Search Documents

By S. A. Hoenig

In an earlier publication, the application of exoelectron technology to the monitoring of dry grinding in a ball mill was reported. Recently, the author has investigated the ball mill problem in more detail with the system shown in [Fig.1]. Here, some of the current generated in the ore-ball-water mixture was picked up by the metal chains and served as a measure of the rate of grinding. While the mechanism of current generation has not been completely clarified, a parallel study of electrical effects associated with rock drilling indicated that the major driving force is the zeta potential*, while oxidation of the freshly fractured material provides the remainder of the current. Both of these effects are sensitive to the exposed surface area, and it might be expected that the observed currents would provide a measure of the grinding rate. This "surface area" effect allows the measurement system to be used in any type of rock or ore grinding. Some studies with sulfide copper ore indicate higher currents than those observed with silica sand, but the overall pattern of current versus grinding rate is essentially the same. Experimental Studies The experimental system was set up as shown in [Fig. 1]. The initial studies were done with silica sand because of its availability and for comparison with the data of reference 1. The sand was sized to an average of 425 /MI (40 mesh); a typical charge consisted of 2.5 kg (5.5 lb) of sand, 0.85 L (0.22 gal) of tap water and 2.5 kg (5.5 lb) of iron grinding balls 25.5 mm (1 in.) in diameter. For a typical "run," the mill was loaded with a fresh charge of ore and operated for periods ranging from 10-60 min. During this time, the current was measured with a Keithley 417 picoammeter and a chart recorder. At the end of the grinding period, the charge was removed and sieved to recover the 425, 300, and 212 µm (40, 50, and 70 mesh) fractions which were then drained and weighed. A fresh charge was used for each test and every attempt was made to keep the draining and weighing processes uniform.

Jan 1, 1985

The Ashanti mine is located in the Gold Coast region of West Africa in Ghana, where gold is found over a wide area of about 105,000 sq km (40,000 sq miles). Ashanti has been the most productive of all the lode mines and has been one of the world's notable gold producers for over 50 years. The mine is located at Obuasi, 113 km (70 miles) north and east of Tarkwa, which is 80 km (50 miles) inland from the coast. The Ashanti lode is worked on 300 m (1,000 ft) of strike length over a width of 12 m (40 ft), and by 1934 it had attained a depth of 700 m (2, 300 ft). The lode is in pre-Cambrian granite intruding a system- of shists, phyllites, etc., containing fragments of the wall rock with quartz, carbonates, sericite and small amounts of pyrite, arsenopyrite, sphalerite, galena, and gold. The shattered quartz fractures carry sulfides and gold, most of which are invisible. (William Harvey Emmons, "Gold Deposits of the World," McGraw -Hill, 1937.) Because the mill treats an ore composed of refractory sulfides - chiefly arsenopyrite and fine free gold - the flowsheet reflects the complex ore characteristics. Plane tables are used in the grinding, circuit for free gold recovery. After roasting the sulfide flotation concentrates, additional free gold is recovered from the calcines with a rotary belt concentrator and the two concentrates are combined for feed to the amalgamation pans, with the resulting gold amalgam being retorted. Following four-stage crushing to minus 9. 5 mm (318 in.) with two stages of grinding, the cyclone overflow is floated for sulfide recovery. The flotation concentrate is roasted with the calcine reground and roughly cyanided to scalp out the gold readily dissolved in one of two cyanidation circuits. The cyanide residue joins the thickened flotation tailing for cyanidation in a complete CCD circuit using filters. The gold precipitates are calcined before melting in pot-type furnaces. The tonnage to the mill of 3,175 mtpd (3,500 s tpd) with a content of over 14.7 g per mt (0.43 oz per st) places the Ashanti production as one of the top producers in the world; and with its past long life, the total production rates it as one of the world's great mines.

