sand concentrates. The four concentrates studied are examples of the different products that can result from various degrees of alteration of primary ilmenite. CONSIDERABLE uncertainty is revealed in the literature regarding the nature of the titanium minerals which make up the bulk of the heavy, opaque fractions of numerous beach sand deposits of the world. An investigation was made, therefore, of beach sand concentrates of North Carolina, Florida, Brazil, and India. Magnetic concentration, X-ray, and microscope data were obtained which show that these concentrates consist essentially of ilmenite and its alteration products. The alteration, brought about by oxidation and leaching of iron values, has resulted in upgrading the ores to a range of 56 to 64 pct TiO², as compared with 52.7 pct in ilmenite of theoretical composition. Conclusions drawn regarding the nature of the dominant titanium-bearing mineral in beach sand deposits have been based mainly on chemical composition, specific gravity, and petrography. This material has usually been referred to as ilmenite or weathered ilrnenite.: It has also been referred to as arizonite because in chemical composition it resembles an Occurrence in in which was described by Palmer' in 1909. The chemical composition of Palmer's arizonite corresponded closely to the formula Fe²O³ . 3TiOs. From approximate measurements of crystal angles on a large imperfect crystal with rounded faces, the

Jan 1, 1955

By D. L. Katz

The critical phenomena have been studied during the past century but our knowledge of the critical temperatures and pressures of complex hydrocarbon mixtures still is very limited. The critical temperatures and pressures of pure substances have been examined in large num-bers,20 and in great detail.11,17 No experimental determinations of the critical phenomena have been reported on such complex hydrocarbon systems as a reservoir fluid. The critical temperature is defined by Taylor18 as follows: "there is some temperature for each gas above which the gas cannot be liquefied. This temperature is called the critical temperature." The critical pres-sure of a pure substance is the vapor pressure at the critical temperature. It should be noted that these definitions refer to a given substance in the pure state and do not mean that the pure substance cannot be liquefied in the presence of a second constituent. The normal procedure for obtaining the critical temperature of a substance is to heat it in a glass tube 1,20 under pressure until the meniscus between the liquid and vapor phase disappears, although other methods, especially for mixtures, have been used. 11,14 However, when considering oil and gas reservoirs, it is more enlightening to consider a critical phe-nomenon that occurs when a mixture of oil and gas are compressed at a reservoir temperature until the meniscus disappears because the two phases become equal in composition. This conception, along with erroneous applications of the definition of the critical phenomena of a pure substance to that pure substance when it is part of a complex mixture, has caused confusion even among persons familiar with the classical theories.

Jan 1, 1938

By C. H. G. Bushell

The author maintains that selectivity in flotation depends in part on differences in rates of flotation. The rate of flotation should be directly proportional to the frequency of particle-bubble collisions. In this paper, it is suggested that floatable particles of the mineral must be distinguished from nonfloatable particles. Success in flotation is entirely a matter of selectivity. All minerals can be made to float. The problem is to make one mineral float and leave the others in the tails. For a typical ore, with all minerals naturally hydro-philic, a collector which is adsorbed by only one mineral and not at all by the others would give perfect separations. The hydrophobic, collector-coated mineral would separate cleanly from the remaining minerals. In practice, no such highly specific reagents are known. All standard collectors adsorb on most minerals to some extent, and selectivity then becomes a matter of extent of adsorption rather than adsorption on some minerals and not on others. Flotation is therefore a compromise process: if enough reagent is used to float all the desired mineral, the concentrate will be low grade; conversely, high grade concentrates can be attained only at low recovery. With many minerals coated with collector to varying degrees, selectivity appears to depend in part on each mineral floating at a different rate. The study of flotation kinetics is therefore a basic requirement to quantitative understanding of the process. REVIEW OF PREVIOUS THEORIES Before a particle enters the froth it must strike a bubble and adhere to it. Flotation rate will therefore depend on the number of particle-bubble collisions

