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By Thomas Lane Carter

The history of mining in South Africa differs somewhat from that of other countries in the part taken by the aborigines in the development of the mineral deposits. The Spaniards in America, and the fortune-seekers of Australia and New Zealand, found large numbers of natives in these new countries, but the inhabitants did not become willing or efficient workers in the mines which the white men started. The Kaffirs of South Africa have not shown the same antipathy to labor, nor do they show any signs of dying out in the presence of the white man's civilization. They are a virile race, and so far the vices of civilization have not killed them. While it is true that the brain and skill necessary for the exploitation of the mineral resources of this sub-continent have been supplied by the white race, it is also a fact that most of the rough labor in the development of the mining industry of South Africa has been done by the Kaffirs. The Kaffir tribes differ greatly in their mental and physical capabilities. Compare, for instance, a Zulu of Natal with a Bechuana, or a Xosa of Cape Colony with some of the degenerate tribes of Central or East Africa, and you will find that they have little in common, save that their skin is black and that they do not believe in clothes. As a general rule, the tribes in the milder, healthier climates are far superior, both in mind and body, to the Kaffirs brought up in the hot malarial sections of Central Africa; and it naturally follows that the black men from the temperate zones of the country are much finer workmen than the degenerates from less favorable sections. It is universal in South Africa to speak of the Kaffirs as " boys." No matter if he is 90 years old, the Kaffir is always a a boy," and in this paper the word " boy " is synonymous with Kaffir.

Jan 1, 1909

By Edward Halse

THE occasional occurrence in metalliferous veins of rounded fragments of rock, matrix or ore, lying loose, embedded in clay, or enclosed in some kind of cement, may be attributed to four causes:¬ I. They have been washed in from the surface, or from an upper portion of the vein. II. They are of concretionary origin. III. They have been produced by movements in the country-rock or in the walls of the vein. IV. They have been found in situ, by the upward, downward or lateral flow of water in the vein itself. In this paper the word " conglomerate " is confined to a rock composed of rounded fragments or pebbles cemented together, as distinguished from a " breccia," in which the rock-fragments are angular. I. BOULDERS AND PEBBLES WHICH HAVE BEEN WASHED IN FROM THE SURFACE, OR FROM AN UPPER PORTION OF THE VEIN. In this type it is presupposed that the vein at onetime com¬municated by a fissure or open space with the surface, or with the upper portion from whence the fragments have been washed. One well-authenticated occurrence was described long ago by Fournet. Owing, no doubt, to later dislocations in the lode, pebbles from an old alluvium and sands containing titaniferous iron, as well as fragments of wood, were found in a vein at Huelgoët, in France. "Toutes les parties tendres du filon de Pranal ou ces pédnomènes sont les plus prononcés ont été excavés jusqu'a d'assez grandee profondeurs par l'impétuosité des torrents, qui ont deposé la matière alluviale."1

Jul 1, 1905

By E. P. Polushkin, Henry L. Shuldener

This paper describes the results of microscopic examination of a series of brass pipes removed from apartment and office buildings in New York City, adjacent localities on Long Island, and Philadelphia. They were selected as typical of approximately four hundred pipe specimens obtained over a period of five years during an investigation of corrosion in hot-water installations. A part of the investigation is reported in this paper and includes a brief history of the pipes, a description of their inside surface and microstructure, and a study of the effects of corrosion, with particular reference to the structural aspects of local and selective dezincification. Although the bibliography on the corrosion of brass pipes is quite extensive, it refers almost entirely to corrosion in sea water. The authors believe that their examination of this series of pipes, which had been subjected to the corrosive action of fresh water for various lengths of time, may throw some additional light on the problem of corrosion. Pipes Examined The pipes were made by different manufacturers and their sizes range from 3/4 in. to 4 in. nominal inside diameter, the majority being within I to 2 in. They can be divided into two groups according to chemical composition: (I) with a copper content of 60 to 62 per cent and (2) with a copper content of 65 to 68 per cent. The first group (pipes made of Muntz metal) comprises 22 pipes and the second (pipes made of high brass) comprises 18 pipes. The pipes had been in service in various locations in the hot-water systems of the buildings involved. Some were taken from horizontal lines in the basement, some from overhead distributors and some from vertical risers. The distance, in terms of feet of pipe, of the specimens from the hot-water generator was no less than 75 ft. and often IOO to 300 ft. In the majority of cases the water-heating equipment was provided with a regulator to limit the temperature of the hot water supply. The normal range of temperature in pipe systems of this kind is Ioo° to 160°F. Water Supples The average chemical composition of the water supplies carried by the pipes is shown in Table I. In evaluating the corrosiveness of a natural water, four factors are considered of prime importance: namely, hardness, alkalinity, pH and silica content. The waters listed in Table 1 are characterized by relatively low hardness, 10, alkalinity, low pH and low silica content. The waters of lower pH and higher CO2 content are more corrosive. A characteristic of all of these waters is that they do not deposit a protective mineral coating as do waters with high bicarbonate of lime content, which would be reflected

