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By Claudia Gasparrini

Silver occurs in nature in major, minor and variable amounts in a very large variety of minerals and in several mineral species in the same ore. Because these minerals may respond differently to the same flotation or leaching agents, detailed studies to establish the correct silver mineralogy become essential for optimum recoveries in those situations where the silver is treated as a primary product. On the other hand, fine grain sizes, which often affect gold recoveries, are not generally as critical in silver metallurgy, due to the lower market price which allows for more of the element to remain In the tailings before incurring in economical losses.

Jan 1, 1984

By F. W. Bryan, D. H. Lynch

Introduction This paper is a general description of current central Florida phosphate mining, beneficiation, and product transportation. It is directed and believed to be of interest to engineers not familiar with this industry. Deposit: The phosphate deposits of central Florida are generally located in a five county area which includes Polk, Hillsborough, Hardee, Manatee, and DeSota counties. Geologically, the deposit is of marine origin and is identified as the Bone Valley formation. This formation is Pliocene to Recent in geological age and overlies a Miocene limestone formation known as the Hawthorn. The Bone Valley formation sediments are regionally characterized by equal proportions of apatite, quartz, and clay. The clay is predominantly of the mont-morillonite family. On a local scale, however, the proportions of these three major constituents vary considerably. The phosphate occurs as the apatite mineral (Ca 10F2(PO4)(6) and with the clay and sand, the minable ore is commonly referred to as matrix. This matrix is overlain by unconsolidated overburden of sand and sandy clays, ranging in depth from 10 to 45 ft. The matrix usually occurs in fairly horizontal continuous beds from 3 to 25 ft in thickness. The bedded limestone formation lies directly below the matrix and is generally well defined. The phosphate particles range from 3/4 in. to 200 mesh (Tyler) in size. The phosphate particles coarser than 14 mesh are called pebble phosphate and those less than 14 mesh are termed flotation feed which, when beneficiated, subsequently become concentrates. Through mining and beneficiation, phosphate quality is measured in BPL percent which stands for bone phosphate of lime units. In subsequent chemical manufacturing, the quality is indicated by P205 content. The deposit is economically characterized by various ratios such as tons of product per acre and cubic yards handled per ton of product. Magnesium, iron, and aluminum content are also considered in evaluating ore reserves. These elements are often critical to the chemical fertilizer processes. Presently, an ore body is considered economically minable if it meets the criteria shown in [Table 1]. These, of course, are general guidelines and specific costs and returns on investment must be considered in each case for acquiring reserves. On a new grass-root venture, a 20-30 year life is generally expected with a mineral recovery of 80%. History and Uses Phosphate mining in central Florida began around the turn of the century. However, in the early days, only pebble phosphate was produced until about 1930 when technology was available to beneficiate the -14 + 150 mesh particles. The -150 or -200 mesh material was discarded as it is today. The basic processes for beneficiation are washing, scrubbing, desliming, sizing, and flotation. These basic unit processes are essentially the same today although many improvements have been developed since the early days. Phosphate is used primarily in the production of high analysis fertilizer chemicals, typical of which are triple superphosphate, monoammonium phosphate (MAP), and diammonium phosphate (DAP). Phosphate is also used in the production of food preservatives, dyes for cloths, vitamin and mineral capsules, steel hardeners, gasoline and oil additives, toothpaste, shaving creams and soaps, bone china dishes, plastics, optical glass, photographic films, light filaments, water softeners, insecticides, soft drinks, road fill, and livestock feed supplements. Florida produces over 80% of the nation's marketable phosphate rock and one-third of the world production, according to the US Bureau of Mines. This amounted to approximately 35 million tons in 1975. Exports of Florida phosphate rock were to such countries as Canada, Japan, West Germany, Italy, and India, with Canada and Japan being the major users. Almost 95 o of all outbound cargo shipped through the port of Tampa is phosphate rock or related products. Beneficiation Following is a description of Agrico's new Fort Green beneficiation plant which is typical of the newer large capacity plants being built in the field. Agrico's Fort Green mine was completed in 1975 and is located in the southwest corner of Polk County and is directly adjacent to Manatee, Hillsborough, and Hardee Counties. With some minor differences, Fort Green is typical of a modern central Florida plant. The rated capacity is 3,000,000 plus tons of product per year and this varies according to the richness of the ore being handled. A simplified flowsheet is presented in [Figs.1 and 2]. This plant is served by three draglines of the 40-cu-yd class. The phosphate beneficiation is usually divided into three major functional steps: (1) washing and screening to produce a pebble product and flotation feed, (2) feed preparation and (3) flotation to produce concentrates. The typical plant is similarly divided into these three functional areas. Washer: Briefly, the slurried matrix is pumped from two draglines simultaneously at a combined rate of about 20,000 gpm at 2000 tph (solids) to rotary trommel screens sized to make a 7/8-in. separation. ([See Fig. 1]-) The trommel oversize is sent to hammermills where it is crushed and returned to the trommel screens, or pumped to tailings if minor impurities (Fe203, A1203, MgO) are too high. The trommel undersize is pumped to 14 mesh stationary (static) flat screens. The flat screen over¬size is subjected to three stages of 14 mesh vibrating screening and two stages of log washing in order to produce a final pebble product. The pebble product (+ 14 mesh material) is conveyed by belt conveyor to a large on-ground storage pile. Pebble product is reclaimed through a tunnel and loading system below

