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By T. Brasier, K. Oakes, S. Crabtree, B. Lusk

Destructive wave interference has been studied in theory for many years. In application however, limited information can be found. Recently, circumstances have enabled a multidisciplinary team to utilize electronic detonators and seismograph analysis to create destructive wave interference in an underground production blasting application. Springfield Underground, located in Springfield, MO, in conjunction with Orica, ETI, White Industrial Seismology, and the University of Missouri – Rolla has shown the ability to use destructive wave interference in underground blasting to reduce ground vibrations directly above. In order to develop additional reserves a reduction in vibration levels was necessary for tunneling under the Springfield Municipal Water Supply. The paper discusses the process by which the reduction in vibration was achieved in practice, as well as a technical explanation of the effects of destructive wave interference and sacrificial holes.

Jan 1, 2006

By V. A. Evans, D. L. Hellier

Introduction Preparing a report on fluorspar economics in the US could have been somewhat complicated at one time. This was because the number of producers, both large and small, derived production from different locations through-out the western US and the southern Illinois and western Kentucky fluorspar districts. Companies, such as Allied Chemical and Williamson Mining, operated in the Jamestown district of Colorado. In Walden and Salida, CO, the Colorado Fluorspar Co. operated mines and mills. In New Mexico, both Du Pont and Allied had mines and mills. In the Illinois-Kentucky district, US Steel, Rosiclare Lead and Fluorspar, Minerva Oil Co., and Marathon Oil all produced spar for the US market. Now all of the companies are out of the fluorspar business and, with the closing of the Seaforth Mineral Co.'s Inverness Mining Co., only Ozark-Mahoning Co. survives as a domestic producer. History Ozark-Mahoning Co., as it now exists, was formed in 1946 by the merger of Ozark Chemical Co. and Mahoning Mining Co. Ozark Chemical Co. was started in the 1920s to produce sulfuric acid for two refineries located in Tulsa, OK. Mahoning Mining was originally formed by the founders of Ozark Chemical Co. and the Youngstown Sheet and Tube Co. to produce fluorspar and associated minerals from properties in the southern Illinois and western Kentucky fluorspar district. In 1937, Mahoning Mining started an exploration program, employing contractor-operated churn drills to look for reserves in Hardin and Pope Counties in southern Illinois. Based on known reserves in the area and the results of the exploration program, work was started in the fall of 1938 to build a selective flotation plant at Rosiclare, IL. The mill was completed and put into operation in August of 1939. The company's first mining efforts were in the Cave-In-Rock district just north of Cave-In-Rock, IL. The deposits in this area were of the Manto or bedded type. They have been the mainstay of the company's operations in the Illinois-Kentucky fluorspar district. In 1950-51, the company expanded its operations by purchasing fluorspar properties from Colorado Fluorspar Co. at Walden, CO. This location was operated from 1952 through 1958 and from 1968 through 1973 when it was closed permanently. In 1974, Ozark-Mahoning Co. was purchased by Pennwalt Corp. Presently, it is a wholly-owned subsidiary of that corporation. As the only major domestic producer of fluorspar in the US today, the company's ability to survive under the flood of imported material is directly related to the four major segments of its operations. These are: exploration, mining productivity, maintenance, and marketing. All are done in-house. Exploration The Southern Illinois fluorspar district is located in the most complexly faulted area of the central US. The formations are sedimentary in nature and range in age from Devonian through Pennsylvanian. The deposits are small, they range in size from a few thousand tons up to 900 kt (1 million st), with the average minable deposit being around 544 kt (600,000 st). The ore occurs in both nearly vertical vein deposits and in Manto or flat lying bedded deposits. Due to the relatively small size of the deposits and the depth at which they occur, a good low-cost exploration program is essential to ensure that new finds of ore are equal to the mining extraction rate. Ozark maintains a leased land position in Pope and Hardin Counties that will fluctuate somewhere between a low of 40 km2 (10,000 acres) up to a high of 129 km2 (32,000 acres), depending on total size of tracts leased. Most all lands are obtained through a standard lease purchase option, with a small minimum royalty per acre during the normal 10-year option period. All leases are standard and without deviation to control land cost. All land leasing is done through Ozark's geological staff, who also

