In any situation where visible gold (VG) is noted in core, only a sample size of considerable weight can provide a "reasonable" estimate of the grade to be expected from mining. The size of the bulk sample necessary can be estimated by a combination of the grain size distribution of the native gold particles and the statistical distribution of the gold assays from the core. There are numerous papers which one can review for the analytical process.

Whatever, the larger the bulk sample, the better the accuracy and precision of grades to be expected as this is the next best thing to actually mining the ore.

Hope this helps. I have personally been through this exercise several times.

Best regards

geoprof