Search Documents

By Howard Brown

High purity, high brightness limestone deposits in the San Bernardino Mountains and Mojave Desert region occur in upper Paleozoic carbonate rocks which are part of an upper Precambrian and Paleozoic sequence that unconformably overlies crystalline basement. The Paleozoic strata are divided into formations and members, and correlated with strata of the inner Cordilleran miogeocline. The region has been affected by multiple Mesozoic intrusive, contact, and regional metamorphic events. Structure is complex, and includes polyphase Mesozoic folding and thrusting, and complex Cenozoic structures. The area continues to be seismically active. High brightness (white), high purity crystalline limestone deposits are uncommon because their formation is dependent on several geologic processes which include; 1) depositional environment, 2) contact and or regional metamorphism, 3) folding and faulting, 4) uplift and erosion, and 5) preservation through geologic time. The complex geologic history of the San Bernardino Mountains and Mojave Desert region has allowed the formation of several large high brightness, high purity limestone deposits which are currently being mined or will be mined in the future. Specialty Minerals, Inc. (formerly Ptizer), Pluess-Staufer (California), Inc. and Partins Limestone, Inc. produce high brightness, high purity limestone from several quarries in the San Bernardino Mountains. These active mines combined with undeveloped deposits controlled by Pluess-Staufer in the San Bernardino Mountains, New York Mountains, and Bristol Mountains in the Mojave area, contain proven and or indicated reserves sufficient to sustain production through the 21st century Detailed geologic mapping, intimate knowledge of stratigraphy, recognition of complex structures, sampling, drilling and assay data, are proven tools in the discovery and delineation of high brightness, high purity limestone deposits in the San Bernardino Mountains and Mojave Desert region of southern California.

Jan 1, 1995

By Joseph L. Condon

The U.S. Department of the Interior, Bureau of Mines, is doing research on methods to obtain premining information on problems such as detection of old mine workings, abandoned oil wells, channel sands, faults, and other geologic features that are undesirable from a production or safety aspect. Techniques being developed to acquire the necessary information include seismic and electromagnetic. The seismic methods include high-resolution seismic and acoustic methods applied from the surface and inseam channel waves applied under- ground. The electromagnetic, or radar, methods are applied from the surface, from boreholes, and from the working face underground. All of these methods are useful under certain site-specific conditions, but none of these methods is universally applicable for all mining conditions.

Jan 1, 1980

By O. MacIntosh

The Round Mountain gold mine, located 90 km (55 miles) north of Tonopah, NV began large-scale production in 1977. During 2008 Round Mountain Gold Corp. (RMGC) relocated the primary crusher facility approximately 300 m (1,000 ft) to make room for the next phase of openpit mining activities. This facility was installed in 1988 and used a log-crib retaining wall and dump pocket. RMGC selected Hilfiker Retaining Walls and Collins Engineers, Inc. to provide design and materials for a new 17-m- (56-ft-) high mechanically-stabilized embankment (MSE) wall to support the haul trucks at the new location. The construction contractor was EarthTech West Ltd. of Norwood, CO. An MSE wall with a cast-in-place concrete face was chosen as a durable, yet less expensive alternative to the reinforced concrete dump pocket that was originally designed for the project. The arrangement of the MSE wall is of an unusual configuration to meet a variety of operational and maintenance requirements. This paper outlines the selection process, design and construction of the MSE wall.

Jan 1, 2010

This paper examines the feasibility of combining network modeling and computational fluid dynamics for modeling of underground mine ventilation systems. Both simulation methods have specific advantages and disadvantages for analysis of mine systems. Network modeling is widely utilized by many operations and allows for assessment of current systems and simulation for planning purposes. Alternatively, CFD has been utilized only marginally by operations and is typically a research tool, requiring considerable computational power, complex models, and careful analysis and calibration of results. Network modeling allows for a holistic approach to the ventilation system, giving quantity, velocity and pressure in every branch, but CFD modeling can resolve the flow regime in 2-D or 3-D, which is idea when examination of an area on a more detailed basis is useful, such as dust and gas control. Integration of the two can allow for more flexible systems analysis. The feasibility of integration, along with application to limited underground mine data are examined.