Jan 1, 1945

By E. C. Carris

THE particular field of application of machines utilizing air currents as the primary separating medium is in the cleaning of the fine sizes of bituminous coal. Approximately 12,000,000 tons of bituminous coal were cleaned by air machines during 1940.They have not found any application for cleaning anthracite. Since the development and introduction of the first successful commercial pneumatic oscillating machine for cleaning bituminous coal in 1916, by the Sutton, Steele and Steele Co., Dallas, Texas, and the American Coal Cleaning Corporation, formerly of Welch, W. Va., four other successful pneumatic coal-cleaning machines have been developed and introduced to the American coal-mining industry: 1. Peale Davis: "Pneumo-Gravity" machine, 1924. 2. Arms "Concentrator," oscillating table, 1924. 3. Hey1 and Patterson oscillating table, 1927. 4. "Stump Air-Flow," pulsating air jig, 1932. Out of these five developments only the Sutton, Steele and Steele, or American Oscillating, and the Stump Air-Flow Jig remain on the market. They are the predominating pneumatic coal-cleaning machines in use in the United States. HISTORY OF AMERICAX TYPE SEPARATOR The first successful American machine, the CJ table (Fig. 1) was developed by the Sutton, Steele and Steele Co. The SJ table was the first standard model designed specifically for the cleaning of coal. It was installed in the original Crane Creek plant, owned and operated by the American Coal Co. at McComas, West Virginia. This plant was designed by The Roberts and Schaefer Co., Chicago, Ill., working in cooperation with the American Coal Cleaning Corporation, which had taken over the patent rights and sale of the pneumatic separators. Eight machines were installed in this plant. They were known as the type SJ. They were 60 by 84 in., the short dimension being the width of

Jan 1, 1943

By E. P. Pfleider, W. G. Pariseau

This paper reports the theoretical and experimental results of an analysis of ore pass drawdown as a problem in soil plasticity. The method of analysis developed appears to be a promising technique of investigating the mechanics of fragmented materials. A reconstructed plasticity theory brings experiment and theory into reasonable agreement, and hence may provide the foundation needed for rational ore pass design. The gravity-induced movement of broken rock through ore passes is an economical method of transporting fragmented materials through large vertical distances in underground mines, provided the ore pass is well designed. Unfortunately, the design procedures now followed do not very often result in ore passes that function properly. On the one hand, the huge accumulation of empirical data pertaining to the movement of materials in gravel bunkers, storage bins, deep grain silos and other structures that have features in common with ore passes remains uncorrelated. On the other hand, there is a dearth of experimental data substantiating theoretical models of material behavior. Consequently, reliable generalizations encompassing the broad spectrum of problems involved have not been forthcoming. AS an initial step towards improving the situation, a detailed case study of two-dimensional ore pass drawdown was made. The mechanics of the process were analyzed theoretically as a problem in soil plasticity and tested experimentally through observations of a laboratory ore pass model. THEORY Taylor1 defines a soil as a "mass commonly considered to consist of a network or skeleton of solid particles, enclosing voids of varying size." Broken rock in an ore pass is such a material. In plasticity theory this material is replaced by an idealized substance that deforms elastically up to some state of stress at which slip or yield occurs,2 For com-pressive states of stress, the Mohr-Coulomb criterion is a satisfactory yield condition. After the yield point is reached, the ideal soil deforms in accordance with the concept of plastic potential.4 Under plane strain conditions the governing equations separate into a system of stress equations and a system of velocity equations.' Only stress variables appear in the stress system. The velocity system, however, contains a stress variable. The two systems are, therefore, coupled. Both systems are hyperbolic, and each has two real, distinct families of characteristic curves that coincide according to the classical theory of ideal soil plasticity. The