Jan 11, 1986

By R. H. Seraphim

The name is derived from an Egyptian myth, "A beautiful lone bird which lived in the Arabian desert for 500 or 600 years and then consumed itself in fire, rising renewed from the ashes to start another long life." HISTORY This account of the first history is gleaned from old reports and documents which are listed in the Bibliography and from discussions with old-timers of the district. Prospectors were active in the vicinity of Greenwood in 189 1, and in that year staked the Mother Lode, Crown Silver, and Sunset. Henry White staked the Knob Hill claim in Phoenix on Jul. 15, 1891, and by the end of the year, other prospectors had staked most of the claims covering the valuable ore bodies in the camp. Much surface work done in the early years indicated that the values in copper, gold, and silver were low. Large capital investments were required to develop the ore bodies and build smelters. The discovery that the ore was practically self-fluxing greatly enhanced the value of the deposits. A map of the area showing the geology is given in Fig. 1. The bedded Brooklyn conglomerate is shown in Fig. 2.

Jan 1, 1991

By Heribert F. Broicher

As of 1998 German companies have been engaged in research and development of LIF analyzers for rock identification, i.e. for the fingerprinting of rock by the analysis of laser-induced fluorescence (LIF). Test work in Germany, Sweden and South Africa showed the potential of this new technique, which operates online and in realtime (1). In 2003 the Finnish company IMA Engineering Ltd Oy commenced building and marketing LIF analyzers under the trade name OreSpex. Today, one OreSpex analyzer has been installed in the Kiruna Mine, Sweden to check the phosphorus content of train loads. In 2004 a second OreSpex analyzer was built for dilution control in the Argyle Diamond mine, Australia. In 2005 another LIF analyzer will be used for test work in various mines in the US. The principles of the technology and status of ongoing work are presented.

Jan 1, 2005

By Ruckmick J. C.

Elemental sulphur occurrences are widely distributed in two geological environments: -1-Basins containing hydrocarbons and zones of Cenozoic vulcanism. However, very few of these constitute deposits large enough to be of commercial importance. Almost all of the elemental sulphur mined in the world comes from bioepigenetic deposits in petroliferous basins. These deposits occur in two general structural styles: diapiric (salt domes) and stratiform. Examples of diapiric deposits occur in the Gulf Coast basins of Texas, Louisiana, and southern Mexico. Examples of stratiform deposits occur in the Fergana and Amudarya depressions of Central Asia, the Mesopotamian Depression in Iraq, the Cis-Carpathian Trough in Poland and Russia, and the Permian Basin in Texas. Economic bioepigenetic sulphur deposits range in size from approximately 1 million tons of sulphur in the smaller salt dome deposits to more than ZOO million tons of sulphur at the Mishraq stratiform deposit in Iraq. Total world production from bioepigenetic deposits amounts to approximately 16 million tons of sulphur per year, one-half of the world's present annual consumption of elemental sulphur. Most of the balance of the annual consumption is recovered from sour gas and petroleum. All bioepigenetic sulphur deposits share remarkably similar origins and characteristics. They are formed by anaerobic bacterial replacement of gypsum or anhydrite in tilted basins where evaporite beds are underlain by petroleum. Figure 1 illustrates a generalized cross-section of a salt dome sulphur deposit. Figures Z, 3, and 4 are cross-sections of three types of stratiform sulphur deposits. In terms of sulphur genesis, the only significant difference between the salt dome and stratiform deposits is that the positioning of the anhydrites above the petroleum in the salt domes is caused by diapiric rather than sedimentary processes. In the salt domes, the residual anhydrites of the cap-rocks are accumulated by solution and removal of halite by artesian ground waters.

Jan 1, 1978

By J. Lancaster

World demand of sulphur-in-all-forms (SAF), which in 1985 is estimated to total 57.5 million tonnes S equivalent, is expected to increase to 77.6 million tonnes S by the year 2000. Key factors are the evolution of sulphur demand in the USSR, China, and the developing countries notably India, Brazil, and the countries in North Africa and the Near East with vertically integrated phosphate industries. Brimstone will remain the dominant sulphurous raw material notwithstanding the progressive increase in the supply and use of sulphur in other forms resulting mainly from the enhanced recovery df pollution sulphur and the increased use of sulphur in pyrites in those countries with this sulphur resource. Sulphur demand for phosphate fertilizer manufacture is expected to have the main impact on world sulphur demand, but in contrast to the industrially advanced countries where non- fertilizer sulphur use is not expected to increase measurably, this demand sector is expected to be of some importance in those developing countries with dynamic economies and in the centrally planned economies of East Europe and the Far East.