Jan 1, 1981

By O. H. Hahn

I have lately had occasion to conduct a campaign at the works of the Empire City Company, in Railroad District, Elko County, Nevada, which, if not highly satisfactory, was at least very interesting in a technical point of view, and which I therefore think worthy of communication to the Institute. The lead ores in this district occur in lenticular masses along and near the contact of crystalline limestone with a dioritic porphyry, and consist of argentiferous carbonate of lead and galena, the latter occurring in solid blocks, or in ribbons running through the limestone. Associated with these are silicate, carbonate, and suboxide of copper, and brown and calc-spar. Adding to this, that the proportion of galena in the ore is small, and that no iron pyrites exists in the district, it is at once evident that the ore-mixture is difficult to treat. For a successful reduction by smelting, it would be necessary to introduce into the charge: 1. The proper quantities of sillphur-bearing ingredients, to effect a complete separation of copper and lead; and, 2. Sufficient silica and iron oxide, to form with the lime and magnesia of the ore, a slag of the required fluidity. The first condition could be fulfilled only very imperfectly, there being no iron pyrites in Railroad, nor in the surrounding districts. The nearest occurrence is in Battle Mountain, whence a supply could not be procured in time. The second condition, i. e., the addition of iron ore and quartz, was easily complied with, there being an abundance of these materials in the vicinity. The furnace of the Empire City Company, is a small shaftfurnace, with an area of hearth of six square feet, and is supplied with blast by a NO. 4 Root blower. In spite of this small size the furnace smelted during this campaign, which lasted 31 days, an average of 28 tons of ore, and 13 tons of fluxes, together 41 tons of charge, per twenty-four hours. The following tables give the complete data in regard to the smelting process, and the results obtained:

By Gilbert P. Moore

The production of petroleum in Argentina during 1932 was greater than in any preceding year. The total amount produced was 13,012,-756 bbl. This figure represents a decided increase in the production of oil in Argentina and can be attributed largely to the increased activities of the Royal Dutch operations at Kilometer 27 in the Comodoro Rivadavia district and those of the Standard Oil Co. of Argentina in the Salta region. Production from the Royal Dutch wells amounted to considerably more than 10,000 bbl. per day over quite a long period during the year. Of the 13,012,756 bbl. of oil produced during 1932, the Government Agency (Y. P. F.) was responsible for some 5,578,954 bbl., while 7,433,-802 bbl. were produced by private companies. Although in 1930 the Y. P. F. produced about 55 per cent of the total production and in 1930 50 per cent of the total, in 1932 its production had fallen to about 42 1/2 per cent of the total. This decrease in the proportion produced by the Y. P. F. was not due to a decrease in its production but to the decided increase in the production of private companies, particularly those two whose names are given above. One new discovery was recorded during the year. This was a well drilled by the Y. P. F. at Cacheuta in the province of Mendoza which came in pumping 80 bbl. of 15" gravity oil from a depth of 673 meters. This well was completed at approximately the same time that the provincial government of Mendoza granted a concession to the Y. P. F. and declared the whole province as a reserve in which no concessions may be granted for a period of 10 years. Under these conditions, the federally operated Y. P. F. will have no competition in the Cacheuta area from private companies such as they have in the other three fields of the republic. The Y. P. F. wildcat west of Comodoro Rivadavia at Pampa Maria Santissima on the Rio Senguerr was completed as a dry hole during 1932. This we11 was reported as a producer in 1930 by persons returning to this country from Argentina but it appears that they had been misinformed. The site of this test has been abandoned and a new location made north of the Rio Senguerr.

Jan 1, 1933

By V. R. Garfias

A survey of the resources of mineral fuels, coal, petroleum and natural gas presupposes a clear distinction between the known amount underground and the "proven reserves"; the'portion that can be economically brought to the surface and made available for utilization. Only a fraction of the coal and petroleum in producing fields is or can be economically brought to the surface and not all of this is economically utilized; also, although practically all the natural gas can be economically recovered and utilized, in actual practice a large part of the total volume that reaches the mouth of the wells is wantonly blown into the air and wasted. It is thus estimated that of the total amount of coal underground about 40 per cent remains unrecovered, or is otherwise wasted, before it reaches the consumer; that only some 25 per cent of the petroleum in proven fields is actually brought to the surface; and that even if practically the entire volume of natural gas can be economically utilized, in actual practice close to 25 per cent of the total produced is now absolutely wasted. And the dissipation of this gas, unwarranted as it is, not only diminishes the gas supply but diminishes also the proven reserves of petroleum from such fields as the Panhandle of Texas, where petroleum and natural gas are produced simultaneously. Many factors affect the estimates of the proven reserves of mineral fuels, such as the capacity and nature of the reservoir, its depth, the quality of the product, the efficiency of recovery, the price of the fuel and its byproducts, etc., etc., but superseding at times all of these in connection with petroleum and natural gas deposits is the effect of "subsoil ownership" on the rate and methods of exploitation of the deposits. As a result it should be a comparatively simple matter to eliminate waste and overproduction, and thereby increase the proven reserves of petroleum and natural gas, in Russia, Iran and Iraq, where the subsoil rights are nationalized, or in any country in which there is or can be quickly established an effective legal control of the underground deposits and the manner of their exploitation. It has been and it is now, on the other hand, almost an impossible undertaking to intelligently regulate the petroleum and natural gas production in the United

