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By Bruce Bryant

Silver ore was discovered at Aspen in 1879, but the district did not reach full production until 1888 after lawsuits were settled and railroads furnished less expensive transportation to the outside world. The boom years were 1888-92; production declined thereafter. From the middle 1920's until 1950, the Midnight mine in the Richmond Hill district furnished most of the output in the Aspen quadrangle. Since 1950, little mining has been done at Aspen. The metals produced were silver, lead and zinc. Native silver dissolved from the sulfide ores was redeposited by waters circulating as deep as 300 m below the land surface, resulting in great secondary enrichment of many of the deposits. Over 100 million ounces of silver were produced in the Aspen quadrangle. Low-grade lead-zinc deposits remain between the old workings locally, and data available suggest that primary ore below levels mined is also of low grade. The ore occurs in the Mississippian Leadville Limestone and the lower part of the Pennsylvanian Belden Formation in sites that were made favorable for deposition by a number of stratigraphic and structural factors.

Jan 1, 1982

By Bill Mariucci, Gary Almeraris

All Rights Reserved. Printed in the United States of America. Information contained in this work has been obtained by SME, Inc. from sources believed to be reliable. However, neither SME nor its authors guarantee the accuracy or completeness of any information published herein, and neither SME nor its authors shall be responsible for any errors, omissions, or damages arising out of use of this information. This work is published with the understanding that SME and its authors are supplying information but are not attempting to render engineering or other professional services. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Any statement or views presented here are those of individual authors and are not necessarily those of the SME. The mention of trade names for commercial products does not imply the approval or endorsement of SME.

Dec 1, 2009

By Michael A. Piepenburg

The East Side Access (ESA) Project will extend Long Island Rail Road (LIRR) into midtown Manhattan via 11 km of tunnels, a new terminal station and associated support facilities. In addition to the hard-rock tunneling currently underway in Manhattan, soft-ground tunnels in Queens will traverse beneath Amtrak?s Sunnyside Yard and Harold Interlocking, the busiest rail interlocking in North America. This paper details ESA?s coordinated approach to interfacing with both Amtrak and LIRR with regard to the planned tunnels, shafts and related construction beneath or adjacent to the operating railroads. This interface includes integration of railroad staff, extensive presentations, reviews and agreements with the railroads regarding settlement mitigation, real-time automated geo-instrumentation monitoring, ground improvement, and geotechnical/environmental controls.

By Meyer Klein

Decision theory is the formal theory of the logic of decisions in view of the decision maker's objectives, preferences, I beliefs, and available information, It usually deals with weighty economic problems involving irrevocable (or costly to reverse) decisions. Capital investment planning problems constitute an instance par excellence for application of the decision theory concepts. Decision theory as it is presently conceived has evolved in recent years. At first it concentrated on decisions in the face of total lack of information and on games with intelligent adversaries. The results of these efforts proved theoretically interesting, but practically of little applicability. In the last few years, stress has shifted to the introduction of subjective probabilities and preferences, and the results have been eminently successful in applications both in government and with- in business firms in the resolution of complex problems.

Jan 1, 1970

By A. F. Marques

The Azores islands are located on a triple junction where the American, African (AFR), and Euroasian (EUR) plates meet. The Mid-Atlantic Ridge (MAR), oriented N-S, represents two branches of the T; an E-W branch defines the EUR/AFR boundary called the Terceira Rift. The nature and structure of this plate boundary, as well as the dynamics of the interaction of tectonics and volcanism remain unconstrained. The Azores plateau is seated on a mantle domain of anomalously low seismic S-wave velocities, and gravity and geoid anomalies, where the apparent thick crust is thought to relate to larger degrees of melting initiated at greater depths [1]. The cause of these anomalies is controversial but many authors consider the presence of an anomalously hot/wet enriched mantle probably supplied by a plume [2]. The geochemistry of the subaerial and most submarine lavas from the plateau reinforces the plume model beneath the Azores [3-4]. The origin, size and present location of the plume is under debate but an area near Terceira is the favoured plume centre [5]. [ ] SEAFLOOR HYDROTHERMAL SYSTEMS IN THE AZORES AREA (36ºN ? 40ºN) More than 150 active and fossil hydrothermal systems are known in the oceanic seafloor [6]. Many more are yet to be found on vast oceanic areas that haven?t been explored [7]. Ever increasing knowledge shows that modern seafloor hydrothermal systems can be hosted in felsic to ultramafic rocks, vary in size and shape and exhibit diverse amounts of sediment cover

