Garnierite is not a single mineral but a mixture of the Ni-Mg-hydrosilicates serpentine, talc, sepiolite. These minerals occur in garnierite ores individually and in intimate mixtures. The lateritization of ultramafic rocks gives rise to a strong dissolution and removal of magnesium and silicium which leads to a strong residual concentration of iron and nickel in a goethite-rich surface layer (nickel limonite ore). A portion of the nickel is leached downwards and finally fixed in the underlying decomposed ultramafic rock. This process gives rise on the one hand to a moderate nickel increase of the total decomposed rock (nickel silicate, nickel saprolite); on the other hand relatively small amounts of nickel-rich garnierite ore are precipitated in hollow spaces.