Search Documents

By Ihor Kunasz

The high lithium demand forecasted for some high tech applications and batteries for electric and hybrid-electric vehicles, in particular, has sparked increased exploration for lithium, particularly for lithium- and potassium-bearing brine deposits. The latter have generally followed the Canadian Institute of Mining, Metallurgy and Petroleum (CIM) NI 43-101 guidelines on resource reporting, formulated for hard rock deposits (metals and industrial minerals). While a number of the requirements can be appropriately applied to brines, brines are fluids and require a specific analysis leading to a distinct set of reporting requirements. Brines cannot be considered industrial minerals because the various elements occur as ions in a dynamic fluid, rather than being chemically bonded in a solid. Although chemicals are produced from brines, brines have no relation to industrial mineral deposits. This article analyzes the recently released (Nov. 1, 2012) document CIM Best Practice Guidelines for Resource and Reserve Estimation for Lithium Brines, in light of the practical knowledge available from existing brine operations. It recommends modifications to the guidelines, which, if applied in their present format, will result in overstating resources and reserves and mislead potential investors. The CIM Best Practice Guidelines for Resource and Reserve Estimation for Lithium Brines document is generally descriptive and does not fully address the methodology for brine resource or reserve definition. Lithium and other elements (potassium, magnesium) are contained in a fluid, the hydrologic characterization of which should be the principal focus of a brine exploration program. The fundamental requirement in defining lithium brine resources and reserves in a salar is the identification and definition of those formations ? the aquifers ? that will yield brine in a usable quantity to a well, because brines can only be extracted by pumping wells. Fine-grained sediments will never, as required in the summary Table 1, have ?reasonable prospects of economic extraction,? cannot be considered and, therefore, need not be tested. However, the guidelines recommend the collection of solid samples and a high-core recovery for laboratory testing of various sediments instead of focusing on the brine.

Oct 1, 2013

By Beth Robinson

Central Mexico's mining districts, opened centuries ago during the Spanish conquest, still form the backbone of metal mining in the country today. Beginning at Chihuahua City, the Second Mexican Mining Rail Excursion traveled southeast from camp to camp through this major mining area to Taxco. Improved exploration, exploitation, and beneficiation methods have permitted continuous mining of many old deposits, and led to the discovery of new ones. Minerals not sought by early miners-lead, zinc, copper, and fluorite-now contribute substantially to mining activity in central Mexico. Of Mexico's five physiographic provinces, the rail excursion passed through two: the Mesa Central, and the Sierra Madre Occidental. The Mesa Central province is a wide tableland with basin and range topography, containing important base metal deposits. Mining in this region is primarily of limestone replacement ore bodies. Massive deposits form horizontal mantos or vertical chimneys. In northern Zacatecas, the Santa Eulalia and Naica mines demonstrated this character. The Sierra Madre Occidental lies west of Mesa Central in northern states, then widens to almost the entire width of the country from outside Mexico City to the southern border. The area consists of volcanic beds, several kilometers thick. These intermediate volcanics are primarily andesitic, of Tertiary age. Resting on older strata of adjoining physiographic divisions, the volcanic beds are overlain by a thick series of acidic flows and tuffs. Economic mineralization in the Sierra Madre Occidental is vein-type, primarily gold and silver. Mines at Fresnillo, Guanajuato, Pachuca, and Taxco contribute to the claim that this region is the center for precious metals in Mexico. A third type of mineralization, contact metamorphic deposits, is commercial at Santa Eulalia. First Stop, Santa Eulalia Mine tours began with the Santa Eulalia unit, located 25 km east of Chihuahua City. Mining in the region dates back to the early 1700s. The oxidation zone was worked until 1790, but mining declined until Asarco arrived in the early 1900s, building a selective flotation plant for treating primary sulfides. Asarco still owns 34% of Industrial Minera Mexico, S.A. (IMMSA), operator of the Santa Eulalia mine. Santa Eulalia currently has a milling capacity of 850 t/d. The San Antonio and Buena Tierra mines provide feedstock. Head grades at San Antonio, the mine participants toured, average 80-120 g/t of silver, 1.5-4.5% lead, 4-16% zinc, and 0.1-2.5% copper. Tin and vanadium were also recovered between 1930 and 1940. Estimated proven and probable reserves total about 7.6 Mt, although 1.8 Mt of reserves are located in areas of high water pressure and volume, which makes extraction difficult. Water is a significant production problem at the San Antonio mine. In one area, an AX drill hole encountered 2.6 m3/min (700 gal/min) at a pressure of 2.5 kPa. Precautions are taken to cope with the problem: protective drilling in advance of blasting is performed;

