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By Joseph G. Selmeczi

Lime and limestone-based SO2 scrubbing processes have demonstrated reasonably good success in removing low concentrations of SO2 from flue gases. While most of the operating problems experienced in the early days of scrubbing have been worked out, problems usually increase and removal efficiency drops with increased amounts of SO2 present in the gas stream. In order to overcome these difficulties, yet still taking advantage of lime and limestone as the lowest cost neutralizing agents, a host of so-called double- alkali systems were developed. These processes take advantage of cations such as Na+ and NH4+ capable of forming highly water soluble bases or basic salts, such as hydroxide, carbonate or sulfite, which having been neutralized or acidified by the absorbed SO2 can be regenerated with a lower cost base such as lime.

Jan 1, 1974

By A. T. Stroebel

Diatomite deposits, the skeletal remains of tiny aquatic plants called diatoms, are found in many parts of the world. Only a few of these de- posits are of commercial value. Open pit mining is used in nearly all deposits now being worked. Processing methods range from simple drying, crushing, sizing and packaging to carefully controlled and highly sophisticated calcining and air classification procedures, employing the latest control and testing techniques. The major uses of processed diatomite are in filtration as filter aids and fillers and extenders.

Jan 1, 1979

By T. Hayashi

A sophisticated process of extracting ultrafine sulfide mineral particles of under 1µm size suspended in clay slurry has been developed through studies of electrochemical properties of particle surface. Experimental procedure and data of the process applied to some clay ores containing sphalerite and pyrite, and molybdenite and other sulfide minerals are reported. Discussions concentrated on the function of process reagents, particularly on various modifying reagents, and on the effect of dispersed or flocculated state of ultrafine particles in slurry which affect significantly the performance of the process.

Jan 1, 1982

By William J. Miles, Raymond E. Blair

Introduction There has been much publicity of the boom and bust in oil and gas well drilling in the US, and many comments on oil and gas gluts. Despite this, the drilling industry remains the largest consumer of functional industrial minerals. The boom years of 1981 and 1982, compared with the bust year of 1983, show a sharp reduction in the consumption of industrial minerals-1981, 7.4Mt (8.2 million st); 1982, 6.3 Mt (7 million st); and 1983, 4.4 Mt (4.9 million st). Industrial mineral use rebounded in 1984 to 4.7 Mt (5.2 million st). This was the second highest year in history in terms of wells drilled and third highest in footage drilled. Table 1 shows the history of drilling activity and mineral consumption from 1971 to 1984. The uses of functional industrial minerals in oil and gas well drilling were detailed by Miles and Blair (ME, 1983, October, pp. 1397-1400). As an update, this article addresses only the changes that have occurred in the industry in the past two-and-a-half years. It will be directed to mineral use and new products introduced to the industry. Drilling practices A partial explanation of where wells are being drilled with lower quantities of minerals consumed is: • In the boom year of 1981, there was a proliferation of number of suppliers chasing the same business. This resulted in multiple sourcing, multiple warehousing, and a huge increase in inventory that became surplus in the following years. The bust year, 1983, caused a severe shakeout in the number of suppliers of minerals and associated drilling fluids. • In 1981 and 1982, the wild speculation in the oil and gas industry led to drilling of speculative deep gas wells. Oil wells were drilled on a wildcat basis - in areas of unproven productivity. • Presently, the oil and gas well drilling industry is very active. But drilling is directed toward proven areas of production and working over old wells for increased production. This means a large number of wells are being drilled with lower average foot-

