The targeted deposit type for all projects is tropical (wet) lateritic nickel and cobalt. Particular emphasis is placed on the definition of reasonable thicknesses (i.e. >4m) of (garnieritic) saprolite.

This style of mineralisation is best developed in areas of moderate topographic gradient over olivine-rich ultramafic cumulates; particularly in areas of relatively higher bedrock fracture density.

Vertical zonation within nickeliferous laterite is distinct, with nickel content generally increasing with depth. Garnierite, the principal saprolite nickel host mineral, is a variety of serpentine, a silicate mineral developed below base of total oxidation in the weathering profile. Overprinted on the saprolite is an iron oxide zone of massive, microscopic scale goethite (limonite) needles termed “ferralite”. This zone is characterized by higher iron and manganese and lower magnesium content than the saprolite (garnierite) horizon. The presence of higher proportions of manganese oxides (“asbolite”) can frequently result in bonanza grades of cobalt (up to 3% locally), which readily incorporates into the asbolite crystal structure. Nickel content is generally lower than in the saprolite.

Geology:
- The nickeliferous laterite deposit at Rio Tuba was formed by the in-situ weathering of the ultramafic rocks. High moisture content and the occurrence of boulders and hard saprolite that hold 2% and above nickel are its outstanding characteristics (Hirai, et al., 1987);
- Practically, there is no active fault in Palawan, and there is no threat from faulting or fault ruptures, and local earthquakes;
- The steep slopes in the project site are occasionally affected by landslides while the rivers are flooded during the seasonal monsoon and typhoons, although debris flows have not been documented; and
- No active tectonic features are present on this region. No active faults and volcanoes are found in the region. Very rare occurrence of earthquakes is observed in Palawan, and these have magnitudes of only 5 or lower.

The Rio Tuba mine site is located in Barangay Rio Tuba, municipality of Bataraza, in the southern tip of the province of Palawan. RTNMC exports saprolite and limonite ore, and provides limonite ore and non-mining services to the adjacent Coral Bay HPAL plant.

As one of the biggest nickel open pit mining sites in the Philippines, it has become Rio Tuba’s mission and goal to provide top quality end products to two of their biggest client countries which are China and Japan. After nickel is mined from an open pit, it goes through several phases of operation namely Saprolite Operation, Limonite Operation, and lastly, Gotok Limestone Operation. The company boasts of 5,200 hectares worth of mine sites but has only touched approximately 658.39 hectares of land for the past 35 years.

Nickel Asia Corp is also the exclusive supplier of limonite ore from its Rio Tuba mine to the Coral Bay plant, the country’s first hydrometallurgical nickel processing plant owned by Coral Bay Nickel Corporation (CBNC), where NAC has a 10% equity interest.