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By Reinhold Schulze

Thiourea is being applied as an industrial leaching agent for gold and silver only in a few cases. A CIP technique was developed which eliminates most of the obstacles against its use. Mild conditions for precious metals stripping from the loaded carbon simplifies process conditions in comparison to cyanide CIP technique. Examples are given.

Jan 1, 1998

By W. R. VanSlyke

Scrubbing is gaining increasing recognition as a valuable tool in the treatment of Mesabi Range intermediate iron ores. In general, the earliest washing plants included log-washers in their various flowsheets. While log-washers certainly did impart a degree of scrubbing to the crude ore, such treatment bears little resemblance to the type of scrubbing being practiced today. At the time that these early plants were erected, only the true wash-ores were being processd. ("Wash-ores" are defined as crude ores in which relatively coarse chunks of almost completely liberated iron are found in a matrix of loosely-consolidated fine sand.) To treat ores of this type, sizing at approximately 65 to 100 mesh was sufficient to produce a merchantable concentrate. As crudes were being treated in which there was little "locking" of iron and silica, log-washers tended to disappear and large screens and classifiers took their place in Mesabi range flowsheets. The "screening and classification" type of flowsheet 'had its greatest usage in the 1945-55 period, generally speaking. During this same period, many operators found it necessary to supplement the "wash-ore" type flowsheet with heavy-media treatment.

Jan 1, 1959

By J. Herman

The Mid-Continent Geophysical Anomaly (M.G.A.) which extends from Michigan into Wisconsin, Minnesota, Iowa, Nebraska, and Kansas, has recently been the object of intense preliminary oil and gas exploration activity involving widespread land leasing, seismic data collection, permitting of deep exploratory holes and other activities (Paul et al., 1985). This report describes the remote-sensing techniques and results of the application of these techniques to study the geology of the M.G.A. and the surroundings in Iowa. In early 1981, Coal Valley Natural Resources contracted Geospectra Corporation to find a large, (100,000 acres or larger) lease block for wildcat oil and gas exploration. The southwest Iowa area was chosen for several reasons. First, southwest Iowa contains the northeast portion of the Forest City basin (Figure 1) which has produced oil and gas from numerous fields in Kansas, Missouri, and Nebraska (Landes, 1970; Petzet, 1982).

Jan 1, 1986

By David R. Baughman, Ray V. Huff, Paul D. Chamberlin

ISL Ventures, Inc. (ISLV) is developing a process for recovering gold and silver from ores using a chloride-hypochlorite lixiviant. The leach solution, composed of water, NaCl and NaOCl, is maintained at a pH of about 7. At this pH most base metals are not leached. This is important for deposits that contain cyanide-soluble copper. An inhibitor can be incorporated to slow the decomposition of the oxidant. This paper reviews the history of development, presents details of the chemistry and indicates the nature of deposits, which we believe to be amenable to production using the process.

Jan 1, 1999

By R. Zhang, S. Azam, S. Liu, J. H. Golbeck, V. Kurashov, S. Bhattacharyya

Free radicals (FRs) present in coal dust directly influence the interaction behavior between lung cells and dust particles. FRs are atoms or groups containing unpaired electrons, with strong chemical reactivity and a short lifespan. FRs which are quite persistent in natural environments, termed environmentally persistent free radicals (EPFRs), have recently received much attention as new environmentally hazardous substances. EPFRs present on coal dust serves as an active intermediary to catalyze reactive oxygen species (ROS) production by oxygen molecules endangering mine workers’ health. Many EPFR species may be bonded to the particle surface or trapped within the particle during coalification and can be modified with progressive size reduction through cutting at the mining face or crushing/pulverization in the plant. This study measured EPFRs for lignite, sub-bituminous, and anthracite coal dust at various sizes. We especially focused on EPFRs for submicron coal dust prepared by cryogenic methods. The outcome of this study will directly improve the free radical-dependent toxicity quantification and ultimately contribute to the size-dependent coal dust toxicity quantification.