Feb 23, 2014

By T. J. Lyman, M. J. Robison, W. A. Ruemmele

INTRODUCTION The first phase of the Los Angeles Metro Rail Project consists of 7.1 km (4.4 miles) of subway and stations running through downtown Los Angeles from Union Station to MacArthur Park. Contract A171, the Wilshire/Alvarado Line, involves tunnel construction beneath 7th/Street from the 7th/Flower Station to the Wilshire/Alvarado Station. The project consists of the excavation and lininig of 3000 m (9900 ft) of twin-bore, 6.7 m (22 ft) excavated diameter, 5.5 m (18 ft) finished diameter subway tunnels. The location of the project is shown in Figure 1. The majority of the excavation passed through weak siltstone/ claystone bedrock; although, portions of each tunnel approaching the 7th/Flower Station passed through fine-grained alluvium. Both tunnels were excavated with a digger shield. The project also included the excavation and lining of 6 cross passages, 2 communication rooms and a sump, all at tunnel grade between the two bores. A program of geotechnical instrumentation and building monitoring was performed to detect and document the response of the ground and adjacent structures and facilities to tunnel excavation. The instrumentation program was also intended to provide information that would permit implementation of remedial measures, when and as required, to prevent damage to structures, facilities and utilities along the tunnel alignment. The purpose of this paper is to discuss the ground response to tunneling on Los Angeles Metro Rail Contract A171. This paper presents a description of the tunnel project, the excavation and support method used in construction, the subsurface geology, and

Jan 1, 1989

By M. G. Papasotiriou

For our company, S&B Industrial Minerals S.A., restoration of areas which were mined and the effort for bringing up again a balance of nature is an important priority over the last 3 decades. The successful qualitative results of restoration works have delivered to nature over 1.700.000 m2 of surface after mining activity. Our fundamental method in order to achieve the best results for restoration of mined areas is the use of local plants (bush or tree type). Grass and herbs are installed by using the method of hydroseeding. Small trees and bushes are produced and they grow up at our fully owned Milos nursery and they are installed during winter when weather conditions are suitable. During the initial stages of restoration activities a great amount of surfaces, adequately shaped, are delivered by the mining department covered with top soil. These surfaces are suitable not only for the local nature community but also for a combination between natural and agricultural environment. The above fact was a great chance to create small horizontal agricultural cultivations as pilots inside the restored areas. At the beginning the agricultural items that could potentially be installed in these pilot areas were studied and examined analytically. The following agricultural items were finally qualified to be furthermore researched: 1) Vineyard (Vitis vinifera ) 2) Prickly pear (Opuntia ficus indica) 3) Jojoba (Simmonsia chinensis) 4) Olive tree (Olea europea)

Jan 1, 2007

Nuclear power currently produces about 20% of the electricity in the US, with 104 nuclear power plants located in 31 states. The commercial US nuclear industry contributes over $4 billion annually to US workers in salaries and wages. 25,000 new jobs need to be filled in the next 5 years. There are over 30 new power plants under consideration by US utilities. The operating reactors use uranium oxide fuel enriched to about 4% U235 and fission is the process used to generate heat to form steam to drive the turbine generators. Nuclear energy is an important element in the US generation portfolio and represents the largest producer of nearly emission-free electricity. Most, if not all, of the operating plants will secure an extended 20 years of operation or more. The last plant constructed was ordered in 1978. New smaller, modular reactors are under design to provide less expensive, expandable generation options.

Jan 1, 2011

By S. B. Castor

Although production generally satisfies demand for rare earths, new markets may make undeveloped resources, particularly those rich in yttrium, more interesting. A Precambrian carbonalite orebody at Mountain Pass, California, has been the world's largest rare earth producer. Minor rare earth production comes from titanium placer mining in Florida and uranium mining in Canada. Prior to operations at Mountain Pass, North American production was mostly from placer deposits that constitute large, low-grade rare earth resources. Newly discovered North American rare metal resources in peralkaline igneous rocks are potential yttrium producers. Most of these resources are in a continent-wide belt of anorogenic magmatic rocks approximately coeval with mineralization at Mountain Pass. Other untapped rare each resources in North America are generally light rare earth-dominated and small or of low grade.