Jan 1, 1969

By S. M. Marshall, B. M. Bird

For a number of years European investigators have used laboratory methods of predicting the probable strength of coke made from coal, and recently several investigators in the United States have reported the use of various tests for this purpose. There is at present no method accepted as standard, however, nor is there even agreement as to the general type of test that should be used. Furthermore, because the details of most of the tests have not been worked out carefully, one investigator can not hope to duplicate the work of another. The extension of coke manufacture to new localities in the United States, and the increasing need for cokes of exceptional qualities made from the most economical mixtures, made it desirable to have some simple laboratory test which will determine whether given coals, alone or blended with other coals, are more satisfactory from the standpoint of coke strenpth- than others of different cost. The work described herein has resulted in the development of a simple laboratory test which, it is believed, can be generally adopted in coal laborat,ories, and which will give concordant results even though performed by different investigators in different laboratories. The general method of predicting whether a coal or a mixture of coals will produce a strong coke, resistant to crushing and shattering, has been to correlate the known strengths of the cokes produced in commercial ovens with some measurable constituent or with some property of the coals, and then to use the relationship so found for forming an estimate of the coking strengths of coals unknown. Several such correlations have utilized the percentages of the various ultimate constituents of coal, such as the oxygen content and the hydrogen-oxygen ratio;(39)§ other correlations have involved the proportion of a, B and r com-pounds, (17,21,30c) or of "oil and solid bitumens."(16,30) Also a relationship has been traced between the coking properties of coal and the rate of change of the resistance offered to the flow of an inert gas by fine particles of the coal while being slowly heated. (11,176) But the most general corre-

Jan 1, 1930

By M. C. Manderson

Abstract-The sharp drop in world phosphate demand that took place in 1975, due to temporarily high prices, now seems to be reversing itself. And prices for both phosphate rock and phosphate fertilizers, which declined dramatically from their 1975 highs, now appear to be bottoming out. This recent price weakness has delayed new mining ventures that had previously been planned for completion by around 1980. While there is ample capacity to supply near-term rock needs, the stage seems to be emerging for a better supply-demand and price environment in the late 1970's and early 1980's.

Jan 1, 1978

By Eduardo J. Chibas

Location.—The principal manganese-deposits of the Department of Panama, Republic of Colombia, are located almost clue south of Viento Frio, a native village bordering on the Caribbean Sea, and about 45 miles northeast of Colon (Aspinwall). The mining-claims are the Viento Frio, the Carrano, the Nispero, and the Soledad. Each property is to the south of the preceding one in the order mentioned. The first one is about one mile from the coast, and the most southerly boundary of the Soledad is about five miles in a straight line from the same coast-line. I shall confine my remarks to the four properties mentioned and to La Guaca, west of the Carrano, because these are the only ones where mining has so far been done to more or less extent. Manganese has also been found, however, in the neighborhood of these deposits, and a large area adjoining them has been divided into sections and " denounced " as mining-claims. The relative position of the manganese-deposits and Nombre de Dios, the present terminal of the railroad and shipping-port, as well as Viento Frio and the adjacent coast, can

