Search Documents

By David S. Young

All pigments and extenders or fillers whether organic or inorganic fall into the following broad general classes: I. Colored II.-White III. Black IV. Metallic A pigment- is any particulate matter that is essentially insoluble and chemically unaffected by the media into which it is dispersed. According to this very broad definition, colored pigments, white pigments, fillers, extenders, and functional pigments would all be included. The particulate size range would also be quite broad ranging from very fine colloidal particles (~0.01µ) to relatively coarse particles (~100.0µ). This broad definition is usually subdivided into more practical divisions which tend to relate the classification of the pigment to its primary function in the system in which it is used. Hence, the word extender implies that its major purpose may be to extend the system.

Jan 1, 1985

By V. Aghazadeh, E. Bidari, M. Aazami

In this study, mineralogical and microanalysis characterization, as well as diagnostic leaching and cyanidation tests, were performed to gain a better understanding of the refractory nature of the arsenical zone of a Carlin-type gold deposit and also to evaluate possible treatment routes to maximize gold recovery. The results obtained showed that only 56% of the ore’s gold content is amenable to direct cyanidation. The majority of the remaining gold was found as submicroscopic gold and in association with sulfide minerals, such as orpiment, pyrite, and sphalerite. It was also found that despite the abundance of silicate and carbonate minerals in the arsenical zone, they do not play a key role in the refractory nature of the ore, and gold can be liberated from such minerals by appropriate grinding. The analyses further revealed that orpiment dissolves readily during cyanidation, and this dissolution retards the kinetics of gold extraction. Pyrite and sphalerite were generally found to occur in fine network texture and in association with quartz. Flotation of such auriferous sulfides may be difficult due to their oxidized surface. Fine grinding (−20 μm) was found to be partially effective in improving gold extraction.

May 28, 2020

By Wayne A. Van Voast

Many coal beds that will be mined in southeastern Montana are aquifers that provide essential local water supplies. Mine cuts along aquifer outcrops create almost imperceptible piezometric changes. Monitoring near such operations at Colstrip has detected almost no water-level declines in observation wells. Mine cuts between outcrops induce rapid storage depletion and associated piezometric depressions. One such cut near Decker induced 1,250 m3/day of flow from storage and created a piezometric depression of 3 meters or more as far as 1,500 meters from the mine. No wells have yet become non-productive but losses of some are inevitable as operations expand. Alternative supplies are available from aquifers stratigraphically below the disturbed materials. Effluents from active mines are chemically similar to other area waters because they are mixtures or ground waters entering the mine cuts. Occasional high concentrations of nitrate do occur, however, as residuals from explosives. Spoils generally consist of confined aquifers of wasted coal and coarse rubble at their bases, overlain by finer-grained sand, silt, and clay. Hydraulic conductivities and storage coefficients are comparable with those of undisturbed confined aquifers. Water quality in mined lands is highly diverse because of diverse spoils lithologies and poorly-established ground-water circulation. Ground water in spoils is more mineralized than in the coal beds and chemically resembles waters from sandstone aquifers. Hydrologic effects of mining will not be catastrophic or widespread but may have local significance. Most notable changes will be in water quality; availability will not be permanently reduced.

Jan 1, 1978

By C. Hosten

This paper presents the results from an extensive research program on the vacuum filtration of iron ore slurries. Experiments were conducted with the addition of several types of flocculants and surfactants. The filtration response of the slurries was studied in terms of the cake formation rate and the residual cake moisture. An analysis of the results is presented in ascertaining the role of flocculants and surfactants during filtration

