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By Jackson M. Langton

INTRODUCTION The Morenci-Metcalf district is located on the southern slope of the white Mountains in Greenlee County, Arizona. Both porphyry copper deposits are four to six miles northwest of Clifton, the county seat, and the new Metcalf mine is situated approximately one mile northeast of the Morenci open pit (Figure 1). Chase Creek, a south-flowing tributary of the San Francisco River, dissects the district and separates the two ore bodies. More than 1,200 exploration and development drill holes have been completed in the district and the Morenci-Metcalf ore bodies have been delineated on a 400-foot grid. Recently initiated drilling programs have revealed new data about deeper protore and associated hypogene alteration. This information, correlated with surface mapping and petrographic studies, was utilized to propose a plausible geochronologic sequence for this region. The reasoning behind this study has been helpful in locating new ore beneath leached capping indicative of only protore mineralization. The scope of this paper is to establish a practical solution to a highly theoretical problem of ore genesis and to familiarize the reader with stratigraphic, structural, and mineralogic events responsible for localizing ore in this district. Continued research will possibly alter the proposed time span and relative displacements, but it is doubtful that the order of events will vary significantly. Geochronologic conclusions are therefore presented as general hypotheses and additional geologic mapping,

Jan 1, 1972

By R. A. Allwes

In-plane bending and torsion tests were conducted on full-scale masonry walls to evaluate three post-reinforcement designs. The designs were developed to minimize longwall mine subsidence damage to existing residential masonry foundations. The bending tests show that vertical and horizontal post tensioned tendons significantly increase the resistance of a masonry wall' to in-plane bending. The torsion tests reveal that post tensioned tendons increase a masonry wall's limit of deformation but do not increase its torsional stiffness. The torsion tests also show that the masonry units minimally contribute to the torsional stiffness of a masonry wall.

Jan 1, 1995

By C. O. Brawner

Approximately 7 billion tons of soil, rock and ore are currently being excavated in open pit mines and quarries on the North American continent at the present time. As the depth of excavation increases and the grade of ore being mined reduces, the safety and economy of the stability of the pit slopes becomes increasingly important. The magnitude of the potential influence on economics can be appreciated from the results of recent full scale field studies by Kennecott Copper Corporation at the Kimbley pit near Ely Nevada (Merrill, 1968). This pit was originally excavated with an average wall slope of 45°. Based on detailed studies it appeared that a slope of 610 would be stable. Subsequent excavation to this slope proved the original pit could have been steepened by 16° during production.

Jan 1, 1968

By Robert Moore Lewis

Extensive exploration is being undertaken throughout the world in search for heavy minerals, particularly rutile and other titanium minerals. The federal government is sponsoring research involving rutile ores and recovery of stockpile-grade concentrates from domestic sources. Producers are being forced to turn to deposits with a heavy mineral content as low as 0.50% (essentially rutile and zircon). The North Carolina State University Minerals Research Laboratory investigated the possibilities of recovering heavy minerals from the amine tailings of the Texasgulf Inc.'s phosphate plant at Aurora, North Carolina. One laboratory beneficiation procedure using gravity, electrostatic and magnetic processes, resulted in the recovery of 78.7% of the heavy minerals in the amine tailings. Based on this percentage recovery and the present rate of phosphate mining, approximately 13,000 tons per year of heavy minerals (principally ilmenite and zircon) with a potential value of approximately $1,045,000 (1977) could be recovered. The economic potential for recovery of these heavy minerals appears to be favorable. A flotation procedure for up-grading the heavy minerals content in the amine tailings has been developed at the Laboratory, which could allow for concentration of heavy minerals and storing them in tailings area other than main tailings for future processing.

Jan 1, 1978

By B. H. Kim

The use of a 25.4 mm diameter water-only hydrocyclone for separating fine-size (-150 µm), high-density (>4.5 g/cc) particles from similar-size, lower-density (2.65 glee) particles was investigated. It was found that a single-stage separation recovered nearly 90% of the heavy minerals (7.0 g/cc), while achieving a volume reduction of about 70%. The use of dense medium in a single stage improved volume reductions to 90% at similar heavy mineral recoveries. In addition, computer simulations of a three-stage circuit were performed, which showed that recoveries approaching 97% with volume reductions of 95% were possible.

