Agrimin Ltd.'s JORC 2012-compliant drainable mineral resource for its MacKay project in Western Australia swelled 470% to 123.4 million tonnes of sulfate of potash, or SOP.

The drainable porosity, or specific yield, resource estimate includes 23.5 Mt in the measured and indicated category, and 99.9 Mt in the inferred category.

The in-situ mineral resource, based on total porosity, now stands at about 1.10 billion tonnes of SOP, confirming Lake Mackay as Australia's largest SOP deposit, the company said Jan. 20.

Agrimin appointed Stantec Consulting Services Inc. to update the mineral resource. Stantec will also complete an ore reserve estimate, scheduled for the first quarter, and a definitive feasibility study on the project, scheduled for the second quarter.

The company reached a deal with Newhaul Pty. Ltd. in December 2019 to form a 50/50 joint venture for the road haulage and maintenance services for the Mackay project.

A May 2018 pre-feasibility study for the project estimated a posttax net present value, discounted at 8%, of US$453 million, an internal rate of return of 20% and a 4.2-year payback period.

The study was based on a potash price of US$555 per tonne, with a specific yield resource estimate of 26.1 million tonnes of potash and a total porosity resource estimate of 264.4 million tonnes of potash.