Jan 1, 1983

By K. K. Kohli

Since the adoption of the Surface Mining Reclamation and Control Act of 1977, which mandates that surface subsidence be an intergral part of the underground coal mine design, there has been a sudden rise of demand on guidelines for minimizing surface subsidence and its associated structural damages. Unfortunately there is no sufficient amount of systematic subsidence data to fill such a gap, although considerable research has been devoted to the subsidence-induced damages of surface structures in the past. However, it was said that many surface subsidence surveys have been performed and monitored by coal companies during the past twenty years, and that it will be a great source of information for subsidence engineering design if they can be collected and assembled together. An effort was therefore initiated in the Department of Mining Engineering, West Virginia University, under contract with the U. S. Bureau of Mines in December 1978 to contact each individual coal company in the Northern Appalachian Coal Field for any surface subsidence survey data. After 10 months' survey, the data collected include 17 longwall panels and 2 room and pillar sections. The data in-each panel and section cover the complete set of subsidence survey raw data, underground mine layout maps, surface topo maps, geological loggings showing the stratigraphic sequences and thickness of the overburden, and if available, locations and types of surface structures. On-site visits were followed to study the surface terraines and structures. Interviews were conducted with the owners of the surface structures in most cases about, if any, the history and characteristics of damages.

Jan 1, 1980

By J. Kuti

In room and pillar mining a large number of working points are arranged to follow a mining pattern. Geological and roof control problems can be overcome or their effect minimized by varying this pattern. Longwall mining on the other hand, fixes the mining pattern for anyone panel. This aspect of longwall mining leads to constancy, so that a well-conceived organization, ventilation, dust and roof control systems lead to daily repetition and subsequent simplicity of control. All the same, a fixed mining pattern calls for a very careful consideration and selection of design parameters. (Ref. 1.)

Jan 1, 1971

By Jurgen H. Kleinau

This paper details Keeler/ Dorr-Oliver's experience with the application of fluid bed combustion technology to the burning of coal-mining waste. The designs of two stage fluid bed combustors/dryers are demonstrated as useful in the drying of coal, slag and coke, using coal and coal refuse (gob) as fuel. Anthracite mining refuse (culm) is more than abundant in Northeastern Pennsylvania. After demonstration at Shamokin, Pennsylvania, a full commercial-sized fluid bed boiler using culm is used for district heating in Wilkes-Barre, Pennsylvania. Limited research work has shown the utility of using fine coal as filter aid in sludge in¬cineration. With the rising avenues of the suitability of coal as auxiliary fuel in fluid bed sludge incineration, an expansion of these concepts combines the use of coal or coal refuse as filter aid and auxiliary fuel. Lime¬stone addition controls SO2 emission.

Jan 1, 1985

By Cengiz Karagüzel, Ömer Canıeren

The mobility of gold and silver metals from refractory ores is very low due to free metal ions in their bodies that bind the transportable and free metal molecules or they are encapsulated in minerals such as sulfides, arsenosulfides, carbonaceous, and clayey materials which make it difficult to extract them. As known from the literature, the enrichment of oxide refractory gold, silver ores, Ag, and Au-rich flotation concentrated from sulfur refractory ores can be leached in the chloride-hypochlorite solutions. In this work, the leaching approach was studied to extract silver ions from refractory ores in the presence of hypochlorite media under high pressure. The mineralogical and scanning electron microscopy analysis of the sample indicated that the silver was encapsulated in barite and quartz minerals in fine sizes. In order to obtain the optimum leaching conditions for the silver ore, the effects of several parameters, namely, temperature, leaching time, NaCl and NaOCl concentration, solid ratio, and particle size on the leaching recovery were investigated in detail. The leaching experiments showed that the highest silver recovery of 62.35% was obtained under the following conditions: temperature of 150 °C, oxygen pressure of 1800 kPa, leaching time of 2 h, concentrations of 2 mol/dm3 and 0.4 mol/dm3 for NaCl and NaOCl, respectively, the solid ratio of 30%, and particle size (d80) 15 μm. The results obtained from this study indicated that the enrichment of refractory silver ores to extract the silver encapsulated in barite and quartz minerals could be possible in the chlorite-hypochlorite under high pressure, a relatively shorter leaching time compared to conventional cyanide leaching.

