Preconcentration strategies in the processing of nickel laterite ores Part 5: Effect of mineralogy

Nickel (Ni) laterites are characterised by low Ni grades, complex mineralogy and high moisture contents which have significant technical and economic impacts on their processing. These limitations can be reduced by the choice of appropriate preconcentration strategies leading to the production of a material with more favourable characteristics (e.g. higher grade of values, more easily treated material) being sent to the metal recovery process. Underpinning all this is the critical importance of a detailed knowledge of the mineralogy of the material to be processed. In this paper, various techniques have been described which can interrogate the mineralogy and associated chemistry of these ores, leading to a better understanding which can be used to determine the optimum preconcentration flowsheet for processing the material. Examples have been given for various scales of operations including commercial operating plants, pilot plants and laboratory investigations. Detailed mineralogy and examples have been given concerning several Western Australian Ni laterite ores that have been processed commercially, the Falcondo Mine in the Dominican Republic, and the complex, low Ni grade chromite overburden at Orissa, India. In all cases, the wide variation and complex mineralogy of these deposits compromises any simple upgrading processes, leading to complex and expensive flowsheets. It is the aim of this paper to review how detailed mineralogical and chemical knowledge of Ni laterite ores is essential in determining cost-effective methods for preconcentration of these ores prior to the recovery of metal values.