EnviroGold Global Limited reported successful completion of its pilot plant test work campaign for the Hellyer tailings reprocessing project in Tasmania. Hellyer is a joint effort between EnviroGold Global and Hellyer Metals.

According to a press release issued by EnviroGold, the pilot plant test results confirmed excellent liberation of critical and precious metals using its proprietary hydrometallurgical process.

Testing, said the company, was conducted at the ALS Laboratory in Perth, Western Australia, and involved processing roughly 500 kg of Hellyer tailings. The pilot plant results confirmed earlier bench-scale findings for gold and silver recoveries from a cyanide leach on process solids, and generated a pregnant leach liquor suitable for the recovery of critical metals via conventional solvent extraction (SX) or ion exchange (IX).

The head grade from the 500 kg of Hellyer tailings processed in the pilot plant averaged 2.59 g/mt gold, 59 g/mt silver, 0.11% copper, and 0.84% zinc. Data analysis showed the average gold and silver recoveries were both 90+% and were achieved on a cyanide leach feed material using Leachwell Accelerated cyanide leach techniques. In addition, 91% of the copper and 82% of the zinc contained within the tailings reported to the pregnant leach solution, where it is available for conventional SX and IX recovery.

EnviroGold said preliminary process control data on its proprietary hydrometallurgical process indicated that reactions lasting about one hour at atmospheric pressure and at temperatures of <90°C can be run continuously and can be easily controlled.