Jan 1, 1998

By D. R. Nagaraj

Based on our finding that commercial copper chelating solvent extractants such as LIX65N® and LIX63® are excellent collectors for copper minerals, a detailed study was made using several water-soluble chelating agents belonging to the class of aromatic hydroxyoximes and having a gradual structural variation. A basic study of the system salicylaldoxime-tenorite was also carried out. Microflotation tests as a function of concentration of oxime, pH, addition of copper etc., using oxidic copper minerals such as chrysocolla and tenorite, and batch laboratory flotation tests using synthetic mixtures of quartz and oxidic copper minerals were carried out. The studies were aimed at an understanding of the collector function of the hydroxyoximes and of the general flotation behavior in these systems, in addition to studying the structural aspects of oximes vis-a-vis flotation. The results have demonstrated that all of the hydroxyoximes studied here have comparable collector property, and in all cases the oxime was found to be partitioned between the mineral surface and the copper in the bulk aqueous phase in the form of a bulk copper chelate. The occurrence of the latter could be accounted for by the formation in the bulk phase of a chelate between oxime and copper released from the mineral and/or by the detachment of the surface chelate. The role of surface and bulk chelates in flotation is discussed based on the results of partitioning of chelating agent into bulk and surface chelates in the system salicylaldoximetenorite. The effect of substitution of CH2 groups or benzene ring in the chelating agent molecule on its collector property is also discussed, in addition to the finding that only the anti-isomer has the ability to collect.

Jan 1, 1979

By L. P. James, W. W. Atkinson

Utah has produced about 31.7 kt (1 billion oz) of silver, more than any state in the United States except Idaho. Several high-grade ore systems in Utah, where the mines are now closed, occur within large polymetallic limestone-hosted districts related to plutonic complexes. These mines fed several major lead smelters for nearly a century. Interaction of magmatic chloride-rich fluids with carbonate rocks localized significant bonanzas within these districts. A low sulfidation state was produced in the fluids by their passage through limestones. The Bingham openpit mine has also yielded more byproduct silver than other porphyry copper-molybdenum-gold systems. Away from exposed intrusive rocks, some large silver-only systems occur in Mesozoic sandstone and in caldera-related veins in volcaniclastic rocks. Thick permeable latest-Proterozoic basement metaquartzite sequences present beneath western Utah may have been important, as perhaps they were in the Coeur d'Alene district of Idaho, in providing chloride and silver-rich ore fluids. However, it is clear that specific Tertiary magmatic events played an essential role in the evolution of the Utah silver-rich metallogenic province. The largest silver districts in the state are genetically related to Tertiary porphyritic plutonic rocks.

Jan 1, 2003

By A. S. Ibrado, D. W. Fuerstenau

"Gold, silver and copper form various complexes with cyanide, of which only the singly charged dicyano form adsorbs appreciably on activated carbon. The adsorption of the dicyano complexes appears to be controlled predominantly by chemical reaction at the surface of a shrinking unreacted core. Metal uptake over time is non-linear, which eliminates control by boundary layer diffusion. The rate of adsorption is not enhanced by a reaction interruption, which suggests the absence of concentration gradients in the pores. Finally, the rate of adsorption increases with decreasing activated carbon size in a manner consistent with the shrinking core model. The results of this investigation accentuate the importance of efficient acid washing of carbon and removing carbon fines from the barren carbon stream. INTRODUCTION With the dwindling reserves of high-grade ores, most of the world’s gold is produced from low-grade ores by cyanide leaching. In the past, leaching was followed by the Merrill-Crowe process, in which gold is precipitated from clarified pregnant solutions by zinc cementation. This process is still being used for high-silver ores, where the cost of carbon stripping becomes prohibitive. For deposits with silver-to-gold ratios of about 4 or less, adsorption on activated carbon would be the usual solution purification step taken. The process simplifies solid-liquid separation and offers a viable solution to preg-robbing organic carbon in some ores. The modern industrial application of carbon adsorption started with the carbon-in-pulp (CIP) process, where carbon adsorption was used mainly as a solution purification step. In 1973, Homestake Mining Company commissioned the first large-scale CIP plant in the U.S.A.1 Later, carbon was added earlier in the circuit to control preg-robbing by adsorbing gold cyanide onto activated carbon as soon as it is dissolved. The scheme is successful because activated carbon is a stronger adsorber than the organic carbon found in preg-robbing ores. This process came to be known as the carbon-in-leach (CIL) process. Numerous research investigations have been performed on the chemistry involved in the CIP process, which at the time of its introduction was not clearly understood. Of these, research on the kinetics of adsorption probably bears the most immediate impact on industrial practice,2,3 where adsorption systems rarely reach equilibrium, if at all, and slight slowdowns in the adsorption rate can translate into significant decreases in revenue. To illustrate this, organic compounds, like flotation reagents, have been known to impair CIP circuits. However, laboratory tests showed that the organic compounds do not significantly affect the adsorption capacity of activated carbon. Rather, the harmful effect may be attributed to a lowered adsorption rate.4,5 Also well known is the faster rate at which fine activated carbon powders reach equilibrium compared to coarse activated carbon, even though the final (equilibrium) amount of material adsorbed per unit weight is the same."

