The Ramu deposit is a typical laterite nickel and cobalt deposit formed by weathering and leaching of the original ultramafic intrusive rocks, mostly dunite with small amount of harzburgite and pyroxenite in a tropical climate with large amounts of rainwater, saturated with atmospheric carbon dioxide, and a local monsoonal rainfall pattern. When the ultramafic rocks are subject to strong weathering, olivine, augite and other ferromagnesian silicate minerals rich in nickel, cobalt and other elements will decompose; the released SiO2 is progressively removed by ground and/or surface water in the form of colloid or siliceous acid, and the ferrous iron is oxidised to ferric iron and converted into hydroxides and oxides, such as lepidocrocite, goethite and hydrohematite, and left in situ. Nickel, cobalt and other elements are absorbed by the clays in the saprolite, or directly precipitated from the colloidal solution, or enriched in secondary nickel silicate minerals, consequently forming a lateritic nickel-cobalt deposit within the weathering crust. At Ramu, nickel and cobalt have been enriched from a background of around 0.3% Ni and 0.01% Co in the ultramafic bedrock up to grades averaging 0.9% Ni and 0.1% Co in the laterite profile.

The Ramu laterite nickel and cobalt deposit occurs in the weathering crust of ultramafic intrusive rocks, mostly dunite. The deposit above the dunite bedrock is divided into six laterite layers, from top to bottom, the humic layer (Q), t ........

The Kurumbukari (KBK) owner-mining operation utilizes conventional open-pit mining methods. MCC carries out all mining operations with a fleet of excavators and trucks along with other ancillary equipment to support the mining fleet. After an initial trial period, hydro- sluicing, using hydraulic water jets, was introduced in 2016 as a second form of extraction where the geometry was suitable; hydro-sluicing has accounted for around 30% of production since its introduction.

The hydraulic water jets dislodge and transport fine material from the mining face, down an inclined drainage channel to a collection point, where it is pumped directly to the wash plant for transfer to the beneficiation plant.

After the initial logging of the trees by specialised teams, the humus/topsoil and overburden are generally removed by bulldozers; excavator and truck haulage are used if the quantities are significant. The topsoil is temporarily stockpiled on the mining area, and then excavated and hauled to the mining area boundary and stockpiled for later mining rehabilitation reclaim. Overburden is excavated with small-scale excavators and hauled in articulated sixwheel dump trucks. Overburden is either placed directly into pit voids, backfilling the old mining areas in preparation for mining rehabilitation, or stockpiled at the mining area boundaries for later reclaim.

Limonite, saprolite, and rocky saprolite ore are excavated and hauled to either one of the ........

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