Cominco Res. Nevada mine yields high grade hole

International has encountered paydirt at its Buckhorn mine in Nevada. The company describes the discovery as a “possibly significant high grade gold intercept,” noting the hole was drilled beneath the West Sinter deposit which is being prepared for open pit mining.

The 870-ft-deep hole intersected 3.8 oz gold per ton and 11.3 oz silver over a 15-ft section starting at 415 ft. The overlying 25 ft of drill core averaged 0.09 oz gold and the underlying 15 ft graded 0.22 oz. So the 55-ft interval from 390 ft to 445 ft averaged 1.1 oz.

George D. Tikkanen, president, believes the hole might have encountered a feeder zone which is common to epithermal gold deposits. He also suggests the vertical hole may have traced the zone down dip or it could have encountered “stacked orebodies” with, of course, significant tonnage implications.

Stepout holes are being drilled around the discovery on 50-ft centres and he concedes the zone “has the potential to contain a lot of gold.” Cominco Resources spent about $250,000 exploring the property to mid-year and it is planning to spend another $500,000(US) by year-end.

Vancouver-based Equinox Resources has a 24.6% interest in the Buckhorn mine which it purchased last September. (It has been said that timing is everything in the mining business and this is probably a good example.) Equinox President Ross J. Beaty views the discovery as “an exciting development” which he claims fits a classic epithermal model. In some respects, the find is analogous to discoveries made by American Barrick in Nevada and Asamera at Wenatchee, Wash., he argues.

The high grade hole contained anomalous gold values throughout, including a potentially economic intercept from 725-750 ft which graded 0.23 oz gold. A shallower intercept between 480 ft and 505 ft averaged 0.11 oz gold and five intervals in the upper portion of the hole graded 0.04 to 0.05 oz.

Check assays from two laboratories have confirmed the high grade results with variations due to nugget effect, says Cominco Resources.

The West Sinter zone, which is about two miles from the main Buckhorn orebody, contains some 300,000 tons of reserves grading 0.06 oz gold, almost double that existing before the program began. Mining is currently confined to near oxide reserves and gold is extracted by heap leach methods.

At least 800,000 tons of sulphide reserves exist at a similar grade but these are not amenable to heap leach extraction techniques. Cominco Resources has been doing test work on a satisfactory extractive process to extract the gold from the sulphide material.

Gold at the Buckhorn mine occurs in linear trends of highly altered volcanics and drilling has generally focused on areas where alteration is exposed and on projections of the trends. Mr Tikkanen says the exploration emphasis has been directed at near surface targets (200-250 ft) and about 500,000 tons of reserves have been added to inventory in recent months.

The mine should produce about 30,000 oz gold this year and exploration is geared towards maintaining the present production rate for as long as possible. The company can also foresee increasing production with an increased reserve base. Delineation of an economic reserve base in the new high grade zone might justify an underground program, says Mr Tikkanen. But these reserves would have to be processed by conventional milling techniques.