Pilot Gold Inc. is pleased to report additional metallurgical results designed to test the amenability of gold mineralization hosted in the Dunderberg (Candland) Shale at the Kinsley Mountain property to produce a saleable concentrate.
The Dunderberg Shale was the primary host rock in the historical mining operation, and is the shallow host rock at the Western Flank. Previous concentrate testing of deeper Secret Canyon Shale-hosted gold mineralization produced up to 89.6% recovery and up to 312 g/t concentrate grade in metallurgical testing (see press release of January 19, 2015).
Matt Lennox-King, Pilot Gold's President & CEO commented, "These recent metallurgical test results demonstrate that, combined, Kinsley's main host rocks can produce a high-grade concentrate with excellent gold recoveries and the potential of low capital cost options for possible mining and processing at Kinsley."
The test work, initiated in March 2015, used the same flowsheet developed for mineralization hosted in the Secret Canyon Shale.
||Overall Au Recovery (%)
||Concentrate Grade (g/t)
||Calculated Feed Grade (g/t)
Overall, these results indicate that the Dunderberg Shale material, like that from the Secret Canyon Shale, may be amenable to production of a concentrate. The results may be improved with further study of primary and regrind sizes and flowsheet refinements particular to the Dunderberg shale.
Flotation testing of Dunderberg Shale-hosted mineralization was undertaken after analyses revealed a relatively coarse grain size for gold-bearing pyrites, relatively low sulfide sulfur concentrations and high gold to sulfide sulfur ratios (ranging from 2.3 to 2.6) when compared to typical Carlin-style sediment-hosted gold deposits. These data suggested that the mineralized material may be amenable to producing a concentrate of sufficient grade to support low cost on-site or off-site treatment, over more expensive whole ore treatment options such as roasting or autoclaving.
Two composites with calculated feed grades of 4.72 and 2.37 g/t gold were selected. The scope of work was intended to provide a preliminary determination as to how the two composites would respond to the flowsheet developed previously for Western Flank Secret Canyon Shale-hosted gold mineralization (see press release of January 19, 2015). In the current study, samples were subjected to rougher and scavenger flotation testing over a range of conditions including variations in grind size, followed by cyanidation of the flotation tails. Combined concentrate recoveries ranged from a low of 76% to a high of 89.6%. Combined with cyanidation of the flotation tails, the total recovery increased to 89.0% to 95.0%. The concentrate grades ranged from a low of 98.6 g/t gold to a high of 312 g/t gold, with gold recovery to concentrate highest in the higher-grade and less oxidized samples.
The two composites from Dunderberg Shale-hosted gold mineralization returned concentrate grades of 52.3 and 42.0 g/t gold, corresponding to overall recoveries of 83.0 and 82.6%, respectively. The mineralized material was not oxidized, and no benefit was realized from cyanide leaching of the tails. However, cyanide leach testing of tails would likely result in recovery of additional gold from partially oxidized material.
Concentrates were assayed for deleterious elements and were found to contain arsenic and antimony. Arsenic in the concentrate tested ranged from 0.95% to 3.66% and averaged 2.35% while antimony in the concentrate tested ranged from 0.042% to 0.069% and averaged 0.058%. While arsenic and antimony are somewhat elevated, it is believed the levels would not preclude direct sale to a typical Nevada refractory ore processing facility.