Jan 1, 1962

By T. A. Rickard

INTRODUCTORY. THE presentation to the Institute, eight years ago, of the paper of Pošepny on " The Genesis of Ore-Deposits " has borne fruit in much fresh: investigation, as is evidenced, for example, by the group of very valuable papers, by distinguished members" of the United States Geological Survey, read at the Washington meeting-discussions of general principles particularly suggestive to those who are engaged in mining. Pošepny, in the discussion of his famous treatise, said that the present writer seemed to look at every new conception in ore-deposition" from the sole standpoint of its immediate usefulness in mining."* Protesting mildly against " sole " and "immediate," I accept the impeachment. It calls for no defence. THE DEVELOPMENT OF RECENT THEORIES. Given the idea of an underground water-circulation as the chief factor in the deposition of ore, the next step in the inquiry as to the genesis of such deposits is, the endeavor to determine which particular part of the general water-circulation is responsible for the results. Around this question have centered the controversies of a generation, and to these controversies we owe the gradual clarification of our ideas upon the processes of ore-formation. It is unnecessary to sketch here their progress from Werner to Le Conte, who combated in 1883 the extreme views of the lateral-seeretionists, and in 1893 opposed the narrow interpretation of the ascensionist-theory. The generally accepted opinions of to-day are a well-deserved tribute to his philosophic discrimination. Thanks to Prof. Van Hise and Mr. Slichter, whose work he utilizes, we have now arrived at a comprehensive conception

Jan 1, 1902

By Thomas D. West

The occasional reports of progressive furnace-men, giving the results of physical tests to prove the superior qualities of their pig-irons, have encouraged the writer to believe that the time is ripe for the discussion of such work, and the inauguration of some correct system by which the furnace-man and the founder could make intelligent comparison of the elements of strength, deflection, contraction, and chill presented in pigmetal. In most cases the physical tests now made by furnace-men define but one quality in the iron, and are generally too vague to permit any true comparison. For example, one furnaceman tells us he can punch holes in his cast-iron, wishing it to be inferred that the iron is very soft and strong. Another furnace casts a long wedge, the thin end running to a knife's edge, which is supposed to prove the fluidity of the iron, for the founder's benefit. Another casts in square-cornered " chills," to define the hardness or softness of the metal. To the writer's knowledge these tests are not advocated by their originators as suitable for standards; and they are, to his mind, but evidence of unrest on the part of progressive furnace-men, who feel that something should be done in the line of physical tests. The writer knows of no furnace-men who make and keep records of the strength of their iron obtained by means of tests made on recognized standard testing-scales ; but he does know of a prominent furnace-salesman, who, not long ago, came into possession of a 1-inch square bar that stood 1400 pounds

Jan 1, 1897

By H. B. C. Nitze

A description of some of the magnetic ore-deposits in this region should be of interest to the mining and metallurgical public, inasmuch as very little has been said or written concerning them. I refer to the magnetite deposits of Franklin and Henry counties, Va., and of Stokes county, N. C. These deposits remained comparatively unexplored until recently, when the construction of the Roanoke & Southern R. R. through this territory has called attention to them, by furnishing the means of transportation for the ores. It is true that the ores have long been known, at least locally, and were smelted in catalan forges and old-fashioned, cold-blast charcoal-furnaces long before and during the late war. At the present time, however, the old workings are caved in, filled up and over-grown to such an extent that, as a rule, but little can be learned from them. No prospecting of any consequence has been done, and as my time was too limited and the territory to be examined too extensive to permit additional openings of a more satisfactory nature to be made, the incormpleteness of some of the data I have to offer (notably, those referring to the absolute width of the veins) will be pardoned. It will hardly be necessary to say that this ore-bearing formation belongs to the Archaean, or Eozoic age, the usually occurring rocks being schist, shale, gneiss, granite, sandstone and quartzite. The stratigraphy is, as a rule, quite regular (excepting in the Danbury section, Stokes county, N. C.), the general strike being northeast and southwest, and the dip nearly vertical. The country is gently roll-

