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By Norman F. Schulz

The technical excellence of separation achieved in a mineral concentration process, or any other process where two constituents of any kind are physically separated from each other, is expressed uniquely and quantitatively by the separation efficiency (E,): E. = (R - R,), where R is the percentage of the valuable constituent and R, the percentage of the waste appearing in the concentrate. The separation efficiency meets all the usual requirements of a true efficiency and is independent of the nature of the process used. It can be visualized as the percentage of the feed material that, in effect, actually undergoes complete separation while the rest of the feed is distributed randomly and unchanged into the two separation products. The problem of quantitatively assessing the results of a mineral concentration process recurs whenever one tries to decide which of two similar test results is more desirable. Although economic factors may greatly influence the eventual choice of process, they usually have very little to do with the technical excellence of a separation and are, therefore, not a consideration at this point. Concentrate grade and recovery, used simultaneously are the most widely accepted measures of performance, and if both the grade and the recovery are greater for one case than for another, the choice is simple. However, when the results of closely competitive operations are compared, it often occurs that one set of test results shows a higher grade and a lower recovery than another and the choice is no longer obvious. Laboratory investigations of a mineral concentration process applied to a given feed material can often be designed to yield successive paired values of concentrate grade and recovery over the practical range of the course of a separation process.' These results may be plotted as some combination of the cumulative values of grade, weight recovery, or unit recovery in the concentrate. The resulting correlations for two slightly different sets of conditions can then be compared qualitatively, or even quantitatively in particular cases.2 Such comparisons are not applicable, however, to individual concentration test results. The reduction of a separation test result to a single efficiency figure, preferably as a percentage of ideality, would afford the simplest and most precise means for comparing the results of competitive tests. The effective proportion of feed material that undergoes complete separation in any real concentration process, hereafter referred to as "separation efficiency," is such a figure. It is essily calculated from the usual feed and product data and can even be evaluated, in many cases, from data in publications describing various concentration processes. Mineral Concentration Processes and Their Evaluation Mineral Concentration Processes: The overall concentration process may be subdivided into a liberation process which severs the bonds between unlike mineral species, and a separation process, which sorts the resulting liberated particles into two products—a concentrate rich in mineral A and a tailing lean in mineral A. A perfect mineral concentration process is represented by the idealized scheme shown in Fig. 1 in which liberation and separation are not differentiated. The feed mixture consists of two mineral types which are completely liberated early in the process and then sorted by type. All the mineral particles of type A which respond uniquely to the selection forces acting in the ideal separator, report to the concentrate, while all the mineral particles of type non-A report to the tail-

Jan 1, 1971

Recent work on decoppering lead is reviewed CUS is formed rapidly even from dilute solutions of copper in lead. The mechanism of decoppering is discussed and an explanation for the retention of metals such as silver in lead is advanced. As decoppering tin appears to be an analogous process, the, Cu-Sn-S system is studied at 300°C.. CuS, which is not an equilibrium product, is found m decoppermg drosses. In the removal of nickel from lead, Ni3Pb2S2 is formed; preliminary measurements show the equilibrium nickel content to be greater than that obtained by stirring in sulphur. Decoppering bIsmuth IS thermodynamically favoured, but is complicated by the occurrence of CuBiS2 The Cu-Pb-S system IS the only one of the four studied where the equilibrium can be calculated simply, as the presence of ternary sulphIde or other phases invalidates calculations based on binary data.

Jan 1, 1971

By Robert W. Greene

Next month, American Commercial Barge Line Company will begin moving coal from mines on the old Camp Breckinridge property in Western Kentucky to TVA's new 2600 MW steam plant at Cumberland City, Tennessee. By April of 1973, this movement will reach a level of 7,000,000 tons per year. TVA bought the coal rights to this property from the General Services Administration in 1965 for approximately $7 million. The reserve contains about 120 million tons of recoverable No.9 coal, and about the same recover-able amount of No. 11 coal. TVA then contracted through competitive bidding with Peabody Coal Company to mine the No.9 seam through two slope shafts. The mines are about 300 feet deep and are separated by the one major fault on this property. The mine portals are approximately 3-1/2 miles apart, with the northern portal being over nine miles distant from the Ohio River (see Figure No.1). In 1969 TV A took bids on alternate methods for transporting 120 million tons of coal to Cumberland City at seven million tons per year. These alter-natives included overland transportation to the Ohio River by rail or conveyor, water transportation from Union County, Kentucky to Cumberland City, and total transportation packages from Camp Breckinridge to Cumberland City. The latter could be a joint land/water package, or all land (rail). Ultimately American Commercial Barge Line was awarded an $88 million package transportation contract to convey the coal from Camp Breckinridge to Uniontown, Kentucky; to store it at Uniontown in a quantity sufficient to allow ratable delivery to the steam plant; and to barge from Uniontown to Cumberland City via the Ohio and Cumberland Rivers.

