PhotonAssay™ vs fire assay at low grades | Hamish Blakemore, Manager, Geology at Macraes Gold Mine
Hamish Blakemore, Manager of Geology at OceanaGold’s Macraes mine, on what changed when they moved away from fire assay: fewer steps from a 40 kg drill sample to a 500g assay aliquot means more reliable data, better precision at low grades, and enough confidence from PhotonAssay™ to change the way they mine. Macraes runs a cut-off grade of between 0.2 and 0.3 g/t. When they compared assay results from the mill tails grade at the extra-low end of 0.1g/t, the difference between fire assay and PhotonAssay™ was about 10% – which got their attention!
