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Jan 1, 1915

By S. Chander, D. W. Fuerstenau

Hallimond tube flotation, contact angle measurements, electrokinetics, and electrode potential measurements have been used to investigate the natural floatability of molybdenite. The effect of surface pretreatment and the role of hydrogen, hydroxyl, molybdate, and calcium ions on the flotation of molybdenite has been studied. The surface potential of molybdenite has been suggested to be controlled by HMoO[ ] and MoO4= surface species whose properties are strongly influenced by pH. Calcium ions, which appear to be specifically adsorbed, are able to reverse the zeta potential of molybdenite. The experimental results have been analyzed in terms of the Derjaguin model of wettability, namely in terms of van der Waals and electrical double layer interactions and hydration effects at interfaces.

Jan 1, 1973

By H. P. Allen

THE Achotla mill of the Cia. Minera de Peñoles is of special interest in that it is one of the few still employing the chloridization process. The ore milled comes from the Suriana mine and consists of both oxide and sulphide, from neither of which can the gold or silver be extracted by a simple cyanide treatment. The mill was built in 1927, after several years of study in the development of the process1, and operated from December of that year until October 1930. Operations were resumed in February 1935, and have been continuous since, treating approximately 5000 tons per month, while the mine is getting up to full tonnage of 6500 tons per month.

Jan 1, 1937

By A. Rakshit, W. E. Kolb, Y. C. Kim

An IBM/XT microcomputer with 10 MB hard disk storage, together with automatic sensing capability of truck movements at several key locations in the pit, formed the core of this automatic truck dispatching system. System software is written primarily in MICROSOFT FORTRAN with supporting subroutines in MACRO assembly language. The software is designed to automatically monitor truck movement throughout the pit, to make heuristic assignments based on expected shovel availability and truck travel times, and to record production statistics. It is currently dimensioned to handle 50 trucks, 10 shovels, 10 dump sites, and three material types. Due to the lack of funds to purchase the necessary communications hardware, the work related to the automatic sensing of truck movements has not been performed to date. Otherwise, the system is fully operational on a realtime mode.

Jan 1, 1986

By John A. S. Dow, Garry G. Lowder

Tapadaa is one of several centers of porphyry copper mineralization in northern Sulawesi. Host rocks are mainly varieties of quartz diorite porphyry. Structural control of mineralization is indicated by elongation of the sulfide system (5 x 1 km) parallel to prominent NW-trending structures, but in detail mineralization is strongly influenced by relative age and lithology. Hydrothermal alteration is characterized by widespread occurrence of advanced argillic assemblages and the presence of sodic rather than potassic alkali feldspar. Propylitic alteration surrounds the mineralized area. Phyllic and advanced argillic alteration occur in structurally controlled zones and in limited pervasive areas. Hypogene copper mineralization develops in rocks with sericite-albite alteration and comprises low total sulfide chalcopyrite-bornite or chalcopyrite-pyrite.

Jan 1, 1978

Jan 1, 1917

By R. A. Bloom, John Birtalan

CONSIDERABLE interest has been shown in recent years toward determining the crystal structure, mode of formation, and chemical composition of the x phase, designated as such by Andrews,' who was the first to establish its presence in Fe-Cr- Ni-Mo alloys . Later work2 by the same author has shown that the occurrence of x depends on the presence of some molybdenum in the alloy. The phase, which appears to be identical or very similar to a manganese, has a body-centered-cubic structure and is closely related to s phase. Koh observed a similarity in composition between x and s and speculated as to whether x might be an ordered structure of u which is known to have a tetragonal crystal

Jan 1, 1957

By Milton E. Wadsworth, W. Martin Fassell, William H. Dresher

A study of the rate of dissolution of molybdenite (MoS2) in alkaline solution was carried out under carefully controlled conditions. Effects of temperature, oxygen over-pressure, and KOH concentration were evaluated. Studies were made in the temperature range 100°C to 175°C and in the pressure range 0 to 700 psia of oxygen. Under these conditions molybdenite was found to leach according to a linear mechanism. Both oxygen over-pressure and KOH concentration were found to control the rate of leaching. The mechanism has been explained in terms of adsorption of oxygen at the molybdenite surface followed by configurational rearrangement of the adsorbed molecules. The hydroxyl ion dependency is believed to be diffusion-controlled. Laboratory batch studies have shown that molybdenite can be readily dissolved in alkaline solutions under moderate conditions of temperature and pressure. Commercial application of this process to the production of ferro-molybdenum and molybdenum chemicals is promising in view of the ease of dissolution of molybdenite and the relatively noncorrosive conditions involved in the process.

Jul 1, 1956

By J. Leja, N. Sheikh

The stability of lead ethyl xanthate precipitate in aqueous environment of different pH (4.5 to 10.5) and at temperatures 25°C-60°C was investigated. Dissolution leads to a wide variation of pH, xanthate, and lead ions concentration in solution and to a deposition of solid products of reactions. X-ray diffraction patterns of these solids enabled identification of Pb(OH)3, PbCO3, and PbS as constituents of the remaining undecomposed Pb(EtX)1, together with some unidentified compounds (which give rise to intensive peaks with d values of 2.82A and 1.71A, and numerous peaks of lesser intensity).