Jan 1, 1898

By B. F. Oliver, C. W. Haworth

Pure tin and Sn-0.5pct Pb ingots have been frozen unidirectionally from the base. For quiescent melts that were initially undercooled, a transition from lower eqlciaxed structure to an upper columnar structure is found in the alloy ingots. Columnar to equi-axed back to columnar transitions are observed in superheated alloy ingots, but no such equiaxed band is observed impure tin. The reproducible equiaxed band is associated with a thermal undercooling followed by a recalescence. This undercooling is <5"C, whereas the critical (maximum obtainable) under-cooling for both the pure tin and the alloys used is -20°C. A similar undercooling is observed at the same position in the pure tin ingots, although in this case no clear transition in structure can be seen. The structure of the pure tin ingots is either entirely columnar or mixed columnar-equiaxed. A consideration of the detailed thermal history of the ingots indicates that the ingot macrostructures are determined by the occurrence of a local therlnal undercooling in conjunction with nuclei multiplication and transport mechanisrris. GENERALLY it is found that a pure metal ingot solidifies so as to produce an entirely columnar structure. Frequently an alloy ingot is found to have a columnar outer zone and an equiaxed central portion. Early systematic work to examine the factors controlling the formation of the equiaxed structure was reported by Northcott&apos; who showed that, for copper alloys frozen unidirectionally with a given ingot practice, the alloying element influenced the length of columnar crystals and the extent of the equiaxed structure. Northcott showed that alloys with a wider freezing range more readily produced the equiaxed structure. The nucleation process can be important in producing equiaxed structures; frequently an alloy which readily solidifies with an entirely columnar structure will produce an entirely equiaxed structure when a nucleating agent is added to the melt.&apos; The formation of the equiaxed structure was attributed by Winegard and chalmers3 to the presence of constitutional supercooling; that is, a region of liquid in front of the growing solid could have a temperature below its equilibrium liquidus temperature. Thus, with a small enough temperature gradient in the liquid, it was suggested that the presence of constitutional supercooling may be sufficient to bring about the nuclea-tion necessary for the formation of an equiaxed structure. Although this explanation is plausible, and may be relevant in many ingots, Walker has described an experiment&apos; for which constitutional supercooling seems to be an unlikely cause of nucleation. A Ni-20 pct Cu alloy, repeatedly undercooled more than 50"C, was crystallized and found to show the typical colum-nar-equiaxed structure. The separation between the liquidus and the solidus for the alloy is 40°C. Thus, in this experiment the nucleation required for the formation of the equiaxed structure must have come about in some other way than by the nucleation catalysis constitutional supercooling hypothesis. Chalmers has suggested more recently5 that nuclei (in a typical ingot) are present immediately after pouring and are prevented from redissolving by the constitutional supercooling effect. More recently Uhlman, Seward, Jackson, and ~unt&apos; have shown direct evidence using ice and organic materials that freeze dendritically that the "remelt mechanism" may be an extremely effective crystal multiplication process during the freezing of ingots under conditions involving dendritic growth. JSlia" experimentally demonstrated the detachment of dendrite arms. chernov14 has analyzed the dendrite arm detachment process as a coarsening phenomena driven by the minimization of interphase area. Katta-mis and ~lemings" working with undercooled steel melts give evidence supporting this mechanism. Mechanisms of dendrite arm detachment such as those assisted by convection are believed to be the origin of the macrostructures obtained in this study. This study makes no attempt to distinguish the relative contributions of these mechanisms. The object of the present work was to obtain accurate temperature measurements during the solidification of an ingot and to correlate these measurements with the formation of equiaxed grains in the resulting ingot structures. Similar previous work is very limited. The measurements carried out by Northcott are neither sufficiently extensive nor sufficiently accurate for any interpretation. Plaskett and winegard7 carried out experiments on A1-Mg alloys in which they observed values of the temperature gradient, G, in the liquid and rate of freezing, R (for a given alloy solute content Co), at the transition from a columnar to an equiaxed structure. They reported that equiaxed crystals were produced at values of G/G approximately proportional to the solidus composition. Similar experiments using Pb-Sn alloys carried out by £111011" showed a linear relation between G/R and the solidus composition. However, the thermocouples were in the mold wall rather than in the melt and, in one case, ingot surfaces were examined. There is ambiguity in the meaning of the values of G and R measured in all these experiments. APPARATUS AND EXPERIMENTAL PROCEDURE Alloys were prepared by induction melting 99.999 pct Sn and 99.999 pct Pb to form a Sn-0.5 wt pct Pb alloy in air in a graphite crucible and casting into a cylindrical graphite mold 6 in. long, 1 in. in diarn , and with a & in. wall thickness. This mold was mounted on a copper base through which cooling water could be

Jan 1, 1968

By Oliver Bowles

A HEAVY gel of bentonite clay has been proposed as an effective lubricant to speed down the ways to sea, river, or lake, the mighty cargo ships now hitting the water at the rate of about three a day. Another unusual application of a nonmetallic mineral is in food conservation, for the claim has been made that the next new item on the menu for poultry and rabbits will be vitamin tablets prepared from mont-morillonite clay. These uses have minor importance but illustrate not only the diversity in utilization, but the notable trend in 1942 toward mobilizing nonmetallic minerals for the war program. Although occupying less headline space than iron, steel, copper, aluminum, magnesium, and other metals, the nonmetallics are filling important emergency needs. Mica and quartz crystal are essential to communication; asbestos is urgently needed in fireproof heat and electrical insulation; and strontium minerals are utilized in the manufacture of signal flares and tracer bullets.

Jan 1, 1943

By Earle C. Waite

THE Industrial Minerals Division this year held no individual sessions of its own except the business meeting Tuesday afternoon. One session was held jointly with the Society of Economic Geologists, one with the Milling Methods Committee, and two with the Society of Economic Geologists and the Mining Geology Committee. At all of these meetings the attendance was better than usual and the Tuesday afternoon session, with nearly 400 present, probably set a new record for the Division. Joint sessions seem extremely popular when papers of mutual interest are presented. On Monday afternoon, mica was the predominating subject. The North Carolina mines provided most of the information presented, although the discussion brought out similarities with the New England mines. B. C. Burgess particularly stressed the fact that with the existing curtailment of mica from India it is necessary to get the most mica in the shortest time from the mines in this country. He said that the Colonial Mica Corp. hopes to have 1000 mines operating in the near future. This seems a great number, but when one considers that these mines employ from 3 to 28 men, mostly nearer the low figure, the output of each mine is relatively small. Although the price of mica is from six to ten times the prewar price, the yield of 8 to 150 lb. of mica per ton of raw ore does not provide high returns to the producer.