Jan 11, 1985

By Jock McGregor, Deepak Malhotra, Leonard Harris

After more than 100 years, alkaline cyanide leaching of gold and silver ores, either directly in the case of oxidized ores, or after pretreatment of refractory ores by roasting, pres­sure leaching or bacterial leaching, remains the dominant r leaching method to extract the precious metals f om ores. Leaching with halides (chlorine, bromine and iodine) and with thiourea and thiosulfates is less common but prac­ticed in some cases to dissolve the precious metals both from ores and jewelry and electronic scrap. Cyanide solutions can contain from 1 ppm Au to 30,000 ppm Au. According to the source, i.e., agitated tank leach­ing, heap leaching, eluates from stripping activated carbon or waste electroplating solutions. Similar variations occur with silver which can have a profound influence on the recovery method. The presence of other elements in the leach solu­tions, particularly mercury and copper, likewise play an important role in the procedures required to recover the gold r and silver values f om solution. The same circumstances are found when lixivants other than cyanide are used to dissolve the precious metals. For decades, the preferred method of recovering gold and silver values from alkaline cyanide leach solutions was by zinc dust precipitation according to the Merrill Crowe process developed in the late 19th century. Finely ground gold and silver ores or concentrates were either leached directly or after roasting, in agitated tanks or Pachucas and subjected to solid/liquid separation by filtering or by treat­ment in counter-current-decantation washing thickeners (CCD). This solid/liquid separation step was often very dif­ficult especially when ores containing high quantities of clay were treated which caused filtration or thickening problems. Following testing and development by the U.S. Bureau of Mines (USBM) in the late 60s, the introduction of carbon­in-leach (CIL) or carbon-in-pulp (CIP) plants to recover gold and silver from leach pulps was one of the greatest opera­tional and cost saving improvements made in the industry in South Dakota and quickly spread around the world to be the most common process to recover gold and silver from cyanide solutions.

Jan 1, 2000

By Nelson R. Shaffer

Secondary minerals, amorphous materials, and biologic entities that form on building stone can cause aesthetically unflattering changes in color and may even result in stone decay. Techniques to determine causes of such changes generally have entailed destructive sampling and often required chemical, thin section, X-ray, or other relatively slow, expensive measurements. We have found that a rapid leach of in-place stone using small volumes (50-100 ml) of very pure distilled, deionized water provides recovery of sufficient dissolved material to help diagnose stone anomalies. Water is sprayed onto the stone and collected in a nonwetting plastic pan. Ion chromatograph analysis of waters thus collected from more than 160 sites showed wide variations in concentration of anions F, Cl, NO3, and SO4. Anion analyses were made in minutes for less than $20 per sample. Cations Ca, Mg, Fe, and Sr also were detected, and analyses might be used to determine mineral sources using equilibrium computer models. Solid particles filtered from the samples can be examined microscopically to provide further information about atmospheric agents affecting the stone. The collected water can even be evaporated to precipitate dissolved minerals. Chloride values in samples rinsed from stone ran as high as up to 17,000 ppm, nitrate to 100 ppm, and sulfate to 1,000 ppm. Limited data also indicate that measurable amounts of fluoride were found in some of the rinse waters. Chlorides were most abundant in areas where the stone has become dimpled or spalled. Nitrates were generally higher near ground level, and sulfate tended to be more abundant in samples taken from higher sites or from sheltered sites. Dark-stained limestone tended to yield less soluble material than clean-looking stone. Leachable elements were higher in samples from urban areas. Most of our data are from limestone buildings, but the technique works on other types of dimension stone, man-made construction materials, and even natural outcrops of rocks. Longitudinal studies show that soluble materials vary through time and are affected by climate. This rapid, in situ leach technique, although still being perfected, shows great promise in the diagnosis of stone alteration and in the evaluation of stone treatments because it is completely nondestructive.

