Preparation and Certification of Nickel Ore and Nickel Concentrate Reference Materials

The only available nickel ore reference material in China, which has a Ni content of 4.33%, is currently out of stock. Therefore, three nickel ore reference materials (GNi-1, GNi-2 and GNi-3) and two nickel concentrate reference materials (GNi-4 and GNi-5) have been developed and are described in this paper. The samples of nickel ore and nickel concentrate were collected from the Hongqiling Nickel deposit in Jilin province. The samples were crushed and sieved to less than 20 mesh and ground for 48 hours in a high alumina ball mill, which was filled with Ar gas in order to avoid oxidization of the sulfide, until the particles were less than 0.074 mm. The samples are stored at temperatures below 8℃. The homogeneity was tested by WD-XRF and ICP-AES, and the relative standard deviation was less than 1.0%. The F-test result, which was less than the threshold value, showed that all five samples were homogeneous. Good stability was verified by repeating the analysis four times within two years without any changes. Nineteen laboratories were involved in the inter-laboratory programme and provided 2002 values for 23 oxides and elements. Classical chemical methods such as Spectrophotometry, Volumetry and Gravimetric Analysis, were taken as the dominant methods in the determination of Ni, Cu and major oxides (SiO₂, S, and Al₂O₃ etc). Minor and trace elements were determined by ICP-AES, ICP-MS and AAS. The estimation of certified values and uncertainty conform to ISO guide 35 and Technical Norms of Primary Reference Materials. 23 components of nickel ore were characterised as certified values. Ni concentrations for GNi-1, GNi-2 and GNi-3 were 0.11%, 0.33% and 1.02%, respectively. 19 components of nickel concentrates were characterized as certified values, 4 components were taken as reference values. Ni concentrations for GNi-4 and GNi-5 were 5.93% and 9.01%. The Ni concentrations which were selected from cut-off grade to industrial grade, have a good range and meet the requirements as the reference materials for nickel exploration and metallurgy.