Jan 1, 1943

By Richard H. Jahns

Gem materials, comprising those minerals and closely allied natural substances used for personal adornment, for the fashioning of ornamental objects, or for other decorative purposes, have been valued in human commerce for thousands of years. Amber, jet, natural glasses, and at least 15 mineral species were sought and used by primitive man, and most of the materials in common use today were known well before the time of Christ. Their variety is remarkably great, and the traceable relationships among their respective sources, modes of occurrence, properties, and histories of production, preparation, and valuation are extremely complex. Their uses have been affected by numerous shifts in fashion, and from time to time by superstition, by decrees of church and state, by personal interpretations of religious significance, and by various presumptions concerning medicinal value and influence on human behavior (Ball, 1935, 1950; Kunz, 1913; Pogue, 1915; Whitlock, 1946). Thanks to their durability, portability, and relative scarcity, some gem stones have been employed as media of exchange, and the investment value of the more precious stones has long been recognized and exploited, especially in Asiatic and European countries. Demands for gem materials have stimulated trade among various peoples for centuries, and they also were responsible for much early geographic exploration. During more recent times they have prompted numerous geological studies and a considerable amount of research on the growth and properties of crystals. Apart from decorative uses, some naturally occurring gem materials also are employed directly in numerous fields of industry. Substances that are manufactured for gem or industrial uses are termed synthetic gem materials; most of these correspond in composition and crystal structure to certain minerals found in nature. Imitation materials are those whose use is based upon their resemblance to substances of different composition and greater intrinsic value. Gem stone is a designation commonly restricted to those materials suitable for personal adornment, and the complementary term ornamental stone is applied to the remaining materials not used industrially. This distinction is arbitrary and somewhat inconsistent, owing to numerous geographic differences and historical shifts in end uses. Further, there is a complete gradation between the category of ornamental stones and that of dimension stone. Substances that lose their identity in use are excluded from the gem category; thus a transparent crystal of beryl would not be classified as a gem stone if it were processed as a source of beryllium metal. The adjectives precious and semiprecious have been employed as a means for distinguishing different gem materials on the basis of recognized value. Diamond, emerald, ruby, and sapphire consistently have been regarded as precious stones, and in cut form they commonly are referred to as the noble gems. Opal, pearl, turquoise, and chrysoberyl also have been classed as precious at various times. In recent years, however, it has been increasingly recognized that no satisfactory distinction can be based upon assessed value or any group of specific properties, and now all gem stones normally are referred to as precious. Indeed, the tendency is to extend this term to include many of the so-called ornamental stones, and the designation semiprecious has been essentially discontinued. Unlike most mineral commodities of economic value, gem materials are little altered in processing for end uses. Some stones are used in essentially their natural form, and most are reshaped and polished without significant changes in their fundamental properties. Thus the preparation of gem and ornamental stones is intended chiefly to emphasize or enhance

Jan 1, 1983

By H. L. Hazen

THIS is the story of the recent operations of the Standard Cyaniding Co., which owns the Standard mine, a low-grade gold property in sight of Highway 40 about thirty miles from Lovelock toward Winnemucca, Nev. The ore is mined by power shovel and cyanided after grinding to only 3/S in. A total direct cost of $1.24 was attained in 1941 on 600 tons a day. Mining operations ceased, under Government edict, in 1942, and only in recent months have been resumed. The operating difficulties of today are: (1) the high cost of supplies; (2) labor problems; and (3) Federal laws as interpreted and enforced by executive bureaus of the Government. Of these, the increased cost of supplies is the least important.

Jan 1, 1947

By Wilson T. Lundy

The history of the production of sulfur from salt domes in Louisiana and Texas originated with the operations of the Union Sulphur CO. at Sulphur, La., followed by the Freeport Sulphur Co. at Bryanmound, Tex. Including the present development of Grande Ecaille by the Free-port Sulphur Co., which constitutes the tenth dome to be equipped for the production of sulfur in the Gulf Coast, less than 10 per cent of all the known domes have proved to contain sulfur in commercial quantities. The Grande Ecaille salt dome is in the tidal marsh of the Mississippi River delta in Plaquemines Parish, Louisiana. It is 10 miles southwest of the right descending bank of the river approximately 45 miles below the city of New Orleans and is within 4 miles of the shore line of the Gulf of Mexico. Terrain Characteristic of the delta region, the terrain consists of a low, flat, uninhabited area of marsh land intersected by many shallow lakes and bayous. With the exception of salt grasses, the region is devoid of vegetation and presents, in all directions, an unobstructed path to the vagaries of the winds. The general character of this area can be best visualized from the mechanism of its formation.&apos; Offshore bars formed enclosing long narrow lagoons between the bar and the inner shore line, the lagoons communicating with the sea by means of tidal inlets. The water in the lagoons, being comparatively quiet, favored the deposition of fine debris composed of sand carried into the lagoons by action of the waves, tides and river-borne sediments from the land surface. As this material accumulated the bottoms of the lagoons were built up and eventually salt grasses obtained a foothold. The successions of growth and decay of these grasses formed a brown fibrous mat varying in depth from a few inches to several feet. This mat of vegetation virtually floats on an ooze that is several feet thick and is composed of alluvial sediments and very fine sand, and the whole is underlain by an unctuous clay. The decayed vegetation from the upper layer when dried has a peaty appearance.