Jan 1, 1986

By R. Q. Phillips

INTRODUCTION Since Canada commenced sulphur exports in the early 1960's, the volume of exports has grown steadily and by 1984 Canadian sulphur accounted for 45% of internationally traded sulphur. In 1984 a total of 7.6 million tonnes of Canadian sulphur was shipped to offshore markets and the U.S.A. Total shipments, including domestic sales, were 8.3 million tonnes. With a production of some 5.6 million tonnes, inventory was drawn down by nearly 3 million tonnes in order to keep pace with demand. Since 1979, world consumption has exceeded total world production and Canadian sulphur inventory has played a truly crucial role in balancing world supply and demand. Consequently, by the end of 1984 the Canadian inventory, which stood at 21 million tonnes in 1978, had been almost halved to 12 million tonnes. This inventory, however, is still by far the largest in the world and will continue to play a vital role in the world supply until expected depletion around 1990. Canada is the world's second largest producer of sulphur following the U.S.A.. The Current production level of between 5 and 6 million tonnes per annum is forecast to be maintained to 1990 with only a marginal fall in that production level in the following decade to the year 2000. This will ensure that Canada retains its position as one of the largest producers and most important suppliers of sulphur in the world market well into the future. CANADA AS WORLD SUPPLIER OF SULPHUR Since Canada commenced sulphur exports in the early 19601s, exports have grown steadily. (Figure 1) The rate of growth accelerated in recent years and in 1984 a total of 7.6 million tonnes was sold for export, compared to 3.0 million tonnes in 1975 and less than 1 million tonnes in 1964. World trade in sulphur also increased during this period, from 11 million tonnes in 1975 to 17.0 million tonnes in 1984 (Figure 2). Most of this increase in volume was accounted for by Canada and Poland. As a result, the importance of Canada as world supplier expanded from 28% in 1975 to 45% in 1984. The markets for Canadian sulphur can be divided into two broad categories, i.e., solid and liquid (Figure 3). The solid market is the largest, taking about 70% of Canadian output, virtually all of which is sold offshore. The U.S.A. and the Canadian domestic market take about 20% and 10% respectively, in liquid form. In 1984, (figure 4) total Canadian sulphur sales exceeded 8 million tonnes with offshore export sales at a record 5.8 million tonnes and sales to the U.S. of 1.8 million tonnes. Domestic sales accounted for only 0.7 million tonnes. The general trend for offshore export sales has been upward whereas there has been relative stability in domestic sales. The exceptional growth in offshore sales in the 1970's necessitated considerable capital investments by the industry in order to establish a logistics system capable of handling increasing offshore tonnages. Over 50 sulphur plants are currently operating in Alberta and British Columbia. Some of these are connected by rail, (Figure 5) the balance being generally connected by road. There are currently fourteen of the larger rail-connected plants designated as export plants, and these are equipped with sulphur forming facilities. The long distances between these plants and tidewater terminals in Vancouver is a very significant factor in complex logistics of Canadian offshore sulphur exports (Figure 6). Alberta and B.C. plants are located an average of 1,400 kilometers from tidewater.

Jan 1, 1986

By William M. Hartzler

The Powder River Basin (PRB) refers to the coal deposits located in southeastern Montana and the northeastern Wyoming counties of Campbell, Converse, Hot Springs and Sheridian (Wyoming PRB). In 1993, there were 20 active surface mines with 3109 employees in the Wyoming PRB (Annual Report, The State Inspector Of Mines Of Wyoming, 1993). Early PRB production growth was primarily in response to the passage of the Clean Air Act of 1970. The disproportionate growth in Wyoming as compared to Montana can be attributed to the differing coal taxation policies of the two states. The state severance and production taxes were significantly lower in Wyoming. However, Montana passed legislation in 1987 reducing the severance tax rate, substantially narrowing the severance tax gap. Campbell and Converse counties in Wyoming have benefited the most from the production growth in the region. Cyprus Amax's Belle Ayr Mine, south of Gillette, in Campbell County, was the first modern commercial coal mine to be developed.