Jan 2, 1982

By Z. D. Hora, W. N. Hamilton

Introduction Some unique opportunities exist for industrial minerals in British Columbia and Alberta. The region's diversified geology, particularly in British Columbia, offers favorable environments for a rich variety of mineral resources. Many minerals have been produced for years. For some, however, the level of production is far less than the potential. Others have had production in the past, but are not currently produced. Still others are known to exist and may have been actively prospected. But they are not yet developed. In addition, a number of speculative possibilities have recently come to light. The potential significance is not fully confirmed, but is suggested in showings in favorable geologic settings. Location and geography British Columbia and Alberta are the westernmost provinces in Canada (Fig. 1). The region overlaps two major physiographic divisions of the country, the Cordillera and the Interior Plains. It also takes in a small segment of the Canadian Shield on the east. The entire territory is greater than 1.6 Mkm2 (618,000 sq miles). Most of British Columbia lies within the Cordillera, a mountainous belt some 800 km (500 miles) wide. The belt is made up of three main physiographic components, the Eastern, Interior, and Western subdivisions. The Eastern subdivision embraces the rugged, linear ranges of the Rocky Mountains, elevations between 2600 and 3300 m (8530 and 10,800 ft). They form a 100-km (62-mile) wide band straddling the BC-Alberta border and extending northwest across northern British Columbia. The Interior subdivision includes several ancient mountain ranges but is dominated by an intermountane plateau area of low relief (average elevation 1200 m or 3900 ft). The Western subdivision is dominated by the Coast Mountains (elevations between 1800 and 4000 m or 5900 and 13,123 ft). These form a band about 175 km (110 miles) wide into which are sculptured the spectacular fiords of the BC coastline. Alberta lies largely within the Interior Plains, a prairie region of low to moderate relief (elevations between 200 and 1200 m or 650 and 3940 ft) formed of nearly horizontal bedrock strata. The Plains surface rises gradually to the southwest toward the deformed belt of the Rocky Mountains, where the bedrock strata are upturned, folded, and faulted. To the east, the Plains merge with the Canadian Shield, which exposes the Precambrian crystalline basement of western Canada. The total population of the BC-Alberta region is about five million people. Minerals, forestry, and agriculture are the primary industries here. It has well developed infrastructures to service these industries. British Columbia is third among the Canadian provinces in metal mining - $1.1 billion in 1985 - and first in forest products. It is also second in hydro-electric power development. Alberta leads all provinces in total mineral production, largely due to its extensively developed petroleum and natural gas resources - $26.2 billion in 1985.

