New 4,500-ton mill opened at Barrick’s Goldstrike bet

Toronto-based American Barrick Resources (TSE) has taken a significant step towards expanding gold production at the Goldstrike mine at Carlin, Nev.

In a bid to increase its gold output from 40,144 oz last year to around 750,000 oz by the early 1990s, Barrick has commissioned a new 4,500-ton-per-day mill. It poured its first gold bar in early August.

Initially, the new facility will process ore from the high grade portion of some 26 million tons grading 0.55 oz gold per ton in near surface oxide reserves, Barrick says.

In about three years it will be converted to handle an additional 100 million tons of grade 0.17 of deeper sulphide ore reserve.

Prior to the first pouring, all gold at Goldstrike was produced via a heap leaching process which involves heaping broken ore on sloping impermeable pads and repeatedly spraying the heaps with cyanide solution.

While Barrick will continue to heap leach about seven million tons of low grade oxide material on an annual basis, President Robert Smith said he is happy to have the control which a carbon-in- leach mill will bring to the operation.

A carbon-in-leach mill can achieve up to 90% recoveries, compared to a maximum of about 75% in the less efficient heap leaching process.

“Having the mill in place means that we don’t have all our eggs in one basket.”said Smith.

Built at a cost of $27 million(US) by Kilborn Engineering, the new facility was up and running just seven months after the foundations were poured. Scheduled to contribute about 40,000 oz to this year’s Goldstrike production quota (115,000 oz), it is already operating at design capacity and achieving the targeted 85% recovery rate. “There aren’t many mills of that size built in such a short time frame,” said Smith. It represents the first phase of a Goldstrike development plan designed to handle 100 million tons of ore annually by 1990. An autoclave unit designed to handle the sulphide ore is scheduled to be in place by 1990 and Barrick is also planning to construct a second mill.

At a capital cost of around $250 million, the company is also working on a development plan to mine 81.9 million tons averaging 0.16 oz of proven/probable reserves which were recently outlined in the Deeper Post-Betze sulphide deposit.

Although details won’t be revealed for another six to eight weeks, the plan will probably involve the construction of a large open pit and a joint venture with neighbor Newmont Gold.

Meanwhile the emphasis at Goldstrike has changed from finding new deposits to developing the reserves which are already in place. Barrick is currently in the final stages of an in-fill drilling program on the Post-Betze deposit. But Smith said the results will be used to complete the mining plan and any additional reserves won’t be announced until year-end.