Jan 1, 1935

By R. V. Ramani, G. W. Luxbacher

The approach proposed in this paper is, as stated by the authors, an update of methods well discussed in the literature. The authors are to be congratulated for their excellent effort in quantifying a difficult problem with realistic cost data. Economic analysis of the components of a mine ventilation system is complicated by both the dynamic nature of the system and the uncertainty as to the time when system changes occur. We wish to address three specific areas of this paper which require further consideration: shaft designed air capacity, shaft location, and economic criteria used within the analysis. With regard to ventilation shaft size optimization, the system complexities are illustrated in the quantity flow through the shaft. Obviously, the capacity chosen by the designer is a static parameter while the utilized capacity is usually a dynamic variable over the life of the shaft. The designed capacity may be used for a short or a long period, and this may occur during the beginning, middle, or near the end of the shaft life, leading to different operating costs at different times. Operating costs, as shown by the authors' Eq. 8 are more dependent on air quantity than any other single factor (quantity cubed as compared with other factors to the single power); hence, extreme accuracy in the assessment of some of the other factors discussed by the authors may be secondary to the quantity estimation. Incorporation of a variable usage factor for air quantity over the life of the shaft in this optimization problem deserves some consideration. Although the authors have chosen to examine optimum ventilation shaft sizing, it must be remembered that optimization of the whole system-is the primary objective of any optimization process; unit optimization of such items as shafts may not complement the overall process. We have discussed this subject in some detail in another paper in this Transactions volume (Luxbacher and Ramani, 1979). While the recommended process by Wang, et al. can be used in shaft sizing, the shaft operating conditions (pressure head and air quantity) are intertwined with the shaft location within the mine infrastructure:

Jan 1, 1980

By Enrique Touceda

As in the case of steel and the non-ferrous alloys in general, the use of the microscope in connection with the manufacture of malleable cast iron has proved of inestimable value to the industry. Had its use not been invoked, many facts either would not be known at all or, if suspected, would be confined to the realms of conjecture. No fairer statement could be made than that the start of real progress in the industry was coincident with the application of metallography to the product, though the full significance of this statement can hardly be appreciated except by those who not only are conversant with conditions as they existed at the time referred to, but are familiar with the character of works' practice at the present time.. A few years ago, about the only test made to ascertain the physical properties of the product, except in the case of certain plants, was the bending of a casting to destruction, not only with the object of discovering whether or not the metal was ductile, but for the purpose of inspecting the fracture. The characteristics of the fracture, if correctly interpreted, were known to be of value in locating the trouble in castings that were inferior. In general, it was found that if a casting of medium or heavy section would bend through a wide angle before failure took place, the fracture in the majority of cases would have a black velvety appearance; while if it was held at different angles to the direction of the rays of light, it would show a change of color and an iridescent sheen. But an inferior air-furnace heat or anneal might yield castings which, if thin and consequently largely decarburized, could be bent double on themselves and still not possess the fracture described. If, on the other hand, a casting broke short, its fracture might have one of a great many different color and structural peculiarities. Depending on the cause of the trouble, such castings might have any of the fracture characteristics, of which the following is but a partial list.