Jan 28, 2021

By Jay F. Colinet

Coal workers’ pneumoconiosis (CWP), commonly known as black lung, is caused by the inhalation of respirable coal mine dust and is a disabling and potentially fatal lung disease with no cure. Historically, CWP has taken a tremendous human and financial toll in the US coal mining industry. Recent health surveillance data indicates that CWP continues to occur at elevated levels. Respirable coal dust exposure must be controlled to prevent the development of CWP. The Pittsburgh Mining Research Division of the National Institute for Occupational Safety and Health (NIOSH) conducts laboratory and mine-site research to identify control technologies that can be used to successfully reduce respirable dust levels. Various technologies, using multiple methods of control, can be applied in order to reduce dust levels. An overview ofCWP’s impact and a general methodology for controlling respirable dust in underground coal mines are discussed in this paper.

Jul 30, 2020

By Thiemo Hagedorn, Gerhard Weissbach, Ralph Bergmann, Wilhelm J. Kogelmann

The objective of this unique method is to multiply the advance rate of conventional tunneling while improving both ground control and the safety of the crew. The high advance rate is achieved by concurrent rock excavation and installation of concrete lining at fully synchronized work phases. The novel TACHUSMATIC system consists of a high-production, robotic cutter boom, an automated slip form and continuous mucking and conveying. This novel system utilizes the inherent bearing capacity of the rock that is activated by a small, initial deformation. The supporting resistance is then provided both by the rock mass itself and the pumped in concrete lining. During the hardening of the concrete, the hydraulic cylinders of the TACHUSMATIC automatically apply the appropriate support resistance, thus providing safe ground control. This novel tunneling system is practically a fully automated, fail-safe NATM that does not require highly skilled engineers and crew. The TACHUSMATIC can be used for construction of circular, rectangular and horseshoe-shaped tunnels. When equipped with the Alpine Multi-Tool Miner (MTM) systems, the machine can work in a wide range of ground and rock conditions. The use of novel, diamond-tipped cutter bits (picks) will increase hard rock cutting capabilities and will significantly reduce pick consumption. Because of its moderate cost, the novel system is an economic alternative to conventional tunneling even at short drivages. A new installation is cost-effective for tunnels longer than 750 meters (2,500 ft.) At a typical tunneling project, the cost permeter is about 25% lower than with conventional methods.

Jan 1, 2003

By Zohreh Kazemi Motlagh, Evan J. Owen, Virginia T. McLemore, Jakob Newcomer

Five-element style deposits are unusual hydrothermal systems that are typically characterized by a nickel-cobalt-arsenic- silver-bismuth metal assemblage. This mineralization is often represented by abundant native silver, arsenic, or bismuth, and followed by nickel, cobalt, and iron arsenides (skutterudite, safflorite, nickeline, rammelsbergite, and lollingite). The Black Hawk district in Grant County, New Mexico is one of the few examples of this mineralization style in the United States. Despite the differences in formation temperature, depth of emplacement, and host rocks between five-element style deposits worldwide, there are commonalities in mineralogy, ore texture, and composition. A detailed exploration of the native metal and arsenide phases will be performed to compare ore forming fluids between systems and the effects on styles of mineralization and paragenesis, as well as to aid in broader classification of the deposit style. Mineralogy and mineral relationships of the Black Hawk District and other five-element deposits worldwide will be characterized by reflected light petrography, scanning electron microscopy, X-ray diffraction, and electron microprobe analysis. Mineralogical phase diagrams will be generated to better understand the driving processes and evolution of the systems through native metal and arsenide precipitation.

