Deep underground in the South Australian outback beneath an arid orange-dirt plain speckled with saltbush, lies an enormous mass of copper.

It’s shaped a bit like a giant carrot and is one of the largest undeveloped deposits of the precious metal in Australia.

Think of all the copper pots and pans, hanging lamps, wiring and pipes that could be made if the ore was mined, processed and sold.

Oz Minerals plans to do just that with the site at Carrapateena, about 160km north of Port Augusta, and on Thursday it ticked off two major milestones.

Officials from the mining company signed a partnering agreement with Traditional Owners, the Kokatha people, setting out their working relationship throughout the planned life of the project, including site access and rehabilitation.

Kokatha chairman Chris Larkin said the negotiations between his people and Oz Minerals were smooth and respectful.

“It left our directors feeling valued, respected and included as part of the process,” Mr Larkin said.

“That is not the way we often feel after negotiating with mining companies.”

He said the project would empower the Kokatha people and deliver benefits like employment and training, helping them to look forward to a better future.

Also on Thursday SA Premier Jay Weatherill officially opened the mine’s decline, which will provide access to the copper deposit.

He said the Carrapateena project represents $1 billion in investment and would create 1000 jobs over the construction and production.

“It is going to be for some time one of the most economically valuable and technically impressive projects we’ll see in the mining industry in our state,” Mr Weatherill said.

“If the project fulfils its potential, it will produce millions of tonnes of copper and other minerals over the course of its expected 20-year plus life.”

The proposed project will also include a copper processing plant, likely to be located on a coast nearby, to turn the ore into a product that is ready for export.

Oz Minerals expects to spend about two years carving out the 5.5km long Tjati Decline, edging forward five metres at a time.

A hulking machine drills 80 holes in the rock face and these are packed with explosives and detonated before the rubble is removed.

The decline is named after the Kothka word Tjati for the local knob-tailed gecko.

“He’s a pretty little fella,” Mr Larkin said of the gecko. “You can get a lot of them on a kebab.”

Carrapateena is still in the pre-feasibility stage as exploration work continues and the Oz Minerals board will make a final decision next year on whether to progress.

But chairman Neil Hamilton is confident because the quality of the ore is so high.

The deposit detected so far is 700m wide and at least 2.5km long but could be much larger.