Jan 1, 1999

By D. Mannino, M. Townsend, E. Daniloff, E. Petsonk

Nonspecific airway hyperresponsiveness is a central feature of chronic obstructive pulmonary disease and has been associated with atopy in the presence of environmental exposures such as smoking. Coal miners may develop emphysema and lung function decrements related to their dust exposure. To investigate the roles of airway responsiveness and atopy in these effects, we evaluated the relationships among smoking, a history of hay fever or seasonal rhinitis, and airway responsiveness (AR) in a group of underground bituminous coal miners and nonmining controls. All subjects had a normal baseline percent predicted FEV1. Increased airway responsiveness was defined as a 15% or greater decrease in FEV1 following methacholine inhalation. 85 miners (45%) and 99 controls (46%) were current smokers, 59 miners (31%) and 55 controls (26%) were lifetime nonsmokers; former smokers were excluded from further analysis. Overall, 25% of 144 miners included in this analysis had increased AR, as opposed to 29% of 155 controls. Thirty-seven percent of both miners and controls had a history of seasonal rhinitis. Significantly fewer miners (15%) had a history of hay fever compared to controls (25%, p< 0.05). Figure 1 shows the prevalence of increased airway responsiveness in miners and controls in association with hay fever. In both smoking and non smoking miners the presence of a hay fever history was significantly (p < 0.05) associated with a higher prevalence of increased AR. Little effect was seen in smoking (p = 0.827) and nonsmoking (p = 0.940) controls. Figure 2 shows a similar higher prevalence of increased AR associated with symptoms of seasonal rhinitis in the mining group. This was significant (p < 0.01) only in the smoking miners. No effect was noted in the controls. These data suggest that the association of a history of hay fever or seasonal rhinitis symptoms with increased airway responsiveness may be more common in coal mining, compared to non-dusty occupations. Although the implication of these data are unclear, further study of miners with a history of hay fever or seasonal rhinitis is warranted. (Supported in part by Grants G1135142 and G1105142, US Bureau of Mines, Generic Mineral Technology Center for Respirable Dust)

Jan 1, 1991

By John Keay, Douglas R. Shaw, Gregory J. Olso

Rhodes Mining NL, Perth, Australia, is developing the Lahoca Gold Project which is located in Hungary, about 30 km from the town of Eger. The preliminary resource is estimated to contain approximately 1.5 million ounces of gold. The project is being evaluated for an annual process capacity of 2 million tonnes. The test samples contain just over 2 g Ault and 6% sulfur as sulfide. Copper and arsenic levels are approximately 0.2 and 0.1 %, respectively. The ore is refractory due to submicroscopic gold occurrences and structural associations with pyrite. A small amount of the gold is finely encapsulated in quartz. Approximately 30% of the gold in the crushed ore is soluble in cyanide and up to about 55% is cyanide-recoverable with ultra­fine grinding. The ore has little preg-robbing ability. Metallurgical test work done by Colorado Minerals Research Institute (CMRI) and other investigators has shown that as much as 85 to over 90% of the gold was recovered by the relatively severe conditions of pressure oxidation or roasting of the whole ore or a flotation concentrate. The Lahoca ore responds to flotation with gold recoveries of 87% into a low grade concentrate. Subsequently, with a view toward defining a process route with potentially more attractive economics, Rhodes Mining and CMRI conducted an extensive review of biooxidation technologies and concluded that, in particular, heap biooxidation methods promised lower process costs which normally are associated with heap leaching. Based on the study, which included the analysis of the closely related practices of copper dump/heap bioleaching now well established in that industry, CMRI conducted simulated heap biooxidation experiments which evaluated factors such as ultra fine ore crushing, agglomeration techniques, heap design, forced aeration oxygen supply, and whether or not the heap is irrigated. Separate flask biooxidation tests at Little Bear Laboratories showed that the finely crushed ore is biooxidized readily, with a near linear relationship between sulfide oxidation and gold cyanide solubility. Gold recoveries of as high as 66% have resulted after biooxidation of crushed ore. This paper highlights the metallurgical developments of the Lahoca project, and focuses on recent biooxidation laboratory test work aimed at enhancing the treatment of crushed ore.