Jan 1, 1934

Open pits and quarries are the major sources of all hard rock tonnages mined today. Normally, ore is fractured from the pit bench face by blasting and then truck-hauled to a primary crusher on the pit rim for conveying to the concentrator; overburden (or waste) is generally truck- hauled from the pit to dump areas. This system of truck haulage of blasted ore and waste accounts for some 25 to 50% of total mining costs in a typical open pit operation and commonly is the largest single cost factor. In an effort to reduce these costs mining companies are continually replacing their older and smaller trucks with larger ones and at the same time are studying conversions to conveyor haulage, since this method of transport seems to offer possibilities of lower costs per ton of material handled. In these studies it seems logical to consider installing these conveyors as close as possible to the mining face for maximum use of conveyors and minimum use of trucks, since a conveyor is much less labor intensive than a trucking system. However, direct loading onto a conveyor near the retreating bench face is impractical because of excessive lump size. Consequently, it is conventional practice to load the blasted rock into trucks at the face for haulage to the crusher. After crushing, the rock is fed onto a conveyor. The closer the crusher is to the mine, or if it is in the mine, the shorter the truck haul and the greater the potential for cost saving. At first appearance, in-pit conveying might seem to be an obvious solution, yet many mining companies have considered such a move while few have implemented it. To determine why, it is necessary to consider the factors influencing such a decision. A conveyor system tends to be capital intensive but can have a lower operating cost per ton than trucks. Trucks, on the other hand, tend to cost less to buy but more to operate; thus, economics tend to favor the conveyor if it can be operated close to capacity and if a sufficiently large tonnage can be passed over the system to mitigate the effect of its high capital cost. In a typical hard-rock, open-pit mine it is necessary for a variety of reasons to mine several faces of both ore and waste at the same time; and any mining system must have sufficient flexibility to permit loading from one face or another at short notice. This makes it impractical to place small mobile crushers and their consequent network of conveyors at each working face. To date no alternative has been found to using trucks for bringing all rock of the same class to some convenient marshalling point from which it may be crushed and conveyed from the pit. Another advantage of trucking when compared to conveying is flexibility. Many mines wish to deliver their shot-rock to different locations, depending on the mineral content. For instance, a typical copper mine may have to simultaneously mine milling ore, leach ore,

Jan 1, 1978

By A. H. Tousley, C. L. Vickers

The author presents a history of the development of the Port of Long Beach from its beginning in 1905 to the present construction of a new bulk loading facility. In describing this new facility, emphasis is placed on such aspects as rail car and truck handling, gravity yard, rotary car dumping, bottom dumping, car dumping equipment, feeding and conveying, ship-loader-stockpiler, stockpiling and reclaim, dust control, and construction problems. Development of the Port of Long Beach, Calif. (see Fig. I), began in 1905. In that year private Long Beach interests acquired 800 acres of marshland in the Inner Harbor area and initiated a program of channel dredging and land reclamation. Efforts to establish a municipal port began a short time later and culminated in the opening of Pier 1 in 1911. An event of even greater significance to the port future also occurred in 1911. This was the tideland grant enactment by the state legislature that conveyed to the city of Long Beach all of the state&apos;s rights in the tidelands located within the city boundaries. The grant stipulated that all revenue produced from the tidelands be used for the development of navigation, commerce, and fisheries. During the next 15 years up to 1926, the port&apos;s commercial growth was steady, although relatively slow. During this period, several fundamental steps in the development of a major harbor were accomplished. These included the creation of the Board of Harbor Commissioners in 1917, the dredging of the Inner Harbor and entrance channel to accommodate deep draft vessels, and the correction of a serious silting problem through construction of the Los Angeles River Flood Control Channel. These efforts bore fruit during the ensuing 10 years in the establishment of more than $30,000,000 worth of industrial plants and private marine terminals in the Inner Harbor. Commerce over municipal wharves also increased more rapidly, and it became necessary to start the development of the harbor in a seaward direction. In 1936, oil was discovered in the harbor area, and the first Harbor Dept. well was brought in 2 years later. It soon became evident that the city of Long Beach would receive substantial revenue that, under the terms of the state grant of 1911, must be used in the development of the port. It was further realized that to properly guide and coordinate such development, a long range comprehensive plan was essential. The Board of Harbor Commissions contracted with G. F. Nicholson and J. F. Collins, consulting engineers, for the preparation of such a report that was completed in 1940. The Nicholson-Collins report proposed the development of an East Basin, between the entrance channel and the Los Angeles River, and a West Basin in the area now occupied by the Long Beach Naval Shipyard. Twenty full-size berths were to be provided in the East Basin and more than fifty berths in the West Basin. The report recommended extensive modern terminal facilities for handling waterborne cargo. Attention was given to improvement of the street and highway system to give better vehicular access and to avoid congestion within the port. To a large extent the recommendations of the Nicholson-Collins report were followed in the subsequent development of the East Basin. This development was greatly accelerated by World War 11, with its need for increased oil production and additional shipping facilities. The wartime and immediate postwar construction was largely concentrated on Pier A, with the development of Piers B, C and D following in more recent years. An important factor in the planning of these piers was their dual function as oil drilling sites and cargo piers. The Navy&apos;s acquisition of the West Basin area made it necessary to depart from the Nicholson-Collins plan and find other areas for future expansion. At the present time only one Inner Harbor Port-owned area having protected deep water frontage remains undeveloped. This is the property fronting on Channel 2 in the Inner Harbor acquired in December 1957, from Pacific Dock and Terminal Co. The growth of the port has been in a southerly direction since the construction of the Long Beach Naval Shipyard in the West Basin area. Recent extension of Piers F, G and J into the ocean follows typical port construction methods developed during the expansion of the Middle Harbor during the last 20 years.

