Photon Assay: A New, Revolutionary Technique Everybody Wants to See Succeed – An Independent Evaluation Part 1: Experimental Bias Detection and Synthetic Sample Simulations
DOI: 10.62178/sst.005.004
Abstract
Photon Assay (CPA), a gamma-ray excitation technique marketed by Chrysos for rapid, non-destructive gold determination on ~450 g samples, has attracted strong interest in the mining industry for its speed and grade-control potential. Early, anonymous reports and comparative tests at nine anonymous gold deposits suggested systematic biases: crushed-material CPA readings were frequently lower than paired pulverized readings and diff ered from fi re assays to extinction by 4–8%, though experimental designs were not always optimal. To isolate eff ects attributable to sample preparation, controlled synthetic samples were prepared by spiking barren rock with ≥99.99% pure gold fragments of known mass and size. Four combinations of coarse/fine gold and coarse/fine barren matrix were tested under the standard PAAU02 service, with ten replicate analyses per jar. Student’s t-tests (95% confi dence) revealed statistically significant negative biases in three of the four cases, except for fine gold in a finely pulverized matrix. Coarse-gold samples also showed unexpectedly higher measurement variance, consistent with positional redistribution within the jar. These findings confirm the importance of full pulverization prior to CPA and demonstrate the need for rigorous, site-specific validation before adoption. Further mechanistic studies are recommended.
Published in Issue 5 · June 2026
Citing this article
François-Bongarçon, D. & Oliver, R. (2026). Photon Assay: A New, Revolutionary Technique Everybody Wants to See Succeed – An Independent Evaluation Part 1: Experimental Bias Detection and Synthetic Sample Simulations. Sampling Science & Technology, June 2026(5), 59-63. https://doi.org/10.62178/sst.005.004
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