Jan 1, 1980

By W. A. Hustrulid, N. A. Ross

An analysis of the design of medium to hard rock tunneling machines is presented. The developed equations are used to compare performances and machine requirements using kerf and fixed pick cutters to bore a given rock. With the use of pick cutters, required thrusts can be greatly reduced and still achieve the same boring rate as with present day tooth or kerf cutters. It appears that the cutting coefficient, which for most boring machines is of the order of 0.1, should be increased to one or larger to facilitate rock removal by cutting rather than grinding. The depth of cut and the indexing distance should be greatly increased to make use of inherent rock weakness.

Jan 1, 1971

By J. Nutting, D. H. Kirkwood

IT is clearly of great metallurgical interest to know the conditions of temperature and gas composition under which different products will form in sulphide roasting. A method of graphically presenting the relevant thermodynamic data will be demonstrated, such that these conditions are readily obtainable. The products of sulphide roasting may be oxide, sulphate, or oxysulphates, and the equilibria between these may be represented in the following way: 2 MSO4 = MOMSO4 + SO3 MO-MSO4 = 2 MO + SO3

Jan 1, 1961

By George A. Packard

THE experiments here described were made under my supervision while temporarily acting as head of the Department of Metallurgy at the Missouri School of Mines, at Rolla. The work was done by Messrs. W. E. Brown, W. C. Richards, and F. L. L. Wilson, and the description of the results forms a portion of a thesis presented for the degree of Bachelor of Science. These results are submitted because I have seen no description of the application of pot roasting to the treatment of a copper-concentrate. This work followed that already described in the discussion of the ' Lime-Roasting of a Galena-Concentrate,"' and was similarly occasioned by the lack of a furnace of the reverberatory type in which the copper-concentrates could be smelted. The material for the tests was a mixture of three lots available. The first consisted of 8-mm. jig-concentrates and the second of 0.5 mm. table-concentrates, from the San Juan district, Colo. Both contained pyrite, chalcopyrite and galena. The third was a lot of copper-ore, found in the laboratory, which had been crushed through 8-mm. screen, and had at some previous time, before the laboratory roasting-furnace was torn down, received a partial roasting. The analyses of these ores are given in Table I. In order to determine the applicability of pot-roasting as to each lot of ore, and the effect of varying proportions of lime, six preliminary tests were made in a " size N " Battersea crucible, 9 in. high by 6 in. in diameter at top, with a 5/8 in. hole bored through the bottom. The crucible was set in the upturned elbow of a 2-in. pipe, the joint being luted with clay; and air was obtained from a receiver supplied by a compressor. The