Mar 2, 2022

By Robert M. St. Louis, Janet M. Edgecombe

The Mercur Mine's autoclave is an alkaline pressure oxidation system, operating at 220°(428°F) and 3061 kPa (444 psig) (total). Up to 725 metric tons (800 st) of ore, grading 2.02 g per mt (0.059 oz/st) Au and containing 1 to 2% sulfide sulfur, are treated daily in this circuit. A mineralogical and chemical investigation was initiated to locate the cause of lower than anticipated gold recoveries. Greater than 70 wt. % of reduced sulfur is oxidized; therefore, the autoclave is operating at specification. The low recoveries were attributed to increased concentrations of organic carbon in refractory ore. Activated carbon concentration in the attached CIL circuit was increased from 15 to 40 g per 1, leach temperature held below 21°C (70°F), and carbon flow changed to counterflow. These measures resulted in gold recovery improving from 75 to 82%.

Jan 1, 1990

By H. K. Conn

This paper discusses briefly the evaluation of chrysotile asbestos deposits in ultramafic rocks. Such deposits are limited to serpentinized peridotite and/or dunites. The purpose of any evaluation is to determine whether a deposit contains sufficient ore mineral to justify profitable exploitation. Dimensions of a mineral zone are established by conventional methods, such as mapping, ground magnetic surveys, diamond drilling or underground exploration. The value of the contained asbestos fibre Is dependent on numerous physical properties such as fibre length, strength, flexibility, as well as the actual amount of fibre present. The determination of grade is difficult. The Quebec Standard Test (Q.S.T.) is used to grade fibre according to the proportionate lengths of fibre present. A method of visual vein counting allows calculation of an approximate percent fibre together with a simulated Q.S.T. Various drilling methods are discussed, diamond drilling is favored. Bulk sampling is required to determine fibre quality. Correlation of visual techniques and laboratory methods are often difficult. Reasons for any variance are discussed. Underground bulk sampling of most potential ore zones is strongly recommended to confirm the viability of the property. Evaluation of slip fibre deposits requires greater reliance on laboratory testing as visual methods are difficult to apply. Cross fibre has greater inherent strength.

Jan 1, 1971

By Ulrich Maidl, Gustavo Aguiar, Argemiro Ferreira, Marco A. Peixoto Silva, Marc Comulada

"Metro Line 5 in Sao Paulo is being constructed. This lot extends for 4,940 m with twin EPB shield tunnels under a dense and busy urban area, with an excavation diameter of 6.9 m. The tunnels run predominantly in the tertiary soils of Sao Paulo where extensive experience exists from previous EPB shield tunnel projects. However, new experience is being gained in Sao Paulo in shield tunnelling through Saprolite, the weathered product of the underlying Gneiss crystalline basement, through the resulting residual soils and in rock-soil mixed face conditions. Furthermore, experiences in difficult mixed face soil conditions with overconsolidated clay at the face in combination with loose sands at the crown under the groundwater table will be presented. Additionally, the design, operational and controlling approach followed for the shield drive at particular critical cross-sections where the shields were driven close or under buildings. INTRODUCTION Within the framework of Sao Paulo´s metro network expansion, the excavation of the shield tunnels for Metro Sao Paulo Line 5 is currently taking place. The present paper deals with the description of the most relevant features from the construction of the Line 5 – Lot 3 tunnels. The paper presents how particular challenges were dealt maximising potential of EPB shield tunnelling technology. Challenges were posed not only by the difficult boundary conditions of urban shield tunnelling, such as shield drive under buildings, but also by complex geotechnical situations. PROJECT DESCRIPTION The great urban area of São Paulo is one of the biggest cities in the world, with around 20 Million people living in the city and in the suburb area. The city faces great mobility problems and in the last years the government has been investing great amounts on the megacity´s metro expansion. The Line 5 Extension plays an important role to connect the south area to the central area of the city, with a whole extension of 11 kilometres, including 11 new stations. It is estimated that this line will transport almost 900.000 passengers/day. The first stretch of the expansion, Lot 3, consists of two single tunnels, almost 5 kilometres long each, crossing 4 stations. Figure 1 shows details of the Line 5 Expansion."

Jan 1, 2016

By Douglas M. Dwosh

INLAND STEEL COAL COMPANY'S experience with a gypsum cement, with and without fiber glass filler, indicates that the concept of utilizing standard rock dust equipment to dry handle and apply gypsum cement as a mine sealant is feasible, simple and economical. Prior to 1975, Inland had casually experimented with a few sealants and had discussed the advantages and shortcomings of other sealants with various users. Hower in mid-1975, Inland foresaw the need to seriously acquire a practical sealant system. There were nearly a dozen sealant materials on the market at that time: silicate-based materials, Portland cements, vermiculite cements, gypsum cements, and magnesium-oxysulfate cements, each with their own fillers and additives. The applicating equipment ranged from simple to complex: wet mix or slurry machines operating on either a batch or continuous basis, high viscosity pumps, and pneumatic, dry conveying machines with water nozzles. Compounding the selection process, two or more products could often be used with the same machine, or a given material could be successfully applied with more than one type of machine.