Jan 1, 1892

By Charles H. Eldridge, Robert J. Anderson

When a metal or alloy is poured into a mold, internal stresses are set up by the cont,raction in volume on passing from the liquid state at the temperature of pouring to the solid state at the ordinary temperature. It is assumed by the writers that all castings are internally stressed. That any casting is internally stressed is shown by its warping or distortion on maturing at the ordinary temperature, by warping or cracking on heating, or by cracking or distortion on machining. In the investigation made by the writers, the internal stresses in cast non-ferrous alloys were studied with a view to examining the effects of heat treatment (i.e., simple anneal) on the release of such stresses. Data have been obtained that show quantitatively that internal stresses can be removed by appropriate heat treatment. The investigation was limited to a study of the effect of heat treatment on stress release in cast rings of the 87:7:5:1 copper-tin-zinc-lead alloy. The writers are indebted to E. G. Fahlman for the method used for inducing stress in cast rings; to M. E. Boyd for microscopic examination and for other aid; and to G. B. Dalrymple for the chemical analyses. General Information While casting stresses have been discussed considerably, they have usually been treated in a general way, and so far as the writers know no measurements of the magnitude of internal stresses in castings have been reported. It has been suggested by many investigators, particularly in the case of steel castings, that castings are internally stressed, and that these stresses can be removed by annealing. In a casting, the internal

Jan 1, 1923

By Robert J. Anderson, Charles H. Eldridge

When a metal or alloy is poured into a mold, internal stresses are set up by the cont,raction in volume on passing from the liquid state at the temperature of pouring to the solid state at the ordinary temperature. It is assumed by the writers that all castings are internally stressed. That any casting is internally stressed is shown by its warping or distortion on maturing at the ordinary temperature, by warping or cracking on heating, or by cracking or distortion on machining. In the investigation made by the writers, the internal stresses in cast non-ferrous alloys were studied with a view to examining the effects of heat treatment (i.e., simple anneal) on the release of such stresses. Data have been obtained that show quantitatively that internal stresses can be removed by appropriate heat treatment. The investigation was limited to a study of the effect of heat treatment on stress release in cast rings of the 87:7:5:1 copper-tin-zinc-lead alloy. The writers are indebted to E. G. Fahlman for the method used for inducing stress in cast rings; to M. E. Boyd for microscopic examination and for other aid; and to G. B. Dalrymple for the chemical analyses. General Information While casting stresses have been discussed considerably, they have usually been treated in a general way, and so far as the writers know no measurements of the magnitude of internal stresses in castings have been reported. It has been suggested by many investigators, particularly in the case of steel castings, that castings are internally stressed, and that these stresses can be removed by annealing. In a casting, the internal

Jan 1, 1923

By J. H. Bechtold, R. Kossowsky

1 HE superplastic behavior of the eutectoid A1-78 wt pct Zn alloy has been thoroughly investigated by Back-ofen et al.' The superplastic elongations and the marked resistance to necking were rationalized in terms of high strain rate sensitivity. In a subsequent paper2 superplastic behavior was formulated to show Nabarro-Herring diffusional creep as rate controlling at low strain rates, giving way to a dislocation climb process at higher strain rates. In a paper devoted to an interpretation of superplasticity in two-phase alloys, Packer and sherby3 have included the results of an examination of the structure of an Al-Zn eutectoid specimen before and after superplastic deformation. No significant change in grain size or directionality was observed in the deformed microstructures. This one observation led the authors3 to suggest that con- tinuous recrystallization or grain boundary migration was responsible for superplasticity. The purpose of this note is to report our observations on the superplastic behavior of the Al-Zn eutectoid alloy which differ in certain respects from works previously reported. Following Hayden et al., the results are discussed in terms of dislocation climb as the important factor during superplastic deformation. A heat of nominally high (99.995) purity 22 wt pct A1-78 wt pct Zn was induction-melted and cast into a 0.5 by 6 by 12 in. slab. The slab was heated to 350°C and rolled to 1/8-in.-thick plate. The plate was then cold-rolled to 0.040-in. thickness, annealed at 35OaC, and rolled to the final thickness of 0.020 in.* Speci-

Jan 1, 1969

By C Gunther

Ore deposits are commonly divided into two classes, syngenetic and epigenetic, according to whether the ore was deposited together with the enclosing rock or was introduced after its deposition or solidification. Epigenetic deposits, which are by far the more important class, owe their formation to the channels that permitted the ingress of their metals, and both classes are subject to great modification by post-mineral changes in the containing rocks. A discussion of the structural features of rocks, therefore, necessarily precedes any consideration of ore deposits or processes of ore deposition. The arrangement of sediments in parallel and approximately horizontal layers is called stratification, and is an original prop¬erty of sedimentary rocks. Successive strata of the same sedimentary bed commonly differ from each other in some minor characteristic, such as texture or color, which results in a bedded or stratified appearance. The subjection of a rock to pressure develops within it parallel planes of weakness, called cleavage planes, along which the rock breaks into relatively regular slabs or blocks; the direc¬tion of these cleavage planes, which bear no relation to stratifica¬tion, is determined by the direction of the pressure that produced them. Where there are more than one set of cleavage planes, one of them is likely to be more prominent than the others. In sedimentary rocks, the cleavage may coincide with the stratifica¬tion but more commonly cuts across it. Van Hise has defined cleavage as the "capacity present in some rocks to break in some directions more easily than in others." Cleavage, therefore, does not imply the existence of subdivisions, but rather the tendency to subdivide along certain planes.

