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By P. F. Hara, O&apos

Stratabound Proterozoic precious metal mineralization in central Arizona is associated with felsic and adnesitic to mafic volcanic rocks and sediments derived from these rocks. Hydrothermal fluids associated with felsic volcanism form gold mineralization within hotspring vent complexes or within asymetric basins, which flank the vent complexes and are filled with tuffaceous sediments. Massive to semi-massive sulfide copper-zinc systems associated with felsic volcanism may locally contain small gold occurances either laterally or vertically zoned from the ore. In andesitio to mafic rocks, zinc-lead-gold-silver-copper bearing mineralization and gold mineralization are both associated with feruginous sulfide bearing cherts. The partitioning of gold into these specific geologic environments may be related to variations in temperature and composition of the hydrothermal fluid and the depth of the seawater-sediment interface below sea level during the mineralization event.

Jan 1, 1988

By Jan M. Mutmansky, Y. J. Wang

In the mathematical analysis of electrical networks, the electrical devices are often modeled using idealized network elements such as current sources, voltage sources and resistors. An analogous approach is outlined for the modeling of mine ventilation networks, which can be considered nonlinear resistive networks. The proposed modeling technique uses the following five basic (nonreducible) elements: H, Q, D, R and N. These elements are characterized by their pressure gain or loss, their air quantity and their pressure-vs.-quantity relationships, each of which may be known or unknown. In addition to the definition of the basic elements, the necessary conditions for which there exists a unique solution are discussed. This is performed using theoretical developments derived from electrical circuit theory and illustrated in example networks. The proposed procedures are useful in the solution and characterization of mine-ventilation networks.

Jan 1, 1998

By T. N. Patra, Sanjeeva Latchireddi, B. K. Mishra, Sravan K. Prathy

The motion of grinding balls has been the subject of study since 191 9 when Davis published the first treatise on this subject. Subsequently came the notion that knowing mill power draft, using Bond equation or others, is sufficient to do an analysis of grinding. Next, population balance models provided accurate scale-up from small laboratory size mills to very large plant size mills. However, this success was not repeated when dealing with semiautogenous grinding mill. The study of charge motion with the discrete element method provides support and answers to such issues. Besides providing an accurate picture of charge motion in large mills, the method begs the investigator to study grate and pulp lifter equally critically with fluid dynamic principles. Hence, in recent years, the field of comminution in grinding mills is advancing on a firm footing.

Jan 1, 2005

By Robert Sutton, Milan Sjaus

Conveyor pulleys are an important and integral component of a conveyor. Conveyors work in sequence to make up conveyor systems. Each conveyor system is only as reliable as its crudest component. If the pulley fails, then the whole material handling system stops. So what is the effect of this downtime? What are the costs of repair? How much are we willing to pay to solve the problem? What should we spend to prevent an unscheduled shutdown? Do we use the technological improvements at our disposal or do we ignore them to satisfy immediate cost savings? This study will focus on the cost of pulleys relative to the total conveyor cost, the cost of downtime, the maintenance costs and the costs for resolution of the problem. Some philosophic and design concepts are injected for illustration and discussion.

Jan 1, 2000

By G. T. Adel

As a prerequisite to removing mineral matter from coal by any physical separation technique, the mineral and coal particles must be sufficiently liberated. In the case of the production of superclean (< 2% ash), low-sulfur products, the appropriate liberation size may be less than 10 µm. Unfortunately, much of the liberation data obtained at these fine sizes is only qualitative due to the lack of appropriate instrumentation. In the present work, computerized image analysis has been used to characterize several common eastern U.S. coals. In most cases, it has been found that micronizing of the coal is necessary in order to achieve sufficient liberation for deep cleaning. Liberation analyses of the products from the microbubble column flotation process have been used to distinguish problems in liberation from problems in selectivity, especially as they pertain to pyrite rejection.

Jan 1, 1989

Surface contamination of minerals during fine grinding may occur due to coating of one material on the other. This can alter the surface chemical properties and adversely affect the separation of minerals by physico-chemical processes. In dolomite-silica system, selectivity was completely lost (compared to a synthetic mixture) after wet grinding of the minerals in spite of using a dispersant. Adsorption and surface characterization studies were conducted on silica particles separated after grinding with dolomite. SEM-EDAX analysis indicated the presence of dolomite on silica particles, which could cause the loss of selectivity.

