Streamlined Atomic Absorption Procedures for Copper Exploration and Mining†

Abstract

Assessment of copper ores requires the establishment of both the total copper (TCu) content and the mode of occurrence of the copper, e.g., as oxide or sulfide minerals. In establishing the latter, cyanide soluble copper (CNCu) and acid soluble copper (ASCu) determinations are important. This paper describes flame atomic absorption procedures for determining TCu (and, in the same solution, ‘partial iron’) with 500 mg subsamples (>85% minus 200 mesh) and CNCu and ASCu with 250 mg subsamples. Extractions are performed in sealed, vertically secured, 50 ml polypropylene tubes at room temperature with (i) for TCu, a mixture of 3 ml of HCl and 2 ml of 1 + 1 HNO₃, (ii) for CNCu, 10 ml of 2% m/v NaCN–0.1% m/v NaOH and (iii) for ASCu, 10 ml of 1 + 19 H₂SO₄. QA/QC measures are described. AAS calibration solutions were prepared by mass. The 3s limits of detection were 0.004% TCu, 0.009% CNCu and 0.002% ASCu. For the TCu procedure, the within-laboratory between-batch RSD was <3% for samples containing between 0.15 and 4.40% TCu. The TCu procedure was used to determine splitting and subsampling components of typical copper ore sampling variance; it has yet to be used to determine the variance of sampling particular portions of a copper orebody in situ. The results obtained by these procedures agree well with those obtained by commercial laboratories using their own procedures.