Jan 1, 1994

By K. Biswas, S. S. Peng

The stability of pillars in old mined-out districts is greatly dependent on the weathering action caused by moisture penetration into the pillar structure. Field observations in old mining districts indicated that this weathering action becomes critical in terms of the stability of the pillar if the coal seam contains parting or binder (layers of claystone or mudstone). The weathering action caused by moisture penetration over a long period of time degrades both parting and coal. However, it has been observed that the structural deterioration is more severe in parting. Moisture-penetration rates in parting and coal are different. The extent of the weathered zone in various layers of the pillar is primarily time dependent. This paper investigates, both in the laboratory and in the field, the effects of weathering action on coal and parting. In the laboratory, slake durability indices and uniaxial compressive strength tests for dry and saturated specimens are compared for coal. In the field, the in situ strength profiles for coal and parting layers are obtained, and the effect of time (in terms of the pillar age) on the strength profiles is studied An attempt was also made to establish formulae for time-dependent strengths of coal and parting.

Jan 1, 2000

By John P. Weir

The coal industry is ever changing and complex. This article discusses some problems that must be faced and their projected economic effects. Coal's dominant market is for electric power generation. While growth rates in the 1980s will be nominal compared to historic growth rates, such growth will be substantial in absolute terms because it comes from a very large base. Higher growth is expected in the 1990s. History When looking toward the future, an examination of the past is helpful. Figures 1 and 2 present production and consumption statistics (expressed in short tons) on bituminous coal and lignite in the US from 1945 onward. After an all-time peak of 572 Mt (631 million st) in 1947, total production dropped to 356 Mt (392 million st) in 1954. Sustained growth in total production did not begin until the 1960s. Coal production from under-ground mines declined from more than 400 Mt (440 million st) in 1947 to about 295 Mt (325 million st) during 1965 to 1970. A further decline ensued until a strike in 1978 reduced production to only 218 Mt (240 million st). Underground mines produced 283 Mt (312 million st) in 1983. Coal production from surface mines has increased steadily since the early 1960s. While some of this increase has come from mines east of the Mississippi River, most has resulted from surface mines developed in the West. Production from surface mines west of the Mississippi River was 224 Mt (247 million st) in 1982. Total coal production from under-ground and surface mines, other than Western surface mines, continues to approximate levels of 40 years ago. In spite of several wage increases, increasing productivity in surface and underground mines enabled the coal industry to hold the average value f.o.b. mine to about $5.50/t ($5 per st) from the end of World War II to 1969. Under-ground mine productivity peaked at more than 13.5 t (15 st) per man-day in 1969. The Coal Mine Health and Safety Act of 1969 was a major factor in underground productivity declining to 7.6 t (8.4 st) per man-day in 1978. However, pro-