Jan 1, 1971

By Donald P. Schlick

This Information Circular presents a brief historical digest of the early attempts of the Bureau of Nines and the U.S. Public Health Service to establish coal mine dust exposure standards. It reviews current, accepted standards of the United States as well as available standards of other countries.

Jan 1, 1971

By Irven A. Jacobson

The thermal reactions of l-methylindole were studied in the temperature range of 525° to 627° C in a flow reactor. The major products consisted of 2-methylindole, 3-methylindole, indole, quinoline, hydrogen, and methane. 2-Methylindole is formed from 1-methylindole by an irreversible isomerization reaction. The 2-methylindole isomerizes in a reversible manner to 3-methyl-indole, the equilibrium favoring the 3-methyl isomer. Indole is formed directly from 1-methylindole. Quinoline is formed from l-methylindole, 2-methylindole, and 3-methylindole.

Jan 1, 1971

By George H. Davis

The Caribou sulfide deposit near Bathurst, New Brunswick (Figure 1) is illustrative of one variety of strata-bound sulfide deposits. It consists of numerous near-vertical sulfide lenses which are concordant to the foliation and lithologic layering of low-grade metamorphic host rocks. Pyrite is the chief mineral in these lenses, but appreciable quantities of sphalerite, chalcopyrite, and galena are also present. Rocks in the Caribou mine area belong to the Tetagouche Group of Ordovician age. They consist chiefly of (1) quartz-sericite and quartz- sericite- feldspar schists, (2) greenschists, and (3) slate and phyllite. The trends of these steeply dipping rocks define the trace of a tight, steeply plunging fold structure, the Caribou fold (Figure 2). This fold plunges approximately 750 to the north-northwest; its axial plane strikes N.20°E. and dips steeply westward. Sulfide lenses of the Caribou deposit are associated spatially with the Caribou fold. The deposit is located in the fold along the contact between quartz-sericite and quartz-sericite-feldspar schists on the hanging wall and quartz-chlorite-sericite phyllites and graphitic schist on the footwall (Figure 3). Genesis of the Caribou deposit is ambiguous because its strata-bound form suggests syngenetic sulfide deposition, whereas its location within a fold suggests structurally controlled epigenetic mineralization. Acceptability of a particular genetic model rests on establishing the time of mineralization relative to deposition, deformation, and metamorphism of the associated rocks. To establish the timing for Caribou mineralization, the deformational histories of rock and sulfide, respectively, were compared. Epigenetic and syngenetic models can be tested against this interpreted structural history of the Caribou deposit.

Jan 1, 1971

By Robert B. Tippin

A number of recent studies 1-4 suggest that steelmaking expansion might be achieved more economically by a combination of the prereduction furnace and the electric steelmaking furnace rather than through new blast furnace construction. Supergrade concentrates would be the first step in an evolving technology which bypasses the blast furnace and in which the concentrates are first made into pre¬reduced pellets and then used directly in electric steelmaking, Prereduced pellets made from superconcentrates should not only be competitive with scrap, but should be a preferred feed for the electric furnace because of the absence of such residual elements as copper and nickel. Furthermore, geographic areas remote from present steelmaking centers may find the electric furnace to be an economical method of providing local steel requirements. The development of successful methods of producing superconcentrates may also be expected to find application to conventional blast furnace burdens. The need for methods of increasing grade of domestic concentrates will become increasingly urgent in the face of competition from high grade imports. Only a small percentage of domestic iron ore production can qualify as superconcentrates, (Superconcentrates for the purpose of this investigation are limi¬ted to those concentrates which contain a maximum of 2 percent S'02). During the last several years the Twin Cities Metallurgy Research Center of the Bureau of Mines has directed research efforts to develop methods of manufacturing superconcentrates from present standard grade products by cationic flotation, screening, and magnetic separation.