Jan 1, 1963

Boiler-Room Economy "Establishing and Maintaining Boiler-room Economy" is the title of a paper presented before the Ohio Society of Mechanical Electrical and Steam Engineers by Geo. H. Gibson, of which the following is an excerpt: Boiler-room economy depends less upon equipment than upon operation, i.e., it depends largely upon the condition in which the apparatus is maintained and how it is used. A given boiler may operate this week with an efficiency of 78 per cent., and next week with an efficiency of 65 per cent., while using the same fuel and developing the same rating. If there are variations ii; character of fuel and in load and other factors, the falling-off may be even greater, possibly to less than 60 per cent. The steam produced may cost twice as much per 1,000 lb. at one time as at another. Most steam plant managers know from their own experience that these statements are not exaggerated. It does not take much of a plant to run up a coal bill of $5,000 per year, many "spend $10,000 for coal, and fuel bills of $50,000, $100,000, or $200,000 per annum are not uncommon. As it call be shown in the majority of these plants that 10 per cent. of this amount may be saved, and in large numbers of them 25 per cent., while in some the expenditure can be cut in half, there is no disputing that we have here a subject worthy of attention. In the production of steam the greatest variable is the human factor. Before we can pass judgment, however, we must first have standards. This implies accurate quantitative knowledge of fuel consumption and steam production. We must measure the output and know how much the steam costs per thousand pounds, and how many pounds of steam are obtained from a pound of coal. We can then begin to analyze the problem, and find where and how methods and conditions can be improved, and how much. Many favor buying coal on a B. t. u. basis. This is advisable where the amount purchased warrants the considerable expense involved in systematically gathering samples that: are. truly representative and in having analyses made, of every carload. Coal analyses, combined with. an honest endeavor on the part of the miner to ship good coal, should insure the receipt of the heat units paid for. , It often happens, however, that the coal which is cheapest on a B.t.u. basis is not the cheapest or most suitable for producing steam, because of peculiarities of the plant in which it is to be burned, or conversely, the fuel which furnishes cheap B.t.u. may require special methods or equipment for its economic utilization.

Jan 2, 1916

By G. B. Gould

Every mathematical statement of a measure of anything (as distinguished from a count&apos;) is followed by a qualification—always implied if not explicity stated—-that the statement is only an estimate, which may vary from absolute accuracy within certain limits, according to the accuracy of the measuring instrument. This basic fact, so obvious to engineers, is not so well understood by many that make use of laboratory coal tests. The tolerances that must be allowed in measurements of coal quality are very important in both their commercial and engineering applications—and the significance of these tolerances depends upon the use made of the laboratory coal test. Only in recent years has there been any intensive study of this question of tolerances as applied to measurements of coal quality. There is very little in our published literature on the subject, and what has been published is not readily comprehended by those who sell coal, or buy coal and use it, unless they happen to have made a study of the subject themselves. There is great need for more widespread understanding of what lias been discovered and how it applies to the use of laboratory coal tests. What follows is an attempt to condense into a few pages the results of the major investigations so far reported, and to explain their meaning in simple nontechnical language, with the addition of some recent illustrative experiments. Determining Deviations in Quality It is necessary at the outset to distinguish between: (I) the accuracy with which one test indicates the quality on one lot of coal; and (2) the accuracy with which a test of one lot of coal represents the average quality of a commercial product, of which the buyer will presumably receive a series of shipments—perhaps many thousands of tons. It is necessary to make this distinction because coal is a variable material—a heterogeneous mixture of a variety of components—the quality of which will vary from one lot to another. Therefore an absolutely accurate determination of the quality (if that were possible) of one lot of a coal is an