Jan 1, 1908

By G. R. Wilms

A study has been made of the structural changes in polycrystalline high purity aluminum during the tertiary stage of creep under conditions of constant tensile load. It appears that there is no basic modification in the particular mechanism of deformation that characterized the preceding secondary stage of creep, but that the changes in crystalline structure produced during the tertiary stage are only a consequence and not a cause of the accelerated strain. Intercrystalline fissures were observed on entry into the tertiary stage, and these might supplement the accelerated rate of strain owing to local stress concentrations. There is evidence that the formation of these fissures may be associated with the presence of surface imperfections, and it is suggested that a more generalized treatment of the results may explain certain creep characteristics of commercial alloys. IN previous work'-4 a study was made of the changes produced when specimens of annealed aluminum were deformed at various temperatures and rates of strain, especially under conditions leading to creep under constant tensile load. It was shown that, as the temperature was increased or as the rate of strain was decreased, elements of the substructure produced within the grains became coarser, and with the strain rate constant at a given temperature, their size tended to an equilibrium value. The preliminary process of the breaking down of the grains into a substructure was identified with primary creep.' The subsequent equilibrium, condition was associated with secondary creep. The question then arose whether the tertiary stage corresponded to any further significant change in the substructure. The question is also of interest in view of the opinion, expressed for instance by Andrade,5 that the tertiary stage is merely an accelerated rate of strain due to the reduced area of section of a specimen under continuous tensile load, and the other opinion, as suggested by the observation by Sully, Cale, and Willoughby6 of a tertiary stage in com-pressive loading, that this third stage is a real effect in its own right. The object of this paper is to record some observations on the tertiary stage of high purity aluminum. Experimental Procedure The material was aluminum of 99.98 pct purity as previously used. The specimens had a rectangular section of l/8 x l/2 in., and extensions were measured over a 1 in. gage length. After machining to shape, the specimens were annealed to give a standard grain size of 0.2 mm and then electropolished. The general procedure involved metallographic and X-ray diffraction examination at progressive stages of elongation (marked by arrows on the curves shown in Figs. 1 and 2), the specimen being extended to fracture under constant load at a given temperature. The X-ray tests were made by the back-reflection method from a stationary specimen, using CoK radiation. The longer edge of the micrographs in the paper corresponds to the direction of applied stress. Results The previous work showed that, in the secondary stage of creep in aluminum, three basic types of structure could be developed according to the temperature and rate of strain. These were: 1—slip, which predominated at the lower temperatures and higher rates of strain and produced the finest and least perfect substructure; 2—cell structure, which superseded slip as the temperature was raised and the rate of strain decreased and which was characterized by a coarser and more perfect structure and an absence of slip lines; and 3—a stage termed "boundary microflow," which predominated at still higher temperatures and lower rates of strain when the cell size had increased and become comparable

Jan 1, 1955

By R. S. Dean

ALTHOUGH it is obvious that in any flotation process we must have a froth, in recent years the development of collecting reagents has caused the possibilities of better frothing agents to be overlooked. Some investigators have even gone so far as to say that the number of satis-factory frothing agents was sufficient. A little consideration will show, however, that the reagents available in the past were far from ideal frothers. The properties of an ideal frother for flotation work may be set down as follows: 1. It. must form in low concentrations a copious but not too persist-ent froth. 2. It must be insensitive to hydrogen-ion concentration of the pulp; that is, it must froth equally well in an acid or alkaline medium. 3. It must be insensitive to salts, even in high concentration. 4. It must be absolutely noncollecting to both sulfides and nonsulfides. 5. Its frothing properties must not be affected by collecting reagents, including soap, the most generally used nonsulfide collector. 6. It must readily emulsify and disperse any insoluble collecting agent that is likely to be used. Clearly the existing frothers do not qualify. Pine oil, for example, is an acceptable frother for many purposes but if used in soap flotation a delicate balance between pine oil and soap must be struck because, as pointed out by Coghill1, these two reagents are incompatible in certain concentrations. The objections to soap itself as a frother are obvious, and the cresols and their substitution products all have some collecting Dower and very little emulsifying power.

