Isabel laterite nickel project

The Isabel laterite nickel deposits are located on Santa Isabel and San Jorge Islands in the Solomon Islands. These typical tropical nickel and cobalt laterite deposits were first explored and defined by International Nickel Company Limited (INCO) from 1957 until 1975.

INCO outlined two deposits, reporting conservative reserves with less than 30% Iron (Fe) of 13.5 Mt with weighted average grades of 1.39% nickel (Ni), 0.058% Cobalt (Co) and 27.3% Fe.

The extensive work performed by INCO included grid based sampling as follows:

Pitting                                   4409
Gemco power auger                1484
Hand auger                             394
Banks drill                               121
Wankie diamond core                 43

In addition to this work, detailed INCO archival records show feasibility studies and bulk sampling was also undertaken with an intention to proceed to mine development. Mining did not proceed as customary landowner access and title matters could not be successfully resolved.

Between 1993 and 1995 Kaiser Engineering (now Hatch Limited) undertook a validation program, excavating 34 pits to compare analytical results with 43 INCO pits. Kaiser classified the laterite deposits into high Fe Limonite and low Fe Saprolite separated by a narrow transition zone up to a metre thick. reserve/resource guidelines.

 

 

 

They also reported that less than 10% of the deposits had any overburden cover at Ni equivalent grades of 0.9% nickel equivalent (NiE) and that a reduction of NiE from 1.4% to 1.25% increased resources threefold. In conclusion, the deposits had a combined resource of approximately 159 Mt containing 1.045% Ni, 0.088% Co and +40% Fe as per 1995 AusIMM.

This resource calculation was considered conservative as the total thickness of the Saprolite zone of the deposit had not been sampled due to limitations of the equipment used and large areas of Limonite were not sampled at all as access was not possible for either INCO or Kaiser. Kaiser pits averaged 5.2 m in depth and they commented “most of the pits failed to penetrate the entire laterite profile…” and “any future work will require a larger excavator and other equipment”. It is important that the full thickness of the Saprolite is tested as this zone contains the highest concentrations of Ni in tropical laterite deposits.

As well as the site work Kaiser also undertook metallurgical studies and mine and financial modelling. It concluded that “…economic analysis, the operation breaks-even at nickel and cobalt prices of $1.50 and $6.00 per pound, respectively.” The scoping study was based on pressure leaching of the laterite on site. Although there have been appreciable cost and metal price changes since 1995 the project today looks very robust economically.
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