Jan 1, 1976

By T. M. Barton, M. Gauna, A. A. Campoli

Coal mine bumps, the violent failures of overstressed coal, present a safety hazard to miners when longwall mining is conducted in deep, bump-prone coal mines. Two different longwall gate entry systems were evaluated in a southern Appalachian coal mine located in the Pocahontas No. 3 coalbed under approximately 610 m (2000 ft) of overburden that included a massive sandstone member. Both gate entry systems employed a center abutment pillar flanked by yield pillars. The original design used a 24.4-m (80 ft) square abutment pillar, while the new design employed a 36.6-m x 54.9-m (120 ft x 180 ft) abutment pillar. Rock mechanics instrumentation data analysis and in-mine observations indicated that this increase in abutment pillar size significantly decreased bump potential. The new design in worst-case conditions increased effective bearing area 62%, with only a 9% increase in gate entry system width, and eliminated face bumps that were experienced with the original gate entry design.

Jan 1, 1993

By Hassan El-Shall

The results of laboratory and pilot plant testing of a newly developed process to dewater waste slurries from different industries are presented. Data indicate that an increase in solid contents from 6% to over 30% can be obtained in few minutes retention time in comparison to several years as required by currently used technologies. The economical as well as the environmental impacts of such process are discussed.

Jan 1, 1992

By T. W. Meikle

Three nutrient amendments and a biological seed inoculant were evaluated for use in establishing vegetative cover on waste rock substrates. Randomized blocks were placed on three substrates. Treatments included two types of organic fertilizer, mineral fertilizer, Azospirillum bacterial inoculant, plus controls. The seed mix consisted of native grass species adapted to low nutrient conditions. Canopy cover has been monitored for three growing seasons. Results indicate: 1) two of three substrates support plant growth following amendment with organic fertilizers; 2) organic fertilizers increase cover substantially over mineral fertilizer; and 3) Azospirillum had no effect on canopy cover.

Jan 1, 1999

By James E. Palmer

Geologic constraints on mining and recoverability include the following: coal seams too thin or thick for conventional mining methods; coal seams with insufficient stratigraphic separation; unstable roof or floor strata; discontinuous or lenticular seams; coal seams that have high dips or are intensely faulted; water problems due to proximity of aquifers; and coal quality problems such as excessive sulfur, ash, chlorine, sodium, etc. The demonstrated reserve base for western coal of 220 billion tons is considered misleading as it does not adequately incorporate the above parameters in estimating procedures. Current reserve base estimating procedures involve an abstraction of data from generalized resource estimates. The authors believe the reserve base should be determined independently beginning with well-known deposits, with all mining and recoverability constraints fully incorporated.

Jan 1, 1981

By W. R. Reed

NIOSH continues to conduct respirable dust control research for surface mine blasthole drilling operations. Research areas have included testing variables (shroud leakage area, drill deck cross-sectional area, shroud height, collector-to-bailing airflow ratio, etc.) that have the most impact on respirable dust control, development of a dust collector inlet hood, development of a dust collector dump point shroud, and testing of a small diameter water separating sub. This paper summarizes the results of the aforementioned research that has been completed. Additionally, past dust control research for drilling operations of both underground and surface mines completed by the U.S. Bureau of Mines, created in 1910 and incorporated into NIOSH in 1997, is reviewed.