Jan 1, 1932

By W. O. Crosby

Washington Camp, in Santa Cruz county, Arizona, is a small and little-known mining-district situated on the lower, eastern slope of the Patagonia mountains, about 20 miles east of Nogales and a like distance south of Patagonia Station on the Sonora railroad, which connects at Benson, 83 miles from Nogales, with the main line of the Southern Pacific. This district is also about 4 miles north of the international boundary, 35 miles west of Bisbee and 40 miles north of Cananea, in Sonora. The topography of the district, which lies at a general elevation of 5,500 ft. above the sea, is only very moderately rugged, and presents no obstacles to mining-operations. Although some of the claims of the camp, including the Pride of the West,, Belmont and Holland, were extensively worked for silver 25 years ago, they passed, at moderate depths, as in so many other districts, out of the argentiferous lead carbonate and sulphide, into zinc, copper and iron sulphides ; and for two decades the camp was abandoned and almost forgotten. In recent years, however, its apparent possibilities as a copper-producer have led to a revival of mining-activity; but not, as yet, with conspicuous success. Although economically relatively unimportant, the deposits of Washington Camp are, mineralogically and structurally, nevertheless, typical examples of ore-bodies developed in connection with the garnet ledge now recognized as a normal feature of granite-limestone contacts; and, in the opinion of the writer, this is an instance where a minor example is yet essentially normal and capable of throwing important light upon the origin and genetic relations of the type.

Jan 1, 1906

By James R. Dunn

The purpose of this chapter is to review the uses of sand and gravel by the construction industry. The specific intention is to give tech¬nical people the general perspective and frame¬work which they need to help in making tech¬nical and business decisions. In the sand and gravel industry such decisions are based on an understanding of sociologic, economic, and technologic factors. In order to discuss the sand and gravel industry intelligently, it is necessary to define sand and gravel. "Sand" as most often used by industry is not sand in an engineering or geo¬logic sense but should be called "natural fine aggregate." The expression "fine aggregate" is preferable to "sand" because fine aggregate in¬cludes grain sizes which, according to engineer¬ing or geologic classifications, are defined as pebble or grit size. Natural fine aggregate is distinguished from manufactured fine aggregate in that the manufactured material is crushed and screened to produce the required sizes and natural fine aggregate is only screened. Coarse aggregate is generally defined as aggregate which will not pass a No. 4 or %o-in. sieve. Coarse aggregate may be natural (gravel) or manufactured (crushed stone, crushed gravel, slag, or coarse lightweight aggregate). Gravel is usually considered sufficiently crushed to qualify as manufactured coarse aggregate when two or more sides are broken. Sand and gravel (crushed or uncrushed) is used in asphaltic and portland cement concretes, is subbase for pavements, as fill where good drainage is needed (such as around structures), and for many other uses. About 96% of all he sand and gravel produced is used in construction.

Jan 1, 1975

By Joseph T. Singewald

AMONG the genetically interesting iron ores of the United States are those of the St. Francis Mountains near Ironton and Iron Mountain, Missouri. They are specular hematite in porphyry. The Iron Mountain and Shepherd Mountain deposits are generally spoken of as veins and those of Pilot Knob, Cedar Hill, and Russell Mountain as bedded deposits. Iron Mountain has produced nearly 4,000,000 tons of ore and Pilot Knob about 1,500,000 tons. The output of the other three localities has been insignificant. Pilot Knob is no longer worked as an iron mine, but the rock is now being crushed for use as road metal. Iron Mountain has continued as an active producer. In 1927, the property was acquired by the M. A. Hanna Co. and an extensive prospecting and exploration campaign was undertaken, so that the ultimate production of Iron Mountain will doubtless greatly exceed the figures mentioned. Previous Theories of Origin Descriptions of the deposits and theories of their origin have been concerned mainly with Iron Mountain and Pilot Knob, which represent the two contrasting types of occurrence. The Iron Mountain deposits have been considered of close magmatic origin by Whitney' in 18.54, Geijer2 in 1915, and Spurr3 in 1927. Whitney referred to them as of eruptive origin. Geijer considered them fissure fillings at magmatic temperatures. Spurr called them vein dikes formed from ore magma which was essentially fluid iron oxide. Schmidt4 in 1872 ascribed them to fissure filling by thermal chalybeate waters of meteoric origin. Nason5 in 1892 advanced essentially the same explanation. One of the best