Jan 12, 1987

By Christine M. Kammer

In 1852, six barrels of iron ore were loaded aboard the steamer Baltimore at Marquette, MI, after a trip by mule wagon from the nearby Cleveland Iron Mining Co. Shipped to Sault Ste. Marie, they were portaged around rapids and reloaded onto another ship for the final journey to the steel mills of Cleveland. In 1855, the same company-the predecessor of Cleveland-Cliffs Iron Co.-chartered the brigantine Columbia to carry the first iron-ore cargo through the newly opened Soo locks. In 1981, about 2,190 iron-ore shipments in the form of taconite pellets were transported by water from US Great Lakes-ports. The total volume during the 284-day shipping season was 63 Mt (62 million It). Counting Canadian ship¬ments, almost 76 Mt (75 million It) of iron ore were moved on the lakes last year. The five Great Lakes-Superior, Huron, Michigan, Erie, and Ontario-contain 20% of the world's fresh water. The area surrounding the lakes has 26% of the nation's populations, 47% of its steel production, and over 80% of the raw materials required to make steel. That figure includes 71% of the country's iron ore and 40% of its limestone. Only the availability of low-cost water transportation of raw materials has kept the heartland steel producers competitive. Iron ore shipped on the lakes originates in the Lake Superior district's Mesabi and Marquette iron ranges. Major mines and their principal partners are Cleveland-Cliffs Iron Co.'s Empire, Republic, and Tilden; Armco and Republic's Reserve Mining Co.; Oglebay Norton Co.'s Eveleth; Hanna Mining Co.'s National and Butler; Inland Steel Co.'s Minorca; Pickands Mather & Co.'s Erie and Hibbing, the latter operated in conjunction with Bethlehem Steel Corp.; and US Steel Corp.'s Minntac. Pelletized ore products at these facilities is shipped through seven principal ports on the upper lakes: Duluth, Two Harbors, Silver Bay, and Taconite Harbor, MN; Superior, WI, and Marquette, MI, on Lake Superior; and Escanaba, MI, on Lake Michigan. In 1981, tonnage volumes ranged from 13.3 Mt (13.1 million It) shipped from Duluth, to Marquette's total of 5.4 Mt (5.3 million It). The ore docks, with two exceptions, are operated by railroads, most of which are owned by mining companies. Table 1 illustrates US iron-ore shipments in 1981. In the lower lakes, ore is discharged at dock facilities close to the great steel-producing centers of Chicago, Detroit, Cleveland, Pittsburgh, and Buffalo. Between the mines and mills, lakes and connecting waterways form one of the country's most effective transportation systems. Each year, vessels on the Great Lakes transport about 181 Mt (200 million st) of bulk industrial and agricultural materials-a greater quantity at a lower cost than can be achieved by any other transportation mode. Major commodities in Great Lakes trade are iron ore, coal, grain, limestone, cement, sand, and petroleum products. About 125 US flag vessels serve this trade, among them 13 "1,000-

Jan 10, 1982

By Paul M. Jr. Musgrove, Thomas D. Henderson, Mark B. Nesbitt

Introduction History. Vat leaching operations began in October 1953. Since that time, about 4.2 million tpy of oxide ore averaging 0.72% copper have been treated. Economic conditions, improved operating methods, and increased production facilities have allowed the ore grade to be reduced over the years. The average ore grade was 0.84% Cu during the 1950s, 0.68% in the 1960s, and was 0.50%, or below, during the 1970s. By 1961 some 35 million tons of oxide ore had been removed from the mine, exposing the underlying sulfide ore body. A 5,000¬ tpd concentrator was constructed and put into operation to treat the sulfide ore in November 1961.1 The original crushing plants were used for both oxide and sulfide ores, but by adding a third crushing shift, six days per week, the total ore treated was raised from 12,000¬17,000 tpd. Dwindling oxide ore reserves prompted expansion of the concen¬trator to 13,500 tpd in 19672 so that exhaustion of known reserves of both ores would occur at nearly the same time. Again, no additional crushing facilities were added during the expansion. It was anticipated that the treatment rate of oxide ore would be reduced from 12,000 to about 9,000 tpd. Instead, the addition of two crushing shifts per week and improved operating procedures have increased the treatment rate to 26,500 tpd-13,000 tpd to the leaching plant and 13,500 tpd of sulfide ore treated in the concentrator. Geology. The Yerington ore body is a disseminated porphyry copper deposit where a quartz monzonite porphyry intrusive contains the major part of the ore values, with some copper mineralization found in the adjacent granodiorite and other rocks. The geology of the Yerington Mine was aptly described by J. R. Wilson (Mining Congress Journal, June 1963). The ore body is one of few porphyries where geologic conditions were optimum for the formation of an important concentration of oxidized ore with minimum economic effect of secondary enrichment. The principal mineral in the oxidized zone is chrysocolla, which irreg¬ularly occurs dispersed throughout the rock and as narrow seams along fissures. The grade of the ore in the oxidized zone is generally the same as in the primary sulfide below, although some massive concentrations do occur as vein-like fissures and as filling of breccia zones. Cuprite, tenorite, melaconite, malachite, and azurite occur but are not abundant. Lying between the chrysocolla horizon and the primary sulfide is a transition zone whose limits are irregular but seldom with vertical range exceeding 50 ft. Chalcocite, cuprite, melaconite, native copper, and chrysocolla occur superimposed on the primary sulfides. Chalcocite replacement of chalcopyrite, as well as secondary chalcocite, do occur. The primary sulfide minerals are chalcopyrite and pyrite, with minor amounts of bornite and covellite. There are no appreciable gold or silver values, and molybdenite has rarely been noted.