Feb 1, 2024

By T. BACHMANN, G. SHAPLAND, E. Amini, N. BEATON, M. BECERRA

Process plant modeling in the computer environment has been developed over the past 40 years by implementing the comminution models formed by the Julius Kruttschnitt Mineral Research Centre, University of Queensland, in the early 1970s. The models for the other processes in a mine value chain, such as blast fragmentation and flotation, were continuously developed and improved in parallel as well. Other research and commercial entities have also developed process modeling methodologies in the computer environment, which evolved as specialized commercial software or through equations set up in Excel spreadsheets. These were performed on a local computer, in thousands of simulations over a long period of time due to hardware limitations and the lack of a fully automated process. This limits the application of detailed process simulations for scale-up and strategic planning analysis, as they require many simulations to cover all possible scenarios which would take a lifetime when using local computers. The Integrated Extraction Simulator (IES), as the next generation of cloud-based software package, has made it possible to run simulations on the entire operation value chain in the same platform, including drilling and blasting, crushing, grinding, flotation, and other downstream process and material-handling units. This capability has allowed IES to handle multivariable simulations across the mine value chain, including pre-concentration and in-pit size reduction, and modify the process simultaneously.

By Virginia T. McLemore, Abena S. Acheampong-Mensah

Critical mineral endowment of mine wastes in two mining districts in New Mexico (Copper Flat at Hillsboro and Carlisle-Center mines in the Steeple Rock district) will be characterized and estimated. “Beta-testing” of USGS procedures was performed. Potential critical minerals at these deposits include As, Bi, Te, Zn, Co, Ni, Mg, Mn, and fluorite. pH and particle size of samples were analyzed to determine weathering and migration potential of heavy metals. Soil pH was also measured to determine the potential for Acid Rock Drainage. The pH of the waste rock piles ranged from 3.66 to 5.67 which indicates fine- grained pyrite or sulfide oxidation. The samples collected from the tailings however, showed a different range of pH, from 6.30 to 8.62, probably due to the presence of carbonates. Difference in particle size fractions and its distribution along the slope are generally influenced by natural occurrences (e.g., gravity and pre-mining hydrothermal alteration) and operational activities such as material piling or dumping. Future work includes analyses of mineralogy and particle size correlation and estimation of critical mineral endowment of these mine wastes at New Mexico.

Feb 1, 2024

By Rudolf E. Greuer

Modeling a mine ventilation system is a formidable mathematical problem requiring the solution of twice as many equations as there are airways with half of these being quadratic equations. The addition of a mine fire to the problem adds many more complexities. The U.S. Bureau of Mines and Michigan Technological University attacked this problem in stages. During the 1970's and 80's, a series of computer simulation programs were developed which offered progressively increasing levels of modeling capability and accuracy. The current version of this software, MFIRE 2.0, was released in 1993. This programs provides for full dynamic state mass flow-based modeling of a mine ventilation system, and includes natural ventilation, mechanical ventilation, air reversals and recirculation, methane and fire contaminant spread, and moisture condensation and evaporation in the mass flow and heat exchange calculations. This program is a useful tool for routine ventilation planning and can significantly improve mine safety by enabling detailed quantitative analysis for mine emergency preplanning. This paper reviews the evolution of the MFIRE program from its infancy as a simple digital network simulator replacing analog computers to the present version.

Jan 1, 1994

By James B. Lincoln

The Schaffer linear kimberlite complex and Aultman kimberlite diatremes comprise a major part of the State Line kimberlite district of Colorado and Wyoming, which encompasses approximately 200 sq mi (500 km2). The district is located along the eastern flank of the northern Front Range and is underlain prin- cipally by Precambrian granites (approx. 1.4 b.y.) which have been intruded into an older (approx. 1.75 b.y.) metamorphic complex. The kimberlite occurrences are Devonian in age and are related to older Precambrian linear structures. The Schaffer kimberlite complex is a dike or fissure system with enlargements or blows developed at the intersections of cross faults; the two Aultman occurrences are diatremes. Kimberlite within the Schaffer complex is predominately grey to green phlogopite-calcite kimberlite breccia and tuffisitic breccia. Carbonate is abundant in some phases. Inclusions of host granite are common and locally abundant. Upper mantle peridotite, pyroxenite, and eclogite and lower crustal granulite xenoliths are present at many localities. Four phases of tuffisitic kimberlite breccia occur in the Aultman diatremes. These breccias are characterized by high carbonate and serpentine contents. Xenoliths of upper crustal granite, lower crustal granulite, and upper mantle assemblages are abundant locally. Lower Paleozoic sedimentary rock xenoliths are also abundant in the Aultman diatremes but are absent in kimberlite of the Schaffer complex. From 1979 through September 1982, Cominco American, Inc., conducted geologic mapping, petrographic studies, geophysical surveys, geochemical surveys, and auger drilling in the Schaffer-Aultman project area as part of an extensive evaluation program of kimberlite occurrences. Forty bulk samples (approx. 8,000 metric tons) were excavated from the occurrences and then were processed for diamonds at Cominco American's heavy media separation and diamond recovery test plant at Fort Collins, Colorado. Indicated grades from the Schaffer and Aultman kimberlites range from approximately 0.5-1.0 carat per 100 metric tons and as such, the occurrences do not appear to approach economic viability at this time.

