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By S. L. Bolivar

The Prairie Creek intrusion, near Murfreesboro, AR, is the site of the most famous diamond mine in North America. Three major rock types are associated with the intrusion-a hypabyssal peridotite, a volcanic breccia in which the majority of diamonds occur, and tuft. Previous studies, including geological, geophysical, petrological, and whole-rock and mineral chemistry are reviewed. The recent suggestion, by other workers, that this intrusion may be more correctly called a lamproite is examined. This has serious implications for diamond exploration in Arkansas and elsewhere in the US.

Jan 1, 1987

By J. Burgess Winter

It is an honor to present the lecture in honor of Daniel C. Jackling, the developer of the technology of copper mining that we continue to use 100 years later. He made a dramatic breakthrough in the early part of this century in the development of bulk-mining methods for large, low-grade porphyry copper-sulfide ore bodies. At Magma Copper, we are particularly proud that the Jackling Award states we have "made significant contributions to technical progress." Before Jackling's time, copper mining had exploited with primitive equipment very high-grade underground ore bodies and high-grade open pits. During the 20th century, the situation changed. Three significant innovations occurred within about 10 years around the turn of the century. In 1903, Jackling's concept of large-scale mining with steam shovels and rail haulage was implemented at the Bingham Canyon mine in Utah. Eighty years after the introduction of rail haulage, the mine converted to truck haulage with large-capacity high-efficiency haul trucks and reduced the stripping ratio from 3.5:1 to less than 1:1.

Jan 1, 1995

By Christian F. Baiz

The author will present a discussion of the steps which must be taken by the prospective developer of a small mining operation to establish technical credibility when seeking financial backing. Particular emphasis will be given to the differing levels of technical work (and their relative cost) which must be accomplished to supply the information necessary to satisfy potential investor groups, whether they be other mining companies, equity investors, or financial institutions such as venture capital firms or commercial banks.

Jan 1, 1981

By Robert G. Benson, David M. Jones

The San Luis deposit of Costilla County, Colorado contains 11,021,000 tonnes (12,149,000 tons) of ore at 1.4 g/t (0.040 oz/st) gold in two mineable zones. Gold mineralization is associated with silicification and quartz-sericite-pyrite alteration localized in breccias along a low-angle "detachment" fault zone in Precambrian gneiss. Gangue minerals include chlorite, specularite, chalcopyrite, molybdenite, and fluorite. Mineralization is mid-Tertiary in age and may have an indirect genetic relation to the emplacement of felsic intrusions. Portions of the ore body are unconformably overlain by sedimentary rocks of the Tertiary Santa Fe Formation. The deposit formed during the early stages of extensional tectonism along the eastern edge of the present day Rio Grande rift.

Jan 1, 1990

By P. K. Davis, B. Gharib

The results of a previous basic study of the flow and design characteristics of hydrocyclones demonstrated that a recovery as high as 99% with a product rating* of 0.95 can be achieved on a batch+ basis with a single, water-only cyclone if it is configured properly. The next logical step was to demonstrate continuous processing of gob for the efficient recovery of coal by means of a laboratory-size demonstration system. A project to design and construct such a single-¬cyclone system was sponsored by the US Department of Energy, which also sponsored the initial study. A recovery of 93% with a product rating of 0.89 was demonstrated. The system design and the data taken are discussed.

Jan 1, 1990

By S. D. Bearden

Color enhances expression and communication in all physical objects experienced in life. Pigments provide color and in some applications have a specific additional function. Natural iron oxides are widely distributed throughout the world but only a few deposits are sufficiently pure and possess acceptable color and brightness properties to merit their processing into pigment form. Ochre, the common name for goethite ore, is the best and most under used material in the buff colored pigment market. The geological occurrence of ochre in the basal Shady Formation of the Cartersville Mining District (Georgia) is described. Exploration, processing, and product applications of New Riverside Ochre Company, Inc. are discussed. An overview of the worldwide pigment market is presented with emphasis placed upon the North American activity in iron oxide production and application. The purpose of this paper is to increase the awareness of ochre and its potential market in the colored iron oxide pigment industry, encourage research on the origin of ochre deposits, and stimulate interest in new applications of this unique substance.

Feb 27, 2013

By K. Ohga, V. J. Hucka

The presence of methane gas in mines creates hazards of explosions, fire and suffocation. Under certain conditions the occurrence of methane also poses a danger of gas and coal outbursts. Consequently, prevention of gas and coal outbursts in coal mines requires a sound knowledge of methane gas occurrence in mine workings. However, the direct method of determining methane content of coals developed by the U.S. Bureau of Mines is time and labor consuming for measurement, a new transportable methane tester was developed for Japanese coal mines. The instrument automatically measures emission gas from coal samples in the underground and also records and stores the data. Back on the surface, the tester can be connected via a RS 232 port to a PC computer for methane content estimation. Details of this technique are described here. Results on methane content determined in Japanese and U.S. western coal seams are discussed, as well.