Jan 1, 1991

By S. F. Diehl

Suites of monomineralic sulfide and carbonate minerals, as well as mine-waste composite samples, were analyzed using chemical and microanalytical techniques to understand behavior and bioavailability of mine waste elements such as Cu, Fe, Pb, or Zn. Petrographic, scanning electron microscopy (SEM), and laser-ablation inductively-coupled mass spectrometry (LA-ICP-MS) studies of mineralogical residence sites of trace elements are important because trace elements affect the chemical and physical behavior of minerals. Leachate solutions show that chalcopyrite, bornite, azurite, malachite, and galena are host to the trace elements Ag, Al, As, Cd, Co, Cr, Mn, Ni, Pb, and Zn. SEM studies reveal whether these trace elements occur within mineral inclusions or are substituted within lattice structures. SEM analysis reveals mineral phases not identified by X-ray diffraction (XRD), such as inclusions of sphalerite and cobaltite(?) within chalcopyrite.

Jan 1, 2010

By Michelle Stokes, Alexandra Miller, Campbell McKenzie

"The ancestral Ringarooma River in northeast Tasmania has transported alluvial tin and other heavy minerals from their onshore source of stanniferous Devonian granites downstream into what is now Ringarooma Bay. Previous exploration work has demonstrated the presence of potentially economic tin mineralisation within the palaeochannels and terraces associated with the submerged river.The offshore tin resource lies directly on the seabed or with less than 2 m of overburden, and within 5 - 50 m water depths in the wider bay area. The main river channel continues offshore for at least 13 km, with high tin grades found within the palaeochannel but also dispersed across the sea floor as a sheet wash, a result of Quaternary sea level change reworking the placer deposits. This drowned portion of the coastal plain contains a continuation of rich tin leads as low gradient anastomosing channels, and has been delineated by marine seismic and drilling activity since the 1960s. Tin grades in the Tertiary and Quaternary alluvial profiles vary from 50 - 300 g/m3, with the highest concentrations in the coarser basal horizons. A previous offshore explorer estimated a resource of 194 Mm3 at 150 - 250 g/m3.Kenex Ltd created 3D models of the paleochannels and the mineralisation with the aim of better constraining the resource estimate and identifying additional depositional areas. The modelling was undertaken with the input of geophysical data, bathymetry and geochemical sampling of the seabed surface and from historic offshore drill holes. A prospectivity model covering Ringarooma Bay was produced to target tin-bearing gravels. Predictive maps were created to represent various features of the offshore mineral system, including assessing gradient changes in palaeochannels and their sinuosity. The model identifies areas with higher potential for alluvial tin mineralisation and will be used to focus the exploration programme over tenements currently held by Kenex Ltd."

Sep 1, 2014

Dunn has written an excellent paper providing a wealth of advice on what is often the most costly consumable in the mineral processing plant. As he pointed out, grinding media selection and quality control can play a major role in successful plant operation. Owing to the economic importance of this topic, there are some important factors related to media sizing that I believe merit further comment. Dunn made reference to a slightly simplified version of the Azzaroni (1981) equation and pointed out its successful use for the Henderson SAG and Climax ball mills. Although both formulas are empirically based on successful plant experience, a notable discrepancy between them is that Bond has factored the work index by the ore specific gravity. This is invariably so, as the Bond work index is derived from the mass grindability (in grams per revolution) measured in a test mill with a fixed volume of solids load (Bond, 1961). A material having the same structural integrity but double the density of another will have double the grindability and just over half the work index. Thus, for the general case, specific gravity should be incorporated into any media sizing formulation that uses work index as the criterion for resistance to breakage.