Jan 1, 1938

By G. B. Gould

Every mathematical statement of a measure of anything (as distinguished from a count&apos;) is followed by a qualification—always implied if not explicity stated—-that the statement is only an estimate, which may vary from absolute accuracy within certain limits, according to the accuracy of the measuring instrument. This basic fact, so obvious to engineers, is not so well understood by many that make use of laboratory coal tests. The tolerances that must be allowed in measurements of coal quality are very important in both their commercial and engineering applications—and the significance of these tolerances depends upon the use made of the laboratory coal test. Only in recent years has there been any intensive study of this question of tolerances as applied to measurements of coal quality. There is very little in our published literature on the subject, and what has been published is not readily comprehended by those who sell coal, or buy coal and use it, unless they happen to have made a study of the subject themselves. There is great need for more widespread understanding of what lias been discovered and how it applies to the use of laboratory coal tests. What follows is an attempt to condense into a few pages the results of the major investigations so far reported, and to explain their meaning in simple nontechnical language, with the addition of some recent illustrative experiments. Determining Deviations in Quality It is necessary at the outset to distinguish between: (I) the accuracy with which one test indicates the quality on one lot of coal; and (2) the accuracy with which a test of one lot of coal represents the average quality of a commercial product, of which the buyer will presumably receive a series of shipments—perhaps many thousands of tons. It is necessary to make this distinction because coal is a variable material—a heterogeneous mixture of a variety of components—the quality of which will vary from one lot to another. Therefore an absolutely accurate determination of the quality (if that were possible) of one lot of a coal is an

Jan 1, 1938

By Richard H. Jahns

Gem materials, comprising those minerals and closely allied natural substances used for personal adornment, for the fashioning of ornamental objects, or for other decorative purposes, have been valued in human commerce for thousands of years. Amber, jet, natural glasses, and at least 15 mineral species were sought and used by primitive man, and most of the materials in common use today were known well before the time of Christ. Their variety is remarkably great, and the traceable relationships among their respective sources, modes of occurrence, properties, and histories of production, preparation, and valuation are extremely complex. Their uses have been affected by numerous shifts in fashion, and from time to time by superstition, by decrees of church and state, by personal interpretations of religious significance, and by various presumptions concerning medicinal value and influence on human behavior (Ball, 1935, 1950; Kunz, 1913; Pogue, 1915, Whitlock, 1946). Thanks to their durability, portability, and relative scarcity, some gem stones have been employed as media of exchange, and the investment value of the more precious stones has long been recognized and exploited, especially in Asiatic and European countries. Demands for gem materials have stimulated trade among various peoples for centuries, and they also were responsible for much early geographic exploration. During more recent times they have prompted numerous geological studies and a considerable amount of research on the growth and properties of crystals. Apart from decorative uses, some naturally occurring gem materials also are employed directly in numerous fields of industry. Substances that are manufactured for gem or industrial uses are termed synthetic gem materials; most of these correspond in composition and crystal structure to certain minerals found in nature. Imitation materials are those whose use is based upon their resemblance to substances of different composition and greater intrinsic value. Gem stone is a designation commonly restricted to those materials suitable for personal adornment, and the complementary term ornamental stone is applied to the remaining materials not used industrially. This distinction is arbitrary and somewhat inconsistent, owing to numerous geographic differences and historical shifts in end uses. Further, there is a complete gradation between the category of ornamental stones and that of dimension stone. Substances that lose their identity in use are excluded from the gem category; thus a transparent crystal of beryl would not be classified as a gem stone if it were processed as a source of beryllium metal. The adjectives precious and semiprecious have been employed as a means for distinguishing different gem materials on the basis of recognized value. Diamond, emerald, ruby, and sapphire consistently have been regarded as precious stones, and in cut form they commonly are referred to as the noble gems. Opal, pearl, turquoise, and chrysoberyl also have been classed as precious at various times. In recent years, however, it has been increasingly recognized that no satisfactory distinction can be based upon assessed value or any group of specific properties, and now all gem stones normally are referred to as precious. Indeed, the tendency is to extend this term to include many of the so-called ornamental stones, and the designation semi- precious has been essentially discontinued. Unlike most mineral commodities of economic value, gem materials are little altered in processing for end uses. Some stones are used in essentially their natural form, and most are reshaped and polished without significant changes in their fundamental properties. Thus the preparation of gem and ornamental stones is intended chiefly to emphasize or enhance

Jan 1, 1975