Jan 1, 2011

By P. K. Chatterjee, G. D. Just

Sublevel open stoping is a low-cost method that has been successfully employed in many large underground mining operations. Where ore body characteristics are suitable, extensive mechanization and the use of large-scale stoping techniques can considerably reduce operating costs. However, careful long-term planning of mine layouts and large capital commitments in development are required prior to production. Implementing precise mine design procedures and carefully controlling operations can result in considerable benefits. This article describes methods to achieve these objectives based largely on mining operations at Mount Isa, where sublevel open stoping has been used since 1932. Ore won by this method accounted for a very large percentage of the total tonnage produced at Mount Isa. Major costs associated with sublevel open stoping can be classified as drilling, explosives and charging, and LHD costs. In this article, analyses of these costs are made with particular reference to stope design. Parameters such as burden, drill hole diameter, explosive density, specific charge, etc., are considered in establishing the interrelationship of unit operating costs, as well as total costs of sublevel open stoping.

Jan 10, 1981

By R. E. Scheffel

Most supergene copper heap leach operations today employ forced-aeration, irrespective of ore grade. Unfortunately, there is little published quantification of its benefit. There is a natural desire to strive for the ideal chemical kinetics. The reality, however, is that physical mechanisms control the commercial extraction rate. This paper presents the performance of a number of operations, their operating conditions and physical ore characteristics, which contribute to non-ideal solution distribution and variable extraction rate. Regardless whether one uses forced-aeration, commercial experience to date suggests it is prudent to design for longer leach cycle times to ensure the production target is met.

Jan 1, 2006

By Donald W. Breck

Zeolites were first recognized as a new group of minerals by Cronstedt with the discovery of stilbite in 1756. The word zeolite was coined from the two Greek words meaning "to boil" and "a stone" because of the loss of water when heated in the mineralogist's blow pipe. (1) In 1845 it was discovered that certain soils have the power of retaining ammonium Salts. (2) These were the first ion exchange experiments. Later it was discovered that it was the hydrated silicates in the soil that produced this phenomenon and several years later a paper was published dealing with the action of dilute salt solutions on silicates which showed that this base exchange principal, which we now call cation exchange, is reversible. The quantitative cation exchange behavior of zeolite minerals, such as chabazite, was studied. As a result any aluminosilicate which exhibited the property of ion exchange was referred to as a "zeolite;" even today the term has been applied to clay minerals as well as synthetic organic ion exchange resins.

Jan 1, 1973

By S. K. Bhatt

This paper reviews major developments in continuous haulage technology for underground coal mines. Haulage systems, both in use and development, are investigated through a comprehensive literature search and visits to mines and manufacturers. The systems include flexible conveyor train, mobile conveyor, multiple-unit continuous haulage, extensible, and belt turning systems. Strengths and weaknesses of the systems are assessed in light of their operating under remote control and their application to the computer-assisted continuous mining machine being developed by the U.S. Bureau of mines. Through mining scenarios, candidate haulage systems are conceptualized to be consistent with the capabilities of the mining machine.

Jan 1, 1990

The Environmental Session will consist of five papers dealing with various aspects of trace elements associated with coal. Analytical procedures to determine the amounts of trace elements will be discussed. Other papers will deal with trace elements in streams downstream from coal mines, potential pollution from wastes from coal preparation plants, potential recovery of trace elements, and potential pollution from trace elements as a result of the combustion of coal.

