Cost questions over heap leach trial

Heron Resources Ltd’s decision to place its Jump-Up Dam nickel heap leach operation on care and maintenance has not deterred similar trial programs from going ahead, despite calling into question the viability of the technology as a low-cost method of nickel production.

Significant escalations in the cost of acid, as well as increased labour, construction and oil costs, led to a blow-out in capital expenditure to $681.9 million, 50 per cent higher than indicated by the scoping study in April 2007.

The pre-feasibility report also pegged operating costs at $6.39 per pound of production, a 56 per cent rise.

Heron managing director Mathew Longworth said while trial mining was expected to continue, the company would now focus on the more commonly used atmospheric leach technology.

Atmospheric leaching requires less acid than heap leaching, and extracts nickel within a 12-24 hour period, compared with heap leaching, which can take between six and nine months.

Mr Longworth said at the time of the scoping study, heap leach presented a viable, cost-effective option to be explored.

Since then, rises in both capital and operating costs had eroded the benefits.

“We’ve seen a lot of factors play catch-up,” he said.

Heron will spend about $4 million evaluating atmospheric leaching, with a view to completing pre-feasibility studies within the year.

The company had spent up to $6 million on the heap leach aspect of the project.

Heralded as a new, low-cost method of extracting nickel from laterite deposits, heap leach is currently being tested by a number of WA nickel miners.

The most advanced study is being undertaken by Minara Resources Ltd at its Murrin Murrin nickel project, with its demonstration heap leach plant operating since January 2007.

Minara is due to make a decision on whether to pursue a possible expansion of the heap leach pad area in the coming months.

Nickel hopefuls including GME Resources Ltd, Barra Resources Ltd, and Nickelore Ltd, have also flagged their intention to hold heap leach trials.

GME, which late last year signed an agreement with Norilsk to undertake a trial program at its Cawse mine, is expected to start construction of its heap leach program in March 2008 at a capital cost of $3.3 million.

GME managing director Jamie Sullivan said results from column test work showed that the ore responded favourably to heap leaching, supporting its claim that the process was the most viable option for the company to explore.

Mr Sullivan said results from the Murrin Murrin project to date were encouraging for the company, with GME sharing about 40 per cent of the Murrin Resource.

“The Murrin laterites are very unique,” he said. “We believe that if they can successfully heap leach their ore then we can do the same.”

GME expects to commence its leach cycle by June.