Jan 1, 1997

By Steven Tubbs

Steven Tubbs From mine to farm is a long journey for Florida&apos;s phosphate, but it is an important one to the American farmer who uses phosphate fertilizers to replenish the soil and produce the crops which eventually wind up on the American dinner table. In this phosphate-food connection, transportation plays a vital life-giving role, a role that is unique because of the large quantities of phosphate produced and the mineral&apos;s location in relation to its markets. Florida Leads World Florida is the world&apos;s largest phosphate producer, supplying 80% of the nation&apos;s and a third of the world&apos;s annual total. About 95% of Florida&apos;s phosphate goes into agricultural chemicals, with 90% going into fertilizers. Phosphate production is primarily concentrated in west central Florida, with the exception of mining and processing in north Florida by Occidental Chemical Co. The phosphate rock is beneficiated at the mine sites and then is transported out of Florida in a raw state, or to one of the industry&apos;s 18 chemical complexes where it is processed further. In 1981, Florida produced more than 42 Mt (46 million st) of phosphate rock-a 1% decrease from 1980. The industry also produced more than 12 Mt (13 million st) of phosphate chemical products in 1981 and transported them to both domestic and foreign customers. This year, the state&apos;s phosphate production and shipments are substantially lower than recent annual levels because of a depressed worldwide phosphate market. With production down slightly in 1981, shipments declined and company inventories increased dramatically. Phosphate-related shipments through the port of Tampa alone fell 20%. As a result, in 1982, phosphate operations cut production to reduce inventories. According to the Fertilizer Institute, during the fiscal year ending June 30, 1982, phosphate rock production fell 18%; phosphate rock shipments, 28%; finished fertilizer production, 30%; finished fertilizer shipments, 25%; and phosphate rock exports declined by 20%. Despite depressed conditions, Florida phosphate production and shipments are expected to increase in the near future with more rock being processed into fertilizer products. Phosphate is one of Florida&apos;s major industries. The US Bureau of Mines estimates it contributed $3 billion to the state&apos;s economy in 1981 and an additional $1.4 billion to the US economy. In addition, phosphate exports contributed to

Jan 10, 1982

By Yasutaka Izumi, Tuneyoshi Funasaki, Keizou Miki, Makoto Kanai

INTRODUCTION The Tokyo metropolitan region, inclusive of the three neighboring prefectures (Kanagawa, Chiba and Saitama), has the highest concentration of population and industry in Japan; with an area of 13,500 km2 or only 3.6 percent of the national land, but a population of 31.8 million or 26 percent of the national total, and a Gross Regional Product (GRP) of146 trillion yen (US$1.33 trillion) or 36 percent of the overall GDP of Japan as of 1990. Tokyo Bay, embraced by the metropolitan region as shown in Figure 1 (a), (b), is open to the Pacific Ocean as a marine gateway and is ringed by large cities and coastal industrial zones together with port facilities, all constituting a concentration of prime importance for socio-economic activities. The Trans-Tokyo Bay Highway (TTB highway), which crosses Tokyo Bay and provides a direct transportation link between the west and east sides of the bay, has long been a sort of “dream-come-true” project in Japan. As shown in Figure 2, linked to the Tokyo Bay Shore Highway, Metropolitan Inter-city Expressway, Tokyo Outer Ring Road, Tateyama Express-way, and others, it will play an important role as an integral part of the regional highway network to help promote spatial redistribution and multi polarization of urban functions, thus strengthening cooperation between cities and restructuring the metropolitan region. The TTB Highway is a project of 15.1 km in length designed as a toll highway to cross the bay by tunnel and bridge, and will require ten years to complete at a total cost of more than 1,438 billion yen (US$13.077 billion). Following more than 20 years of feasibility and environmental assessment studies, construction of this giant offshore highway project commenced in May 1989 as the first large-scale highway project with private-sector participation under the prevailing Road Law in Japan, and is now steadily proceeding toward the goal of completion in fiscal1997. This report outlines the entire TTB Highway project, including the waterproofing measures against high water pressure and the rapid construction method applied in the construction of shield tunnel sections.