Jan 1, 1979

By Russell B. Dix

Laboratory column leach tests are used routinely to evaluate gold and silver ores for heap leaching. The tests are fairly straightforward. The ore to be tested is placed into an appropriately sized leach column. Then an alkaline cyanide solution is applied to the ore and the effluent solutions are collected. The effluent solutions are then put through a column of activated carbon to recover the gold and silver in solution. Zinc precipitation may also be used for silver ores or if the ore contains a significant amount of soluble silver in addition to gold. The length of the leach time in the tests is mainly a function of how quickly the precious metals are recovered from the ore. At the completion of the tests, the tailings are assayed and the recoveries determined from the calculated head grades. The amount of ore to be used for a test is partly a function of its crushed size. The coarser the size, the larger the sample size for the column. A typical small-scale laboratory column test on ore crushed to -12 mm (-0.5 in.) would usually be conducted in a 100- to 150-mm-diam (4- to 6-in.-diam) column 2 m (6.6 ft) in height, containing about 20 to 45 kg (44 to 99 lb) of ore. A comparable test on the same ore crushed to 50 mm (2 in.) would be conducted in a 200- to 300-mm-diam (8- to 12-in.-diam) col¬umn 2 m (6.6 ft) in height, containing about 80 to 200 kg (176 to 441 lb) of ore. Larger-scale tests can be run by increasing the column heights and diameters. Conducting larger-scale tests results in increased costs for sample procurement, preparation, and running of the tests. The additional data obtained from

Jan 1, 1989

By J. C. Reid

Pre-cambrian scheelite deposits in Northeastern Brazil are widespread in a high grade metamorphic terrain. Previously these deposits had been interpreted as contact-metasomatic. In this paper, a volcanigenic model is invoked based on the volcanic setting (proximal to distal) and the absence of associated felsic intrusives and spatially associated metasomatic skarns. The tungsten was introduced into sediments by volcanic- exhalative processes and subsequently remobilized and further concentrated by heat and metamorphis fluids associated with high-grade metamorphism and migmitization. An alternative syngenetic - diagenetic model is discussed which requires the transport of tungsten by heteropoly acids and deposition of the tungsten as a function of Eh and Ph conditions and different clastic depositional environments. While such stratabound tungsten deposits are considered rare in North America, the hypotheses developed in this paper may open new areas for exploration.

Jan 1, 1983

By W. J. Atkinson

The first recorded discovery of diamonds in Australia was in 1851 in New South Wales. Subsequent prospecting has shown alluvial occurrences of diamond to be widespread through much of the Tasman fold belts of Eastern Australia. Production is estimated to be some 500,000 carats from several small alluvial fields. Despite extensive exploration, though, no primary rock source carrying significant diamond content has ever been confirmed in Eastern Australia. Conversely, diamond exploration of the older Western and Central Cratons of Australia during the past 30 years has discovered 12 fields containing 360 kimberlites, lamproites and lamprophyric volcanic pipes, dykes and other intrusives. Of those, 180 have been confirmed to be diamondiferous. Only one pipe, however, the 1200 Ma high-grade Argyle lamproite and associated nearby alluvials, has proved to be economically exploitable. Its current annual production is 40 million carats valued at about US$400 million. Production from the open pit will be sustainable until at least 2003.

Jan 1, 1995

By D. Robert Weir, M. J. H. Ruscoe, R. M. Berezowsky, M. A. Clegg

The metallurgical processing involved in the produc-tion of the new Canadian one dollar coin is reviewed starting with the hydrometallurgical production of pure nickel powder, followed by the powder metallurgy process for the production of nickel strip and coinage blanks, and concluding with the Aureate bronze electroplating and heat treatment procedure. Coinage requirements are then reviewed with regard to economic, public acceptance, and service requirements. Finally the properties of Aureate nickel coinage are presented in the light of the many and varied coinage requirements, and it is concluded that the new Canadian dollar coin exceeds the requirements admirably.

Jan 1, 1990

By Christopher B. Kapes

To reduce concentrate dewatering and drying costs, the Concentrator Division at Phelps Dodge Morenci, Inc. investigated available filtration technologies. Numerous methods were explored, including: drum, disk, belt, pressure, hyperbaric, and ceramic media filtration. An economic evaluation of the individual filtration technologies indicated the advantages of ceramic media filtration for Morenci concentrates. This paper discusses the technological development culminating in the first full scale application of ceramic media disk filters in North America. Low moisture contents are obtained at high production rates and greatly reduced operating costs.