Jan 1, 1922

By A. J. Lanza

THE prevention of illness among the employees of the mining industry is especially important in view of the importance of the industry, the unsettled conditions of labor, which emphasize the economic necessity for conservation of labor, and for humanitarian reasons. The burden of chronic illness is altogether unwarranted and unnecessary. If the industry is to maintain its labor supply in an efficient manner and keep the standard high, it is essential that it make every effort to keep its labor in good physical condition. The basic principles underlying health conservation are the same for any industry, but they are here applied especially to the mining industry, and more particularly, perhaps, to metal mining, as it is with this phase of the industry that the writer is most familiar, and as it is conceded that metal mining presents more health hazards than coal mining. The first step in the prevention of illness lies in securing employees who are in sound health and free from organic disease. I do not mean that all men who go underground should be physically perfect, but they should be free from organic defects of the heart, lungs, and other organs, or from anatomical defects that would- markedly increase their liability to accident. The number of men working underground in mines in this country whose physical, condition totally unfits them for such work presents-a situation that should not be allowed to continue, and which I believe is 'not equalled in any other, industry in the country. There is but one way to secure men who come up to the required standard, . and that is by a thorough physical examination before employment. I am fully aware of the objections felt toward such a procedure by many employers and employees. There is much to he said on both sides, but to any one who is at all familiar with the mining industry as it is today in this country, and who approaches the matter with an unbiased mind, there can be absolutely no doubt as to the necessity for physical examination. As a purely logical proposition this is self-evident, but there remains the further necessity of placing physical examinations on such a

Jan 2, 1919

By Fred T. Greene

(San Francisco Meeting, September, 1915) MOST of. the recent discussion of the mineral land law published in the Transactions is in the abstract-an exception being Mr. Goodale's paper, The Apex Law in the Drumlummon Controversy,1 which illustrates in concrete instances many of the practical disadvantages of what Dr. Raymond has. called "The Law of the Apex." The present paper, it is hoped, may serve a similar purpose, emphasizing the necessity for a change in our mining laws, and bringing home to mining engineers some of the defects and dangers of our present code. There are many storm centers of "apex litigation" in the Rocky Mountains; and not the least of them is the Wardner camp, where such litigation has been almost continuous since 1892, and the end is not yet. In their decisions, the courts have accepted the claims of the litigants that the " Wardner vein" is a broad zone varying from 250 to 500 ft. in width at the surface. This is the simplest theory which could have been advanced, and probably decreased, rather than augmented, the number of contests; in fact, every one of the claim owners seemed to feel that the greatest advantage would accrue to him if this theory were adhered to. The dominant structural feature of the Wardner vein is a persistent fault, striking N. 40° W., clipping about 40° to the southwest and called the "Wardner foot wall." Fig. 1 is a composite of two adjacent cross-sections of the vein and is a fair representation of the relative size and shape of the orebodies and their relation to the "Wardner foot wall." The country rock is a comparatively thin-bedded sericitic quartzite which has an average strike of N. 80° W. and clips at high angles to the north and south.

Jan 5, 1915

By Frank A. Wardlaw

My subject covers the effect that recent metallurgy has had on operations at the Utah-Delaware mine. This mine is the old Highland Boy mine of Bingham Canyon, Utah, one that has now been in operation for about 30 years. It was first operated by Messrs. Weir and Newhouse as a gold mine, under direction of the Highland Boy Gold Mining Co. The ore was oxidized gold ore and it was treated on the property in a cyanida-tion plant. During the process of development, sulfide ore was found assaying about 5 per cent. copper. It proved to be the discovery of what is yet the largest sulfide copper orebody in the State. The first shipment was made in December, 1896. A smelter was built in Salt Lake Valley to treat this ore and not long after the property was sold to the Utah Consolidated Mining Co. From 1900 to 1924, the mine was a large producer of direct-smelting ore which averaged for many years 4.5 per cent. copper, then later dropped to 2 per cent. copper. During the years 1912 to 1920, direet-smelting lead ore was also mined. In 1918 and 1919 ore developments at depth showed a decided increase in silica content and a porphyry sill so closely associated with the ore that it was impossible to mine the ore clean and it was found necessary to build a copper flotation concentrator at Tooele. The mill had a capacity of 1000 tons a day and made a recovery of 90 per cent., and would have been responsible for a continuance of profitable operations had it not been for a slump in the copper market and the necessary high cost of mining ore on the lower levels. Results of Selective Flotation In 1924 the mine was on the point of a shutadown which had all the earmarks of being permanent; it was being operated at a heavy loss and preparations were made to pull the pumps and salvage the machinery. The plant at Tooele was remodelled for selective flotation by the International Smelting Co. in order to treat custom ores, and incidentally to clean up a possible 10,000 tons of lead-zinc ore which it was thought possible to get in the Utah-Delaware before shutting the mine down. Results were so encouraging that an effort was made to develop more lead-

