Characterization of low crystalline Ni host minerals in Ni laterite ores

Abstract

Ni laterite deposits are formed by chemical weathering of ultramafic rocks in tropical to sub-tropical climates. The identification of Ni host minerals is challenging due to the formation of amorphous weathering products from complex weathering processes. In this study, we applied sequential extraction, SEM, and Raman spectroscopic analysis to determine the Ni host minerals in the ores. The sequential extraction results reveal that silicate minerals such as serpentine and smectite are the main hosts of Ni. However, Ni was also extracted from the iron oxide and organic matter phases, even though the sample had negligible organic matter content. We inferred the dissolved minerals from the chemical composition of the solution extracted from the organic phase, SEM, and Raman spectroscopic analysis. The results indicate that the Ni extracted from the organic phase originates from smectite with low crystallinity and far from the ideal chemical composition. Therefore, in addition to silicate minerals such as serpentinite and smectite, iron oxides and low-crystalline smectite may also enrich Ni.