Nickel laterite deposits in the Sorowako and Petea area are generally classified into two main types, West Block and East Block types, depending upon the nature of bedrock, the level of serpentinisation, ease of mining, size of boulders, degree of fracturing of the bedrock, optimum screen fraction that carries nickel grades, and the silica-to-magnesia ratios in the mineralisation.

West Block type deposits
These deposits are developed over a relatively unserpentinised peridotite bedrock; commercially mineable grades are confined to the -1" fines fraction; and silica to magnesia ratios are high (2.2 to 2.6 range).

West Block type deposits are categorized into Types 1, 2 and 3, depending on the degree of fracturing in the bedrock and the size of the resulting boulders. Type 1 deposits are the most difficult to mine due to weak fracturing of the bedrock and the resulting large size of the boulders. Type 2 and Type 3 deposits are successively easier to mine and are formed over more fractured bedrock resulting in boulders within the mineralisation profile that mining equipment can handle.

Optimum nickel grades in all West Block type deposits are confined to -1" screen fraction. Oversize is generally barren or very low grade. Exceptions exist in breccia mineralisation where siliceous garnierite carries respectable grades in the +1" fraction.

East Block type and Petea deposits.
These deposits are developed over bedrock that ........

The surface mining is not traditional pit mining but more an “open cast” system by truck and shovel where contour side cuts are made into a hill. Anywhere from eight to ten hills are actively mined to provide ROM that meets the quality specifications (ore chemistry) of feed for the nickel processing plant.

The processing plant in Sorowako has three furnace dryers, five oil-fired reduction kilns, four electric furnaces and three Pierce-Smith converters.

The pyrometallurgy nickel processing involves in initial mineralisation drying process, followed by reduction, smelting and converting to produce the final dried product.

Drying - Wet mineralisation from the Wet Ore Stockpile is fed to three rotary kiln dryers. This process partially dries the feed mineralisation from a moisture content of 30 to 40% to produce the Dryer Kiln Product , with a reduced moisture content of 19 to 21%. East and West type mineralisation are separately screened to produce -1” the Dryer Kiln Product, with the product of each type mineralisation placed in separate piles in Dried Ore Storage buildings.

Reduction - From the Dried Ore Storage, mineralisation is fed to the counter-current fired reduction kiln. A blend of East and West type mineralisation is used. The reduction kiln com ........