Jan 1, 1985

By E. D. Attanasi, M. W. Bultman

Most statistical measures of mineral exploration continued downward in 1986. Prospects in 1987, however, appear to have brightened for exploration as the overall economic health of the mineral industry improved. The Society of Economic Geologists (SEG) survey of US and Canadian firms documents the marked decline in US mineral exploration since the early 1980's. From 1981 through 1986, the total exploration expenditure by US firms declined by more than 73% (Fig. 1). Exploration expenditures by US firms declined by 66%%. US based professional exploration staffs were slashed by 70% (Fig. 2). Also, many firms have written off some reserves because of weak markets or have not delineated new reserves to replace production. The Canadian government reported that between 1981 and 1986 Canadian molybdenum re¬serves had declined by 30%, lead and zinc reserves by 20%, and nickel and copper reserves by 15%. The SEG survey also shows the immediate impact of the decline in the dollar on US exploration expenditures abroad. Between 1981 and 1986 the share of the exploration dollar spent by US firms outside of the country declined by nearly one-half and exploration acreage abroad declined by 69%. The downward trend of the last six years may finally be near the end as a leaner and more efficient minerals industry starts to gear up for a period of increased activity. An industry survey reported to Mine Development Bimonthly (Metals Economics Group) indicates that mining firms were expected to increase exploration expenditures in 1987 by at least 10% above 1986 levels. Worldwide expenditures for 1987 by companies covered by the report were expected to top $800 million. It is the first time since 1984 that an increase in exploration expenditures was expected. Also, the US Bureau of Land Management reported a 30% increase in new mining claims for fiscal year 1987 over fiscal year 1986. The bulk of the increase in claims was in states having intense gold exploration, particularly Washington and Oregon. Much of the optimism is undoubtedly due to the increases in metal prices that occurred in 1987. Some of these increases include gold, average price up about 20%; copper, average price up 24%; aluminum, average price up 26%; and nickel, average spot price up 20%. The SEG survey shows precious and base metals accounting for 89% of the exploration expenditures in the US in 1986, up 52% from 1981. The US Bureau of Mines estimates that 80% of US exploration activity in 1986 was directed entirely at gold (1986 Minerals Yearbook). Worldwide exploration plans indicate the continued dominance of gold exploration. New programs were announced for Ghana, Malaysia, and Indonesia. Major new exploration programs were also launched for lead-zinc sulfides in Morocco, platinum and palladium in northwest Brazil, rare earth minerals in Greenland, diamonds in Indonesia, and heavy minerals off-shore Australia. Significant gold discoveries were made at Angels Camp in Oregon; South Africa, near Potchestroom; India, in the Chitradgra district; Northern Ireland near Mt. Speerin; Chile, San Cris-

