Minister for Mineral Resources and Energy Tom Koutsantonis joined Weatherill at the site, around 550km north of Adelaide.

The mine, which started production in April, is a 75:25 joint venture between Quasar Resources and Alliance Resources.

"This is one of the most substantial uranium discoveries anywhere in the world in the past 25 years," Weatherill said.

"Following on from the successful mining method of the nearby Beverley and Beverley North deposits, the new Four Mile mine represents another important chapter in continuing uranium mining in this world-class region.

"The project has already involved a private sector investment of more than $A120 million and demonstrates the strength of the South Australian mineral resources and energy sector."

Four Mile is slated to produce 1.6 million pounds of uranium oxide this year with processing occurring through Beverley, which is owned by Quasar affiliate Heathgate Resources.

First sales are expected to begin next month, though the partners have flagged total costs of $40.13 per pound of uranium oxide until December 2014.

It compares to the current spot price of $US28.38/lb ($A30.17/lb).

The Four Mile East and Four Mile West deposits hold a combined resource of 71Mlb uranium oxide.

Earlier this month, Alliance appointed Deloitte Corporate Finance to lead a global marketing process for the sale of its 25% stake in Four Mile.

Any sale would be subject to shareholder approval, consent from Itochu Corporation and operator Quasar Resources not exercising its pre-emptive right over the stake.

Alliance said the funds received would allow it to further explore and expand its exploration portfolio in Australia and Chile.

Alliance shares fell 2.8% to A17.5c.