Jan 1, 2013

By W. G. Pariseau

A study of coal pillar strength at the Beehive Mine in central Utah was done in the 1970s. This study was a cooperative effort by the University of Utah, RE/SPEC, Inc., and the American Coal Company and was funded by the U.S. Bureau of Mines. Mine measurements of closure at 117 points and pillar stress using 119 vibrating wire stress gauges were made during retreat mining in this room-and-pillar operation. Laboratory testing for the strength and modulus of 372 coal cylinders up 0.3 m (1 ft) in diameter and 0.6 m (2 ft) in length was also done. Two-dimensional finite element model analyses complemented the study. However, the real world of mining is three-dimensional and in consideration of the significant advances in computing power since the time of the original study, a revisit of the data seemed warranted. In this regard, a novel finite element method was used that allows for the whole-mine analysis of tabular excavations on the kilometer scale and yet enables details to be obtained at pillar walls on the meter scale. The effects of material properties variability in situ and of joints can also be taken into account. Results that compare computed two- and three-dimensional seam-level closures with mine measurements show noticeable differences; three-dimensional results are reasonable, while two-dimensional results overestimate closure by nearly a factor of two.

Jan 1, 2014

By Todd S. Webster, Matthew J. Pierce, Brad D. Krumel

With the Working Shafts and Starter Tunnel under way, it became apparent this 4.7-mile, 19-foot diameter wet weather tunnel was going to live up to its name. The shaft’s pre-excavation grouting was completed, and ground water inflows were slowing project progress. As the tunnel drive was approaching 50% complete a cooperative effort was underway between the owner, engineer, and contractor to raise the base of the Retrieval Shaft by 65 feet to avoid ground water infiltration construction challenges. The tunnel alignment needed to be raised in kind. The project was behind schedule and rethinking the cast-in-place adit work was next on the agenda due to the very wet environment in the tunnel. The race was on to finish the project within the owner’s time constraints while completing multiple redesign aspects of the tunnel alignment and associated adit construction. This paper will evaluate original design criteria and actual in-route design modifications and change management to meet the owner’s just-in-time schedule needs.

Dec 1, 2022

By M. Sears, W. H. Su, J. Wickline, M. A. Van Dyke, G. Esterhuizen, Z. Khademian

It is commonly recognized that seismicity can be induced by rock failures or slip along geologic structures around mining excavations. The unpredictable nature of these events and their proximity to the working area may raise safety concerns in underground mining operations. Modeling can be a useful tool for estimating seismic potential for a given mine layout, but the challenge is to detect a seismic event and estimate its intensity in the model. One well-documented approach is to monitor the variation in the energy content of the model and record potentially damaging seismic events when there is a significant release of energy. Researchers from the National Institute for Occupational Safety and Health (NIOSH) employed this approach using 3DEC modeling software to simulate the anomalous seismic events that occurred in a deep longwall mine in Virginia in 2005. A four-panel model of the mine was constructed utilizing a 2D cross section at the location of the mining face at the time of the event. Seismic potentials associated with the development of each panel are evaluated by recording the seismic energy released during the simulation. The results demonstrate the occurrence of two relatively significant events during the mining of the last panel, which are consistent with the historical observations at the mine.