Jan 1, 1990

By William W. Wellborn

Abrasives are substances both natural and synthetic that are used to grind, polish, abrade, scour, clean, or otherwise remove solid material usually by rubbing action (as in a grinding wheel), but also by impact (pressure blasting). Facts about the discovery, early use, adaptation, and development of abrasives prior to the 20th century are few. From the sparse, earliest information that is available, it would appear that the science of abrasives began when, to fashion his tools, man began to select certain kinds of rocks in preference to others because of their peculiar properties. There is evidence that stones were sawed by some sort of grinding machine as early as 4000 BC in Egypt. The real expansion of abrasives use coincided with the beginning of metallurgy in the Middle East around 2000 BC. The earliest confirmed use of abrasives for grinding metal comes from a steel dagger found along with a sharpening stone which was dated at about 1500 BC. Natural and manufactured abrasive substances play an important role in fashioning and finishing numerous products with a wide variety of end-use applications. The mining and preparation of crude, natural abrasives for their markets and the manufacture of synthetic and other abrasive materials contribute significantly to the US economy (Table 1). In addition, just as sawing to specific dimensions enhanced the value of the Egyptian stone, the use of abrasives in fabrication of modem products, and the addition of abrasives to others, add value. GENERAL CONSIDERATIONS The most important physical properties of materials that qualify as abrasives are hardness, toughness (or rigidity), grain shape and size, character of fracture (or cleavage), and purity (or uniformity). To fabricate bonded abrasive products such as grinding wheels, additional considerations include stability under high heat and bonding characteristics of grain surfaces. The economic factors of cost and availability are always important. No one singular property is paramount for any use. For some applications extreme hardness and toughness are needed, as in diamonds for drill bits. For other uses, factors of greatest importance are hardness and ability to break down slowly and, in the process, develop fresh cutting edges when grains become worn. In garnet sandpaper, for example, highly cleavable, friable, or extremely tough grains are not desirable. For other uses, extreme hardness may be objectionable. Abrasives for dentifrices and for glass-cleaning soaps are cases in point. For the most efficient uses in more critical applications, different types of abrasives are rarely completely interchangeable. While crushed quartz and garnet are both used in sandpaper, the two abrasives are not at all interchangeable in their applications. In the final analysis, the choice of a high-grade abrasive depends upon the quality and quantity of work performed by the abrasive per unit of cost. Initial cost of an artificial abrasive may be much greater than that of a natural abrasive, but the artificial mineral may do so much better work and do it so much faster that the ultimate cost is less. It is for this reason that artificial abrasives have largely replaced natural abrasives.

Jan 1, 1994

By D. E. Munson, H. J. Sutherland

Empirical methods for describing the shape of the subsidence trough over coal mines in Europe are tested against field measurements of subsidence over longwall panels in the United States. The graphical methods developed by the National Coal Board in the United Kingdom do not correlate well with the U.S. measurements; however, the profile functions typically used on the Continent give quite acceptable fits to the data. In the case of two longwall panels mined at Old Ben No. 24 in Illinois, a trigonometric profile function appears the best choice; in the case of two longwall panels mined at York Canyon in New Mexico, an error integral function is somewhat superior. Analyses of subsidence development curves show that rate effects occur. A comparison of fitting parameters establish influence functions as an important methodology for future analysis. In conjunction with the evaluation of empirical methods, an analytic model based on material failure and bulking was developed. A key element of the model is the void-volume distribution function which establishes a mechanism for transfer of significant amounts of the mined volume to the surface. Preliminary calculations demonstrate the features of the model and illustrate close correlation to physical observations in the field. Moreover, centrifuge models simulating the subsidence process have been used successfully to demonstrate the dominant or key failure modes necessary to the analytic model. General features of the centrifuge simulations and model calculations correlate well.

Jan 1, 1982

By J. G. Groppo

Eastern U.S. oil shale contains approximately 10 to 12 gallons of oil per ton and 7 to 10 percent pyritic sulfur. Physical beneficiation of these low grade shales using froth flotation provides a high grade material which will make extraction of oil more economically attractive. The Alabama oil shale used in the present study contained 16.46 percent organic carbon and 14.5 gallons of oil per ton as determined by Fischer assay. Liberation size of the kerogen was estimated at 10 /-Lm. 'Ken-Flote' column flotation technology provided a high grade concentrate containing as much as 60 percent organic carbon, however, carbon recovery was about 60 percent. Carbon recovery was improved to 75-85 percent while maintaining concentrate grades in excess of 40 percent carbon by providing longer retention time in the column which facilitated effective bubble-particle collision and attachment.

Jan 1, 1993

By V. M. Torres

Arapiraca ore deposit has a mixed chalcopyritelbornite mineralogy, with a copper head grade of 0.7%. The reserve size does no allow profitable exploration by grinding/flotation. The technical feasibility of exploring the reserve by heap leaching was studied. Preliminary agitation tests indicated 85% copper recovery. To simulate heap leaching, column tests were performed. The tests included different ore types and acid addition levels. Operating at pH range 1.6-1.8, 67% copper extraction was achieved. Also, it was found an empirical correlation between the operation pH range, copper extraction and acid consumption.