Jan 5, 1988

By Edie Trimmer

Utah statute defines sovereign lands as "those lands lying below the ordinary high water mark of navigable bodies of water at the date of statehood, and owned by the state by virtue of its sovereignty." The lands within the bed of Great Salt Lake (GSL) are, by this definition, sovereign lands, acquired at statehood in 1896 in accordance with the "equal footing" doctrine, granting each state control and ownership of navigable waters and the lands underneath those waters within its borders. Under public trust doctrine, the state, as trustee for the people, bears responsibility for preserving and protecting the right of the public to use of the waters for navigation, commerce, fishing, recreation, and wildlife habitat. Also by statute, sovereign lands are defined as "state lands," to be managed by "multiple use sustained-yield principles." The Division of Forestry, Fire and State Lands is given management authority for sovereign lands and, as manager, has responsibility to prepare comprehensive plans, initiate studies of the lake and its resources, implement comprehensive plans through state and local entities, and coordinate the activities of various divisions within the Department of Natural Resources (DNR). The Division of Forestry, Fire and State Lands also has responsibility for management of mineral leasing on sovereign lands. The many resources on the lake--water, minerals, wildlife, recreation, archeological and historical values--are managed by as many state agencies which occasionally creates conflicts. The brines of GSL contain several ions that crystalize into valuable minerals during evaporation. The major ions in the lake are, in order of relative abundance, chloride, sodium, sulfate, magnesium, and potassium. Mineral products which are currently extracted from lake brines are sodium chloride, magnesium chloride brine which can be sold as flake magnesium chloride or further processed into magnesium and chlorine gas, and potassium sulfate. Mineral products which have potential for extraction include gypsum, sodium sulfate, and trace amounts of lithium, boron, and bromine. The GSL contained an estimated 4.3 billion short tons (st) (3.9 billion metric tons [mt]) of dissolved salts in 1998. Utah Geological Survey (UGS) estimates of the dissolved salt content in GSL have fluctuated from 4.0 to 5.5 billion st (3.6 to 5.0 billion mt) due to the dynamic conditions in the lake as salts are precipitated and redissolved, and due to the diversion of brines from GSL, such as the West Desert Pumping Project. The lake has four areas of varying salinity, separated by dikes or other man-made structures: north arm and Stansbury Bay brines at near saturation (25 to 27 percent total dissolved solids [TDS]); the main body of the south arm with concentrations ranging from 7 to 15 percent TDS as lake elevations fluctuate; the waters in Farmington Bay at approximately 3 to 5 percent TDS; and Bear River Bay at <1 to 7 percent TDS. The percent TDS in Bear River Bay fluctuates with lake level, and changes in Bear River inflow. The transfer of salts from the south arm to the north arm has raised questions about the viability of the mineral and brine shrimp industries. The UGS and the U.S. Geological Survey (USGS) continue to monitor salinities at designated sites on the lake to document changing lake salinity. A recurrent theme is that placement of dikes and diversions can have significant and rapid impacts on various conditions in the lake. Hydrocarbon resources on the lake are significant, but presently undeveloped. The hydrocarbons are low gravity (4 to 9 degree API) and tar-like, contain high nitrogen concentrations, and up to 12 percent sulfur. The unusual characteristics of the oil have been the subject of studies by chemists at Weber State University and University Louis Pasteur de Strasbourg. However, these resources are difficult, and at present, uneconomic to extract using current technology because of the nature of the hydrocarbons, and production in "an offshore, highly saline environment." Oolitic sand deposits make up many of the beaches and shorelines around the lake. Because of their high calcium carbonate content, oolites have been used by Magnesium Corporation of America (MagCorp) and its predecessors for acid neutralization and dike construction. Oolites are also used in very minor amounts in flower drying. The Utah Division of Oil, Gas and Mining reports up to 130,000 st (118,000 mt) mined annually by MagCorp from U.S. Bureau of Land Management (BLM) lands adjacent to GSL. Currently, there are twelve producing mineral leases which generated slightly more than $1,000,000 in royalties during calendar year 1998. IMC Kalium Ogden Corp. (IMC Kalium) produces potassium sulfate and magnesium chloride from brines concentrated through solar evaporation in Bear River Bay and Clyman Bay. By-product sodium chloride is transferred to IMC Salt, which packages and sells the salt. MagCorp produces magnesium metal from brines concentrated in Stansbury Bay. Cargill Salt produces sodium chloride from brines provided by MagCorp under a lease agreement. Morton Salt produces salt at the southeast end of Stansbury Island. Lastly, North Shore Limited produces cocentrated brines for use in dietary and mineral/vitamin supplements near Spring Bay in the north arm of the lake. Producers of magnesium, potash, and salt from GSL contribute significantly to the value of metals and industrial minerals in Utah. Together these companies contribute approximately $240 million in gross value, or 18 percent of the value of the state&apos;s nonfuel mineral production. Most of this production is exported.

Jan 1, 2001

By J. D. Megeath

In the October 1988 issue of MINING ENGINEERING, J.G. Wargo&apos;s paper discusses the problem of measuring and analyzing permeability, porosity, and fracturing in its relation to in situ leaching of disseminated gold deposits. This paper made me suspect that a good deal of information and analysis may have been done on this in reverse in the petroleum industry. Some years ago, I was involved with the US Geological Survey in a project studying the Devonian shale of the eastern United States. The Devonian shale contains gas deposits that have the characteristic of slowly seeping gas over a very long time period. To understand the rate of seepage, considerable study and analysis was done on the interrelationship of poros¬ity, permeability, and fracturing. The purpose was to find out how and why the gas could escape in the varying rates found in wells throughout the formation. It strikes me that this is the mirror image of the problem faced in attempting to understand how a cyanide solution will travel into a deposit. To possibly invent our own personal wheel a little faster, I would suggest a look at the work done on the Devonian shale. Some of it is contained in "Estimates of Unconventional Natural-Gas Resources of the Devonian Shale," US Geologi¬cal Survey Open-file Report 82-474, 1982, and "Additional Data for the Estimates of Unconventional Natural-Gas Re¬sources of the Devonian Shale," Open-file Report 83-676, 1983. It is entirely possible that some of this previous work could shorten the time required to make in situ leaching of dissemi¬nated gold deposits a profitable technique.

