Development has been under way since 1994, when Chief joint-ventured the project to Vancouver-based Akiko Gold, which agreed to contribute US$10 million in work expenditures. Akiko then brought Korea Zinc into the deal as a major partner. Some time later, however, the junior dropped its interest in Burgin and changed its name to Prospex Mining.
Today, the 14,000-acre property is controlled entirely by Chief through a 75% interest in Tintic Utah Metals. Korea Zinc holds the remaining 25%.
From 1967 to 1978, Kennecott mined the property to the tune of 10.9 million oz. silver, 338 million lbs. lead and 349 million lbs. zinc. Production was discontinued because of poor ground conditions and the presence of hot geothermal water.
Chief has offered to appropriate the water from the state of Utah and then de-salinate it; the treated water would then be used commercially, and the salt sold. Water temperatures range between 115 and 156 Farenheit.
“We are confident the state will grant the application for appropriation by July,” says Paul Spor, executive director of Tintic Utah Metals.
Once the plan is approved, U.S. Filter will begin a feasibility study for a water treatment plant.
Chief has spent much of the past two years exploring for reserves at the property, with the most recent efforts focused on mineralization above the water table.
Burgin hosts mineralization in Cambrian-through-Ordovician limestones, dolomites and quartzites, which are overlain by a thick pile of Tertiary volcanic rocks.
The company is evaluating a recent discovery of silver mineralization in a fissure zone adjacent to known mineralization. This mineralization averages 30 oz. per ton and has been intercepted for almost 1,000 ft. along strike and to a depth of 250 ft. below the water table. The vein varies in width from 1 to 5 ft., with low gold values and a small percentage of lead. So far, none of this mineralization has been added to reserves or resources.
Meanwhile, in a reopened drift, drilling has encountered previously unknown mineralization in a vein parallel to the footwall of the Eureka Standard fault, one of the more important structural hosts in the property. Of the 19 holes drilled into the footwall, 15 hit significant mineralization, and, of those, five intercepted ore-grade values in gold, silver and copper. This vein, the width of which varies from 18 inches to almost 4 ft., has been intercepted for 300 ft. along the strike of the Eureka Standard fault. Assay values run 0.3 oz. gold and 5-7 oz. silver per ton.
This mineralization has not been included in reserves, and federal regulations will not permit production from this easily accessible zone until the company installs a secondary escapeway in the mine.
The company plans to install a borehole that will both serve as an escapeway and provide additional ventilation.
In July 1998, Chief reopened the Trixie mine, which is adjacent to Burgin. Mineralization there is hosted in quartzites, as opposed to the softer carbonates found in the main Burgin deposit. Trixie also contains more gold and less lead and zinc. From 1969 to 1992, the mine produced 150,000 oz. gold and 4.7 million oz. silver.
Having rehabilitated several levels at Trixie, Chief has turned its attention to drilling. In a program of 15 holes drilled on the 750 level and five on the 1200 level, the company is attempting to extend known ore zones.
Also, air circulation will be improved by reopening an access tunnel between the 1350 level of the Trixie and the 1100 level on the Eureka Standard fault.
In all, the company has blocked out reserves of just over 1 million tons grading 16.5 oz. silver per ton, 21% lead and 6.7% zinc, amounting to 17.7 million oz. silver, 450 million lbs. lead and 143 million lbs. zinc. It has also outlined a 407,000-ton resource grading 15 oz. silver per ton, 16% lead and 5.2% zinc.
Above ground, Chief is refurbishing the concentrator at the Burgin mill, having so far spent US$100,000 rebuilding the cone crusher. The overall job is nearly two-thirds complete.
The harder quartzite ores from the Trixie will be milled at a daily rate of 400 tons, and Chief says the mill will be capable of handling as much as 1,000 tons per day of softer, limestone-dolomite ore from Burgin.
A Knelson concentrator will be installed, to recover up to 45% of the gold and 40% of the silver. Rejects from the Knelson concentrator would be sent through the flotation circuit.
The Apex No. 2 shaft will be enlarged into the Burgin. Built in 1927, the shaft measures 5 by 5 ft., is made of wood and steel, and extends 1,300 ft. below the surface. The company plans to construct a concrete-lined circular shaft, 22 ft. in diameter, sunk to a depth of 1,900 ft.
Chief will then dewater the mine from the bottom of the shaft at the rate of 12,000-18,000 gallons per minute. Production could begin two years after construction of the shaft commences, Spor says.
Total capital costs, including shaft reconstruction and rehabiliation of the mill, are expected to reach US$35 million.
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