Jan 1, 1991

By Lyda W. Hersloff

As decommissioning of various radioactively contaminated facilities begins, the question of appropriate residual surface contamination becomes an issue. Surface contamination can result in exposure to people via inhalation, ingestion, and external radiation exposure, There is therefore the potential of exposure to workers involved in the dismantling of a facility as well as members of the general public acquiring salvageable equipment, tools, and building materials. The levels established as acceptable for unrestricted use by national and international organizations vary by as much as an order of magnitude for certain radioactive materials. The calculated doses associated with some acceptable contamination levels can be significant. The principle of ALARA, as low as reasonably achievable, is therefore a necessary element in establishing surface contamination levels for a specific site. Some components in evaluating site specific surface contamination levels for unrestricted use, especially removable contamination, include evaluations of the historical use of a facility, the mixtures of radioactive materials a&sociated with surface contamination, and resuspension factors for various materials.

Jan 1, 1991

By Gordon D. House, J. B. P. Sawyer

The Bannockburn gold prospect is a new discovery in Ontario's oldest gold camp at Eldorado, eastern Ontario. Mono Gold Mines Inc. of Vancouver, British Columbia, acquired the property in 1980 and in 1984 discovered a previously unreported gold bearing quartz vein system to the northeast of the old Bannockburn Mine. Extensive diamond drilling carried out since 1985 defined a quartz vein system over 475 m (1 ,500 ft) of strike to a depth of over 105 m (350 ft). Limited underground exploration by decline to the 22.9 m (75 ft) level in 1988 confirmed the continuity and tenor of the quartz veins. Gold occurs as native metal with minor sulphides and bismuth tellurides in a quartz carbonate vein system within metasedimentary and metavolcanic rocks of the Grenville Province. Metallurgical test work on a surface bulk sample was favourable. Estimates of drill indicated reserves have been made as well as reserves based on the limited underground exploration.

Jan 1, 1989

By C. W. Hoffman

A fairly recent development in the field of particle separation is now under investigation to determine its value to the mining industry. The method employed is probability sizing through a vibrating network of decreasing screen openings. While probability sizing as such is not new, the possibility of using it for coarse, highly abrasive ores at high tonnage rates has only recently appeared to merit practical consideration. The advantages to be gained by the use of probability sizing vs. conventional screening methods are: reduced space requirements for a high capacity unit, fewer moving parts, more versatile product sizing selection, reduced maintenance requirements and lower power consumption.

Jan 1, 1968

By J. Engesser

A research project supported by the Minnesota Department of Natural Resources and the Iron Ore Cooperative Research Committee was undertaken to reduce the dissolution of fluoride into process water during taconite processing. Leach tests were conducted using rod mill feed samples and water containing varying concentrations of calcium and sodium. Laboratory liberation grinds were performed to evaluate fluoride rejection during grinding and magnetic separation. Tube furnace tests were conducted to evaluate fluoride volatilization during pellet induration. The results indicate that fluoride concentration of process water is a function of both calcium and sodium concentration in process water. It appears that less than 1 percent of the fluoride present in rod mill feed will dissolve in process water during grinding. More than 90 percent of the fluoride present in rod mill feed is rejected with tailings during size reduction and magnetic separation. The furnace tests demonstrate that bentonite and fluxstone (calcite and dolomite) addition to taconite concentrate during pellet production increases the amount of fluoride that volatilizes during induration. Lime hydrate addition to pellets decreases the amount of fluoride that volatilizes during pellet induration. During acid pellet production approximately three times more fluoride enters the water during induration-off-gas scrubbing than during grinding. When fluxed pellets are produced three to eight times more fluoride enters the water during off-gas scrubbing than during taconite grinding.

Jan 1, 2004

By R. R. Sacrison

The Barrick Mercur Gold Mine lies in the Oquirrh Mountains of northern Utah. Limestone, sandstone, shale, and chert are the predominant rock types being mined. Recent expansion has encountered rhyolite. Lithology and structural attitudes control most mechanical behavior. Slope steepening, mine planning, and site selection are presented as means by which geological engineering has contributed to the economics of the operation. Geomechanics investments of approximately $700,000 have resulted in cost savings or additional production worth over $16,000,000.