Jan 1, 1974

By M. F. Williams, L. G. Hendrickson

In classification of pulps bearing magnetized ferro-magnetic particles, depolarizing is of great importance. If size separation is to be effective, particles must be individual rather than in flocs. Depolarizing is also practiced in heavy medium separations in which ferrosilicon or magnetite is the medium. When particles of ferromagnetic material have been removed from a magnetic field, residual magnetism causes agglomeration. The term depolarizing refers to the operation of reducing or eliminating this residual magnetism and may thus be considered magnetic deflocculation. The terms demagnetizing and randomizing are also used.

Feb 1, 1956

By H. H. Einstein

Swelling ground is one of the most feared problems in tunneling. Although usually not causing sudden failures during construction, the very large and longlasting deformations give contractors and designers the impression of facing an inevitable phenomenon against which there is no technical defense. Examples are concrete liners up to 1 m (3 ft) thickness that have been cracked or crushed, tunnel inverts that are heaving at 0.1 m (0.3 ft) per week during construction and continue to heave during decades. This paper summarizes essential components of design construction procedures where tunnels in swelling rock can be built to perform satisfactorily. It is important to point out that design and construction cannot and should not be separated. The way the tunnel will be built has to be an integral part of the design. Swelling can be defined as time dependent volume increase and is distinguished from squeezing, another time dependent phenomenon occurring in tunneling. Squeezing involves exceeding the shearing resistance while swelling usually does not. Swelling of rock masses can occur as swelling of the intact rock, swelling of wall rock, of gouge and of filler in the discontinuities of a rock mass, and as a combination of the above. Swelling mechanisms have been discussed elsewhere (ISRM 1983).

Jan 1, 1984

By C. E. Capes

A number of novel but increasingly-important methods of size enlargement in liquid systems are reviewed. These techniques use relatively strong bonding and specialized equipment to form dense and substantially permanent agglomerates directly from particles in liquid suspension. In addition to separation of particles from suspensions, these methods have other broad objectives, including the production of granular (often spherical) materials, displacement of suspending liquid from the product and the selective agglomeration of one or more components of a multi-particle mixture. The underlying principles of the methods discussed include agglomeration by immiscible liquid wetting and by polymeric flocculants. Other procedures to produce granular, free-flowing products based on dispersion and solidification in liquids are also noted briefly. Applications in a variety of fine particle systems are considered with emphasis on minerals and fuels beneficiation and on waste treatment.

Jan 1, 1980

By D. Y. Geng, S. S. Peng

Surface subsidence of two longwall panels, one with a private residence and the other with an arch bridge, was monitored over a period of 1 to 1' ½ years. Surface subsidence data were analyzed in terms of zone of advance influence and delay angle of maximum subsidence velocity. The variational characteristics of both features coincide with the periodic weighting at the advancing longwall face. Surface heaving in the subsidence process can also be attributed to periodic weighting. It was found that residential damages occurred when subsidence velocity exceeded 4.5 mm/day (0.15 ft/day). The effects of locating structures on the panel center and near the gob edges are illustrated. The effect of mining on ground water was also discussed. Finally, methods of reducing structural damages are recommended.

Jan 1, 1984

By C. Edward Capes

Fine particles in liquid suspension can be agglomerated by a number of mechanisms. Well-known methods include the addition of electrolyte to reduce the zeta potential and allow mutual adhesion arid the use of polymeric flocculants to bridge between the particles. A more recent technique, "spherical Agglomeration", is the subject of this paper. The process involves the addition of a second liquid which is immiscible with the suspending liquid and preferentially wets the particles to cause particle adhesion by capillary liquid bridges. Progress in the application of spherical agglomeration to a number of distinct technological fields is reviewed in this paper. The areas of interest include the formation of dense, highly spherical agglomerates, the separation of solids from suspension and the fractionation of complex, multi-component solids mixtures, such as ores. Some of the more interesting recent applications in the energy and environmental fields, such as the beneficiation of' coal and tar sands, are highlighted.

Jan 1, 1977

By F. A. Forward, A. H. Ross, J. Halpern

IN treating carnotite ores by carbonate leaching it is often necessary to subject the ore to a prior roast. Among the advantages that may result from roasting are: 1) improvement in settling and filtering characteristics of the ore; 2) destruction of carbonaceous impurities that would otherwise contaminate the leach solution and consume carbonate reagent; and 3) substantial increase in extraction of vanadium, which is usually low when the un- roasted ore is leached. Recovery of vanadium may be an important factor in processing carnotite ores, and the fact that vanadium is usually recovered in good yield by acid leaching has often been an economic advantage over results obtained with carbonate leaching. It has been found that response of an ore to carbonate leaching, following roasting, depends primarily on its composition and on the conditions of the prior roast treatment, particularly with regard to the roasting temperature, the atmosphere maintained above the charge during roasting and cooling, and the presence of certain reagents. These factors, especially the last, virtually determine the extractions of uranium and vanadium attainable by carbonate leaching, as well as the reagent consumption on leaching, whereas adjustment of the leaching conditions has only a limited influence.

