West Cache PEA Favours Toll Milling at a Nearby Gravity-CIP Plant, With Gravity Recovering a Third of the Gold

Galleon Gold's January 2022 preliminary economic assessment for the West Cache gold property near Timmins, Ontario, compares an on-site gravity-flotation-leach plant with two regional toll mills and prefers the closer one.

The Updated Mineral Resource Estimate and Preliminary Economic Assessment of the West Cache Gold Property, Bristol and Ogden Townships, Porcupine Mining Division, Timmins, Ontario, was prepared for Galleon Gold Corp. with an effective date of January 10, 2022. Based on the metallurgical testwork in Section 13 of the report, two process flowsheets could be considered. Both include crushing and grinding to a P80 of about 60 µm, with the daily rate depending on the processing option chosen.

Critical Data

Overview

The testwork found that gravity concentration of free gold after primary grinding, using centrifugal concentrators followed by tabling, is an important feature for West Cache material. It produces a high-grade concentrate holding about a third of the gold, suitable for direct smelting. Cyanidation recovered more gold after gravity separation than without it. Leaching gravity tails ground to P80 53 µm under mild conditions gave 95 to 97% extraction with moderately low reagent use. Leaching whole ore without gravity gave 83 to 94% at a coarse grind and 90 to 97% at a fine grind. A flowsheet combining gravity, flotation of a gold-sulphide concentrate and cyanidation of the reground concentrate averaged about 97% recovery, regardless of feed grade.

Key Process Stages

Option 1: dedicated on-site plant. A processing plant and tailings facility could be built at the mine. The report says the preferred flowsheet here may be gravity, flotation and leaching of the flotation concentrate. The flotation tailings would be cyanide-free and could be used for mine backfill without the intensive cyanide and cyanate destruction that leached tailings need.

Option 2: toll processing. Two regional plants could treat the ore.

• Option A is a 4,500 t/d plant 25 km from West Cache, with surface ROM blending, crushing, grinding, gravity concentration, cyanide leaching and CIP. It recently treated feed at 2.66 g/t Au with 96.9% recovery, and it destroys cyanide in leach tailings in tanks from its former flotation circuit.
• Option B is a 2,000 t/d plant 60 km away, with blending, crushing, grinding, cyanide leaching and CIP. It recently treated 3.2 g/t Au with 97% recovery and has run on a seven-days-on, seven-days-off schedule.

Selection. Assuming 2,400 t/d of West Cache ore is toll milled, and part of the treated leach tailings is pressure filtered and back-hauled for mine backfill, the report finds Option A more attractive. It is the closer plant, and its gravity circuit is a further reason to choose it.

Additional Interesting Data and Summary

The report also suggests ore sorting at the mine as a way to improve toll milling. Typically a size fraction of run-of-mine ore, for example −75 +10 mm, is screened out and sorted to reject waste, which can remove about 25 to 30% of plant feed and raise the grade shipped by 20 to 25%. X-ray transmission (XRT) sensing would not need the screened fraction to be washed. Sorting was not tested in the 2021 program. Because about three quarters of the gold is associated with sulphides and the deportment of the free gold is unknown, the report recommends mineralogical tests (about $14,000) and a sorting test on 100 to 200 kg of coarse core (about $25,000).

With toll processing, there will be no process plant or tailings facility at the property. The site will have four portals, a central backfill plant, a connection to the Ontario Hydro grid along Highway 101, and no camp. The city of Timmins is 13 km to the northeast.

In summary, the 2022 West Cache PEA shows the ore responds well to gravity and cyanidation, at about 97% recovery, and favours trucking 2,400 t/d to a gravity-CIP toll mill 25 km away rather than building a plant.

Key Processes

• Crushing and grinding to P80 about 60 µm
• Gravity concentration by centrifugal concentrators and tabling
• Cyanide leaching of gravity tails
• Alternative: gold-sulphide flotation with cyanidation of reground concentrate
• Toll milling with CIP gold recovery
• Possible XRT ore sorting at the mine

Source: Updated Mineral Resource Estimate and Preliminary Economic Assessment of the West Cache Gold Property, Timmins, Ontario, for Galleon Gold Corp., effective date January 10, 2022.