Jan 1, 1990

By Harry H. Posey, John Woodling, Miriam L. Renkin

Natural acid drainage is generated from pyritic rock underlying 17 percent of the upper Alamosa River basin. About one-third of these acid producing rocks have nil carbonate buffering capacity; there the streams carry significant acid plus dissolved Al, Cu, Fe, and Zn. In part of the basin, aquatic life is limited by the natural acid drainage. In the four miles where the Alamosa flows through pyritic rock the river grows toxic to trout. Inhospitable conditions continue downstream for at least another four miles. The waters become refreshed, naturally, through metal dilution, metal oxide and hydroxide precipitation, and acid neutralization. Water quality fluctuates in seasonal cycles. Dissolved metals and acid, which are generated year-round by weathering, are stored over winter in the unsaturated zone in the retained water and in soluble metal- sulfate minerals that form by evaporation of acid-metal waters. Seasonal discharge variations cause metal concentrations and pH to shift in the trunk stream; the acid drainage source streams, however, shift only slightly by season. In early spring, metal concentrations and metal loads increase as metals and acid are flushed from the unsaturated zones by melting snow. Peak metal loads occur at this time, and precede peak flow by up to two months. Other metal load peaks occur during peak flow and monsoon flow, even though metal concentrations are diluted at that time by precipitation. In late spring and thereafter, discharge of neutral pH water wanes, so trunk stream pH falls and metal concentrations return to previous high levels. Metal concentrations appear to be low from November through January when dilution from precipitation is lowest, but rise in February to near peak yearly concentrations. In years with high monsoonal flows, metal-laden waters apparently flush from the unsaturated zone and metal concentrations remain low from about October through January. In years with low monsoonal flows, however, metal concentrations in October and November at least are higher.

Jan 1, 2000

By Nikolaos Syrtariotis, Mark Berger, Timothy O’Brien, Vojtech Gall

The Northeast Corridor Superconducting Maglev Project (SCMAGLEV) entails construction of a high-speed train system between Washington, DC and New York City, with the first leg between Washington and Baltimore, MD. This innovative project will shorten travel times between Washington DC and Baltimore to approximately 15 minutes, and connect Washington, DC to New York City in under an hour. In 2021 the draft EIS is expected to be issued for comment with a Final EIS/ROD anticipated by early 2022. This paper provides an update on the project as presented in Gall et al. (2020) and discusses the economic and environmental benefits, preferred alignment alternative, preliminary staging and launching of the TBMs for construction, and preliminary station design.

Jun 13, 2021

By M. Rieber

The recent history of the mercury market results almost entirely from U.S. Government actions. Its derived demand has been curtailed by U.S.E.P.A. mandates; its supply has been augmented by U.S.D.L.A. controlled stockpile releases. The resultant prices have altered its market structure, impacted mercury mining, refiners and recyclers, and affected international production and markets. From a marketplace product mercury is rapidly becoming a disposal problem. Other minerals may follow in its wake. This paper reviews developments in demand, particularly in relation to environmental constraints. Supply side impacts are considered. The impact of stockpiles, both as a market overhang and as a potential supply is reviewed. Government stockpile disposal activity is emphasized, but the size, estimated disposal rate, and quality of the private stockpiles are considered, as is the potential availability of additional material from shut-in mines.

