Ore grade analyses

To obtain the best quality and cost-efficiency in a particular geological project it is important to decide the strategy of analysis by selecting the appropriate analytical methods (element suit, digestion / pretreatment method, detection limits, optimum measurement area etc.) to fit the objectives of the project. Selecting a wrong method may end up in attaining optimised results in wrong concentration levels and introducing problems in laboratory (contamination, additional sample dilutions) which may deteriorate accuracy and precision.

Method 510P is an economic choice when only ore forming base elements are of importance. The method is suitable for mineralised samples with moderate grades. There are limitations in the solubility of Ag and Pb at high concentrations, and samples expected to contain more than 5 % of sulphur should be analysed for sulphur using an alternative method (e.g. by combustion technique, S-analyser, Method 810L; look for Individual analyses).

Refractory ore minerals (e.g. chromite, magnetite, ilmenite, columbite, cassiterite etc.), high-grade base metal ores (e.g. Ni ores) and concentrates can also be analysed using alkaline peroxide fusion and multi-element analysis by ICP-OES (720P) or XRF-analysis (179X). Method 720P can be upgraded with ICP-MS-analysis to include a large set of elements (720PM).

When high quality assays of base metals is required more representative subsamples and traditional high-precision procedures either by ICP-OES (514P) as a multi-element package or by FAAS (514A) using single element methods can be used.

For analysis of sulphidic Ni, Cu and Co Labtium recommends methods 240P and 250P. When low grade Ni ores are studied the traditional assay methods using total methods would give misleading information because of the varying amount of silicate -Ni.