Jan 7, 1984

By E. D. Attanasi, J. H. DeYoung

Several factors contributed to continued declines in mineral-exploration activity in the US in 1985. Low metal prices and, what appears to be worldwide chronic excess capacity in copper, molybdenum, lead, and uranium, have resulted in mineral-exploration expenditures remaining anemic. Economic recovery could result in a healthier mining industry and more cash flow to fund exploration. This is because general economic activity and US mining industry activity have historically been closely linked. However, as the worldwide economic recovery has expanded, the mining sector has continued its downward slide. New cuts in industry exploration budgets in 1985 shocked those who thought the exploration situation could not become worse. Some personnel and equipment had been redirected from base metals exploration to precious metals in the past few years. Last year, continued reductions in exploration sent many professionals out of the mining industry. Recent staff reductions or consolidations of operations were made by Noranda, Chevron, Molycorp, and other exploration companies. The latest data from the Society of Economic Geologists (SEG) summary of exploration statistics show that professional staff at year end in major US exploration companies (domestic and foreign operations) fell from 2355 in 1981 to 1868 in 1983 and 1277 in 1984. By the end of 1985, two economic trends were established that could improve the future profitability of mining and hence exploration. First, the price of crude oil began a decline. If sharply reduced energy prices increase worldwide economic expansion, the substantial excess capacity in some of the base metals industries could disappear, and prices could improve. Furthermore, if energy price declines reduce mining and processing costs significantly, metals may recapture some lost markets. The decline in oil revenues has already encouraged some oil-producing countries, such as Venezuela, to look toward development of mineral resources to earn foreign exchange for debt repayment. Second, the decline of the dollar by 21% during 1985 could also help US producers meet foreign competition. During 1985, industry restructuring continued as many oil companies sold off mining subsidiaries and minerals properties. Gold, silver in new discoveries Precious metals continued to dominate the announcement of new discoveries and exploration projects in 1985. A review of domestic exploration and development activities reported in several industry journals shows that 60% to 80% of these projects were directed primarily at precious metals, particularly gold. Base metals exploration activities frequently involved polymetallic deposits with gold or silver values. Because much of this exploration was done on identified targets (on-property exploration), the decrease in wildcat or grassroots (off-property) exploration may be more substantial than indicated by reductions in total exploration activity. Significant gold discoveries in 1985 included several in Nevada, among them the Genesis property of Newmont (near the Carlin mine), Goldfields' discovery of the Chimney deposit in Humboldt Co., and Freeport's discovery of two mineralized sites near Jerritt Canyon. Gold exploration continued to be focused in the western US and Alaska, but gold production starts at the Haile mine in South Carolina, and the Ropes mine in Michigan as well as Amselco's feasibility studies on deposits near Ridgeway, SC, are evidence that gold exploration is not limited to the West. The dominance of gold projects in exploration is not limited to the US, as demonstrated by gold dis¬coveries and exploration projects in Australia, Brazil, Canada, the Caribbean region, China, Guinea, Ivory Coast, South Africa, the South Pacific islands, and Thailand. From the standpoint of US metal miners, it is perplexing that worldwide exploration and development is also taking place in copper, zinc, tungsten, and other metals with depressed prices. During 1985, the US Geological Survey's efforts to map the sea floor of the Exclusive Economic Zone shifted from the Pacific Coast to the deep water areas of the Gulf of Mexico and to areas off the coast of Puerto Rico and the Virgin Islands. An atlas containing sea-floor maps of the west coast area was published as US Geological Survey Miscellaneous Investigations Series Map 1-1792. Results of the 1985 surveys are expected to be published by January 1987. Exploration trends - Statistical evidence Data from the SEG showed continued decline in the US mining industry's exploration expenditures through 1984. The share of US companies' domestic exploration expenditures directed toward base and precious metals has increased from 51% to 84% from 1980 to 1983 and to 86% in 1984. US mining companies spent about $0.67 of each exploration dollar in 1984 in the US. However, this represents an increase from earlier years. The 1983 data also show that firms spending more than $5 million on exploration accounted for 77% of exploration expenditures. Since 1981, the Bureau of Land Management (BLM) has been assembling data on claims and an-

Jan 5, 1986

By D. W. Olson

Estimated world production of natural and synthetic industrial diamond was about 630 million carats in 2004. Natural industrial diamond deposits have been found in more than 35 countries, and synthetic industrial diamond is produced in at least 10 countries. About 80 percent of the global output was produced in Ireland, Japan, Russia, South Africa and the United States. Russia and the United States are the world’s leading producers of synthetic industrial diamond. In 2004, the two U.S. synthetic producers, one in Pennsylvania and the other in Ohio, had an estimated output of 250million carats. Also in 2004, nine U.S. firms manufactured polycrystalline diamond (PCD) from synthetic diamond grit and powder.

Jan 1, 2005

By Isobel Clark

The four papers in this session illustrate two different directions in which computer graphics seem to be developing. The first of these is in the handling and storage of geological information. The increasing use of micro-computers with limited storage facilities has seen a concomitant increase in the need to store geological data in as efficient a form as possible. It has also seen a recognition of the particular types of data which are used in a geological or mining analysis. Unlike many other fields, observations of drill cores, geological interpretations, structure and many other variables require storage in a readily accessible form. The authors of two papers in this session deal directly with Geological Information Systems. They discuss the setup, the specification of such systems, and the practical uses of the systems once in operation.

Jan 1, 1989

By James C. Norman

The boron review arrived too late to appear in the June issue. The US was the world's second largest producer and the largest consumer of boron compounds during 1990. Boron mineral concentrate and chemical production in the US totaled 1.13 Mt (1.2 million st), including 565 kt (662,800 st) of boric oxide (B2O3) in 1990, according to US Bureau of Mines estimates. Total value amounted to $404 million. This was slightly higher in production than 1989 but down in value, reflecting a softening in boron product prices. Total world production of boron mineral concentrate and chemical tonnage in 1990 was estimated at 3 Mt (3.3 million st), which corresponds to about 1.3 Mt (1.3 million st) of BO,. World production in 1990 was about the same as in 1989.