Jan 1, 1989

By J. D. Megeath

In the October 1988 issue of MINING ENGINEERING, J.G. Wargo&apos;s paper discusses the problem of measuring and analyzing permeability, porosity, and fracturing in its relation to in situ leaching of disseminated gold deposits. This paper made me suspect that a good deal of information and analysis may have been done on this in reverse in the petroleum industry. Some years ago, I was involved with the US Geological Survey in a project studying the Devonian shale of the eastern United States. The Devonian shale contains gas deposits that have the characteristic of slowly seeping gas over a very long time period. To understand the rate of seepage, considerable study and analysis was done on the interrelationship of porosity, permeability, and fracturing. The purpose was to find out how and why the gas could escape in the varying rates found in wells throughout the formation. It strikes me that this is the mirror image of the problem faced in attempting to understand how a cyanide solution will travel into a deposit. To possibly invent our own personal wheel a little faster, I would suggest a look at the work done on the Devonian shale. Some of it is contained in "Estimates of Unconventional Natural-Gas Resources of the Devonian Shale," US Geological Survey Open-file Report 82-474, 1982, and "Additional Data for the Estimates of Unconventional Natural-Gas Resources of the Devonian Shale," Open-file Report 83-676, 1983. It is entirely possible that some of this previous work could shorten the time required to make in situ leaching of disseminated gold deposits a profitable technique.

Jan 1, 1990

By Robert H. Carpenter

Downstream dispersion curves for certain trace metals were obtained from two mineralized areas in the southeastern U. S. In Lincoln Co., Georgia, 7 sample sets were collected downstream from the Magruder mine, a polymetallic sulfide deposit (Zn-Cu-Pb-Ag-Au) in metavolcanic rocks. Five sample sets were collected along Joe Mill Creek in Grainger Go., Tennessee, downstream from a zone of zinc mineralization in carbonate rocks (Mississippi Valley-type). In both areas, analyses were made of Fe-Mn oxide coatings on lithic fragments and quartz pebbles, and the -80 mesh fraction of the stream sediment. A comparison of the dispersion curves reveals the following: 1.) the anomaly/background ratio is markedly higher in the Fe-Mn oxide coatings for zinc and copper; 2.) the anomaly/background ratlo is markedly higher in the -80 mesh fraction for lead which is not concentrated in the coatings; and, 3.) the Zn/Mn and Cu/Mn ratios in the coatings are useful in that they enhance downstream derectability of mineralization as well as provide for a simpler analytical procedure. There are several potential advantages of using coatings vs. the conventional -80 mesh fraction in stream sediment surveys. Because soluble metal is brought into the stream mainly in groundwater, deeper anomaly sources may be detectable from the oxide coatings than from clastic fractions of alluvium where much of the metal is derived from erosion of soils. Variability due to sampling may also be reduced, providing better discrimination of anomalies. In areas of glacial or alluvial cover, coating surveys may be particularly applicable.

Jan 1, 1975

By John E. Auten

The computer program "Spike" is an "expert-rule based system" designed to fulfill two requirements. 1) acquaint unfamiliar personnel with big hole drilling techniques and 2) to stimulate the "old hands" in solving drilling problems. "Spike" will not make anyone a drilling expert The best way to understand a computer program is by example, but first some explanation of an? "expert-rule based system", As the name implies, the program tries to imitate a human expert. Unlike a normal computer program which uses a list of instructions to follow in a set order, a rule-base program has a collection of independent rules without an explicit list of things to do, one after the other. This type of program was mandatory to accommodate the ever changing situations and corrective actions that more accurately duplicate actual drilling operations and the advise of an experienced drilling expert.

