A preliminary economic assessment on the US Grant mine within Transatlantic Mining Corp.'s Alder Mountain gold property in Montana generated an after-tax net present value of US$6.9 million and an internal rate of return of 278%, with a payback period of 1.4 years.

The 3.6 year life-of-mine has estimated total capital costs of US$8.8 million, while life-of-mine operating costs are expected to come in at US$18.2 million, according to a Dec. 12 release.

All-in sustaining costs, meanwhile, are estimated at US$905 per gold equivalent ounce.

The study was based on a maiden mineral resource estimate of 53,800 gold equivalent ounces.

Given that the U.S. Grant mine has only seen a limited amount of exploration, the company said it plans to drill test an exploration target of approximately 500,000 gold equivalent ounces.