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Session Chairpersons: Jan D. Miller, Professor, Univ. of Utah Met. Engineering Dept., Salt Lake City, UT; and Philip Thompson, President, Dawson Metallurgical Laboratories, Inc., Salt Lake City, UT
8:30 am Keynote
PROJECTING LABORATORY AND PILOT TEST DATA INTO OPERATING REALITY: Robert R. Beebe, Consultant, Former Vice President, Newmont Mining Corporation, P.O. Box 32048, Tucson, AZ 85751-2048
Laboratory and pilot-scale tests are almost invariably required before metallurgical development can proceed. Difficulties with sampling, as well as with classical chemical and physical scale-ups are normally anticipated and relatively well-understood, but more subjective factors also come into play, including misunderstandings of the operating scheme chosen, wrong "lessons" learned from similar operations, failures to handle data appropriately, and even arbitrary intervention by management. The paper examines some of these subjective factors and suggests ways to guard against them. Several anecdotal case studies are used as examples, including when and where to heap leach or to mill specific types of gold ore.
PREDICTING PRODUCTION HEAP LEACH CYCLE TIMES FROM LABORATORY COLUMN TEST DATA: Philip Thompson, President, Dawson Metallurgical Laboratories, Inc., Murray UT 84157-0685
Carefully planned Laboratory test programs provide valuable data regarding the amenability of low grade gold ores to heap leaching. Several problems are encountered in laboratory column simulation of gold heap leaching. A problem most commonly associated with column testwork is the limit on test column height. Most laboratories use a 3 to 5 meters (or 9 to 15 feet) high column as a standard test due to building ceilings and sample size limitations, etc. The problem with this column height is that most commercial heaps are at least 10 to 15 meters (25-35 feet) high, with some heaps reaching 100-200 meters (225-450 feet). This paper presents a data interpretation method whereby the data from test columns of virtually any height can be used to predict a first approximation leach cycle time for commercial heaps. Other important factors, e.i. sample preparation protocol, preliminary bottle roll testing, column diameter requirements, and leach solution analysis, are also discussed.
AGGLOMERATION PRACTICE AT KENNECOTT BARNEYS CANYON MINING COMPANY, BARNEY CANYON, UT: Philip L. LeHoux, Chief Metallurgist, Kennecott Barneys Canyon, Magna, UT 84O44
Kennecott Barneys Canyon Mining Company has been a gold heap leaching facility in operation since 1989. In 1994, a flotation plant was commissioned to remove sulfide minerals from refractory sulfide ore. Tailings from the plant are mixed with oxide heap leach material in order to produce a geotechnically stable agglomerate from which the gold is leached and recovered in a conventional heap leach cyanidation process. The experience to arrive at an effective blending methodology is discussed.
9:50 am BREAK
ZARAFSHAN NEWMONT J.V. MURUNTAU HEAP LEACH OPERATION, UZBEKISTAN: Sevket Acar, Senior Metallurgist, Newmont Metallurgical Services, Salt Lake City, UT 841O8; Tim Acton, Newmont Gold Company, One Norwest Center, 17OO Lincoln St., Denver CO 8O2O3
Zarafshan/Newmont is a 50/25/25 joint venture between Newmont Gold and two entities of the Republic of Uzbekistan, the State Committee for Geology and Mineral Resources, and Navoi Mining and Metallurgical Combinat. Zarafshan/Newmont joint venture consists of a heap leaching operation, which will process 220 million metric tons of existing stockpiles of low-grade oxide ore averaging 0.036 oz Au/T from the Muruntau mine. Net recovery over the 17-year life of the project is expected to be 4.8 million ounces of gold. The plant started in October 1993, and the operations commenced on May 25, 1995. The crushing plant consists of four stages of crushing and screening to produce 95% -3.35 mm product followed by heap leaching and gold recovery by Merrill-Crowe process. The Dore metal is refined at the Muruntau refinery. All gold produced by the joint venture is sold on the world market.
PROCESS MINERALOGY OF HEAP LEACHABLE ORE DEPOSITS: J.G. Davidson, N.A. McKay, Lakefield Research Ltd., Lakefield, Ontario KOL 2HO
Heap leachable ore deposits from many countries have been submitted for process mineralogical evaluation and laboratory testwork. Numerous factors must be addressed and integrated by the mineralogist, geologist, metallurgist and engineer. Projects encompass grass roots exploration, preliminary petrographic analysis, predictive and process mineralogy, dye penetration analysis of rocks and thin sections, metallurgical beneficiation testwork and plant optimization studies. The significance of mineralogical factors, such as geological controls, degree of oxidation, dye amenability, liberation, deleterious minerals, refractoriness, and the impact of mineralogy on gold recovery and process considerations, will be presented.
COLD WEATHER HEAP LEACHING OPERATIONAL METHODS: Kenneth E. Smith, Lyntek, Inc. 775 Mariposa St., Denver, CO 80204
Cold weather heap leaching can be grouped into two basic regions; Arctic and near-Arctic, with various operational techniques or combinations of operating techniques dictated by latitude and site topography. The basic cold weather regions are Arctic areas, (between 50( and 60( North latitude). As techniques and operational philosophy have advanced, heap leaching operations have moved into progressively colder regions.
HEAP LEACHING IN EXTREME NOTHERN CLIMATES, AN OVERVIEW OF THE BREWERY CREEK MINE, YUKON, CANADA: Thomas Haper, Sitka Corporation; Rod Samuels, RM Samuels Consulting; Rupert Allen, Consulting Geologist, Viceroy Resources Corporation, Vancouver, B.C., Canada
Viceroy Resource Corporation of Vancouver, B.C., has recently developed and brought into production the Brewery Creek Mine, an open-pit heap leach gold mine, located 55km east of Dawson City in Yukon, Canada. Mineable reserves are 15.2 million tonnes of ore grading 1.45 grams/tonne, containing 22 tonnes (707, 315 oz) of gold. Ore processing employs the heap leach technology using run-of-mine ore. Highlights of 1996 activity included construction of a 158,000m2 of leach pad, placing 1.9 million tonnes of ore at a grade of 1.46 gpt to the leach pad, construction and successful commissioning of the ADR plant, and pouring of the first gold bar on November 15th. Permitting of this mine has drawn significant attention because of the innovated heap leach technology; although this technology has been proven in other jurisdictions, it has not been used at such northern sites where winter temperatures routinely reach -45(C for extended periods. Acknowledgments are extended to the staff of the Viceroy Resources Corporation for their participation in developing the successful heap leaching technology under extreme frigid climatic conditions.
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