Jan 1, 1935

By L. O. Howard

THE practice of using acid-lined converters at the plant of the Old Dominion Copper Mining & Smelting Co. was discontinued early in January, 1913, and they were replaced by basic-lined converters. The new equipment consists of one electrically operated 12-ft. upright converter stand and two basic-lined shells for same. These shells are provided with twenty-four 1 1/4-in. tuyères. The mouths are 5 ft. in diameter. Owing to the fact that there is no bedding system or other large storage capacity between the mine and the smelter, the furnaces must handle as fast as produced ore and concentrates, which may vary considerably from day to day, both in tonnage and copper content. Consequently the converter is often crowded to its utmost capacity by the frequent fluctuations in the daily matte supply. From the foregoing, it will be seen that in no way can the converter be favored by running light charges or by transferring to it from other stands in operation. Neither can it regularly be allowed to cool between blows, and only occasionally can it be run at as low a temperature as might be wished. No copper precipitate or other foreign material high in copper is available to help out the tonnage. Repairs and alterations or the removal of defective tuyères must wait until such time as a slight falling off in the matte supply-allows the converting operations to ease up. These variable conditions all combine to interfere with the systematic operating of the converter.

Jan 7, 1914

By Zay Jeffries

IMAGINE a spinning sphere of hot matter about 8000 miles in diameter, rushing through space at a velocity measured in miles per second, and you have a rough idea of what our earth is supposed to have been like about two to four billion years ago. By applying all of the science known to man and, more especially, by determining the velocity of earthquake waves at different depths, making comparisons with meteorites, studying densities, compressibility of rocks and the nature of surface rocks, a fairly definite conception of the general constitution of the earth has been obtained.1 The earth is supposed to have a central core rich in iron containing a substantial amount of nickel and small percentages of several other elements. The density of the core is assumed to be about ten times that of water and the diameter about 4200 miles. An intermediate shell of density about 4, and thickness of about 1800 miles, is sup- posed to consist of heavy rocks including sulfides, oxides, and silicates. The outer rock shell, probably about 100 miles thick and with a density around 2.8, is thought to be composed mostly of silicates, becoming in general more siliceous as the earth's surface is approached. NATURE'S SMELTING OPERATION Nature seems to have subjected the earth to a stupendous smelting operation, burying beyond reach much of the metal that man recovers in his smelting practices. We live on the surface of Nature's "slag dump" and must be content, for the near term, to recover for man's

Jan 1, 1953

By Richard H. Sprute, Dennis J. Kelsh

Slow-settling, fine-grained suspensions can often be dewatered and densified by applying direct current between buried electrodes. Although water removal rates and power expenditures depend on physical and chemical properties of the treated slurries, metal mine tailings from Idaho, Colorado, and Mexico have responded well in laboratory testing, as have 29 samples of ultrafine coal waste from mines in nine states. This Bureau of Mines report reviews field tests at two Idaho metal mines and describes the recent installation at the Henderson molybdenum mine near Empire, Colorado, and the treatment of coal sludge at a Clinchfield Coal Co. preparation plant near Dante, Virginia.

Jan 1, 1980

A. L. FIELD, Cleveland, Ohio (written discussion*.-)In equation 2, B is used to denote the ratio of bases (lime plus magnesia ) to acids (alumina plus silica) it being stated that this ratio gives more concordant results than the ratio either of bases to silica, or of lime to silica. I find, however, that, by making use of the ratio between true CaO (CaO by analysis minus sulfur calculated to CaS) to acids, equation 2 may he modified to agree with the observed facts within an average error of 0.0041 per cent. sulfur instead of 0.0045 per cent. The revised equation is s = 0.072 + 0.01835 - 0.00061 (t - 1400) - 0.0403B where B is the ratio of true CaO to Al2O3 Plus Si02, and the other symbols have the same significance as before. I would not appear to stress too much this slightly better agreement of the revised equation with the observed sulfur. Yet I believe that the use of this ratio of true CaO to acids is to be preferred, if for no other reason than the fact that it is more in harmony with the previous findings of the Bureau of Mines with regard to the effect of magnesia and other impurities on slag viscosity.1