Jan 1, 1928

By C. A. Hartnagel, D. H. Newland

Detailed production statistics listing the operations according to producing sands, districts, etc., are not available for New York State and are scarcely obtainable without extraordinary effort and expense, hardly warranted by the current rate of developments. The oil industry is practically stabilized, so far as exploration for new sources of supply are concerned; no new pools have been tapped in the last 25 or 30 years. There is little prospect of extending the boundary of the oil fields beyond their present limits, though possibly some additional reserves may be found below the present productive sands. Natural gas, on the other hand, is not restricted to such confined areas. Drilling for gas has been fairly active, under the stimulation of some important finds in formations that previously were overlooked. The year's field operations will be covered somewhat fully. Oil production, which has been steadily advancing for a number of years, showed a further moderate gain in 1936. The output for 11 months (figures for December are not yet available) was 4,217,000 bbl., indicating a total for the year of around 4,600,000 bbl. The increase was about 10 per cent, a rate maintained for some time. Prices were more satisfactory than in the preceding five years, with an advance to $2.57 a barrel before the year's close. New York State yield is all paraffin-base, in the same class with high-grade Pennsylvania oil. Most of the output is now obtained by the water drive, which has given a new lease of life to the fields and promises to bring the total to about 200,000,000 bbl. before the known acreage has been exhausted by this method. Before its introduction the annual production was under 1,000,000 bbl. a year. The fields cover an aggrcgate area of 55,000 acres, with some 17,000 wells in operation. Development Exploring for natural gas in New York in 1936 outside of the old established pools continued actively, as in the previous year. There was an increase in total initial production. Operations were conducted in nine counties of the central and western parts of the state, and 43 wells

Jan 1, 1937

By J. A. Herrick

SOME time ago the writer needed a cheap, light, and portable hydraulic lift or crane, that would be universal in its application, and that might -be suspended from crane-arms, overhead tramways, beams, etc., and serve all the uses of ordinary hydraulic cranes. This was accomplished by the use of a closed cylinder of wrought-iron hydraulic pipe, provided at its top with the ordinary gland and stuffing-box, through the centre of which passed another similar pipe of slightly smaller diameter, forming in effect the ordinary plunger of the regular hydraulic crane. Over the top of this centre pipe or plunger or piston a disk of iron is placed with two arms projecting several inches from the rim, as may be required. Through these arms long iron rods pass, one on each. side, and are fastened in place by nuts screwed to a bearing immediately above and below the disk. These rods also pass through the enlarged head of the lift down through a casting which closes the bottom of the cylinder, which, at the same time, gives them a bearing, and they terminate at a point below the casting equal to the height of the lift of the crane. The rods at this point pass through a disk similar to the top disk and are similarly secured in place. A common hook arranged with a swivel passes through the centre of the disk, and on this hook the load is suspended. For a stationary hanging crane the apparatus is suspended by two rods passing through the head of the lift in similar manner to the two already described, at right angles to the first, and of sufficient length to let the first set play between them and rise to the full height which the plunger will allow. The second set of rods terminates in an iron disk similar to the one at the bottom of the first set, and a hook through this in turn suspends the entire apparatus. In order to adapt the lift to an overhead tramway, single or double, in place of the suspending rods, a projection or offset is arranged on each side of the head of the lift and a journal cast in, allowing the lift to be suspended on pivots arranged as follows