Jan 1, 1997

By Pengfei Pan, Lianjun Guo, Houguang Sun, Donglin Xu, Chi Yang, Lihua Luan, Daning Zhang

"Based on the introduction of production technology of Anqian mining company, the stope ore mass distribution was analyzed in detail. The processability indexes of different grade ores were obtained with magnetic tube whereas the grinding time, concentrate grade and concentrate yield were measured. On the basis of digital ore deposit model which integrates ore natural attributes and processing attributes, two stages of ore blending optimization models were established. The first stage model sought the minimum of stope ore transportation cost under the restraints of output ore grade and stope production. The second stage was a system optional model that aimed at the furthest use of resources meeting not only the production constraints of mining field and process field but also ore beneficiability and the system output requirements of the concentrate grade. Lastly, the solving method of big M simplex algorithm was discussed and used in production. 1. Foreword China is the biggest iron ore consumption market. But most of iron ore deposits in china possess such features as low grade, complex compositions, weak magneticity and refractoriness. Under the current economic and technical conditions, rational utilization of low-grade and refractory iron ore is strongly needed to improve the utilization ratio of mineral resources and keep mine development sustainable (Lei 2011). In recent years, the domestic research institutions and mines made a lot of achievements of rational development and utilization of low grade iron ore resources in the beneficiation technology and equipment, high and low grade balance, cost and tax analysis (Wang and Zhao 2013, Zhang 2014, Zhu and Li 2014), laying the foundation for reasonable utilization of low grade iron ore. In this paper, Anqian mining company is taken as an example in which the production conditions, raw ore quality control, different grade of ore processability, and ore blending optimization mode in mining pit and processing plant were discussed to achieve the maximum utilization of low-grade refractory ores under the economical and reasonable conditions. This will ensure the stable operation of mining joint ventures and maximize the enterprise's production life and therefore, maximize the economic and social benefits in the enterprise life cycle."

Jan 1, 2017

By Zhe Liu, Liping Xiao, Jichi Bai, Xuefei Luan

"In order to study the removal efficiency of Cu2+ from acid mine drainage by prepared bentonite-steel slag composite particles, adsorption experiment was carried out. The composite particles were characterized by X-ray Diffraction analysis technique (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectrometer (FTIR). The results show that: the composite particles can release alkali to neutralize the acid of acid mine drainage; the adsorption and chemical precipitation of Cu2+ occurred in the whole reaction process; the removal amount of composite particles on Cu2+ was 9.88 mg/g when the reaction reached equilibrium; the FTIR spectra revealed the existence of surface complexation; the SEM micrographs suggested that the composite particles would continue to adsorb and coagulate Cu2+ after the composite particles surface adsorbing Cu2+ and forming precipitate, namely, there was synergistic reaction of adsorption and coagulation; the XRD patterns further showed the existence of cation exchange and revealed that the states of Cu2+ in the surface of the composite particles was Cu-Si-O mineral phase and CuO(Cu(OH)2) polymerization precipitation. The bentonite-steel slag composite particles which can play a role of adsorption-coagulation synergism are excellent multifunctional green environmental mineral materials to treat acid mine drainage containing heavy metal ions.Introduction It is reported (Zuo and He 2013) that with the rapid development of industry, the world demand for mineral resources is increasing, while the problem of mine environmental pollution is becoming more and more serious due to the large amount of mining. The pollution of mine wastewater has become a global problem, in which acid mine drainage (AMD) is one of the most serious waste water. It is also reported (Cong and Zhao 2003) that acid mine drainage containing high concentrations of heavy metals and having low pH value, causing serious negative influence to the mining production and ecological environment. Acid mine drainage is one of the most serious environmental pollution to the mining industry. In recent years, it has been widely concerned by scholars at home and abroad."