Jan 1, 1929

By Francis L. Sperry

Up to within a few years, the consumption of nickel has been more directly dependent upon the available supply than that of any of the other useful metals. The Gap mine, in Lancaster county, Pennsylvania,* has been, for the last quarter of a century, the only property in this country furnishing nickel in paying quantities. Its yearly output was about 300,000 pounds of metallic nickel, or nearly half the amount used annually in the United States. Foreign nickel from mines on the New Caledonia islands, in the South Pacific, found entrance into our markets as the production of the Gap mine fell off. The price of nickel was constantly maintained, and no special effort was made to extend its use. Over-production was cautiously guarded against, and all surplus metal was held by the banking-houses of the Rothschilds, who assumed the bonded indebtedness of the Sociètè le Nickel. The opening of the Ontario nickel-mines has, however, brought about a radical change; and nickel from the Sudbury district can be delivered in New York within four days, and in European markets within two weeks, as against two months consumed in transporting South Pacific ores. Former prices have been irretrievably smashed, and European trade-journals comment favorably on the influence which Canadian nickel has had in making lower prices, and breaking the backbone of the " nickel trust." Production and Costs. The quantity of nickel produced and the prices which it commanded may be briefly summarized as follows: The total production of the world from 1840 to 1860 was about 100 to 250 tons yearly of metallic nickel; from 1860 to

Jan 1, 1896

By B. M. Bird

DURING the past four years the experimental work in coal washing carried on by the U. S. Bureau of Mines and the University of Washington has been devoted mainly to the development of special methods for the tabling of fine sizes of coals that are difficult to wash. One important outgrowth of this investigation has been the application of hindered-settling classification to coal tabling. Although used for many years in ore dressing, the term "classification" as used here may be new to many readers. It may be defined as the separation obtained when a bed of particles is held in a uniform state of suspension in an upward current of water, either continuous or pulsating, just sufficiently strong to keep the bed in a mobile condition. A common example of this type of separation is a jig in which there is no suction stroke. When the hindered-settling classifier is used with the coal-washing table, the fine-size raw coal, instead of being fed direct to tables, as is the prevailing practice, is first fed to the classifier and grouped, according to the rate of settling against the upward current of water, into perhaps six separate products. After dewatering, each of these except the sixth, a refuse product, is elevated to a seperate feed bin and washed on a separate table. This paper gives a brief discussion of the basis for the use of hindered-settling classification of a table feed; a description of the experimental work; a comparison of the results obtained with and without classification; and a discussion of the application of the classifier in commercial coal washing.

Jan 1, 1928

By R. B. Moore

Page History................................ 708 What is Radioactivity?........................ 710 Disintegration Series.......................... 711 Radium Ore Deposits......................... 713 Metallurgical Treatment........................ 717 Methods of Ore Concentration..................... 722 Future Supply of Ore......................... 723 Uses of Radium............................ 723 Mesothorium as a Substitute for Radium................. 724 Discussion.............................. 725 Probably no other metal excites as much interest, among both scientific men and the general public, as radium. This is due partly to the high cost of radium salts and partly to the peculiar properties of the element. Since radium-bearing ores were discovered in the United States, the interest of American scientific men has been stimulated and, at the present time, more radium is extracted and refined in this country than in all the rest of the world together. HISTORY The property of radioactivity was discovered, partly by accident, by Henri Becquerel, the French physicist, in 1896. He was experimenting with certain fluorescent substances in order to find, if possible, a connection between fluorescence and the recently discovered X-rays. Among other chemicals which possess the property of fluorescence, he was using salts of uranium. His custom was to expose the fluorescent substance to the action of sunlight and then register the effect of possible penetrating radiation on a photographic plate protected from ordinary light. Bec-querel's experiments gave positive results at once, and he at first believed that he had discovered a relation between fluorescence and X-rays. Later he exposed a plate to a uranium salt which had not been previously exposed to sunlight. To his surprise, on developing this plate, he found that he had obtained the same effect as he had previously secured when