Jan 1, 1993

By Neil S. Fishman

Tabular uranium ore in the Grants uranium region, New Mexico, occurs as tabular layers of a urano-organic mixture suspended within host sandstones of the Morrison Formation. The intimate urano-organic association points to the organic material as the main ore control. Petrographic evidence indicates that the organic material was postdepositionally introduced into the host sandstone, probably as humic acids; however, the mechanism by which these acids precipitated from solution remains uncertain. A model, the cation scavenging model, is proposed in this paper to explain humic acid precipitation. The model, supported by evidence from regional alteration studies of the host sandstones, proposes that cations responsible for humic acid precipitation were scavenged from framework grains which altered during passage of the humic-rich fluids through the host sandstone. This process, coupled with the affinity of organic molecules for each other, caused flocculation of humic acids into tabular zones. The precipitated humic substances then continued to concentrate uranium to form the orebodies. The cation scavenging model requires only one solution, the humic-bearing solution, in the precipitation process. All cations necessary for humic acid precipitation originated in the host sandstones. This model contrasts with a previously proposed model--the brine interface or two solution hypothesis--in which it was proposed that a cation-rich brine introduced into the host sandstones provided the cations necessary for humic acid precipitation. The brine hypothesis has several drawbacks, one of which is unrealistic hydrologic reconstructions necessary to accommodate mineralization at various stratigraphic horizons in the Morrison Formation. Moreover, no mineralogic evidence exists to suggest a brine occupied the host sandstones at the time of mineralization. The proposed cation scavenging model for humic acid precipitation not only readily accounts for humic acid precipitation, but also is consistent with geologic observations and regional alteration studies.

Jan 1, 2013

By A. K. Mukhopadhyay

[The mechanical status of a mine ventilation fan can be monitored effectively through vibration analysis. An expert system can be an effective tool in fault diagnosis for a variety of equipment. Computers have made it possible to implement an expert system to analyze the data for correct and appropriate diagnosis. In addition, vibration analysis can provide important information oil the condition of the machine. This paper discusses an approach for an expert system to determine on vibration analysis, practical problems that can occur with a fan. The frequency of the vibration is the only characteristics considered in the analysis, although other variables are discussed in the paper. Finally, a simple computer program, written in Turbo Prolog, is presented. A friendly query system, menu operation and a disk-resident separate knowledge base are a few of the salient features of this system.]

Jan 1, 1997

By S. R. Rao, J. A. Finch, E. El-Ammouri, K. Ngoviky, P. A. Disten

Sludges produced by lime treatment of acid mine drainage (AMD) can contain significant quantities of base metals which represent both a potential hazard and a loss of values. A new technique for metal recovery from sludge is proposed by combining selective acid leaching and adsorption of metal ions by activated silica sol. The process is demonstrated on two AMD sludges, one containing primarily nickel and the second zinc. They were first treated with sulphuric acid (pH 3.5) to selectively leach the target metals and then activated silica sol was added to the leach solution to adsorb the nickel and zinc. Thickening and centrifuging gave about 90 percent rejection of the input volume to effluent. The adsorbed metals were redissolved by strong acid into a concentrated solution relative to the feed and the silica sol was recycled.

Jan 1, 2000

By J. D. Miller, Z. S. Nickolov

Sum Frequency Spectroscopy (SFS) is a powerful nonlinear optical technique to study interfaces at the molecular level. SFS has one major advantage over conventional vibrational spectroscopic methods, such as infrared (IR) absorption and Raman scattering, in that the method is inherently interface specific. As a result, the spectroscopy of molecules residing in the interfacial region can be probed selectively without any contributions from the molecules present in the more pervasive bulk phases. Analysis of SF spectra can yield information on population, structure, and orientation of interfacial species with several nanometers in-depth resolution. The recently acquired SF spectrometer at the University of Utah opens new possibilities for investigation of interfacial phenomena of great importance for separation technology, materials research, nanotechnology, bioengineering. Its application to studies of liquid/gas, solid/liquid, and solid/gas interfaces will be discussed.

Jan 1, 2004

By John E. Urbanic, William D. Faulkner, Robert W. Ruckel

Guidelines are presented for the selection, handling and regeneration of activated carbon used in gold recovery operations. The guidelines are based on Calgon Carbon Corporation&apos;s own investigations and experience gained in working with gold mine operators all over the world. Gold adsorption rate and adsorption capacity are shown to be independent variables thereby requiring testing of both properties when selecting activated carbon. Means of measuring these properties are provided. Historical activity tests on activated carbon are shown to be minimally useful in selecting carbon for gold recovery. Proper thermal regeneration techniques to maximize recovery of adsorption rate without weakening the carbon structure are suggested. Simple positive means of measuring efficiency of regeneration are presented. The subject of hardness measurement as a predictor of "in process" abrasion is discussed. The cost/benefit issue of carbon activity level is addressed.