Jan 1, 1996

By Paul D. Dupree

Introduction Trapper mine is a dip-line strip coal mine, located about 10 km (6 miles) southwest of Craig, CO. The mine provides the Craig Generating Station, operated by Colorado-Ute, with about 2 Mt (2.3 million st) of coal annually. The Trapper mine is situated on a hillside that climbs in elevation from 2 to 2.5 km (6500 to 7400 ft) at average grade of 15%. The coal seams dip at about 16% down-grade and they outcrop near the top of the hillside. They exceed maximum stripping depth in 1 to 1.7 km (3500 to 5500 ft) of pit length. Stripping in the three existing pits is performed with three Page 752 23 m3 (30 cu yd) walking draglines. Two of the pits are currently being cast blasted. Until the active cut, the Derringer pit was cast blasted only where the lower mined seam exceeded stripping capabilities and the pit was a single seam operation. Now, a 9-m (30-ft) interburden bench has been incorporated into the stripping plan. This bench protects the first seam of coal from shear when the overburden is cast blasted. The cast blasted section of the 1.6 km (53,000 ft) long pit has been increased from the 457 m (1500 ft) casted previ¬ously to 1 km (3500 ft). High speed films show the coal losses due to shear of the blast are minimal. The pit width in Derringer pit is 61 m (200 ft). This is necessary for efficient spoil side stripping of a relatively thin interburden in the two-seam section of the pit. The Enfield pit is entirely cast blasted. The single seam pit is 46 m (150 ft) wide, 1.1 km (3600 ft) long, and varies from 15 and 46 m (50 and 150 ft) in overburden depth. The overburden strata at the mine consists of medium-hard layers of sandstone, shale, and

Jan 1, 1987

By W. J. C. Venter

The use of activated carbon to improve the selectivity in the separation of base metal minerals from bulk concentrates played an important role in the development of separation techniques employed at Tsumeb Corporation's Tsumeb and Kombat mines. In this paper the Kornbat mill flowsheet and metallurgical data are given with particular reference made to the separation techniques using activated carbon. The mine's historical background, geology and mining methods are described briefly.

Jan 1, 1973

By Floyd C. Bossard

In underground mining operations, the over- riding issue has to be protection of worker health and safety. The employees underground, making a living in a dangerous occupation, know these are major issues. These men bargain their lives and health on the presumption that the operating management knows its business, and they, the underground employees, can pursue their occupation with the assurance that management has provided a safe and healthy ambient underground environment. When management assumes the mantle of protection of underground workers, it has to be positive that qualified engineers have designed the project, and that capable operating personnel are in charge and always available. Those persons with these responsibilities must be knowledgeable in the engineering and occupational health aspects of sine ventilation. The ultimate function of a mine ventilation system is to provide a comfortable, healthy and safe ambient environment for the underground workers. The attainment of these objectives has been complicated with the increased application of electrical equipment and diesel-powered mechanized mining equipment underground (discharging toxic diesel emissions); increased production rates with the attendant increased production of airborne dust; and mine development in increasingly hostile mineral formations containing combustible strata gases, radon gas emissions, along with high heat and humidity. In general, the modern mechanization of present mining operations has resulted in a sore complex set of problems for the engineer planning the underground ambient environment.

Jan 1, 1983

By T. L. Carstensen

The Miami In-situ mine of BHP Copper is located in Globe-Miami, Arizona. The mine leaches mineralized leach capping over a supergene enriched sulfide deposit, and has produced over 500 million lbs of copper during the last 50 years. The Miami unit has identified several opportunities to enhance and expand in-situ production. A computer block model consisting of strict geologic controls, mineralogy, and metallurgical data was developed to assist in the determination of the leachable copper resource. An understanding of the accessibility and solubility of the resource to leaching solutions and the integration of hydrogeologic and hydrometallurgical information was necessary for completion of this project.

Jan 1, 1997

By D. D. Banerjee, S. K. Kawatra, T. C. Eisele

A high calcium fluid-bed combustor ash has been shown to be an effective binder at dosages of 1 to 2% of the magnetite concentrate weight. Magnetite pellets 1.3 cm (1/2 inch) in diameter were produced with dry crushing strengths greater than 22.3 Newtons/pellet (5.0 pounds force/pellet), which is comparable to the results produced using conventional bentonite binder. The effectiveness of fly-ash-based binders was considerably improved when calcium chloride was added as an accelerator. Addition of calcium chloride at a rate of 0.1 to 0.2% of the total powder weight increased the strength of dried pellets by as much as 22% compared to the strength of pellets made using fly-ash without accelerators.

Feb 24, 1997