Jan 1, 1991

By H. F. Haller, H. C. Pattison

The research program described in this paper is sponsored by the Advanced Research Projects Agency of the Department of Defense and monitored by the Bureau of Mines, United States Department of the Interior. PROGRAM DEVELOPMENT While Holmes & Narver is better known in other fields, the company has been active in many phases of underground excavation for over twenty years. In the 1950's, H&N participated in design and construction of nearly twenty miles of waste disposal tunnels in Southern California. As Architect-Engineer for the Atomic Energy Commission, we had design and management responsibility for many miles of tunnels and for thousands of feet of exploration and big hole drilling, from coast to coast in the States, and for gas well completions and exploration drilling for the Navy and the National Science Foundation from Pt. Barrow to Byrd Station in Antarctica. In my ten years with the company, we contributed to the development of big hole drilling techniques at a number of sites and analyzed the capability of boring machines for many of the tunnel projects. In a 1965 engineering study of a hundred miles of vehicular tunnels in rock under New York City, we investigated

Jan 1, 1997

By E. (Walt) van Walsum

The MPTM was first applied in the U.S.A. in 1950 as described by Lewis, W.E., 1951. The method was then abandoned in the USA and rediscovered some 20 years later in France where it was greatly improved and widened in its scope of application. It was subsequently successfully introduced to Italy and Spain. The technique, at its present stage of development, provides solutions to tunneling in soil and in the softer rock types, which often were troublesome geological environments for tunneling. When used in conjunction with drilling-and-blasting, over break, excessive vibration, noise and fissuring of the rock can all be avoided. When used as an alternative to the New Austrian Tunneling Method (NATM), the MPTM provides safe, full face tunneling in stead of multiple headings, excavated sequentially; in addition, surface settlement can be virtually eliminated. When used as an alternative to a TBM, the method's flexibility and low capital cost make it attractive. This attractiveness is enhanced when ground conditions are erratic or when the length of tunnel to be excavated is limited. The method holds promise for tunnels of large cross section, to be excavated in soft ground or rock with unconfined compressive strengths of less than 80 MPa (11 600 psi). While in itself not new, recognition and development of the method's potential are. Further development work, aimed at increasing the range over which the MPTM can be applied, is in progress.

Jan 1, 1993

By R. J. Cornelius

Gold with minor associated copper mineralization in the area of what is now the Bougainville porphyry copper deposit has been known since the 1920s and was probably known in German colonial times, pre- 19 14, although no records persist other than a reference by Stanley (1922) to copper specimens from Kieta that he saw in Rabaul. Stanley did not at the time believe that they came from Kieta. Gold was first discovered at Kupei by Jack Comb in 1929 and the Kieta Goldfield was proclaimed in May 1930. In December 1932, the Tapu Reward Claim at Moroni - the site of the Bougainville Copper concentrator, was pegged by C.W.M. Evans who prospected up river from the West Coast. The Pumkuna (Panguna) Reward Claim on the site of the subsequent porphyry copper deposit was granted in February 1934 to G.A. Myers. n May 193 1, the Kupei Reward Claim was transferred to Bou- gainville Gold Options NL and later reverted to Jack Comb and then the Bougainville Syndicate, as did the Pumkuna and Moroni claims. Most of the interested parties had come from the Edie Creek rush on the New Guinea mainland. In 1935, N.H. Fisher, the geologist in Rabaul for the New Guinea administration who later became director of the Australian Bureau of Mineral Resources in Canberra, reported on the three gold areas. Norm Fisher described the gold and copper mineralization and its habit in great detail and this report had a major influence on the events leading to the discovery in the 1960s. Gold production up to the Japanese invasion probably did not exceed $50,000 in value. Half a ton of copper-gold ore from Kupei was sent to O.T. Lempriere's in Sydney for assay in the early 1930s.