Jan 1, 2008

"INTRODUCTION Twin Metals Minnesota (TMM) (operating as a joint venture between Duluth Metals and Antofagasta PLC) assumed control of the property in 2010. Amec became involved with the project in 2011 and in 2012 incorporated additional drilling in order to update historic resource estimates. The Maturi geological model and resource estimate was updated in 2014 to incorporate additional information obtained during 2013 and 2014 drill campaigns. In 2017, Amec was purchased by the Wood Group and is now known as Wood. Geology The Twin Metals Minnesota (TMM) Maturi, Maturi Southwest, Birch Lake, and Spruce Road properties are located in northeastern Minnesota (Figure 1). This talk discussed the Maturi deposit only, although all four deposits share similarities. The following geology is summarized from Peterson and Severson (2002).Maturi lies within the Superior Province of the Canadian Shield which is exposed in central and northeastern Minnesota and extends northward into Ontario. In eastern Minnesota, the Midcontinent Rift System developed during crustal scale extension in the Mesoproterozoic Era. The rift system is traceable, as exposures of mantle-derived tholeiitic to subalkaline mafic lava flows, intrusives, and rift-filling fluvial sedimentary rocks, and in the subsurface as a gravity anomaly (high), from the eastern end of Lake Superior, arcing west across the lake basin, and extending south-southwest to northeastern Kansas. Intrusion of the Duluth Complex, circa 1,108 - 1,099 Ma, was related to rifting and is co-genetic with the North Shore Volcanic Group mafic volcanic rocks that form the hanging wall of the Duluth Complex to the east. Cu-Ni-precious metals (PM) mineralization including Pt, Pd, Au and Ag within the Duluth Complex is hosted by mafic to ultramafic intrusive rocks that are part of the overall intrusive complex. The Duluth Complex is defined as a more or less continuous mass of mafic to felsic plutonic rocks that extends northeastward for more than 170 miles (275 km) in an arcuate fashion from Duluth nearly to Grand Portage in Minnesota. It is bounded by a footwall of Paleoproterozoic sedimentary rocks and Archean granite-greenstone terranes (Peterson and Severson, 2002), and a hanging wall largely of comagmatic anorthosite, rift related flood basalts, and hypabyssal intrusions of the Beaver Bay Complex. Mineralization is hosted in the basal mineralized zone (BMZ) of the South Kawishiwi Intrusion (SKI). The SKI magmas intruded sub-horizontally between hangingwall Anorthositic Series (AN) rocks and footwall granitic rocks of the Neoarchean Giants Range batholith (GRB). The Maturi local geology and the deposit footprint (shaded orange) is shown in Figure 2."

Jan 1, 2018

By W. Nazarewicz

The introduction of continuous papermaking in the early 1800's was the beginning of the industry as we know it today. Since that time, the majority of the paper produced has employed an acid process. However, in the mid 1960?s, European producers began a transition to an alkaline papermaking process. Early European mill conversions to alkaline papermaking begun in the 601s, accelerated during the 1970's influenced by the dramatically higher cost for OPEC energy as well as the high cost of fiber and imported filler clay.

Jan 1, 1986

Introduction The US mineral industry in 1983 participated in the recovery from the recent recession. Compared with 1982, the value of raw nonfuel mineral output rose 8% to $21.2 billion. The $218 billion worth of goods processed from this crude mineral output represented a 9% increase over 1982. Even in real terms, these figures reflect growth. Demand for nonfuel mineral materials, of course, depends on the overall state of the economy, which steadily improved each quarter in 1983. Of particular importance to the mineral industry were surges in key mineral-consuming sectors such as construction and automobile manufacturing. New housing starts rose one-third, to 1.7 million units, while automakers turned out about 35% more cars (6.8 million) and 25% more trucks (2.4 million) than in 1982. These are significant increases, even considering recent trends toward smaller, lighter vehicles, and multiple-unit housing. A comeback for the mineral industry, however, is bound to proceed unevenly, particularly at the beginning. Traditionally, the industry lags behind the rest of the economy during a recovery, and some mineral products respond to overall economic improvement more quickly than others. This pattern has been repeated many times and the industry is used to it. Mineral executives know it is best to be patient and cautious during the first stages of an economic upturn. Many experts say that it may take extraordinary toughness, patience, and caution this time around. Steel Improves Raw steel production - a major indicator of both material use and mineral production - rose 14% to 77 Mt (85 million st), stimulating a 7% rise in domestic iron ore production to 39 Mt (38 million It). Still, the iron ore industry operated at less than half capacity, with most major mines remaining closed for part of the year. Iron ore imports dropped 24% to 10 Mt (11 million st), so demand was partly met by withdrawals from stocks. Despite the increase in steel production for 1983, output remained far below levels of just a few years ago. For example, 1983 production was still 29% less than in 1981. Raw steelmaking capacity actually declined about 10% during the year to 122 Mt (135 million st). The industry continued to cite steel imports, especially those from developing nations, as a major cause of domestic capacity loss. As long as steel production remains weak, steelmaking metals suffer. Domestic producers of bulk ferroalloys of chromium, manganese, and silicon operated at about one-third capacity in 1983, with six of the 19 companies involved being closed all year. The US mined no manganese or chromium, and very little nickel, although the country's only nickel mine did resume production in November. Molybdenum production, at 13.6 t (15 st), was only about one-third as much as in 1982. The major molybdenum mines, Climax and Henderson in Colorado, remained closed all year. To meet demand, molybdenum stocks were halved to 19 t (21 st). Mine shipments of tungsten, another mineral tied to steel production, dropped 30% to 1.1 kt (1,200 st) of contained metal. One of the most positive responses to the general economic recovery came from the aluminum smelting industry. By the end of the year, it was operating at about 79% capacity, compared to 59% in January. Nevertheless, the 3.3 Mt (3.64 million st) of primary aluminum produced represented only a slight increase over 1982. Total bauxite imports were about 27% below 1982 levels. Production of magnesium metal rose 11% to 100 kt (110,000 st). But titanium was more typical of other