Jan 1, 2015

By Iga Trisnawati, Fitria Puspita, Himawan Tri Bayu Murti Petrus, Gyan Prameswara, Idi Amin, Andi Nurfaadhilah Ulfah

Laterite ore is a valuable resource due to its high content of metals essential for modern technology, including nickel, iron, and cobalt. However, extracting nickel from laterite ores is challenging due to their complex mineral composition and low nickel concentrations. This study examined the leaching behavior of pre-roasted laterite ore and the effect of roasting on leaching kinetics. The ore was roasted at temperatures of 280°C and 610°C for 3 h, followed by sulfuric acid atmospheric leaching. The results demonstrated that pre-roasting at 610°C significantly enhanced nickel leaching recovery, with up to 93% nickel successfully recovered. The leaching process of pre-roasted laterite ore was found to be controlled by diffusion through the ash layer, with activation energy values of 20.97 and 18.97 kJ/mol for laterite roasted at 280°C and 610°C, respectively. These findings indicate that pre-roasting can improve the leaching performance of laterite ore, potentially leading to more efficient and sustainable nickel extraction processes.

Feb 27, 2024

By M. S. Enders

The McDonald deposit is a volcanic-hosted epithermal gold resource that is estimated to contain 251,000 kg of gold in 375 Mt of ore at an average grade of 0.7 g/t gold. Phelps Dodge exploration geologists, working for the Seven-Up Pete Joint Venture, discovered the deposit in 1989. By the end of 1992, 494 drill holes for over 113,000 m of drilling, bulk sampling, soil geochemistry, geophysics, metallurgical testing, engineering, and environmental studies had been completed to support feasibility studies. The discovery of McDonald required vision, persistence, and commitment of everyone from the geologist on the drill rig to the senior management of the company.

Jan 1, 1995

By Dan S. Nilsson

Small-scale mines are today expected to provide much of the increased production of metals, industnial minerals and coal this country demands in the future. But what is the size trend in the mining industry?

Jan 1, 1980

By C. Newman

"Over the past decade, as conventional underground deposits have been depleted, mining operations have been forced to produce at greater depths and in more geologically and geometrically challenging conditions. As such, there has been a global increase in the application of cemented paste backfill (CPB) in tabular deposits utilizing open stope mining method with a delayed backfill placement. Despite the extensive use of CPB, many fundamental factors affecting the design of safe and economical fill structures are still not well understood. A critical issue in the design of backfilled stopes is the determination of stress states within the fill material itself as well as the surrounding rock mass. Analytical equations provide a means of quickly evaluating the effectiveness of a given design. However, in developing these equations large assumptions are implemented to simplify the design problem. It is important that one understands these simplifications as well as their effect on the overall design. This paper investigates common analytical equations utilized in the evaluation of single vertical backfilled stopes and their assumptions through comparisons to numerical modeling results. INTRODUCTION AND BACKGROUND As the mining industry continues to produce at greater depths and in more geometrically and geologically complex conditions, cemented paste backfill (CPB) has gained traction as a means of providing localized ground support in modern stope-and-fill mining operations. The application of CPB in stope-and-fill mining as a ground support material has led to the reduction of mine waste costs, while increasing both mine production and stability. In an attempt to achieve total extraction of the mining reserve, stope-and-fill mining operations often employ a primary-secondary excavation-support sequence (see Figure 1). In this practice, primary stopes are initially excavated and then backfilled in a two-stage pour; plug and final pours. During the first stage (plug), a CPB material with increased cementitious content is placed at the bottom of the stope providing a strong base from which to build a backfill structure as well as protect mine works from material breakthrough. Following placement, the backfill plug is allowed to cure to a given strength as designated by the mine design. Upon achieving the required cure strength, a less cementitious CPB material is used to backfill the remaining stope area. This is referred to as the final pour stage. With all primary stopes excavated and supported using backfill, the extraction of the secondary stopes commences as primary stopes are utilized as artificial pillars. While the application of CPB in a primary-secondary extraction-support mining sequence allows for a substantial increase in reserve recovery, it is imperative the mining personnel and planning engineers have a clear understanding of the material’s behavior and stress interaction with the surrounding rock mass to ensure the most efficient, cost-effective, and safe extraction of underground deposits."