Jan 12, 1919

By Paul Pietrokowsky

THE formation of intermediate phases in the solid state reaction of titanium with silicon, germanium. and tin (of subgroup 4B in the periodic table) was the subject of a recent paper.' Further investigation of the system Ti-Sn revealed the presence of a new compound on the titanium-rich side of this phase diagram. Metallographic evidence indicated that this new phase was situated very close to 75 atomic pct Ti. The present work is concerned with the crystal structure of the intermediate phase Ti3Sn. Iodide-process titanium metal, furnished by the New Jersey Zinc Co., was used in this investigation. The metallic tin was received in powder form from Charles Hardy Inc., New York; its purity was 99.80 pct. The titanium rod was machined into small cups 1 cm in diam and about 1.5 cm in height. The tin powder was compacted, melted, and then placed in the titanium cups and alloyed by electric arc melting in a helium atmosphere. The alloys, weighing approximately 8 g, were sealed in evacuated quartz tubes and homogenized at 1030°C for 5 days. This isothermal heat treatment was terminated by a water quench from the soaking temperature. Filings of the alloyed pellets were sealed in evacuated quartz bulbs and quenched from 1030°C into liquid argon. A 14.32 cm Debye Scherrer X-ray camera was used for the powder diffraction study. The copper radiation was filtered. X-ray diffraction data for the compound Ti3Sn are given in Table I. The data were indexed on the basis of a hexagonal lattice. Good agreement between observed and calculated values of the square of the reciprocal interplanar spacings was obtained with the following expression: (1/d)2 = 0.03810 (h2 + hk + k2) + 0.04410 (l2) Unit cell parameters were calculated by the method of least squares from the reflections (20.3), (22.2), (40.1), and (42.1); ao = 5.916 & 0.004A, co = 4.764 ± 0.004A, and co/ao = 0.805. The relatively small size of the unit cell allowed the unambiguous indexing of most of the reflections from planes of large spacing. An inspection of the assigned indices (Table I) reveals the absence of (hk.l) reflections when 1 2n. A systematic absence of this type leads to the space group C 6/mmc or one of its subgroups. Assuming, for a first approximation, a linear increase in the density of titanium with the addition of tin, it follows that there are two stoichiometric molecules of Ti3Sn per unit cell. The density calculated from X-ray measurements is 5.194 g cm-'. At this point it became clear that Ti3Sn might be isomorphous with Mg3Cd. The 6 Ti and 2 Sn atoms were placed in the following positions of space group D4 6h, C 6/mmc: 6Tiin (h): X 2X 1/4; 22;; 1/4;Xx 1/4;x2x3/4; 2x x 3/4; x x 4; with x = 516 2 Sn in (c): 1/3 2/3 1/4; 2/3 1/3 3/4.

Jan 1, 1953

By P. W. Rainier

THE Chivor emerald field is situated on the eastern slope of the Andes in the Department of Boyacá, at an elevation of about 8000 ft. above sea level. It overlooks the Llanos (plains) of the Orinoco and is watered by many streams flowing into the Rio Meta, the Orinoco's largest tributary. The Rio Meta is navigable from the Orinoco to a point within about 50 miles of the Chivor district and may eventually prove to be the reasonable outlet for the future development of this part of the country. The topography of the district is extremely rugged and mountainous (Fig. 1), the difference in elevation between two points on a mining claim 1 km. square being sometimes as much as 4000 ft. The ground is covered with dense forest growth and the available timber is suitable and sufficient for mining purposes, but it is becoming gradually depleted by Indian clearings as the country around the mines becomes settled. The many streams combined with the rough topography give good possi-bilities for hydroelectric power. The center of population nearest to Chivor is Bogota, the capital of the republic and a city of some 300,000 inhabitants; the distance is two and one-half days' travel. The first stage of the journey from Bogota, is accomplished by rail to Chocontá, some 4 hr. travel. From Chocontá the journey is made in the saddle, one night being spent in Guateque. The latter is a small town and the nearest post office to the mines, being some 10 hr. ride distant. The roads are mere bridle paths, in parts hazardous and almost impassable in the wet season. All supplies brought to the mines, other than those produced locally, are carried by pack mule; mule freight from Chocontá costs 3 centavos1 per pound. The climate of the Chivor district is healthful and bracing. The wet season begins in March and concludes in November, the remaining months being dry. The annual precipitation is about 150 in. The temperature throughout the year is nearly constant, varying from about 45° F. to about 65° F. shade temperature. The rains are cold and unpleasant, and for the greater part of each day in the wet season the country is shrouded in dense mist. A fire can with comfort be kept burning in a living room all the year round. There are a few slight