Jan 1, 1879

By W. A. Weimer

Australia, the land of the kangaroo, koala, and the platypus, is often referred to as "down under" by people of the Northern Hemisphere. It is a tropical land and has very little freezing and thawing; consequently the in-place rocks are near the surface, exposing some of the unaltered mineralization. This type of geology induces the prospector and miner to search for minerals which lie at his feet (or not far under them), and it is adapted to open cut surface mining. Some of the rules and regulations applicable to exploration and mining in Australia will be interesting and helpful towards understanding acquisitions and control of minerals. They are common and basic to the United Kingdom. Throughout Australia practically all minerals are the property of the Crown (government), and their exploration and exploitation are administered by the state Department of Mines. Surface owners, or land lessees, do not control the minerals. Their mining codes protect the prospector. If a prospector obtains a permit, "miner's right," it entitles him to search for minerals any place within the state, only holding him responsible for damages he may incur in his exploration. If he finds something of interest, he may then apply for an authority to prospect, which gives greater latitude and protection in his work to develop the find. However, he will be obligated to spend a minimum specified amount to exclusively hold an area. He will be required to furnish maps, analyses, and geological data to the Mines Department. Presuming that he has located something economically valuable for mining, he may then apply for a mining lease or be granted a franchise to produce a specific material. It will contain a quantity clause so that the area cannot be held indiscriminately without production of the mineral. The states have Bureaus of Mineral Resources, Geology, and Geophysics that keep constantly abreast of the search for minerals and often do much of the drilling and deep boring to promote geological study for the states.

Jan 1, 1969

By Byron W. Cheever

While engaged in experimenting with the usual methods for estimating phosphorus in iron and steel, it occurred to me that potassium chlorate might be used to oxidize the carbon, and thus avoid the tedious and vexatious evaporations necessary for successfully carrying out the usual methods. After many trials, the following plan was adopted : Take, for analysis, of Bessemer or other low-carbon steels, from 3 to 5 grammes; of crucible steel, 10 grammes; of pig-iron, 1 to 5 grammes, according to the percentage of phosphorus supposed to be present. Of iron, high in phosphorus (1 per cent.), take 1 gramme. Place in a No. 4 evaporating dish the amount of iron or steel decided upon, cover with a funnel which will just fit inside the dish, and then add gradually HNO3, (1.20 specific gravity), using 12 C.C. of acid for each gramme of steel or iron taken. (A larger quantity of acid will be required for small samples.) When the full amount of acid has been added, and the violent action has ceased, place the evaporating dish on a sand-bath, add 10 C.C. HNO3, (1.40 specific gravity), and boil till the bulk of the solution is reduced about onehalf. Then add 10 C.C. HNO3, (1.40 specific gravity), continue the boiling, and add from time to time, during the next 15 minutes, small portions of pulverized KCIO3, till about 2 grammes have been added. (If the solution shows signs of going dry, more strong acid must be added.) This will precipitate the manganese, with some iron. Sometimes it happens that the manganese does not come down readily, and more KCIO3, or further concentration, or both, will be required. The process is not complete till the manganese is precipitated, which may be known by the appearance of a dark, mirror-like deposit on the dish, at the edge of the solution. Boil the solution 5 minutes after the last addition of KCIO3, and then add cautiously (to prevent sudden explosions) 5 C.C. strong HCl. This will dissolve the precipitated manganese and iron. Continue the boiling till the chlorine is all expelled, adding from

Jan 1, 1885

By James Munroe

APPALLING as has been the loss of life in the last 51 months, there is one slight compensation : no longer will there be in the world a cripple, in the old meaning of the term. Men handicapped by wounds or disease, there will be, unfortunately, and in numbers beyond what the world has known since the wars of Napoleon; but neither they nor the industries from which they were called off to war will be "crippled" in the sense in which both would have been had mankind not learned the lesson of conservation and come to understand that the most important field for such conservation is not in the forests and' the mines but among men and women. From the beginning of the Great War, France, Great Britain, Belgium, and most of the other Allies have studied the problem of restoring the soldiers and sailors injured through war to physical and economic efficiency; and from their experiences, especially from that of Canada, the United States has learned much. Consequently, our task of preparing for the return of our disabled men has been easier and, in some ways, more comprehensive than theirs. Complex as are the details of the machinery which the United States has set in motion to take care of the men injured by wounds or disease, the plan itself is simple. Taught by European experience, the Surgeon-General of the Army and the Bureau of Medicine and Surgery of the Navy have provided, on both sides of the Atlantic, every known surgical and medical facility for restoring the injured or diseased man to a physical condition as nearly normal as possible. While in the hospital in France or England, on the transport coming to America, and in the hospital here, the disabled man is incited in every way to believe in his future efficiency, to want to be a normal worker, to desire to retake his place in that society of workers from which he went, temporarily, to do the greater work of preserving civilization. Furthermore, since purposeful occupation is now regarded as an essential form of, treatment with most men in the hospital, especially in the convalescing stage, many of these men will have been actually started on the road to earning before they are discharged from the army surgeon's care.