Jan 1, 2018

By D. G. Krige

I read the paper “The jackknife approach” with interest. There appears to be a widespread misunderstanding of the kriging variance as a measure of the error variance of the kriged grade estimate of an ore block. Virtually all mineral deposits display skew frequency distributions and are subject to the well-known proportional effect. Thus, it is usual to find in an ore body, when subdivided a really into subpopulations, that the variances of the grades (or the total sills of the variograms) for the subpopulations will be correlated with the corresponding mean grades (usually linearly with the squares of the mean grades). Thus, the variogram will be stationary.

Jan 1, 1996

By S. C. Suboleski

In a high risk venture such as mining where capital is committed and contracts are signed on the minimum of information, decisions are based primarily on production forecasts derived through consideration of such factors as management-labor relations, mining practice, variations in physical conditions and the equipment applied. Among these factors, the physical conditions offer the least opportunity for control and, due to the wide range of mining conditions that may be experienced, little effort has been made to develop objective methods for measuring their effects on mine out- put. The aim of this paper is to demonstrate a method for assessing these relationships that can be applied under a wide range of conditions both in new mines and in working sections where there is a need to determine the impact of proposed operational modifications. psing empirical data from active underground mines, a mathematical model was developed to derive a set of regression equations for predicting production as a function of mining conditions

Jan 1, 1980

By W. J. Wolfe

Using a combined fire assay-atomic absorption method, gold determinations with a minimum detection limit of 5 ppb were made on 345 samples of Early Precambrian felsic plutonic rocks collected 2 2 from intrusions ranging in size from 4 km to 88 km and in composition from syenite to granodiorite. Gold levels in unmineralized stocks are consistently below the 5 ppb detection limit of the analytical method used. In contrast, analyses of samples from stocks containing gold mines within their borders and in nearby metavolcanic-metasedimentary host rocks show a strongly skewed trace element gold population with a substantial percentage of gold values exceeding 5 ppb and ranging as high as 320 ppb. The data indicate that (1) ore-stage hydrothermal metasomatism has produced widespread Au enrichment in Precambrian intrusions that host epigenetic vein-type gold deposits, and (2) geochemical Au analysis of samples collected from 30 to 50 randomly distributed sites can be used to estimate the gold exploration potential of stock-sized bodies and to outline internal patterns of Au variation which may be useful in directing exploration to particular contacts or portions of a stock. The results do not conclusively indicate unusually high Au content in primary unaltered igneous rocks.

Jan 1, 1975

By S. Veeramasuneni

The sign of the surface charge for alkali halides in their saturated brines has been established from non equilibrium electrophoresis measurements and on this basis the flotation response of alkali halides was explained based on the adsorption of oppositely charged collector colloids by heterocoagulation. These surface charge results for alkali halides are generally as expected from simplified lattice ion hydration theory with some exceptions, specifically LiF, KCI, NaCl, KBr, RbBr, KI, and Rbl .The presence of natural oxygen defect states in the crystal lattice and the inaccuracies involved in the gaseous ion hydration free energy values used appear, in past, to be responsible for these deviations. The presence of natural oxygen defect states in KCI, KBr, RbBr, and Rbl as characterized by UV Nis absorption, was found to account for their anomalous surface charge. Further, other positively charged alkali halides, LiF, NaCl and KI, were found to be free of oxygen defect states. Nevertheless, oxygen defects can be created in these alkali halides to make them negatively charged and has been demonstrated for NaCl. Such negatively charged NaCl can be readily floated with positively charged amine collector colloids thus confirming the surface charge/collector colloid adsorption theory.

Jan 1, 1996

By William J. Stone

Large reserves of coal and uranium exist in the San Juan Basin of northwestern New Mexico. The mining and development of these resources necessarily also involves depletion of area water resources and disturbance of the hydrogeologic framework. In an effort to better define the water resources and hydrogeologic framework of this region, the New Mexico Bureau of Mines and Mineral Resources, the U. S. Geological Survey, and the State Engineer's Office are presently engaged in a cooperative study of the Hydrogeology and Ground-Water Resources of Northwestern New Mexico. The purposes of this paper are to introduce our project, review tine coal and uranium resources of the San Juan Basin, and discuss the various hydrogeologic considerations recognized in their exploitation.

