Description
Garnierite is a nickel-rich hydrate silicate that forms in the saprolite zone of nickel laterite deposits. It often develops from the intense tropical weathering of ultramafic rocks such as peridotite and serpentine. In tropical climates, prolonged chemical weathering leaches magnesium and silica from the parent rock while concentrating nickel. During this process, nickel is incorporated into hydrated silicate minerals, forming green vein structures, fracture fillings, and massive aggregates collectively known as garnierite. Mineralogically, garnierite is not a single species, but a mixture of nickel-containing phyllosilicates, often including: nepouite, pimelite, nickel-rich varieties of serpentine, or talc. Typical characteristics include:
Color: pale to bright apple green; Texture: earthy, waxy, or vein-filling masses; Hardness: generally soft (Mohs 2–4);
Nickel content: usually 1–6% Ni, but can be higher in enriched veins. Garnierite is most commonly found in nickel-laterite deposits, which develop in humid tropical regions where ultramafic rocks are exposed at the surface. One of the important geological provinces where such deposits occur is Sulawesi, which harbors extensive lateritic nickel systems that supply a significant portion of global nickel reserves. In the laterite profile, garnierite typically occurs within the saprolite layer, beneath the limonite layer, and above relatively unaltered ultramafic rock. Its presence often indicates zones of nickel enrichment within the weathering profile and can be associated with economically significant nickel ore.