Jan 1, 1986

By J. Litsenberger, T. E. Marshall, P. R. Coyle, L. J. Prosser, A. T. Iannacchione

For the first time in an underground stone mine, the relationship between roof movement and microseismic emissions was examined in conjunction with two distinct roof fall areas. As roof monitoring increases in acceptance and monitoring technology advances, the goal of providing reliable roof fall detection systems to enhance the safety of underground mine workers moves closer to reality. Instrumental to reaching that goal is the ability to interpret accurately and completely roof movement and microseismic emissions, which can serve as precursors to roof falls. This paper examines the capabilities of convergence and microseismic monitoring systems to better understand roof rock failure mechanics and to anticipate roof falls. An understanding of how these techniques are used and how they interact with each other is critical in developing the most effective ground control strategy for our nation’s mines.

Jan 1, 2004

By Wenbing Guo, Gaobo Zhao, Erhu Bai, Brijes Mishra

"Violent damage to overlying strata can occur above the large mined-out space left by high-intensity longwall mining. For the safe mining under the aquifer and surface water body, it is imperative to investigate the criteria of overburden failure degree due to high-intensity mining. In this paper we present the characteristics of high-intensity longwall mining panels and overburden critical failure. Based on the geological and mining conditions of a high-intensity mining panel, 3D numerical models that consider the maximum horizontal principal stress and minimum horizontal stress and their orientations with the panel advance direction were established by using the 3DEC software. Sizes of the panel reaching the critical failure of the overburden under different mining thicknesses (3.5 m, 6.5 m, 9.5 m, 12.5 m, and 15.5 m) were analyzed. Further, criteria of overburden critical failure were proposed for the high-intensity mining. The coefficient of overburden critical failure (Cf) is the ratio of the strike length (Ls) to the mining depth (H). Through curve fitting analysis, a fitting equation between Cf and mining thickness was obtained. The results showed that overburden failure criterion with high-intensity mining panel is 0.38 = Cf = 0.97 with different thicknesses. Field measurements validated the results from the numerical models.INTRODUCTIONHigh-intensity longwall mining refers to a coal mining method with thick coal seam, large panel width, fast face advance rate, and severe damage to the overburden and surface in China (Guo et al., 2018). Violent movement of the roof rock and severe damage to overlying rock strata occur in the large mined-out space left by a high-intensity longwall mining panel, which is a 3D (three-dimensional) structure layout with highly non-uniform stress distribution. Recognition of such fact a will facilitate this overlying rock strata failure problem investigation (Peng et al., 2019).The studies of overlying strata failure due to longwall coal mining have been reported by some scholars with different methods. Kang et al. (2018) studied the sudden massive roof collapse during longwall coal retreat mining by a large-scale two-dimensional physical model and a UDEC numerical model. Ghabraie et al. (2015) researched the mining-related strata movement by applying the three-dimensional laser scanner, optical transducer, and digital image processing techniques to two-dimensional physical models. Wang et al. (2015) analyzed the structural characteristics and fracture failure process of overlying hard and thick main roof by a 3DEC numerical model; this study also investigated the geostress reduction and permeability enhancement redistribution of the adjacent coal measure strata by FLAC3D. Guo et al. (2012) performed a three-dimensional finite element analysis and shared some insights into the dynamic interaction between mining induced strata stress changes, failures, and gas flow patterns. Meng, Shi, and Li (2016) proposed a 3D coupling model between stress and permeability, investigating the dynamics of a stress, permeability coefficient using FLAC3D. Khanal, Guo, and Adhikary (2019) used the 3D numerical modelling approach (COSFOW) to investigate the strata deformation and the change in permeability in the overburden strata due to the underground extraction. However, few studies considered the influence of the horizontal stress on overburden failure in a high-intensity longwall mining panel, and the critical failure criteria of overlying rock strata is unclear."

Jan 1, 2019

By Carol A. Hill

Native sulfur occurs with barite, celestite, and bioepigenetic calcite in the Culberson, Pokorny , and Leonard Minerals deposits, Delaware basin. The sulfur in these deposits, in "castile" masses, and in deposits of the Fort S tockton district have 6 34s values between +9 and -15. Native sulfur in the caves of the Guadalupe Mountains is somewhat lighter [(634s = -15 to -25)]. Barite in the Culberson, Leonard Minerals, and Comanche Creek sulfur deposits have 63% values of +35 to +73; celestite in the Culberson and Leonard Minerals occurrences have values of +38 and +36, respectively, and 87Sr/86Sr values of 0.707808 and 0.708138, respectively. Barite associated with sulfide, deposits, Guadalupe Mountains, have [634s] values of +41 to +62. Barite at Seven aeart Gap, Apache Mountains, is somewhat less enriched in heavy sulfur [(634s = +14 to +37)].