Jan 1, 1991

By M. Dean Kleinkopf, John Callahan, William M. Shepard, R. N. Schnepfe

Despite lower prices and the uncertain future of nuclear power, uranium continued to be the big attraction in 1979 exploration activity. Uranium again dominated exploration programs across the US-not only in primary producing states such as New Mexico and Wyoming, but in potential producing areas from the northern counties of Minnesota to the Grandfather Mountain region of North Carolina. The moratorium on uranium leasing was lifted in Colorado and Montana, and exploration activity intensified accordingly. In Wyoming, what may be the biggest uranium deposit in the state was discovered by Anaconda Copper Co. near Jeffrey City, but in general, there were few major discoveries and activity was concentrated on existing exploration programs. The Department of Energy expects 1979 uranium exploration expenditures to total $339 million, compared to the $314 million spent by industry in 1978. Surface exploration and development drilling in 1979 is estimated at 16.1 Mm, up slightly from 1978 figures. Gold demanded its share of the spotlight in 1979. Soaring prices lured prospectors, investors, operators, and speculators to Alaska, California, Colorado, and Washington in a small-scale gold fever. Exploration for molybdenum remained strong in Alaska, Colorado, and Washington, where mineralization at the Mt. Tolman prospect is now estimated at 816 Mt averaging 0.09% copper and 0.10% molybdenum disulfide. Again this year, one of the major deterrents to exploration was the drive to set aside huge areas of land as wilderness preserves. In Alaska, where Interior Secretary Cecil Andrus has withdrawn millions of acres under the Antiquities Act, BP Alaska decided to close its Anchorage office, reportedly due to the lack of public lands available for mineral exploration. In both geophysical and geochemical activity, the year is best characterized as one of consolidation and development of previous advances in the state of the art, without any fundamental breakthroughs. Many companies were active in the development of instrumentation. Continuing interest in spectral IP resulted in the introduction of two instruments, one by Phoenix Geophysics, the other to be announced shortly by Geotronics Corp. Radiometric and borehole logging equipment received considerable emphasis, reflecting the continued interest in uranium exploration. MINING ENGINEERING'S review of 1979 exploration activity, including state-by-state highlights and a review of geophysical and geochemical activity, begins on the following page.

Jan 5, 1980

By T. Matthews

"One critical factor in mineral reserves reporting, as well as mine-reserves reconciliation, is the impact of dilution and ore loss in the mining process. This paper considers the implications of various factors on dilution and ore loss projections, by orebody geometry, mining method, and ore control systems. We also discuss the implications of resource estimation methodology on dilution for reserves. DEFINITIONS Dilution and ore loss are two critical concepts in mining, which address the differences encountered between modeled grade and tonnages and actual production. Dilution is volume increase and grade reduction caused by multiple factors, chief among which are mining of waste material along ore-waste contacts, mining of internal waste as ore, and misclassification of waste as ore in the ore control process. There are also geostatistical and estimation aspects sometimes lumped with dilution, including the volume-variance effect (the tendency for small volumes of material to include a less regular distribution of grade than large volumes of material). Ore loss is described as reductions of ore volumes in the mining process due to misclassification of ore as waste in the ore control process, exclusion of discontinuous mineralization from mining due to geometry or continuity, and mechanical losses in the mining process. Dilution is typically taken as an increase in tonnes of ore with no change in contained metal (and thus results in a reduction in grade.) (Some workers consider the likely grade of the diluting material as well, particularly in deposits with gradational grade boundaries—this will be addressed later in the text.) Ore loss is typically taken as a reduction in tonnes at average grade of the ore, and thus results in a reduction in both tonnes and contained metal. If model (resource) tonnes are Mt, grade is Mg, and contained metal is Mm, the resource with ore loss (L) and dilution (D) included (Rt, Rg, and Rm) will be:"

Jan 1, 2015

By Steve Kral

The Fourth International Symposium on Hydrometallurgy was organized to give those in the minerals processing field an opportunity to discuss current topics of interest in the broad field of hydrometallurgy. Held in Salt Lake City, UT Aug. 1-5, 1993, this fourth symposium also paid tribute to Milton E. Wadsworth for his many contributions in this area over the past 40 years. The science of hydrometallurgy has made great strides since the last symposium was held 10 years ago. The use of electrochemical principles and techniques has produced encouraging results. For example, the application of in situ electrode spectroscopy has helped to understand the mechanisms operating in hydrometallurgical processes. Sophisticated computer models have been developed to handle the thermodynamic properties of concentrated electrolytes. However, it is up to the hydrometallurgist to continuing working on bridging the gap between theory and practice. The successful application of solvent extraction-electrowinning (SXEW) is one illustration of the successful transfer of technology. Its widespread use in the United States during the 1980s played a significant role in the revival of the domestic copper industry. Currently, electrowon copper accounts for about 30% of total US production. Impressive developments in precious metals recovery have also occurred. Since the last symposium, carbon-in-pulp (CIP) and heap leaching have become widely used in gold recovery. And recovery of refractory precious metals ores and concentrates by pres¬sure oxidation and bio-oxidation have made significant advances. In all these examples, hydrometallurgy has played a significant role in the recovery of minerals and metals from primary sources. In addition, considerable attention has been focused on the treatment and recovery of values from secondary sources.

Jan 1, 1994