Jan 1, 1919

By Guy Ruggles

IN this paper the authors aim to chronicle the experience and salient points brought out in changing flotation reagents at a concentrator which had probably been using a minimum amount of oil at a minimum cost per ton, to a more complicated system requiring a partial chemical control. The original oils were coal tar and pine oil. The new reagents are line, xanthate and pine oil. It was found that there were no insur-mountable difficulties and eventually the cost of the new reagents per ton of ore proved to be very little more than that of the old. LIME PLANT When the question of handling lime came up there were two propositions open: (1) to handle the lime dry; (2) to handle it wet in the form of an emulsion. Granting that a dry lime feeder would function properly, delivering lime uniformly, the chief objection was the dust that would be raised when these feeders were being charged or operated, as the only possible location was on a gallery beneath which men were working. With this objection the handling of lime as an emulsion seemed to he the better scheme. The lime plant which was first installed was for experimental work on one section. This was gradually changed and developed until it was of sufficient size to accommodate 20 sections. The various changes will not be discussed and the following description deals only with the fully developed plant. Crude as it is, and perhaps somewhat expensive to operate, the lime-handling plant has been quite successful. Much has been learned which will pave the way for a better installation in the future.

Jan 1, 1927

By C. A. Stetefeldt

In May and June, 1885, I was engaged in examining the goldores of Las Minas, in the State of Vera Cruz, Mexico, with a view of finding a cheap and efficient method for extracting the gold. The following minerals could be plainly seen in the ore : magnetite, pyrites of iron, pyrites of' copper, quartz, and garnet. Neither galena nor zinc-hlende mere visible, but the ore contained a trace of lead, and in some samples of ore from the Muertos mine, 1.19 per cent. of zinc mas found. Antimony and arsenic were not present. Native gold could scarcely be seen in specimens of' the ore, and it only appeared—mainly in extremely fine particles—after pulverizing and washing. Magnetite was in every instance the most prominent mineral, its quantity varying between 43 and 67 per cent. Determinations of copper and sulphur showed that from 3.5 to 7 per cent. pyrites of copper, and from 3 to 22 per cent. pyrites of iron were present. The gold-value of the ore varied between 0.3 oz. and 0.8 oz. per ton. I do not speak of specimens, but of average samples of large quantities of ore put through the battery. In ore that had been crushed through a No. 40 screen, the gold appeared, in part, as free gold, the rest being thoroughly mixed with the magnetite and pyrites, both minerals containing about the same percentage of gold. If this free gold was brought in contact with pure quicksilver it (lid not amalgamate readily, even if the quicksilver was charged with sodium amalgam.

Jan 1, 1886

By George J. Young

The nature of slimes handled in the treatment of gold- and silver-ores has been discussed in technical literature to a considerable extent. The subject of slime-filtration from the practical worker's stand-point has also received much comment, arid scattered through the literature of the subject are descriptions of many slime-filtration installations. Articles of this nature serve a valuable purpose and assist materially in the design of new and the improvement of old plants. The subject of the physics of slime-filtration has been touched upon to only a slight extent. The underlying principles are worthy of niore intensive study and experimeritation than they have received, and the main purpose of this paper is to present the results of such study and experimental work as will serve to make clear in part at least many of the principles which control the filtration of slime. Nature of Slime. Much has been written concerning an accurate definition of the term "slime," but no comprehensive definition seems to be gcnerally accepted. The reason for this is clear. A slime consists of at least three different substances, each, when separated, possessing distinctly different physical and to a certain extent chemical properties. These substances are extremely fine sand, a colloidal material which may bc and generally is in a coagulated condition, and a colloidal material which is in a non-coagulated condition. Suspending a slime in a relatively large volume of water by shaking and allowing sedimentation to take place, results in the fine sand settling out with comparative rapidity, followed by the coagulated material, which settles niuch more slowly and finally a certain portion remains

Jan 1, 1912