Jan 1, 1992

By R. R. Klimpel

This paper is a summary of the author&apos;s industrial experiences on the selection and optimization of flotation reagent schemes for the recovery of gold species. The trends given are a composite of data and experiences gained on 24 different gold ores from around the globe. The primary emphasis is on the benefits of matching the associated gold mineralogy to a reagent scheme most appropriate for that mineralogy. Two general categories are discussed: the flotation of free or native gold species and the flotation of gold associated with a variety of sulfide minerals. Important plant operating factors influencing each of these two categories are presented with supporting examples. Carefully matching reagent chemistry and appropriate operating conditions to any given gold-bearing ore will not only lower the total reagent cost but, more importantly, can lead to measurable increases in gold recovery.

Jan 1, 2000

By W. K. Pincock

Accident prevention can be portrayed as a science that deals with facts and natural phenomena and must be dealt with in the same manner as any other operating problem. Safety at the Copper Queen Branch dates back to 1913 when a Safety Organization was started and rules formulated for underground mining. Since then the mining industry has made substantial progress in the elimination of accidents and when the Lavender Pit was started in 1951, it adopted the general plan in use at all Phelps Dodge properties. Following is a brief description of the Pit Operations:

Jan 1, 1959

By V. Karra

Based on extensive investigations on the effect of design variables on process performance, during 1982-85, Nordberg developed a 1000 hp cone crusher, with the objective of boosting crushing productivity in existing plants. The 2390 fits on the same foundation as the 7&apos; SHD Symons cone, but is designed to give two times the capacity of the 7&apos;. The economies of scale involved give the customer substantial cost savings. In this paper process performance of the Nordberg 2390 relative to the 7&apos; SHD Symons cone, while crushing the same ore, will be presented. Also, implications of such a crusher scale-up to associated cost savings will be addressed.

Jan 1, 1988

By L. M. English, K. A. El-Nagdy

The mine characteristic curve represents the relation between the airflow in a system and the pressure drop across the system. In a single fan system, this relation can be easily drawn by assuming different values of the airflow and calculating the corresponding pressure drop according to Atkinson’s law. In a multiple-fan system this cannot be done for each fan simultaneously. However, an alternative mathematical method for plotting subsystem characteristic curves on subsystem quantity coordinates is outlined here that achieves this objective. The Hardy Cross algorithm has been combined with a switching-parameters technique and has been used to trace subsystem characteristic curves. An example using four fans in a complex network is presented here. This example illustrates the nature of the problem and the difficulty of detecting unstable conditions in this type of network.

Jan 1, 2001

By L. Buckingham

Barrick Goldstrike Mines Inc. has embarked on a continuous improvement effort to ensure that Barrick Gold Corporation will retain its lead in the gold industry in years to come. The continuous improvement initiative is based on careful mapping of the key levers associated with each activity of business. The individual levers are then evaluated to determine their potential to affect the profitability and safety of the operation. The most promising are diagnosed for root causes. These root causes are then addressed to enhance benefits. Through a structured approach of mapping, brainstorming, evaluating and instigating change with follow up measurement and reporting; Barrick Goldstrike is anticipating an increase in throughput at the autoclave facility of 10% with little or no capital expenditure. The resultant approach to Continuous Improvement will be utilized throughout the Goldstrike facility and then throughout Barrick&apos;s world-wide operations.

Jan 1, 2002

By J. W. Leonard, D. A. Newman

By using physical and chemical means to increase the bulk density of newly broken coal freed from the mine face, the potential to improve coal mine productivity is significantly enhanced. It is estimated that by increasing bulk density, greater tonnages can be placed in fixed volume scoops and shuttles cars to improve production by as much as 10% to 20%. Such improved packaging to achieve new levels of volumetric efficiency might require only small and easy to implement changes to present downstream mining operations. Opportunities exist for improving broken coal bulk density from the moment of breakage, during transport across the continuous miner or loading machine, during discharge into the haulage unit, and after placement in the haulage unit. Physical/chemical methods for broken coal compaction in mobile, fixed volume units in underground operations are discussed.

Jan 1, 1990