Jan 1, 1971

By Kermit Allen

Storing natural gas in solution mined salt cavities appears to be one of the more promising methods being considered by some major gas transmission companies for meeting peak demands. Historically, these companies have been faced with the problem of meeting peak demands when the source of natural gas is located hundreds of miles from the marketing area. Transcontinental Gas Pipe Line Corporation's position was further complicated because some of its offshore Gulf Coast gas supply wells may have to be shut in during hurricane alerts. Transco's solution was to construct. solution mined salt storage caverns adjacent to its pipeline near Eminence, Mississippi. (See Figure 1.) In 1965, Fenix & Scisson, Inc., was engaged by Transco to evaluate the feasibility of storing natural gas in caverns dissolved from salt at selected locations along Transco's pipeline to the East Coast. In June of that year a report was submitted to Transco concluding that this proposal was feasible and recommending several potential sites for storage development. Additional engineering and geological studies followed and in March 1968 the Eminence Salt Dome site was selected and storage construction began that year.

Jan 1, 1971

By Jacques B. Wertz

Although fracture intersections and "domes" seem at a number of places to be the basic structural combination for the occurrence of a mining district, of the porphyry-copper type particularly, this situation is, of course, not always to be expected. For instance, the group of mines comprising Superior, Ray, Miami, Globe, Christmas appeared from the beginning of these structural studies as typical exceptions, and there are others. One had to expect additional parameters to allow for any mineral concentration to occur. One of these apparent parameters is here considered. From the result of stratigraphic studies related to ancient formations in Southeast Arizona, the Martin limestone (Devonian in age) was retained as having a possible relationship with the structure-economic studies in progress, as evidenced for instance by the mineralized O'Carroll bed located at the base of the Martin. This limestone formation has been rather extensively investigated in the past and there are many known sample localities. For this work, the isopach map was drawn by computer to insure more objectivity and, in addition to the available data points, a number of dummy points with a zero value were added around the assumed form-

Jan 1, 1971

June was the month in which AIME was founded in the year of 1871. For some reason, February was selected as the month for the legal Annual Meeting. One can't help thinking wistfully of Annual Meetings in June but of course this is not the reality. Because the Centennial Ceremonies are taking place in February, that month has been chosen as the one in which MINING ENGINEERING, the monthly magazine of the Society of Mining Engineers, a constituent society of AIME, is publishing its Commemorative is- sue to celebrate the event. SME and ME take a proprietary air about AIME. This is mostly because AIME started as the American Institute of Mining Engineers. Metallurgy was added to the name in 1919 and Petroleum in 1956. The official abbreviation of "AIME" has been retained, however.

Jan 1, 1971

Where vertical or near vertical faces are required in open excavations in soils and rocks, some form of stabilization of the 'cut is often necessary. Stressed anchors either alone or in combination with steel, timber or concrete-lagging are often an economical and versatile means of providing support. Stressed anchors are also-a very economical means of anchoring a wide range of structures such as dams, cranes, transmission towers, retaining walls, spillway aprons, bridge piers; and - stacks. The anchors need not be stressed always on installation.other than to proof load them. A number of examples illustrate some of-the more practical aspects of.the design and construction techniques used. No new methods of design or construction are involved, but merely some consolidation of the engineering design, soil and rock mechanics,thinking applied to the stressed anchor tech- nique.

Jan 1, 1971

By P. M. Dranchuk

"""PLANET EARTH seen from space appears as a fragile and limited life-supporting system in a vast emptiness. That such a view is, in fact, an accurate one is now more widely accepted than it was not long ago, before Earth's problems of over-population, overconsumption, limited resources and environmental degradation attained the limelight. The danger is that a government and public now deluged by doomsday prophecies and bemused by equally confident reiterations that technology will cure all may hesitate in coming to grips with the problem, in the hope that, given time, it will go away."" With these words, Preston Cloud begins a recent editorial, in Science(l), in which he presents a brief resume of some of the findings of the Committee on Resources and Man of the National Academy of Science-National Research Council(20.Their report, which is based on a two-year study by an extremely competent group and consists of some 250 pages of text, is even more far-reaching and sobering than the report on Energy Resources(3). It begins by quoting Sir Macfarlane Burnet as follows:""There are three imperatives: to reduce war to a minimum; to stabilize human population, and to pre-vent the progressive destruction of the earth's irreplaceable resources.(4)"