Jan 1, 1919

By Wilbur A. Nelson

All of our accounts say that the discovery of copper ore at Duck-town, Tenn., was made in August, 1843, yet it would appear that samples of copper from this district were found by DeSoto, when he wandered into southern Tennessee, in 1539, in his four years of exploration through the Southern States. The following quotation is taken from his diary: "Towards the north there was a province named Chisca; and that there was a melting of copper, and of another metall of the same colour, save that it was finer, and of a farre more perfect colour, and farre better to the sight, and that they used it not so much, because it was softer. And the selfe same thing was told the governor in Cutifa-Chiqui, where we saw some little hatchets of copper, which were said to have a mixture of gold. But in that part of the country it was not well peopled; and they said there were mountains, which the horses could not passe; and for that cause, the governor would not goe from Cutifa-Chiqui directly quicker." DeSoto sent two of his company to try to find these mines, but after five days' wandering through the mountains they returned, stating that their guides had become lost. Although the Ducktown area may have been known to the ancient Indians, the copper deposits were actually discovered in August, 1843, when a Mr. Lemmons, while panning for gold on Potato Creek, in the Ducktown basin, found some reddish-brown decomposed rock. His disgust on finding that this yellow metal was not gold was so great that he did not try to develop his find. In March, 1847, B. C. Dugger erected an iron forge at this same place, but was unable to work the iron as it contained so much copper that on cooling it would break to pieces. The finding of copper in the iron ore by Mr. Dugger led to further explorations; and in April, of the same year, A. J. Weaver, who was passing through that country, told the people that the black rocks they had dug out were rich copper ore. Mr. Weaver began the

Jan 1, 1925

By R. Ward Grosz

The Robinson mining district in east-central Nevada is itself a century of study in the changing economics of the mining business. It began as a boom and bust area. In the district today, just west of Ely, Nev., the hills are pockmarked with the tunnels and shafts sunk in a frantic scramble for gold and silver before the turn of the century. But as the economics of dwindling reserves, rising costs, and changing markets were stamping out the efforts of the gold and silver seekers, copper took over as the king of the Robinson district. Today, Kennecott Copper Corp. has four open pit mines in the district and is planning a fifth. From these mines, Kennecott produces nearly 40,000 tpy (tons per year) of copper. In its hundred years of history, the district has produced more than $1 billion in mineral values, a richer treasure than that from the more famed Comstock Lode of Virginia City, Nev. Prospectors had reported copper outcroppings in the Robinson district as early as 1872. But the first significant copper orebody was not discovered until 1901. In that year, Dave Bartley and Edwin Gray exposed the top of the porphyry orebody that would become the Ruth mine in a shaft at a depth of 120 ft. Subsequently, other larger orebodies were discovered nearby which have resulted in this area being one of the leading copper producers in the country for some 60 years. Following a period of development and exploration, the Ruth mine started production in 1915 and continued as a prosperous underground mining operation until 1948. The mining industry in Nevada experienced the same increasing cost of labor and supplies that all other mining areas had to contend with, and by 1948 the Ruth mine was no longer profitable. The mine was closed down on August 8 of that year. Now, two decades later, the mine is to produce again. The key factor in the case history of

