New decline and drift for Hecla’s Republic mine

A tour of underground and surface milling facilities at the Republic gold mine owned by Hecla Mining (NYSE) is somewhat reminiscent of a miner’s version of the popular movie Back to the Future. The mine, in Ferry Cty., northeastern Washington, has operated on an almost continuous basis since its opening in 1941. Although some new developments are in the works, the basic mining and milling methods have changed little since then.

While the methods may be old, the high-grade mine is the primary profit cornerstone of Hecla Mining. The cash cost of gold produced at Republic in 1988 was an impressive US$94 per oz., with the mine producing 80,301 oz. gold and 354,077 oz. silver from 79,210 tons of ore.

Mining primarily takes place in the Golden Promise area of the property. Although its development did not begin until 1984, mining methods are the same as those used in the Republic’s old primary producer, the Knob Hill.

The discovery of the Golden Promise dates back to the early 1960s when Day Mines and Knob Hill Mines — then owners of the property — began an exploration program driving a 7,000-ft. crosscut on the 1100 level from the Knob Hill shaft.

Drilling in 1963 encountered three mineralized intersections in the Golden Promise area. The best intercept, 3 ft. grading 6.62 oz. gold and 32.46 oz. silver per ton, prompted further work. A heading was driven to the area but produced inconclusive results, primarily because the intersections were in pyroclastic rocks which were believed at the time to indicate the boundary of an ore zone.

This, paired with the discovery of ore closer to the production shaft, resulted in the area being ignored until 1978. Drilling for structure at that time failed to intersect favorable host rocks and the area was again left alone.

Although drilling in 1983 did not intersect ore-grade material in the area of the previous drilling, by 1984 pyroclastics were finally accepted as a host rock for mineralization and a directional drilling program was begun.

Drilling to the end of 1984 indicated an ore zone at least 2,500 ft. long trending northerly and containing at least two veins. Development work since then has outlined a number of oreshoots in at least seven veins, which are typically 150 ft. long, 600 ft. high and 2-20 ft. wide.

The Golden Promise area has been developed backwards in a conventional mining sense in that the stopes have been developed from the bottom level upwards. However, with the access to the mine originating at the 1100 level, and all ore haulage on that level, the development sequence does make sense.

Mining is labor-intensive, and a cut-and-fill method is used with jack-leg drills and electric or pneumatic slushers in the near-vertical quartz veins.

Perhaps the most striking observation dating the mining methods in production areas of the Golden Promise is the absence of the mechanized rubber-tired mining equipment.

Stope ore is loaded into 1.3-ton capacity rail cars, trammed to the main ore pass, and manually dumped. The main ore pass funnels the rock to the 1100 level where it is again loaded into rail cars for tramming over 7,000 ft. to the Knob Hill No. 2 shaft.

Proven-possible reserves in the Golden Promise zone currently stand at 412,000 tons grading 0.81 oz. gold and 3.33 oz. silver, including a 2-ft. mining dilution.

Although this is significantly lower than the reserve figure of 515,000 tons of similar grade ore at the end of 1988, Tom Salzer, senior mine geologist, is confident the figure will be increased with the driving of a new 6,500-ft. decline and development drift.

The decline, expected to cost about US$6 million, will ramp down to the 8-level of the Golden Promise zone thereby allowing for cheaper transport of ore to the mill. Ore is currently trammed 7,000 ft. on the 1100 level to the old Knob Hill No. 2 inclined shaft, lifted the 2,025 ft. to surface, transferred to a dump truck and hauled to the mill.

The new ramp marks the beginning of the end for the methods of the past with the introduction of electric-hydraulic drill jumbos for development work, rubber-tired load-haul-dump equipment for mucking, and underground haulage trucks which will bring the ore to surface.

In addition to decreasing ore- handling and development costs, the new decline will improve ventilation. More importantly, the decline will allow the development of a newly discovered vein system, the Belligerent, discovered from surface and underground exploration drilling.

The Belligerent is 600 ft. to the northwest in the footwall of the Golden Promise’s current workings. Drilling in 1989 intersected 2.2 ft. grading 5.32 oz. gold and 215.1 oz. silver, 1.7 ft. grading 0.57 oz. gold and 4.96 oz. silver, and a 2-ft. intersection grading 1.92 oz. and 10.58 oz. silver.

If the development program is successful, it could pave the way to increasing production at the mine and mill.

Salzer will also be kept busy, looking for ore overlooked during previous mining in the Knob Hill area. He said at that time mining was “very production-oriented” and, therefore, it would be easy to miss ore blocks. This would be particularly true of large parts of the mine where faulting is common, leaving the potential of finding offset blocks of ore.

In the Knob Hill area, Hecla is driving a short ramp to reach the Baily vein crown pillar containing about 12,000 tons grading 0.58 oz. and 2.49 oz. silver.

The Republic mill, a combination of state-of-the-art 1940s technology and that of today, processes 270 tons of ore per day with gold and silver recoveries of 95% and 88% respectively.

The Golden Promise ore is a precious metal-bearing quartz containing sulphides and clay minerals. The gold occurs in electrum, as native gold, and can be associated with sulphide mineralization, primarily pyrite. Precious metals recovery of the mixed free-milling sulphide ore is by cyanidation of flotation concentrate, middlings, and tailings.

The various final concentrates are sent off site for refining and therefore dore bars — or “doe ray” as termed by maintenance lead man Alan King — are not poured on site.

The Republic employees, having voted down a recruiting attempt by the United Mine Workers Union in 1989, do not belong to a union. Perhaps the company’s gain share plan had some bearing on the employees’ vote; in addition to their regular wages and salaries, employees at the mine and mill belong to a gain share plan.

At the beginning of the year, targets are set for the price of gold and the cost of production among other factors. Employees are then issued 200 gain shares each, which will rise or fall in price relative to the performance of the mine and mill versus that targeted.

By mid-1989, the gain shares were worth more than US$12 each, even with the drop in the price of gold, and by year-end the shares were worth more than US$25 each. As a result, employees received about US$5,000 each from the shares in addition to their regular wages.

Hecla believes the gain share, a direct tie to the Republic unit’s profit, promotes employees’ awareness of maximizing corporate profitability and results in increased efficiencies.

An example of a tangible payoff of the plan is an employee’s suggestion to install a gold recovery plant at the tailings pond.

The plant, a 3-stage carbon column circuit, was installed in the spring of 1989. Residual gold values in the tailings pond is recovered to the tune of 1,000 oz. per year.

With more than five years in reserves remaining, as well as the excellent exploration potential that comes with such a historically rich mining property, it is likely Hecla will be kept busy at the Republic for years to come.