Jan 1, 1929

By P. W. Rainier

The Chivor emerald field is situated on the eastern slope of the Andes in the Department of Boyach, at an elevation of about 8000 ft. above sea level. It overlooks the Llanos (plains) of the Orinoco and is watered by many streams flowing into the Rio Meta, the Orinoco's largest tributary. The Rio Meta is navigable from the Orinoco to a point within about 50 miles of the Chivor district and may eventually prove to be the reasonable outlet for the future development of this part of the country. The topography of the district is extremely rugged and mountainous (Fig. I), the difference in elevation between two points on a mining claim 1 km. square being sometimes as much as 4000 ft. The ground is covered with dense forest growth and the available timber is suitable and sufficient for mining purposes, but it is becoming gradually depleted by Indian clearings as the country around the mines becomes settled. The many streams combined with the rough topography give good possibilities for hydroelectric power. The center of population nearest to Chivor is Bogoth, the capital of the republic and a city of some 300,000 inhabitants; the distance is two and one-half days' travel. The first stage of the journey from BogotB is accomplished by rail to Choconta, some 4 hr. travel. From Choconth the journey is made in the saddle, one night being spent in Guateque. The latter is a small town and the nearest post office to the mines, being some 10 hr. ride distant. The roads are mere bridle paths, in parts hazardous and almost impassable in the wet season. All supplies brought to the mines, other than those produced locally, are carried by pack mule; mule freight from Choconth costs 3 centavos1 per pound. The climate of the Chivor district is healthful and bracing. The wet season begins in March and concludes in November, the remaining months being dry. The annual precipitation is about 130 in. The temperature throughout the year is nearly constant, varying from about 45" F. to about 65" F. shade temperature. The rains are cold and unpleasant, and for the greater part of each day in the wet season the country is shrouded in dense mist. A fire can with comfort be kept burning in a living room all the year round. There are a few slight

Jan 1, 1931

By Samuel S. Wyer

1. The following is an abridgment of a recent report made by the author, covering an investigation of: (A) The necessary use of natural-gas compressors; (B) The effect of gas compressors on natural-gas field operating conditions in Ohio, with special reference to the working pressure relations of gas wells of one company discharging by natural rock-pressure flow without compressors, and adjacent wells of other companies, discharging into intake lines to gas-compressing stations. Tests were made at 107 different places in the counties of fairfield, Licking and Knox, Ohio, which required 7,000 miles of automobile driving, and consumed 6 months' time. 2. A proper conception of the necessary use and effect of natural-gas compressors in natural-gas production necessitates a clear understanding of certain fundamental definitions and judicial doctrines, which are given herein. 3. Gas is a fluid composed of a large number of molecules which are vehicles of energy continually in motion, and havingan inherent tendency to get farther and farther apart. The range of motion of the molecules is limited only by the volume of the closed containing vessel in which they constantly move to and fro. The most distinguishing characteristic of gas is its universal property of completely filling an inclosed space. 4. Gas pressure is the result of the combined efforts of all the moving molecules in the mass trying to get farther and farther apart, that is, a mass of gas inclosed in a vessel expands and fills it, and being restrained from further expansion, it exercises a pressure against the walls of the vessel. This pressure is the same in all directions on equal areas of surface, as shown in Fig. 1. With a given mass of gas, any increase in volume of containing vessel will give the molecules more range of motion, * The public's interest in the age and magnitude of the art of gas compressing and development of the law relating to the use of grs compressors in natural gas production is discussed in the preceding paper. Development of the Law Relating to the use of Gas Compressors in Natural Gas Production; see also Is It Feasible to Make Common Carriers of Natural Gas Transmission Lines, vol. xlviii, 471 to 480 (1914). Consulting Engineer.