Jan 1, 1988

By Chee Theng

"In 2013, Coeur Mining had more than $55 million in general and administrative (G&A) costs and less than $100 million in cash flow. This year, its G&A costs stand at $30 million, down by more than 40 percent, its all-in sustaining costs have shrunk by more than 30 percent, and its cash flow is above $200 million. To realize this, the company aggressively reduced both its corporate overhead cost and operating cost and repaid more than $300 million in debt.The more robust balance sheet meant the precious-metals producer was well positioned to reap the rewards of an upsurge in commodity prices in the early part of 2016. Its stock price soared from $1.75 in January to $15.98 in August. Although the stock price has since dropped to around $9 due to a stronger dollar and a more hawkish Federal Reserve that recently raised U.S. interest rates, shifting the opportunity-cost argument away from buying gold and silver, Coeur remains attractive to analysts in light of its prudent spending and improved fundamentals.Focus on balanced portfolioCoeur is the largest primary silver producer and one of the largest gold-producing companies in the United States and one of the largest silver companies in the world. Incorporated in 1928, the U.S.-listed company has a total of five operations: three in the United States, one in Mexico and one in Bolivia. About two-thirds of its revenue comes from the United States.The company is conscientious about having a balanced portfolio, so no single mine accounts for more than about 30 percent of its business. Being in three different jurisdictions provides further diversification, and its revenue split of about 60 percent from gold and 40 percent from silver gives it some metals mix. This year, it expects to produce about 466 t (15 million oz) of silver and 10.3 t (330,000 oz) of gold."

Feb 1, 2017

By David C. McLean, Peter Penner, Martin de G. Salter

The Rogers Pass Project for C.P. Rail includes a 14.7 km tunnel and an 8.5m diameter concrete lined ventilation shaft to a depth of about 335m. The shaft collar is in bouldered water bearing glacial till to a depth of about 95m. Initial excavation in the overburden was with the aid of dewatering wells. When ground support problems arose the excavation was completed by a two stage freeze programme. Freeze holes were drilled from the shaft bottom. This most unusual method was successful in overcoming the difficulties safely and efficiently. The remainder of the shaft was sunk and lined conventionally. Finally, a central dividing wall was poured by jump forming from the bottom up. The wall was completed to a high standard at up to about 20 vertical metres per day.

Jan 1, 1989

By J. Drelich, J. Pletka

Lost foam casting is a process in which a polymeric material is formed into the shape of the part to be cast. Parts that are more complex are fabricated by simply gluing several patterns together. The pattern is then coated with a refractory material consisting of a mineral mixture and binders. Finally, hot metal is poured into the pattern, evaporating the expanded polystyrene and taking the shape of the coating shell. Prior to casting, a significant number of the patterns are damaged and inevitably landfilled. In this study, a process was developed for the recovery of expanded polystyrene from the coating and glue contaminants. The process consists of shredding, impact comminution, size classification and pneumatic separation. It is successful in separating up to 97% of the contaminants, while recovering 95% of the polystyrene. Key words: Casting, Lost foam process, Expanded polystyrene recovery

Jan 1, 2003

By T. D. Maki

FMC Gold&apos;s Paradise Peak Mine, located 13 km (8 miles) south of Gabbs, Nevada, became operational in April of 1986. Shortly thereafter heap leach testwork began on sub mill grade ore. Presently, testwork continues in combination with production size heaps that account for approximately 6% of total gold production at Paradise Peak.

Jan 1, 1989

By A. K. Smith

Overexposure to noise remains a widespread, serious health hazard in the U.S. mining industry. Most other categories of illnesses and injuries associated with mining have improved, with the exception of hearing loss. U.S. Mine Safety and Health Administration (MSHA) coal noise data from 2000-2004 show that the continuous mining machine (CMM) is first among all equipment, accounting for 35% of noise overexposures. Joy Mining Machinery, in collaboration with the National Institute for Occupational Safety and Health (NIOSH), is conducting research to reduce noise generated by continuous mining machines. This paper describes a "JOY Designed for Noise Reduction" (JOY DNR; patent pending) tail section as a noise control for reducing the noise overexposures of CMM operators. Underground testing shows a 45% to 65% noise exposure reduction for the operator when comparing the JOY DNR tail section results to those for a standard machine. Utilizing this newly developed noise control, along with previously proven controls, will provide CMM operators an opportunity to be within the MSHA permissible exposure limit (MSHA-PEL). Mining Engineering, 2011, Vol. 63, No. 7, pp. 83-85. Official publication of the Society for Mining, Metallurgy and Exploration, Inc.