Jan 1, 1971

By Glenn E. Craig

The practical and effective pulp distributor here presented is believed to be of a completely new and innovative design. It was developed at the San Nicolas Plant of the Marcona Mining Company in Peru, where it has been thoroughly plant tested using iron ore slurries of a particularly abrasive nature. It has proven to be superior to the apparatus originally installed, or to any observed in operation elsewhere. In plant practice the capacity and efficiency of many process units such as screens, magnetic separators, and jigs are strongly affected by the loading pattern, and for better results the flow of pulp must be proportioned across the receiving lip in equal quantities per unit width. The distributors originally installed on the drum magnetic separators in San Nicolas proved to be unsatisfactory, and several trial modifications failed to show any improvement. As is usually the case, feed rates were being steadily increased, and appreciable losses to tailings resulted. A check of the distributors on the market discloses no reasonable substitute, so efforts were directed toward devising an entirely new type. Required was a positive type of action which would guarantee that the pulp flow be spread equally along the length of the drum. Discussion As indicated, the motivation for development was simple necessity. The plant in San Nicolas crushes, grinds, and concentrates magnetic iron ores of a particularly abrasive nature, and depends largely on magnetic separation to obtain a marketable product. Feed to the numerous drum magnetic cobbers and finishers varies from rod mill discharge at a nominal minus ten mesh to a ball mill fine grind of seventy percent minus three hundred and twenty-five mesh. Operational factors affecting the magnetic separators were well controlled,

Jan 1, 1971

By A. F. Laurin, A. L. Dorr

"Because of its wide areal extent, its numerous lithological facies and its high degree of metamorphism, the Quebec portion of the Grenville province has only partly been explored and prospected. Rock types that are economically among the most interesting in the Grenville are those of mafic and ultramafic compositions, because of their great potential for coppernickel and chromium-platinum. The peculiar mode of occurrence and the distribution of these igneous masses in which copper-nickel mineralization is known to occur indicate' two common geological features: (1) aerial photographs and/or topographic maps strongly' suggest close spatial (and possibly temporal and genetic) association of most of these mineralized mafic and ultramafic intrusions with circular structures; (2) when plotted on a large-scale map comprising the Quebec portion of the Grenville, these circular structures fall along two lines which could correspond to major tectonic features. Even though the genetic links among the mineralized mafic-ultramafic masses, the circular structures and the linear features are not yet fully understood, their associations are believed to be empirically valid and should therefore be used as geological tools by those interested in exploring the Grenville for copper-nickel and possibly chromium-platinum deposits. It should be noted that these mafic and ultramafic bodies do not appear to be spatially related to anorthosite complexes."

Jan 1, 1971

By R. V. Higgins

The results of two separate but related studies are given. In the first study, four equations were tested; the object was to determine which would produce a curve that would best fit data points that represent a trend of declining oil production in 90 California fields. Two conventional equations (the Arps and semilog) and two novel equations (extreme-c and double semilog) were tested. The curves were first fitted to the initial 9 years of the 15-year production data and then extrapolated for 6 years to determine how well the extrapolated curve would fit the data points. The generated curves were also extrapolated beyond the last data point to predict rates of future production. The results of the first study showed that no equation was clearly superior to the others in all respects. The semilog equation resulted in the best fit to production data for the first 9 years, but the Arps and extreme-c equations produced a better fit for the extrapolated data for the period of 9 to 15 years. The Arps and extreme-c also gave more realistic production rates when extended to the point where cumulative production equaled reserves. A second study was made to determine if the least-squares technique applied to the Arps equation would result in more accurate extrapolations. The merits of the logarithmic and the nonlogarithmic forms of the Arps hyperbolic equation were also tested. For the logarithmic expression, it was found that one of the constants of the Arps equation reached a value so small or so large that the equation was not applicable to the data of 40 of the 90 California fields. The nonlogarithmic form of the Arps equation was applicable to neither the same 40 fields nor to a few additional ones. When the data and the Arps equation were compatible, the use of the least-squares technique as compared with other methods improved the extrapolation accuracy somewhat.