Jan 1, 2017

By P. W. Hynes

Tg Soda Ash has operated a shortwall mining system in the Green River, WY trona district since August 1982. The system has proven to be highly productive. In an effort to reduce the amount of relatively expensive development mining and improve mine planning flexibility, a method to mine the return air tailgate during the shortwall retreat was tested beginning in April 1987. As of June 1988, four shortwall panels had been completed using the advancing tailgate, producing more than 739 kt (815,000 st). This paper discusses the effects of the advancing tailgate on shortwall production, development mining requirements, costs, strata mechanics, and ventilation. Shortwall mining is a hybrid extraction method combining the self-advancing hydraulic roof supports from longwall mining and continuous mining machines (Fig. 1). The technique has been only marginally successful at the majority of the nearly 20 installations worldwide. At present, the face at Tg Soda Ash Inc. is the only shortwall operating in the United States and the only noncoal shortwall in existence. Despite the method&apos;s record of limited success, the staff at Tg Soda Ash determined that the conditions in its trona mine were well suited for shortwall mining. The commitment to install a shortwall was made in late 1981 and the first panel commenced in August 1982. Between that time and June 1988, about 3.33 Mt (3.67 million st) of trona have been mined with the system from 15 panels. Annual average productivities have ranged from 818 t/shift (902 st per shift) in 1982 to 1.4 kt/t shift (1591 st per shift) in 1987. Overall, the system has produced an average of 1.3 kt/ shift (1450 st per shift). In April 1987, a method of mining the return air tailgate during shortwall retreat was tested (Fig. 2). The objective was to determine if a return airway could be established and maintained by mining a series of rooms and pillars about 7.6 m (25 ft) past the face support line. The method would allow a barrier pillar to be left between shortwall panels without requiring the mining of a separate return air tailgate.

Jan 1, 1990

By H. L. Ehrlich

Marine manganese nodules harbor a mixed population of manganese-oxidizing and -reducing bacteria, as well as bacteria that do not act on manganese. They also host phagotrophic protozoa. Out of several laboratory studies, one line of investigation indicates that some kinds of bacteria found on nodules can catalyze the oxidation of Mn2+ bound to Mn(IV) oxide at the surface of nodules at in situ temperature and pressure. In the absence of appropriate bacteria, the rate of oxidation of the surface-bound Mn2+ is significantly slower. How Fe(III) is incorporated is still unclear. Base metals such as Cu, Ni and Co, which are usually found in marine nodules in various quantities, may be incorporated through scavenging by Mn(IV) oxide. Laboratory evidence shows that some other bacteria on nodules can reduce the Mn(IV) oxide to Mn2+ in the presence of an appropriate source of reducing power in the form of organic carbon. The reduction of Mn(IV) oxide mobilizes manganese and trace metals such as Cu, Ni, and Co in the nodules. These bacteria reduce Mn(IV) whether oxygen is present or not. They could be harnessed in the bioleaching of nodules. The manganese(IV)-reducing bacteria and the bacteria that neither oxidize nor reduce manganese are thought to keep the organic matter in the nodule environment sufficiently low to favor bacterial manganese-oxidation, which in laboratory tests is inhibited by excess organic carbon. The preying by the protozoa on the different kinds of bacteria is thought to control the bacterial population on nodules and ensure continued growth of the manganese-oxidizing bacteria and the nodules. To eliminate interference from seawater salts in the bioleaching of Mn, Cu, Ni and Co, it may be more advantageous to use terrestrial Mn(IV)-reducing bacteria than the Mn(IV)-reducing bacteria resident on nodules. The terrestrial bacteria would allow bioleaching in fresh water. Unlike the marine bacteria, most terrestrial bacteria studied to date reduce Mn(IV) oxide only anaerobically. A general outline for an anaerobic bioleach process of marine nodules with freshwater bacteria is discussed.