Jan 1, 1916

By George Bain

SOME problems concomitant with commercial exploitation of marble are presented as examples of interesting, useful and profitable fields for application of scientific knowledge. The marble industry is only one such field and is selected because its varying new aspects are familiar to the author. However, what is true for marble is equally so in principle for many industrial minerals. The problems of any stone industry are to maintain markets, create new outlets for stone already in demand, and develop varied uses for varieties that are not so popular. Here the geologist has a different role from most of his colleagues in metal mining. The producing branch may ask about the expectable variation in thickness or size of a deposit as development proceeds. The stock department may call for the available amount of a given type of stone before accepting a large order. The sales force requires data on the use for stone from certain parts of deposits in order to divert grades to the most suitable use. The service depart-ment wants defects rectified and the cause determined to avoid recurrence. The mills want data on durability and cutting quality of abrasives. The geologist occupies no special department; he is on general call, as may be illustrated by a few types of problems that may be classified as: (1) dominantly geological in character, (2) dominantly chemical in character, (3) dominantly physical in character.

Jan 1, 1940

By Allan J. Clark

It is nearly three years since the metallurgy of the Homestake ore was discussed with considerable thoroughness, in a paper1 read before the Institution of .Mining and Metallurgy. Certain changes have been made in this period which are perhaps of sufficient interest to justify a brief description, and it is chiefly with such details and miscellanies that this paper will deal. In the circumstances, a certain amount of repetition is inevitable, but matter treated of in the former paper will be referred to here only when it is necessary for the sake of coherency. For full descriptions of equipment and technique, the former paper should be consulted. The mineralized slates and schists which constitute the ore vary considerably in composition, but the unoxidized ore, perhaps constituting the major part of the reserves, contains either chlorite or hornblende (cummingtonite), with quartz, carbonates of lime, magnesia and iron, and arsenopyrite, pyrite, and pyrrhotite. Ferrous minerals predominate, and this fact has been an important factor in determining the metallurgical treatment. With one or two exceptions the minerals noted are of relatively high specific gravity, and the ore as a whole is exceptionally heavy, many determinations giving an average specific gravity of 3.00. This high specific gravity presents one decided advantage, when the cost of treatment is compared with operations elsewhere, in that the ton, almost universally the basic unit, represents a volume probably less by 10 per cent. than that of many gold ores. On the other hand, this high gravity renders more difficult the discharge of pulp from mortars, its distribution on amalgam tables, and its transportation in launders. In the same way, as attesting the usual balance of such variations of different ores, it may be noted that the needle-like fibers of hornblende (cummingtonite), interlacing throughout the mass, render the ore more difficult to crush than would be anticipated, but on the other hand assist

Jan 1, 1916

By Rossiter W. Raymond

It is scarcely necessary to augment or amend the "Appreciation" of Dr. Douglas, from the pen of Dr. Albert A. Ledoux, which appeared in January, 1916, in Bulletin No. 109 of the Institute. The author of that admirable summary enjoyed the great privilege of expressing while Dr. Douglas was yet among us (though already marked for death) the love and esteem with which we all regarded him. But now that his earthly life has ended, the historian must still be the eulogist. No line need be added or deleted in the portrait of him already drawn; it has only to be accepted now as a true likeness, and hung in the gallery of the immortals, illuminated by the crowning glory of another world. James Douglas was born at Quebec, Canada, November 4, 1837. His father, James Douglas, was a distinguished physician and surgeon, known in many lands, especially in the Orient, and famous in his own country for his philanthropy as well as his skill, having established and directed for many years the first retreat for the insane in the Dominion. of Canada. One of the latest literary labors of the son was the editing and publishing of his father's journal and reminiscences—a fascinating volume, the review of which, though a tempting task, I must here forego. Nearly fifty years ago, I had the great pleasure of spending an hour with the elder Douglas, who guided me through his collection of Egyptian and Asiatic treasures. I might almost say souvenirs; so many of them were connected with personal experiences and exalted personages. The veteran's memory had already begun to fail with age, but his vivacity and imagination glowed all the more brightly; and his reminiscences of travel and adventure were embroidered with Oriental magnificence. I felt, after that hour, as if I had visited a stately, half-ruined edifice, overgrown with vines and flowers. The father's genius, adventurous spirit and generous philanthropy descended to his versatile, yet practical son. Like other men of such temperament, James Douglas tried many things before circumstances beyond his own control forced him into the line of his principal lifework. At the age of 18, he was sent to the University of Edinburgh, where he studied for two years. Returning to Canada, he entered Queen's University, at Kingston, Ontario, where he was graduated as Bachelor of Arts in 1858. Subsequently he studied medicine at Lava1 University, Quebec;