Jan 1, 1969

By C. Schlumberger, M. Schlumberger

The object of this paper is to clarify the idea, so important when exploring by potential methods, of the depth of investigation attainable by electrical measurements. After defining, with some precision, .the term "depth of investigation'' in geophysics, the authors show how it is possible to regulate this depth in potential methods and to obtain an 'electrical drilling" from surface observations. They consider also the difficulties encountered in deep measurements and indicate how it is possible to reach greater depths than those having an industrial interest. Depth of Investigation The term, depth of investigation, in its general sense, is easily understood. For instance, a driller who can pull cores from a depth of 2000 m. is capable of working, with accuracy, to that depth. By means of a properly placed drill, he may locate an orebody at a depth of 1999 m., however small this orebody may be. On the contrary, the term as used in geophysics requires precise elaboration. As a matter of fact, no geophysical method, irrespective of the physical property studied (density, magnetic permeability, conductivity), can discover a very small body at a great depth because, in practice, the physical parameter upon which such a geophysical method is based is never regular enough, throughout the ground, to distinguish the feeble anomaly caused by the small, deep-lying body from the numerous anomalies due to irregularities of the encasing terrains. Aside from this question of the ratio between the size of the body being hunted for and its depth of burial, a second factor plays its role in the possible depth of investigation; that is the difference, for the parameter under consideration, between the body and its surrounding material. The greater this difference, and the more homogeneous the encasing terrains, the greater is the possible depth of investigation. This being generally established for all geophysical methods, it is possible to distinguish two main classes of these methods, from this same point of view

Jan 1, 1932

By George Otis Smith

The Secretary of the Interior in his recent report to the President has defined the new public-land policy, which is in fact "but a new application of an old policy." His words may be more acceptable on this subject of land classification than the repetition of phrases which have served some of us for several years. Secretary Lane says of the past: 1'Congress has always been most generous as to the disposition of the national lands.... There was land for all, and it was the government's glad function to distribute it and let those profit who could.... And this generous donor was not so petty as to discriminate between kinds of lands, the uses to which they could be put, or the purposes which those might have who got them. Land is land, save when it contains minerals; this was roughly the broad principle adopted. To classify was a task too difficult or not worth while. The lands would classify themselves when they arrived in individual ownership. And so the door was opened for monopoly and for fraud." Of the reaction and the evolution of a new policy, the Secretary con. tinues: • ' " A reaction was inevitable. If lands were to be withdrawn from public service, why might not the government do the withdrawing itself? The old philosophy that land is land' was evidently unfitted to a country where land is sometimes timber and sometimes coal; indeed, where land may mean water—water for tens of thousands of needy neighboring acres. For the lands of the West differ as men do, in character and condition and degree of usefulness. We had not recognized this fact when we said 'land is land.' Lands fitted for dry farming and lands that must forever lie unused without irrigation; lands that are worthless save for their timber; lands that are rich in grasses and lands that are poor in grasses; lands underlain with the non-precious minerals essential to industry or agriculture; lands that are invaluable for reservoir or dam sites— these varieties may be multiplied, and each new variety emphasizes the fact that each kind of land has its own future and affords its own opportunity for contributing to the nation's wealth.

Jan 1, 1915

By Carl Keuffel

THE manufacture of optical glass is a new industry in this country. In 1914, after the war started, the supply of optical glass from Europe was cut off, but as there was a fairly large stock of glass on hand, it was not until the end of 1915 that the optical instrument makers made serious efforts to produce their own glass. These early attempts were generally made by practical glass men and, due primarily to the fact that very little scientific help was used, the first attempts were unsuccessful. It was not until the whole problem was attacked by technically trained men who used advanced methods of research that good results were obtained. These researches proved that the accurate control of the temperature was a most important factor in the manufacture of optical glass. The early glass maker judged temperatures with his eyes; later, Seger cones were introduced into the furnace at various stages of the melt. Then radiation, indicating and recording pyrometers with rare-metal thermocouples were introduced. Now, in addition to these, an optical pyrometer every hour or so is sighted right into the pot and on the molten glass. Figs. 1 and 2 show how pyrometers are used to control the melt. InFig. 2, Y is the clay pot in which the batch is melted to glass within the furnace X. The rare-metal thermocouple S, protected by a clay tube, extends through the wall and about 4 in. into the furnace. This couple is connected to an indicator T and a recorder U so that a complete record of the furnace temperatures is obtained. The section of the curve ABCD, Fig. 1, shows how gradually and carefully the clay pot must be heated to get rid of moisture AB and during the calcining at CD. The stem of an expansion pyrometer R is extended through a hole in the door Z of the furnace and into the pot in order to more closely follow the temperatures of the clay pot itself during the burning process, that is from A to D. After the pot is calcined, the temperature can be rapidly raised to E (about 1430° C.); from E to F this temperature is much higher

Jan 9, 1919