Jan 1, 2000

By R. J. Hamilton

Considerable success has been achieved in recent years in reducing concentrations of respirable dust in UK coalmines; thankfully this has been reflected in significant improvements in pneumoconiosis statistics. However, continuous increases in mechanisation and in rates of working, accompanied by more stringent dust regulations, necessitate the introduction of improved and often more sophisticated methods of dust control. The increased application of exhaust ventilation and air cleaning techniques seems likely to be the most important step forward in dust control in coalmining during the next few years. A typical drivage in a UK mine is not more than 16 ft (5 m) wide and is supported by steel arches. In the past the majority of such roadways were driven by the conventional means of blasting and loading. Since the main purpose of ventilation was to clear blasting fumes and to provide adequate scouring of firedamp, not surprisingly it was usual to have &apos;forcing&apos; ventilation. Present systems of operation are making increasing use of heading machines and it is not surprising that well over half of all drivages are now ventilated by exhausting methods. (1) The great majority of coal getting in the UK is from longwall faces, usually in seams of less than 6 ft (1.8 m) thickness. Although this method of min¬ing has many advantages in terms of safety and productivity, dust control is made more difficult because of the need for men and machines to work in the same ventilation stream. Much emphasis has been placed on improving the design and methods of opera¬tion of longwall machines to reduce dust production, and improved ventilation has provided greater dilution, and in consequence, reductions in dust concentration. On all machines water is now fed through internal galleries to the cutting elements. Unfortunately, one of the difficulties associated with mining thin seams is that there is some unavoidable cutting in the roof or floor and in many seams there are faults to be traversed and dirt bands which must be removed with the coal. Under these conditions it appears that the use of exhaust ventilation and air cleaning offers the most promising way of achieving satisfactory dust conditions.

Jan 1, 1980

I met Austin Taylor in Vancouver on my way home from my first Pioneer examination. He asked me to examine the unsuccessful old Lorne mine, adjoining and west of the Pioneer. I had no idea that this meeting would lead to one of the outstanding successes and pleasant associations of my career. I knew nothing of Taylor, except that Gen. McRae and associates said that he had been engaged in lumbering and was interested in an oil and gasoline marketing company called Home Oil. But even if the Lorne examination would be only a small one, in the depths of the Depression in 1931, I was glad to have a chance to look at another gold property, so I agreed to visit the Lorne early in August. The start of the trip was not auspicious. I had been working hard on an unproductive study, and was greatly worried by my father&apos;s hopeless illness with tuberculosis. To get a little rest on my way north I had arranged to go from Seattle to Vancouver on the night boat that connected with my train. To my surprise, Bill Boultbee, an associate of Taylor, met me at the train in Seattle at 9:30. He said he would drive me to Vancouver, arriving at one In the morning. I was so tired that I begged off and let him take the drive alone Boultbee was most understanding and friendly, but I knew how I would have felt if I had been kind enough to take the long drive to help a stranger and then had been forced to make the return midnight drive alone. I was lucky they did not call off the examination at once. I got a good sleep on the Vancouver boat and Austin Taylor met me at the Hotel Vancouver for breakfast. After a brief talk he took me to the small steamer that made the 4-hr sail up Howe Sound to the village of Squamish. This was the end of the Province-owned Pacific Great Eastern Railway that was eventually to be a shortcut from Vancouver to the Canadian National main line at Prince George. Because

Jan 1, 1976

By Douglas B. Silver

The key to unlocking value is to find opportunity where others have missed it. How does a company find value in a thoroughly explored asset? This article explores the approach taken by one company and the results it achieved from working this problem. The town of Shafter is located on a small bend in the road in west Texas&apos; Big Bend Country. Its past emulates the glory days of so many other mining camps. A discovery was made, fortunes were built and World War II shut down the operation. The Shafter deposit continues to be one of the larg¬est undeveloped primary silver deposits in North America. Gold Fields Mining Co. recognized the area&apos;s potential in 1977 and embarked on studies to reopen and develop the district. Gold Fields spent $16 million on the Shafter project. It drilled more than 86,240 m (282,940 ft) in 475 holes, sunk two shafts and developed 1,550 m (5,100 ft) of underground workings. Today, the mothballed 447-kW (600-hp), single-drum Nordberg hoist and permanent production-type, single-compartment headframe continue to crown the shaft. Other buildings onsite house compressors, mine pumps, spare parts, drill core and other supplies. All these items look as though they arrived yesterday. By 1982, Gold Fields had completed an extensive feasibility study with ambitions to. construct a 1.36-kt/d (1,500-stpd) agitated cyanidation mill and base metal gravity circuit. Reserves at Shafter stand at 4.23 Mt (4.67 million st) grading 193.5 g/t (5.65 oz/st) silver. Gold Fields planned to produce 71.5 t/a (2.3 million oz/year) of silver at a head grade of 196.2 g/t (5.73 oz/st) silver with a 77% recovery rate. Cash costs were projected to be $5.54/oz with an anticipated initial and total capital cost of $46.2 million and $51.3 million (1984 dollars), respectively. The study assumed a silver price of $8.60/oz that has not been seen since the Hunt brothers quit buying silver. When silver prices declined, Gold Fields put the property up for sale.