Jan 1, 1976

By Harold L. Lovell

The areas of application, the limitations imposed by water chemistry as well as the advantages and disadvantages in the use of limestone for the treatment of coal mine drainage have recently been described by the authors (1),(2), (3). The process has been demonstrated in continuous, full-scale operation to yield a treated water meeting specifications established by the Pennsylvania Sanitary Water Board and containing excess alkalinity. Their final pH levels are usually less than seven, a condition which avoids consumption of excess neutralization reagents, but which occurs with lime-based processes and results from unwanted side reactions. Operating experience has been cited by Calhoun (4) using ferric waters while others (5), (6), (7), (8), (11), have reported on related research efforts. Despite the advantages including ?the relative simplicity, and minimal costs of the process, there have been very limited industrial applications of mine drainage neutralization with limestone. Although any treatment of these waters may be considered as a temporary control measure (9), the lack of feasible, immediate alternatives, the extensive magnitude. of the waters and the high cost of treatment requires that optimum processes should be utilized and that operating experience in their use be developed as is feasible. This paper will review treatment experience with a ferrous water of moderate pollution loading .

Jan 1, 1972

By Rees D. Groves

Cement copper is ordinarily converted to marketable metal by processing in a conventional smelter and refinery. Because of rapidly increasing cement copper production and limited excess smelting capacity, other techniques were investigated for preparing marketable copper products. One route was to make copper powder for industrial use. The process scheme employed flotation for rejecting the bulk of the impurities, acid leaching to remove residual iron and aluminum, reduction sintering to eliminate oxygen, and grinding to obtain powder. Another route was to sinter the floated and leached copper into the form of anodes and electrolyze these to yield refined copper cathodes. At a current density of 30 amperes per square foot, power consumption for electrorefining was 185 kwhr per ton of copper. The feasibility of preparing commercial-size anodes by sintering is still to be assessed.

Jan 1, 1970

"With up to 2,300 m (7,545 ft) of rock on top of it, the Gotthard Base Tunnel, which is scheduled to go into regular operation in December 2016 in the Swiss Alps, is not only the world’s longest, but also the deepest railway tunnel ever built. Accordingly, the temperatures in the tunnel are very high, with the surrounding rock expected to reach 45° C (113° F) once the tunnel is fully operational. Since unrestricted rail operations are only permitted in temperatures of 40° C (104° F) or less, the heat has to be controlled with suitable equipment. Large fans developed and built especially for this application by TLT-Turbo GmbH provide fresh air for regular operations as well as during maintenance and repair work. Separate fans ensure that the emergency exits are properly ventilated in case of fire. In addition to coming up with a technical solution that could handle the special challenges of this project, the engineers and planners had to develop detailed preliminary plans as well as a sophisticated logistics and installation concept.The Gotthard Base Tunnel consists of two 57-km (35-mile) long tubes, one in each direction. Including all connecting and access tunnels, the entire underground system measures 152 km (95 miles). At Faido and Sedrun, at approximately 16 and 36 km (9 and 23 miles) respectively, two multifunction stations were built that cut each of the two tubes into three sections of roughly equal length. Here, trains can make emergency stops and change tracks, if necessary. This is also where eight large axial fans made by TLT were installed that exchange the air, i.e. they extract a certain amount of heated air and inject the same amount of cool fresh air a few hundred meters further down the train tracks. In addition to the four exhaust and four supply fans, 24 so-called jet fans were installed along with associated components like silencers, shut-off dampers, drives and lubrication systems from TLT.In addition to exchanging the air, these fans are used to enable maintenance and repair operations in the tunnel. Current plans call for blocking each tunnel tube for one night per week in order to perform preventive maintenance work, thus enhancing the tunnel’s overall functionality and availability. During these hours, many people will be in the tunnel who require fresh air. “One of the major criteria for winning this bid was the fans’ ability to quickly switch between a wide-range of modes. TLT fans are among the best in the world in this regard,” said Andreas Kuhn, TLT’s project manager for the Gotthard Base Tunnel, about the selection of his company’s fans for this project."

Dec 1, 2016