Jan 1, 1995

By George S. Austin

Perlite is rhyolitic glass with 2 to 5 percent by weight (wt.%) bound water held within the silicic-glass structure. It is often distinguished by vitreous, pearly luster and concentric perlitic fractures ("onionskin"). Occurrences worldwide are associated with Tertiary to middle Quaternary volcanic rocks. Perlite is in silicic domes, plugs, laccoliths, flows, vitric tephra, chill margins of dikes and sills, and welded ash-flow tuffs. It is a hydrated volcanic glass formed through secondary alteration of obsidian by the incorporation of water into the glass/silica structure. Post-emplacement hydration (weathering) of cooled glasses by meteoric water is the principal alteration process, but some hydration by magmatic or meteoric water during or shortly after emplacement, or hydration by water exsolved during cooling may occur. Commercial "perlite" is any volcanic glass that expands or "pops" when heated quickly to plasticity while evolving steam and thus forming a lightweight, frothy material. The expansion temperature typically ranges from 1,100 to 1,500°F. An expanded volume increase of 10 to 40 times the original volume yields expanded densities of 1.5 to 11 pounds per cubic foot (lbs/ft3). Perlite is mined by eight companies at 10 operations in six western states. New Mexico accounts for more than 80% of the total tonnage mined. The rest comes from Arizona, California, Colorado, Idaho, and Nevada. In 1992, domestic production was 571,000 short tons (st), domestic apparent consumption was 591,000 st, and the value of crude perlite was $15.3 million. In 1991, with about the same production and price of crude perlite, the gross value for expanded perlite was $101.7 million. Perlite exports in 1992, primarily to Canada, are estimated an 30,000 st; and imports, from Greece, are an estimated 50,000 st. In 1992, 70 plants in 33 states expanded crude perlite. Construction uses of expanded perlite accounted for 66% of total domestic sales. Expanded perlite used as filter aid accounted for 15%. All other markets, including use as a filler and in agriculture, accounted for 19%. Leading states for expanding perlite, ranked by order of sales, were Mississippi, Pennsylvania, California, Illinois, and Georgia. Domestic perlite encounters transportation disadvantages in some areas of the eastern United States compared to perlite imported from Greece. However, western U.S. perlite exports to Canada offset this in large part, and net import reliance for perlite is about 3% of domestic consumption. Perlite grab samples were tested at the New Mexico Bureau of Mines and Minerals Resources (NMBMMR) for their basic suitability in horticulture, construction, filter aids, and fillers/extenders using Perlite Institute techniques modified by the NMBMMR. Most commercial perlite ranged from 2.5 to 3.0 wt.% bound water for all major types (classical, granular, and pumiceous). Expanded density varied widely, but the lowest density of 1.9 lbs/ft3 was for granular. Average brightness of expanded perlite was 47.6 to 69.3%. Nonexpansibles, commonly obsidian or "dead" perlite, ranged from 18 wt.% to less than 1 wt.%, with granular perlte generally the lowest. Compacted density was not related to either perlite type or nonexpansibles present. Sieve analyses of the -50+100 mesh product showed that, in general, pumiceous perlite produces more fines and classical and granular perlite average 60 to 80% -30+100 mesh after expansion. Samples were tested for crystalline silica that ranged from below the detection limit of 0.5 wt.% to nearly 0.2 wt.%, but most tested below 0.5 wt.%. Although quartz content can be lowered in the expanded product by the expansion process, producers can further lower crystalline silica in the product by mixing low-quartz crude with high-quartz perlite before expansion. Chemical analysis by x-ray fluorescence confirms the rhyolitic composition of perlite, but indicates that surface weathering may increase the concentration of some elements, such as potassium and calcium, by infilling cracks or fissures developed during or after perlite emplacement.

Jan 1, 1995

By Clifford W. Schultz

Four native copper ores, two conglomerate and two amygdaloidal, were tested to determine their amenability to sorting. One of them, a conglomerate ore from the Kingston mine, showed a high sortability as evidenced by an 80 pct recovery of copper in the minus 6-, plus 1/2-inch size range. Using the Kingston as a case example, the cost of mining and concentrating was estimated for a standard case and five optional cases involving varying degrees of sorting. This analysis indi¬cates that the production cost per pound of copper can be reduced on the order of 1 to 1-1/2 cents per pound along with a significant decrease in capital investment.

Jan 1, 1975

By Howard G. Coopersmith

A resource of low grade good quality diamonds has been discovered through the Diamond Company NL-Moonstone Diamond Corp. Joint Venture. A limited bulk sample diamond test of two large kimberlite pipes on the Kelsey Lake Property, Colorado, has been completed. These kimberlite pipes have petrological and mineralogical indications of the presence of diamond. Small diamonds were recovered from surface samples. Drilling and trenching revealed both pipes were complexes of diatreme facies kimberlite. One pipe contains crater facies kimberlite as well. This is the first reported occurrence of crater facies kimberlite in the Province. Approximately 1000 tonnes of kimberlite rock was excavated and processed through a scrubber -HMS -Sortex -Grease Plant. Significant diamonds were recovered. The diamonds were generally of good color and clarity, with many being in the gem and near gem categories. Grades are considered low however. Additionally, a small potential resource of alluvial diamonds is present.

Jan 1, 1991

By Malcolm J. McPherson

There have been numerous recorded cases of mine explosions being initiated by falls of roof. The actual mechanism of the ignition has often been unknown. One possibility is incendive frictional sparking, particularly when the falling rock contains quartz. Another possibility that has received little attention is the increase in temperature of the air due to adiabatic compression under the falling roof. This paper analyses that possibility and concludes that falls which are extensive in plan area but not necessarily of great thickness of falling rock can, indeed, produce temperatures in excess of those required for the ignition of coal dust or methane.

Jan 1, 1995

By Marshall A. Koval

The future of mining in the United States is in question. The cumulative effects of federal, state and local environmental legislation threaten its survival as the cost of compliance skyrockets. Legislation has created pol ari zat ion between government and industry followed by court action, further increasing costs and delays on permitting and remediations. Regulations often call for excessive and rigid requirements that result in unrealistic compliance goals costing tens of millions of dollars. The costs often exceed the value of the remedy. A growing concern is that proper scientific methodologies and engineering practices are being sacrificed because of political and public pressures.

Jan 1, 1991