Jan 1, 1994

By A. Choudhury

Deep open-pit mines are becoming increasingly common in the highly mineralized arctic and sub-arctic regions. Air inversion is a frequent occurrence in these regions, and is exacerbated by the natural topography of an open-pit mine. Due to such inversions, the air quality in open-pit mines deteriorates very rapidly. Transport of gaseous pollutants under arctic air inversion is complex and involves an interaction between flow, thermal and convective transport systems. This paper discusses the construction and validation of a three-dimensional model that simulate the flow of air and the transport of gaseous contaminants in an arctic open-pit mine and the effect of low influent velocity and large gust velocities on the contaminants profiles in the mine. It was found that while higher velocities may remove contaminants from the pit bottom, they may not remove the contaminants from the pit entirely, necessitating artificial mitigation measures.

Jan 1, 2012

By Gordon M. Miner

When I was originally invited to speak to this audience on the subject of the future supply of precious metals I was somewhat apprehensive and suggested that the Program Chairman select someone with more credentials. He declined and the results of our conversation gave me cause to reflect and recall the opportunities I have had over the years and how fortunate I have been to be associated with so many successful companies and knowledgeable people affiliated with the precious metals field. I discovered that since 1935, 1 have worked in or visited most of the gold and silver camps in the United States; have been a leaser of a gold mine in Mohave, California; have both lost and made money in the silver futures market; have worked for two of the greatest precious metals companies in the United States - Homestake Mining Company and Hecla Mining Company, have spent a considerable amount of time in precious metal related discussions with men like Don MacLaughlin, Paul Henshaw, Dick Stoehr, Abe Shoemaker, Bill Love, Phil Lindstrom, Simon Strauss, Herbert and Bunker Hunt and many others. It is those exposures and experiences that I draw onto discuss the subject at hand.

Jan 1, 1980

By CHRISTOPHER D. HEBERT, SCOTT W. HOFFMAN

All Rights Reserved. Printed in the United States of America. Information contained in this work has been obtained by SME, Inc. from sources believed to be reliable. However, neither SME nor its authors guarantee the accuracy or completeness of any information published herein, and neither SME nor its authors shall be responsible for any errors, omissions, or damages arising out of use of this information. This work is published with the understanding that SME and its authors are supplying information but are not attempting to render engineering or other professional services. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Any statement or views presented here are those of individual authors and are not necessarily those of the SME. The mention of trade names for commercial products does not imply the approval or endorsement of SME.

Dec 1, 2019

By Adrian Coombs

The York Durham Sewage System (YDSS) Interceptor Tunnel Project is located in the Town of Richmond Hill, Ontario, Canada, just north of Toronto. Construction commenced in September 2006 and completion is planned for early summer, 2008. The project involved public and agency buy-in of construction technologies and methods that minimized dewatering, design and construction of sealed shafts with jet grout break-in and out blocks in order that Earth Pressure Balance (EPB) mode could be maintained by the Tunnel Boring Machine (TBM) during shaft entry and exit. This paper will discuss the advances that were made possible through the opportunity to apply and test these technologies in order to accommodate the aquifer and artesian conditions present on this project.

Jan 1, 2008

By Bradford F. Townsend, Matthew E. Fowler, Michael F. Smithson, Lawrence R. Eckert

All Rights Reserved. Printed in the United States of America. Information contained in this work has been obtained by SME, Inc. from sources believed to be reliable. However, neither SME nor its authors guarantee the accuracy or completeness of any information published herein, and neither SME nor its authors shall be responsible for any errors, omissions, or damages arising out of use of this information. This work is published with the understanding that SME and its authors are supplying information but are not attempting to render engineering or other professional services. If such services are required, the assistance of an appropriate professional should be sought. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Any statement or views presented here are those of the authors and are not necessarily those of SME. The mention of trade names for commercial products does not imply the approval or endorsement of SME.

Dec 1, 2010