Apr 26, 2022

By K. A. Natarajan, Abha Kumari

"The effect of applied DC potentials on the bioleaching of a chalcopyrite concentrate in the presence of Acidithiobacillus ferrooxidans is discussed. Copper dissolution was the highest at an applied potential of +600mV (SCE), while all the dissolved copper got cathodically deposited at a negative potential of -600mV (SCE). Electrobioleaching at an applied potential of +600mV (SCE) was established at different pulp densities as a function of time. The effect of applied potentials and electrolytic currents on the activity and growth of bacterial cells was assessed. Preadaptation of bacterial cells to the concentrate slurry and electrolytic growth conditions significantly enhanced copper dissolution. Electrochemical and biochemical mechanisms involved in electrobioleaching are illustrated with respect to oxidative dissolution and biocatalysis of anodic oxidation. IntroductionIn recent years, the bioleaching of low-grade chalcopyrite ores as well as their flotation concentrates has been receiving increased attention. Use of mesophilic bacteria such as Acidithiobacillus ferrooxidans in the bioleaching of chalcopyrite does not yield desirable copper extraction rates due to its easy passivation.Bioleaching of chalcopyrite using A. ferrooxidans has been reported to be very inefficient, and use of thermophilic bacteria at higher temperatures is recommended to improve its bioleaching rates. Bioleaching under imposed applied DC potentials or currents has been shown to enhance not only bioleaching kinetics but also to confer selectivity in mineral dissolution (Abhakumari, 1996; Chirpa Selvi and Natarajan, 1998; Natarajan, 1992a, b,c). Electrochemical principles governing electrobioleaching have been earlier illustrated (Jyothi et.al, 1989). The role of applied potentials on the activity and growth of A. ferrooxidans has also been studied (Natarajan, 1992b). Also, the electrochemical aspects of bioleaching of several sulfide minerals when present alone or in binary and ternary combinations have been reported (Jyothi et al., 1989). The electroleaching of copper-nickel concentrate (Natarajan et al., 1985) and electrobioleaching of sphalerite concentrates have already been studied (Selvi et al.,1998). However, it is possible to enhance the bioleaching rate of chalcopyrite in the presence of A. ferrooxidans under galvanic conditions in the presence of nobler minerals such as pyrite (Jyothi et al.,1989). Also, dissolution of chalcopyrite can be significantly enhanced under applied potential conditions. Ali Ahmadi and his coworkers recently studied the electrochemical bioleaching of chalcopyrite concentrates using moderate thermophiles (Ahmadi et al., 2010, 2011)."

Jan 1, 2015

By C. A. Rowland

Wet grinding rod mills have been used for 50 years to grind ores and to make specification sand. The application of wet grinding rod mills is well understood. Until recently, there have been very few installations of dry grinding rod mills. The basic principles learned from wet grinding rod mills that were used in the application of dry grinding rod mills are 1. It is possible to extrapolate the performance of 5' and 6' diameter wet grinding rod mills into larger diameter rod mills with the larger mills performing as predicted. Wet grinding rod mills as large as 14' diameter (inside shell) by 20' long using 19.5' long rods are in use operating satisfactorily. 2. Wet grinding rod mills generally grind more efficiently when the fines are left in the mill feed than when the fines are removed from the feed. 3. Wet grinding rod mills produce little tramp oversize and generally can be operated in open circuit except when very close control on the top size in the product is required. When operated in closed circuit, the circulating load is normally less than 100%. 4. The power required for the desired grind can be accurately determined from the work indices obtained from rod mill grindability tests on the material to be ground. Where required it is necessary to, apply inefficiency factors for oversize feed and for larger or smaller than normal- ratios of reduction. Recent applications for rod mills have developed where it is required that dry grinding be used. These recent applications cover the grinding of 1. Lead sinter, lead slag and limestone. 2. Iron ore. 3. Silica for making glass sand. 4. Cement clinker. 5. Coke.

Jan 1, 1968