Jan 1, 1919

By Wilbur C. Helt

The United States is self-sufficient in bituminous coal and lignite resources to meet the high range of energy demands forecast for the remainder of this century and beyond. The known or proved recoverable reserves of energy from coal in the United States are estimated to be 88% of all fuel reserves, whereas the energy reserves for oil are estimated to be 276, gas 376, shale oil 5% and uranium 2% (as now used). The demand for all forms of energy used in the United States is increasing at a rate of 3% to 4% per year. Presently, coal is competitive on a supply and cost basis with other fuels in conversion to electrical energy and as a source of energy for converting raw minerals to metals and nonmetals, but it is not competitive in transportation and other uses that demand the high flexibility that oil and gas enjoy because of their form. Coal conversion to fluid forms is essential to make it interchangeable with gas and oil to meet the markets they now occupy. Essentially, the chemical constituents that make up coal are the same hydrocarbons that make up oil and gas; it is a matter of reconstituting the proportions of hydrocarbons to make coal interchangeable with the other fuels. The production of coal has fluctuated widely between the peak production of 631 million tons in 1947 to a low of 403 million tons in 1961. Throughout this period, the total value of the production, f.o.b. mines, has averaged more than $2 billion annually. Beginning with 1962, there has been a steady upward trend in coal production with only minor fluctuations that were mainly caused by labor disputes. Output for the latest typical year, 1970, was 588 million tons. Production in 1971 was affected by a major strike and dropped to 548 million tons. Exports of coal from United States to foreign countries have increased steadily and developed into a substantial annual market for over 71 million tons per year. About 56 million tons of this is suitable for metallurgical purposes, and the remaining 15 million tons is exported for electric power generation. The largest single-industry demand for coal is in the electric generating industry, Fig.1. Roughly, the production of electricity has doubled every

Jan 1, 1973

A LARGE attendance at the annual dinner of the Institute, to be held this year on Tuesday eve-ning of convention week, is already assured. Presentation of the Douglas, Hunt and Saunders medals will attract unusual attention since not only in Blaylock, Mathews and Hoover the Institute will be honoring men who have made notable contributions to the advance-ment of their profession, but as to one of them each person as he passes down the reception line will be won-dering whether in renewing acquaintance with our past-president and present Secretary of Commerce, he is not greeting the next president of the United States. Elsewhere in this issue accounts of the professional careers of these three men appear as also of the two younger men, Charles H. Herty, Jr., and P. H. Royster, who are to receive the Robert W. Hunt and the J. E. Johnson awards. Institute honors go for technical achievement, but the Institute will be proud and happy if the nation should later confirm its own judgment by placing larger responsibilities on one of its members. The medals are to be presented at the annual dinner following the President's reception and preceding the dance. There will be no. other speeches and since the occasion falls on Carnival Night a particularly gay evening is anticipated. The event will be at the Wal-dorf as usual, and members are urged to return prompt-ly the reservation cards sent them by mail. Other entertainment features will include a Smoker, Monday evening at 8.15, held at Mecca Temple and in charge of a new committee with Fred Kay of the Petro-leum Division as chairman. He promises that vocal music will not be allowed to interrupt conversation. Lunch will be served each day on the Fifth Floor of the Engineering Societies Building, and ten special luncheons and dinners have been arranged for particu-lar committees and groups as shown by the detailed program. The Woman's Auxiliary has laid out a gen-erous program including luncheons, teas, a theater party on the night the men folks go to the Smoker, visits to museums and, not the least important, a round of the leading shops. The Excursion Committee is arranging for an excur-sion sure to be of interest. The American Smelting and Refining Co. has opened its great Perth Amboy plant to the Institute, and on Thursday, Feb. 23, a party will be taken to it by bus traveling through the Holland Tunnel en route. Full opportunity will be afforded those interested to see the workings of the ventilation system of that great public work. If a sufficient number indicate interest, arrangements will be made for group excursions to other plants in the vicinity of the city.

Jan 2, 1928