Twenty-five White Channel gravel samples were processed in order to estimate the gold content. Selected samples were used to determine the viability of gold extraction by heap leaching.
Gold levels ranged from <0.03 to 0.33 g/t, and averaged 0.08 g/t. Pre-concentration of the gold by screening at 4 mesh was successful in upgrading gold levels by an average of 2.4 times, without gold loss. The average grade of the -4 mesh product was 0.19 g/t Au.
Use of gravity concentration principally as an analytical method (i.e., to upgrade gold for more reliable analysis) and, secondly, as a potential processing method, was not successful as only three samples yielded high gold recoveries.
Metallurgical evaluation of selected samples was completed. Bottle rolls and column tests with cyanide yielded maximum gold extractions of greater than 65%. Cyanide consumptions were less than 1.2 kg/t of leach feed. More testwork is required to confirm extractions and to further develop agglomeration procedures.
Sampling was a problem due to the low grade of the material and the discrete nature of the gold particles, which may result in the heterogenous segregation of the gold during the sampling and assay procedures. These effects are more commonly known as the "nugget" effect. A more suitable method of assaying the feed would be to leach the material with cyanide, and calculate a head assay from the leach products.