Jan 1, 1999

By Mohammad Hossein Sadaghiani

"Construction of underground structures in urban areas is a very challenging work. There are generally two methods of construction, an open cut-and-cover and underground method. To eliminate the subsurface and surface disturbance and street traffic problems, underground method is preferred. The stress redistribution caused by underground excavation induces movements and deformation in the earth mass and ultimately at the ground surface. This is more pronounced in large space excavations. Generally pre-supporting system is used to control ground deformation and thus enhance its stability. In this paper an innovative pre-supporting system is presented. Concrete Arch Pre-supporting System (CAPS) is introduced in Tehran Metro in 2002. This method has roots in construction method of an Old Iranian small water tunnels, called Quanat. CAPS is an efficient method for stabilizing large span underground spaces constructed in shallow and soft ground. In this technique underground reinforced concrete elements are constructed around the proposed underground space prior to main excavation. This method is used successfully in over 50 large span underground structures in Tehran Metro stations and road tunnel intersections. CAPS has potential to be used to pre-support the large span underground spaces at any weak ground condition in an urban area.1. INTRODUCTION Underground subway stations can be constructed either by open cut-and-cover or underground construction. Due to the presence of subsurface utilities and street traffics in urban areas, underground construction is preferred to eliminate relocation of the subsurface utilities, and other urban disturbance. Underground construction in an urban area is a very challenging effort. The complexity of the work is more pronounced in a weak and shallow ground. The stress redistribution caused by underground excavation induces deformations in the earth mass and ultimately at the ground surface causing damage to adjacent structures. The need to control ground surface settlements in urban area is widely recognized and new construction methods are continuously developed. Settlements induced by underground excavation may cause serious damages to nearby structures and subsurface underground utilities, (Sekimoto et. al. 2001). In order to improve stability of underground excavation and reduce settlements, various ground treatment techniques are presented, Johnson, et.al., (1983), Carrieri, et.al. (2002), and Ocak (2008)."

Jan 1, 2016

By Craig Smith

California is the nation&apos;s leading producer of diatomite products. The Lompoc Mining District in Santa Barbara County is the world&apos;s largest source of commercial marine diatomite. Grefco Inc. exploration has defined a large embayment of commercial grade freshwater diatomite in Shasta County. Exploitation of this massive deposit could substantially increase California&apos;s diatomite production.

Jan 1, 1980

By Harry R. Dahlberg

Heap leaching is discussed as a unit process. Five factors are identified as the principal elements that can be measured and/or controlled. These are: 1. Material Size 2. Volume of solution 3. Tonnage of heap 4. Time 5. Solution concentretion. The Rate of Extraction Curves obtained from an actual heap or column tests describes the economic viability of the unit process. By analysis of these curves and the five factors end their inter-relationship it is possible to determine how the extraction rate can be increased. The practice of leach and rest used by many operators is analyzed and shown on a hypothetical rate of extraction curve. The influence of the driving force of the hydrogen ion and ferric Lon as Lixivants and its effect on the rate of extraction curve is discussed.

Jan 1, 1979