Jan 1, 1971

A study of the accessory opaque iron-titanium oxide minerals of the Oiles Complex, central Australia, was an Important complement to an investigation of the magnetic properties of the Complex. These minerals constitute no more than 10 per cent of the rocks sampled, and generally less than 1 per cent of the ultramafic rocks ("magnetite" concentrations were not sampled for magnetic investigation).Titanomagnetite is the main opaque mineral present, although ilmenite exsolution has been widely developed. High-temperature oxidation of these produced mainly titanohematite, pseudobrookite and rutile. Both exsolution and high-temperature oxidation developed along specific crystallographic directions (along {111}), and in Irregular patches. Low-temperature oxidation is generally not well-developed, indicating the small degree of weathering in the rocks sampled.Although the Oiles Complex is layered, no apparent overall preferred orientation of the iron-titanium oxide minerals was observed, other than crystallographically controlled alignment of very fine grains within pyroxene crystals. Other textural features of the opaque oxides are restricted to symplectic intergrowths mainly with the ferromagnesian silicates.

Jan 1, 1971

By F. D. Forgeron

"ONE OF THE FIRST DOCUMENTED APPLICATIONS of soil geochemistry in the Canadian Shield was that carried out by Chisholm in the Kenora district in 1949. This survey proved successful in outlining sulphide-associated gold veins utilizing cold-extractable metals. Since then, mining companies, government agencies - both provincial and federal - and universities have conducted soil investigations. Some of the results are documented in publications, others are on open file in provincial and federal mines departments and, unfortunately, many other investigations with both successful and unsuccessful results are buried in company files or have been discarded. This paper deals with soils within the scope of chemical studies of overburden in the Canadian Shield. The subject is a broad one and some definition is required. The soil investigations discussed herein are those aimed at the testing of specific targets more or less in the source area. This definition distinguishes soil investigations from other overburden studies which commonly monitor metal accumulations at some substantial distance from the metal source. Naturally this distinction is relative, because in many instances there is overlap."

Jan 1, 1971

Rock bolting provides a supplement or alternative to conventional timber and steel supports. The tensile strength of the bolts lies within a range established by manufacturing quality control. Rock bolt testing determines the ability of the rock, anchor and individual bolt as an assembly to accept load. The.test is performed to the yield strength of the bolt or anchor and deflection is observed. The anchorage index, inches deflection per 1000 lb load increment, is a measure of anchorage quality. This allows comparison with anchorages under ideal conditions. It also permits comparative assessment of roof bolt anchors in a particular environment.

Jan 1, 1971

By Robert H. Schutz

This publication lists and describes devices approved jointly by the Secretary of Interior and the Secretary of Health, Education, and Welfare, under the provisions of [§]70.300-1, Part 70, Subchapter 0 of Chapter I, Title 30, Code of Federal Regulations (35 F.R. 5548, April 3, 1970), for use as respiratory protection against respirable pneumoconiosis-producing dusts. Included are type C supplied-air respirators approved under Bureau of Mines Schedule 19R and dust, fume, and mist respirators approved under Bureau of Mines Schedule 21B.

Jan 1, 1971

By K. C. Ko, D. A. Pifer

The theory of probability with respect to the failure of structures is discussed. It is shown that the probability of safety, probability of failure, and factor of safety are directly related to each other and that as standard deviation approaches zero, the probability curves approach a unit step function which can be interpreted as the conventional factor of safety. The factor of safety is numerically the ratio of the load to the strength of the material at a particular point or plane in an engineering structure. Mathematically, it can be illustrated as a unit step function undefined at the point where the factor of safety is one (Fig. 1). The uncertainty of variation of soil and rock strengths require factors of safety much higher than those used in other engineering structures. The factors of safety used are generally determined from past experiences with similar structures. However, the factors thus determined do not have any theoretical meaning or do not indicate any relationship to actual safety.' It seems, therefore, logical to develop a system with a sound theoretical basis to obtain a more suitable factor of safety for structures. An application of elementary theory of probability indicates that it is possible to relate this number to theoretical and practical engineering facts.

Jan 1, 1971