Jan 1, 2011

By RICKARD HANSEN

With vehicles frequently found in mines and tires being a major fuel item, the risk of tire fires will be severe underground. This study presents an analysis of tire fires on mining vehicles to increase the knowledge of the risk and mitigating measures, which would improve the fire safety underground. Data from fire experiments and computational fluid dynamics (CFD) simulations were applied. It was found that the wheelhouse of a loader caused an increase in the flame tilt angle, decreasing the flame impingement and heat flux downstream. The flame temperature of a drilling rig tire was found to be higher than that of a loader tire, increasing the risk of igniting items. The construction of the wheelhouse/mudguard will contribute to a longer flame length by creating a fuel-rich environment. The CFD simulations predicted higher flame tilt angles for a drilling rig for higher flow velocities, indicating the influence of the wheelhouse/mudguard construction and tire geometry on the flame tilt angle. The construction of a loader resulted in flow behavior, where the short distance to the front mudguard/tire and the separation of flow directly downstream of the construction led to gases being steered past the front mudguard/tire. In a drilling rig case, the longer distance to the front mudguard/tire led to gases being directed toward the body of the vehicle after passing the area with flow separation.

By K. Hanna

This paper describes a method to improve coal mine entry intersection design. The method considers the effect of in situ stresses, local geologic conditions, rock physical properties, and mining sequence. Development of the method is discussed, including the results of field instrumentation studies and numerical modeling investigations. Data required to evaluate the effects of roof span, mining sequence, entry orientation, and bolting patterns on intersection stability are also presented. Ground control studies conducted by the U.S. Bureau of Mines in two underground mines in the Illinois Coal Basin have shown that in situ horizontal stresses and roof geology have a critical effect on intersection stability. Methods to reduce the adverse effects of these parameters are emphasized. Typical failure behavior associated with specific geologic and horizontal stress conditions is&apos; presented to illustrate proposed control methods to alleviate adverse ground conditions.

Jan 1, 1988

By W. M. Houston

Pebble phosphate deposits of Florida have been established from south of Hardee County to north of the Georgia state line or a distance of over 200 miles and mining has been carried out in an ever-increasing scale since 1885. Deposits that can be mined on the economical standards of today, however, are confined in a roughly circular area about 30 miles in diameter, generally within Polk and Hillsborough Counties, in the central part of the State. The phosphate deposit, which is in the Bone Valley formation of the Pliocene age, is covered by Pleistocene terrace deposits of unconsolidated quartz sand. The matrix is composed of approximately 1/3 clay slimes, 1/3 silica sand and 1/3 phosphate pebbles. The phosphate occurs usually as rounded pebbles, ranging in size from about 1 inch down to approximately 400 mesh. The phosphate may vary from well- defined hard pebbles to soft weathered rock. The color and character of the phosphate will range from smooth buff pebbles to black and white or "salt and pepper rock." The screen size distribution varies considerably between locations and the recoverable phosphate varies may extend down to the 400 mesh size in some areas, while in others the phosphate may cut off sharply at about 35 mesh.

Jan 1, 1962

By Thomas F. Evans

Niagara Mohawk, like other northern coal users, has long experienced increased costs during winter months as a consequence of handling frozen coal. These costs include operating labor, maintenance labor and materials, equipment rental, fuel for thawing, demurrage, carrying costs for excess coal inventory and substitution of higher cost electrical generation for lost production capacity. In the winter of 1978-79, limited trials of several coal freeze conditioning agents were made to determine whether these would provide a cost-effective means of reducing the problems of handling frozen coal. Since these trials were generally effective, the Coal Purchasing Department arranged that all rail coal received during the 1979-80 winter from early December to mid March would be treated at the mines during loading. Inasmuch as the treatment costs are themselves appreciable and our various coal suppliers made a variety of choices of chemical supplier and equipment for application, an attempt was made to evaluate the unloading performance of each train received at the two generating stations which use coal as an aid in the future optimization of the use of freeze conditioning agents. These stations also receive coal by truck but this coal is not treated because of the short hauling time. The C.R. Huntley Station in Tonawanda, NY has a capacity of 800MW and burns about 5000 tons of coal per day during the winter months. The coal is primarily from central and western Pennsylvania but one source in southern Kentucky is also used regularly. Most of the Pennsylvania coal is washed and the fines are thermally dried. The coal is delivered in unit trains made up of mixed cars of 60, 75, and 90 ton capacity. Time between loading and arrival at the station averaged five days and ranged from three to eleven during the 1979-80 winter season.

Jan 1, 1980