Underground work started by Northern Dynasty

The first of two underground phases has commenced at Northern Dynas ty Explorations’ Little Bald Mountain mine in Nevada.

The 300-ft decline will access a 50,000-ton ore block and production will be stockpiled for leaching next spring.

President Glenn Simpson says the $300,000(US) project will be funded from cash flow.

Underground grades, which will average about 0.16 oz gold per ton, are double those encountered in surface mining. This will allow them to crush smaller and possibly increase recoveries which now are in the high 70% range. He sees no reason why these rates shouldn’t be comparable for underground material.

Surface material is being agglomerated and this procedure will be applied to underground production. The process is simple and a belt agglomeration system is used very effectively, he says. There are 50,000 tons of ore in one stope of which 40,000 grades 0.16 oz gold and the remainder 0.1 oz. Based on an 80% recovery rate, that reserve should yield about 5,900 oz gold and he forecasts 6,400 oz gold production in 1987.

A second underground phase is scheduled for next year which will access 225,000 tons grading 0.16 oz. But that material will be mined at 500 tons per day in 1988-9 and leached through 1990. Mr Simpson says production is forecast at 9,000 oz for each of those years and he adds this would be the maximum with the present underground design.

To expand the rate further, they would need another open pit or underground stoping area and this would require additional exploration. The project is understandably “operations oriented” but Mr Simpson confirms more exploration is planned next fall, particularly drilling.

Underground mining will be done cheaply and a block caving- type method will be utilized. Operating costs over the entire life of the Little Bald Mountain mine are expected to be about $175(US) per oz of gold including the now completed open pit phase and the two underground phases. Stopes will be 200-300 ft long, approximately 300 ft high and 40-60 ft wide, he says, and at today’s prices mine life is 3-4 years.