The study was based on annual throughput of 650,000 tonnes per annum from the Desert Scheelite open pit to produce around 1000 tonnes of scheelite concentrate per annum, as well as copper-silver and zinc-silver concentrates.

Capital costs were estimated at US$30-35 million, while the base case payback period was estimated at 36 months.

The scoping study returned pre-tax profit expectations of $125 million, under a base case scenario, up to $317 million for an enhanced case that includes improved recoveries, higher throughput to lower costs, and the potential inclusion of the Garnet open pit.

The higher grade Garnet deposit was excluded from the study as it has only an inferred resource, but could add 120,000tpa of feed and reduce the payback period to less than 18 months.

There are four deposits in total at Pilot Mountain.

Thor executive chairman Mick Billing said he was delighted with the results of the study.

"Closed circuit metallurgical testwork on Desert Scheelite ore has commenced which will, hopefully, upgrade the results of open circuit work previously conducted, which achieved 72% recovery of scheelite and saleable quality concentrates," he said.

"The Pilot Mountain project hosts four known deposits, and it is anticipated that each of these has potential to contribute further as we continue to explore their potential."

Tungsten has been classified as a "critical mineral" in the US.

"With no US domestic production, and tungsten classified by the US Department of the Interior as a critical mineral, our objective is to restart Unites States commercial mining and tungsten concentrate production after a significant break," Billings said.

Adelaide-based Thor also owns the advanced Molyhil tungsten project in the Northern Territory, where a definitive feasibility study was released last month for a seven-year mine costing around $43 million.

Thor also holds South Australian copper and US lithium interests, as well as a royalty over the Spring Hill gold project.

The company's Australian stock, which trades as CHESS depositary interests, was up by 3.2% this afternoon to A3.2c. Thor last traded at 2p on London's AIM.