Jan 5, 1984

By Melvin E. Poad

INTRODUCTION The placement of concrete by means of pumping is one of the fastest growing practices in the construction industry and is widely used in mining applications. In¬troduced in the United States in 1933, this method has been adapted to many aspects of the industry, especially where space for equipment is either limited or inaccessi¬ble. Concrete pumping offers many advantages over other methods of placement. Using pumping equipment, the concrete mixture can be transported in a single operation from a central mixing site to numerous forms in many remote locations, eliminating the need for rehandling the mixture and reducing the labor costs to a minimum. Pressurized pumping provides an extra mix¬ing and blending step, resulting in concrete of improved uniformity and greater density. In turn, this produces high compressive strength and increased durability. Various placement defects can be reduced or pre¬vented by pumping. The steady and even flow of the concrete minimizes the form distortion and delays caused by vibration problems that are common to fast dumping of the concrete mixes. Segregation, planes of weakness, bleeding, and surface faults are diminished considerably. Perhaps the greatest advantages of concrete pump¬ing are the distances and volumes that can be handled. Depending upon the equipment used, pumping rates of from 8 to 115 m'j/h (10 to 150 cu yd per hr) can be achieved, with a horizontal range of up to 460 m (1500 ft) and a vertical range of up to 140 m (450 ft). Theoretically, almost any concrete mixture could be pumped. However, consistency is an important consid¬eration for efficient operation. Mixes that are too wet, too dry, too hard, or poorly graded can cause difficulties that increase the costs. Similarly, mixes containing aggregate material that is over the maximum size or that is porous and highly absorptive can also result in diffi¬culties and increased costs. For the best efficiency, the mix formulation must have a well-graded sand and aggregate combination, with enough fines to provide flowability. If additional water is required for pumping, additional cement must be used to meet the design criteria of the structure. Each pump manufacturer can provide recommended mix formulations for the specific equipment furnished. Since the 1950s, many improvements have been made in pumping technology. Originally, only rigid steel pipe of 168 to 245 mm (6.625 to 9.625 in.) diam was used; today, both rigid steel pipe and flexible conduit are available in diameters of from 76 to 203 mm (3.0 to 8.0 in.). Improved pumps have been developed, and the introduction of power-coordinated booms has in¬creased the versatility of concrete pumping. The older and more conventional placement methods can no longer compete with the flexibility, efficiency, and econ¬omy of the pumping method, and continued research and development can only improve the system and expand its use throughout the mining industry. PUMPING EQUIPMENT The three major types of concrete pumping units currently available are the piston pumps, the pneumatic pumps, and the squeeze-type pumps. Table I provides a comparison of capacities, horizontal ranges, and vertical ranges for pumps of all three types. Piston Pumps The simplest of all concrete pumps are the piston¬type pumps; they are available from many manufac¬turers. As shown in Fig. 1, each unit consists of a

Jan 1, 1982

By N. S. Tanious

This work was completed prior to the author's appointment with the Nuclear Regulatory Commission (NRC). Therefore the views and conclusions contained in this paper are those of the author and should not be interpreted as necessarily representing the official policies or recommendations of the NRC. Reference to specific brands, instruments, or trade names is made to facilitate understanding and does not imply endorsement by the author or the NRC.

Jan 1, 1987

By F. Milton Lewis

In this paper an attempt has been made to review the cost trends in producing copper by conventional milling. smelting and hydro-metallurgical means during the last five years. The primary objectives of this cost analysis are to provide a base for future projections as well as to indicate which cost items are more volatile in their influence on overall cost of producing copper.

Jan 1, 1977