Newmont getting the bugs out of bioleaching

North America’s biggest gold producer, Newmont Gold (NYSE), is planning to introduce bioleaching technology at its Carlin, Nev., operations by 1994, says Chairman and Chief Executive Officer Gordon Parker.

Tests conducted by Newmont Gold indicate that bioleaching methods can be utilized successfully to oxidize refractory ore at Carlin where the 90.1% owned Newmont Mining (NYSE) subsidiary produced 1.5 million oz. in 1991. While Newmont Gold expects to extract about 1.6 million oz. this year from oxide reserves alone, it will begin mining material suitable for bioleaching in 1994, and be ready with the necessary processing facilities, Parker says. By that time, the Colorado company will have commissioned a $195-million roaster capable of oxidizing both sulphidic and carbonaceous ores, Parker told analysts at a New York gold mining seminar sponsored by U.S. investment banker Donaldson, Lufkin and Jenrette.

He said the roaster is designed to treat such ores for 70% of what it costs Carlin’s other major gold miner American Barrick Resources (TSE) to process refractory ores using autoclave technology.

But even though roasting will make treatment of refractory ore more expensive than the processing of oxide ore, production costs won’t increase by the same factor due to the higher grade of ore being treated, he predicted. The average grade of refractory mill feed is expected to be 0.15 oz. gold per ton, compared with an average of 0.075 oz. for oxide mill ore. Cash costs last year were in the range of US$205-210 per oz.

Meanwhile, having applied for patents on a process for introducing concentrated cultures of naturally occurring bacteria into sulphidic refractory ores, Newmont is now literally attempting to get the bugs out of the system.

The company is also working toward a deal with American Barrick that will allow for the development of the Post gold deposit which straddles the border separating ground owned by both companies.

According to Newmont Mining’s 1990 annual report, probable and possible reserves on its portion of the Post deposit stand at 40.1 million tons of grade 0.14 oz. or 5.8 million contained oz.

Newmont is also planning to spend US$20 million in and around the Carlin Trend this year where the focus has changed from delineating oxide reserves to finding whatever deposits are available, regardless of whether they lie near-surface or at depth.

Of the US$30 million to be spent on exploration outside the Carlin Trend, US$18 million is earmarked for areas outside the U.S. where Newmont has three advanced projects with potential reserves in the

1-million-oz. range.

There are two such projects in Indonesia and one in Peru.

In addition, Newmont is negotiating to establish a gold exploration joint venture with the government of Uzbekistan which contributes about one-third of the gold produced in the Commonwealth of Independent States, the former Soviet Union. “It involves their gold and our technology,” said Parker.