Genesis of Nickel Laterite

Nickel deposits generally formed on ultramafic rocks containing high Fe in olivine and nickel-yield between 0.2% - 0.4% wt. The mineralogy of nickel laterite can be divided into three categories (Brand et al., 1998)

 a. Hydrous silicate DepositsProfiles of this type of vertical from bottom to top: Ore horizon in saprolite layer (Mg-Ni silicate), Nickel grade between 1.8% - 2.5%. In this zone developed box-works (what tuh ..), veining, relic structure, fracture and grain boundaries and can form mineral-rich Nickel; garnierite (max. 40% Ni). Ni dissolved (Leached) from the phase of limonite (Fe Oxyhydroxide) and deposited with hydrous silicate minerals or substitute elements of Mg in an altered serpentinite (Pelletier, 1996). So, although the nickel laterite is a product of weathering, but it can be said also that the supergene enrichment process is very important in the formation and economic value of hydrous silicate precipitated this. This type can be found in several places such as in New Caledonia, Indonesia, Philippines.Dominika and Columbia.

b. Silicate Clay Deposits
 In this sediment type, Si is only partially dissolved by the groundwater. The remaining will join with Fe, Ni, and Al to form clay minerals (clay minerals) such as Ni-rich Notronite in the middle of the saprolite profile (see profile). Ni-rich serpentine also can be replace by smectite or quartz if the profile of this deposit in a long time stay in contact with groundwater. Ni grade of these deposits is lower than Hydrosilicate deposit (1.2%; Brand et all, 1998).

c. Oxide Deposits
 The last type Oxide. Profile below shows Protolith of harzburgitic type peridotites (Mostly minerals olivine, serpentine, pyroxene), are very susceptible to weathering, especially in the tropics. Formed thereon is formed near surface saprolite and limonite and ferricrete (surface) (see profile). In this type of deposit oxide, nickel associated with Goethite (FeOOH) and Mn Oxide.
In addition, Nickel laterite is very rarely or not at all formed in carbonate rocks contain mineral talc.