Jan 10, 1957

By W. W. Roepke

One phase of Bureau of Mines research deals with reduction of primly respirable dust generated by bit cutting action at a coal seam face. This paper presents a summary of coal cutting technology addressing this problem. All aspects of the cutting system affecting miner health and safety are discussed. Cutting design concepts are considered that minimize dust generation, energy used, and Ignitions, while maintaining production. With present equipment, an operator can maintain production and minimize dust energy and conditions by cutting at maximum depth (maximum sumping or advance rate) at all times, at minimum rpm with fewest possible bits, and with lowest possible included bit tip angle, i.e., minimum bit wear.

Jan 1, 1985

By R. F. Frantz, T. P. McNulty

The upper-level mineralization of the din Buttes, Arizona copper orebody consists primarily of dilute copper silicate impregnation in fault clay and throughout the altered limestone hostrock. Cuprite and native copper are minor with true chrysocolla rare. Owing to the high calcium carbonate and to the hydrogen ion exchange capacity of the clays, acid leaching would be economical only with cheap acid available. Leaching of the silicate copper with reagents other than sulfuric acid is slow and incomplete unless the ore is first heated to disorder the mineralized grains and to reduce partially the contained copper. Following heat treatment, 70 to 90 percent of the nonsulfide copper can be dissolved in aqueous anrmonium carbonate. Recovery of a pregnant solution by counter-current decantation is effective provided ammonium carbonate solution is added to the washing stages in order to oppose adsorption of dissolved copper by clays in the residue. Thermal stripping of the pregnant solution permits recovery of ammonia and carbon dioxide while precipitating copper either as oxide or carbonate. The research program was carried from batch tests through continuous miniplant operation to a five-month campaign in a 20 TPD continuous pilot plant. Pilot plant results, the relationships among key varibles, and a detailed flowsheet are given.

Jan 1, 1973

By Arthur Redfield

THE West Indies are the summits of a submerged, mountain chain, the continuation of which must be sought in the mountains of central Honduras. In Haiti, the chain divides, one branch passing through Jamaica and the other through Cuba, the Cayman Islands, and the Misteriosa bank. Suess divides the West Indies into three zones: The first zone is entirely of volcanic origin and includes many recent volcanic cones. It includes the arcùate string of islands, which extends from Saba and St. Kitts to the Grenadines and Grenada. The western half of Guadeloupe belongs to this group. The second zone consists of a geanticline, of which the sedimentary rocks range from the Jurassic to the Quaternary, but consist chiefly of Lower Tertiary sediments. In the west it is broad, including the whole of the Greater Antilles; but in the east it is restricted to a narrow belt, which includes the Virgin Islands (except Anegada), Anguilla, St. Bartholomew, Antigua, the eastern part of Guadeloupe and part of Barbados. The islands that compose the third zone are flat and low. Like the second, this zone is broad in the west and narrow in the east; it includes the Bahamas, Anegada, Sombrero, Barbuda, and part of Barbados. Geologically, Florida and the plain of Yucatan may be regarded as belonging to it. Trinidad and Tobago, though-geographically adjacent to the Lesser Antilles, are geologically a detached part of the South American continent. The crystalline complexes of northern Trinidad and of Barbados are a continuation, en echelon, of the crystalline axis of the promontory of Paria. The folded Cretaceous and Tertiary of the central and southern parts of Trinidad represent a continuation of the folded sediments of the Paria district of Venezuela.

Jan 6, 1922

US 4,195,426-Manganese nodules are recovered from relatively great depths on the ocean floor using a self- propelled remote-controlled vehicle having a V-shaped tubular structure with a system of crawlers at its apexes. Underneath each side of the V-shaped structure is a scraping system for gathering nodules and directing them into a tubular conveying system for elevation to the surface ship. A given area of sea bed is fully mined in a single pass of the vehicle. V. Banzoli, V. Di Tella, and P Vielmo, assigned to Tecnomare, SPA. Apr. 1, 1980. 5 pp. 137-60) Filed. 3-31-78 (892,197). Priority: Italy, 4-1-77 (84119A/77).

Jan 1, 1982

By M. D. Cooper

LUCIEN EATON, Ishpeming, Mich.-It is not the custom in the Lake Superior region, as far as I know, to employ shot-firers. Each man, or pair of men (most of the contracts are given to two men) do their own firing; each contractor keeps his powder separately. The general custom is to distribute powder (dynamite only is used) to the mines 2 days a week. The boxes, marked with the contract number and the level, are taken underground and the men take them to their working places. They are kept in boxes, which must not be nearer together than 50 ft. and are usually away from the timber roads or traveling roads. When holes have been drilled, one man usually takes down the machine, and the other man makes up the charge. He cuts the fuse, puts in the caps, etc., at a distance from the powder box. He then carries the powder charges to the working place where both men charge the hole. They do their own firing and warn others coming from any direction that the holes are being fired.

Jan 4, 1917