Photon Assay: A New, Revolutionary Technique Everybody Wants to See Succeed – An Independent Evaluation Part 2: The Effect of Positional Heterogeneity on Gold Determinations Using PhotonAssay
DOI: 10.62178/sst.005.005
Abstract
PhotonAssay™ employs gamma activation analysis to provide rapid, non-destructive determination of gold in large (typically 400–650 g) samples. While the larger sample sizes are presumed to offer significant advantages for heterogeneous, coarse-gold bearing materials compared with traditional fire assay, the reported gold grades may be influenced by uneven spatial distribution of gold particles within the jar. This study investigates the effect of positional heterogeneity i.e. the uneven weighting of different regions within the PhotonAssay jar, on gold determinations. Low- and medium-resolution maps of instrument response were generated by placing single, accurately weighed gold fragments at precisely controlled locations within filled jars and performing multiple replicate assays. Results reveal differences in weighting: the geometric center of the jar receives the highest response, while regions near the sides and, to a lesser extent, the top and bottom are under-weighted. These findings are consistent with non-uniform irradiation as the dominant source of the observed biases, with gamma-ray attenuation and detection geometry appearing less influential. The positional weighting introduces a previously under-appreciated source of grouping and segregation error, even after the final assay charge has been prepared. This has important implications for assaying coarse-gold ores, where dense gold particles can segregate during handling and jar filling. The results suggest that PhotonAssay protocols may be vulnerable to biases in certain coarse-gold systems.
Published in Issue 5 · June 2026
Citing this article
Oliver, R. & François-Bongarçon, D. (2026). Photon Assay: A New, Revolutionary Technique Everybody Wants to See Succeed – An Independent Evaluation Part 2: The Effect of Positional Heterogeneity on Gold Determinations Using PhotonAssay. Sampling Science & Technology, June 2026(5), 64-72. https://doi.org/10.62178/sst.005.005
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