Company president and CEO Chris Bradbrook said the commissioning, which commenced July 9, comes after a steady increase in recoveries it has achieved since taking over the operations in October 2016.

Specifically, between that point and the June quarter of 2018, he noted, recoveries rose from 76% to an average of up to 90%.

"The incorporation of the gravity circuit, which only required a modest capital investment of $1.7 million, is expected to allow us to increase recoveries even further," he said.

The 100% company-owned Plutonic operation north of Perth, which includes both surface and underground components, has produced more than 5.5 million ounces since 1990.

It is considered one of the largest gold mines in Western Australia in terms of cumulative production.