Advantages and challenges of integrated automated mineralogy (TIMA X-analyser, TESCAN) during Ni/Co laterite ore characterization: an example from Wingellina deposit (Western Australia).

The success of the exploitation strategy for Ni/Co laterite deposits is strictly dependent on the accuracy of chemical, mineralogical and textural characterization of the ores, which can be quite challenging for these types of deposits. In this study we present an accurate characterization and a quantitative evaluation of 4 samples from “limonite” and “smectite” zones of the Wingellina laterite deposit (Western Australia) [1,2]. The analyses were carried out by the combination of routine analytical methods (XRPD, SEM-EDS, ICP-MS/AES) and integrated automated mineralogy methods (TIMA-X analyser, TESCAN) with the aim of investigating the effectiveness of these methods in assessing the nature of amorphous material in the ore zones, quantify the Ni- and Co-bearing Mn-(hydr)oxides. In addition the Ni-Co element deportment is also reported. The final results obtained by the different methods were then compared for validation. Goethite and Mn-hydroxides + amorphous phases were the main phases in the Limonite samples which amount respectively to ~80 wt % and ~40 wt %. TIMA analyses were able to re-classify the amount of the amorphous as both goethite and mixture of lithiophorite-asbolane or only asbolane hosting the majority of Ni and Co. Smectite samples shows remarkable amounts of amorphous phases, which corresponds to smectite (….), with subordinate goethite (…) and trace amounts of lithiophorite (…). Even though the smectite host high Ni …..) we underline that even though in low percentages, Mn-(hydr)oxides contain significant amounts of Ni (….) and more than 70% of Co. Another interesting outcome is that part of Co in both zones, deports in mixed classes (i.e. montmorillonite-asbolane-goethite and asbolane-goethite), which correspond to fine minerals intergrowth that have not been distinguished by TIMA. On the light of the above reported we conclude that the main advantages of Automated analyses on Ni/Co laterite deposits of Wingellina are: i) identification and classification of complex ore-bearing Mn-(hydr)oxides on the basis of their chemistry; this can be useful information during the processing methods as the leaching behaviour of Al-bearing Mn-hydroxides (i.e.lithiophorite) during High Pressure Acid Leaching (HPAL) can promote the formation of alunite which is detrimental for Ni-Co recovery [3]. ii) Elements assays and deportment, which help to predict the recovery during the feasibility studies. The main limitation can be ascribed the fine-grained texture of Ni-Co laterites which can the classification due the production of mixed X-ray spectra because of the beam excitation size as discussed by previous authors [4].