ASX-listed Eagle Mountain raised A$11 million (US$8 million) in February 2021 in order to accelerate activities at Oracle Ridge. The results of the subsequent drilling campaign have included 5.7m at 4.44% Cu, 44.87g/t Ag and 0.93g/t Au from 315m underground, 12.7m at 3.96% Cu, 49.1g/t Ag and 1.4g/t Au from 363m, and 12.0m at 3.47% Cu, 50.22g/t Ag and 0.02 g/t Au from 73m.

Just as importantly, all the results have come outside of the existing 12.2 million tonne JORC resource that was briefly mined in the mid-1990s.

"There is a phenomenal opportunity, in our mind, to make this resource a whole lot bigger. We've already got a significant resource and when you look at the geology in Arizona, large mineralised systems are quite common," Mason said.

Eagle Mountain didn't land in Arizona by accident. The company was founded in 2017 by Charles Bass, a veteran mining entrepreneur and geologist and previously the co-founder of Aquila Resources. Bass had extensive experience working in Arizona, including a stint at the Twin Buttes copper mine nearby to Oracle Ridge.

"He [Bass] is very familiar with the Arizona geology. He has a lot of strong relationships [in the state], which is really important when acquiring and developing any project," Mason said.

The company's first move was the acquisition of the Silver Mountain copper project from Kennecott Exploration Company, a unit of the Rio Tinto Group. It acquired 80% of the Oracle Ridge copper mine in 2019, buying out the remaining 20% in early 2021.

"When we came across Oracle Ridge our geologists got very excited. They could see the opportunity for growth. They could see a lot of the drilling in the existing resource had been very constrained," Mason said.

"The other thing we really got excited about was that the geological understanding (by previous owners) was really underdone. That's where we've been focusing our energy, in understanding geochemistry, alteration, geophysics and structural geology; the building blocks for understanding what we're potentially sitting on."

Oracle Ridge is 26km south of BHP's San Manuel, which was the largest underground mine in the US. San Manuel ceased operations in 1999 due to low copper prices and a decline in mineable ore. The state is also home to many large porphyry copper deposits, most notably Rio Tinto and BHP's jointly owned Resolution, which has an inferred resource of 1.79 billion tonnes at an average grade of 1.47% copper.

"In the case of Oracle Ridge, the source of the mineralisation, potentially a larger system, has never been found and indeed we don't believe anyone has gone looking for it," Mason said.

"We're taking the blinkers off to try and understand that broader geological system. We've picked up a lot more ground than when we originally bought the project. Some of the drilling has been to understand where that's all come from. When you look around a few kilometres of the mine, there are a lot of historical artisanal mines, a lot of smoke up there."

Eagle Mountain currently has three rigs working at Oracle Ridge, and plans to ramp up to five rigs by the end of the year. Initial drilling has also taken place at Silver Mountain, although that project is taking a back seat while the company focuses on Oracle Ridge.

"The key milestones will be around drilling and exploration results," Mason said. "With the multiple rigs we can really start having a significant flow of results coming through. Then at the appropriate time we'll be looking to do a resource upgrade. We need to make sure we get something into the measured status and have a decent number in indicated as well."

Another goal is to find out the centre of gravity, he said. "With so many holes hitting copper, we've got to understand what we're sitting on, to ensure we get the mill the correct size and in the right place."

Eagle Mountain has also been busy on the recruitment front. In February 2020, the company appointed Manuel Ramos as CEO of its wholly owned US subsidiary, Silver Mountain Mining Operations, which is the operator of both the Oracle Ridge and Silver Mountain projects.

Ramos is a veteran of the Arizona copper industry, having served as president and chief operating officer of Asarco LLC (a subsidiary of Grupo México with three large open-pit mines and two smelters in the state) from 2009 to 2018.

The company has also engaged the services of Dr Larry Meinert, an expert in magmatic-hydrothermal systems that form world-class skarn deposits. The company hopes that Dr Meinert's understanding of skarn zonation will help it find the source of the mineralisation at Oracle and, in doing so, may add further high-grade mineralization or a mineralised copper porphyry.

"In the mid-1990s they [the previous owner] mined about a million tonnes. They left 18km of development underground, which is still in really good condition. That's a fantastic asset. If you had to put that in today, that would be about $80 million you'd have to install in terms of capital development," Mason said.

He aaded: "The resource is located on the side of a hill. That means you're not going to be mining it at depth, which can significantly increase mining costs. You're essentially just going to be mining it off the side of the hill."

The topography also presents Eagle Mountain with a golden opportunity to be a low-carbon-emitting producer, in Mason's opinion.

In an underground mine with a steep incline, the currently available battery-electric trucks can only go so far before they run out of energy. But if the EV is running on largely flat ground - a possibility at Oracle Ridge due to the hill - then it can run for a lot longer, he explained.

"One of your biggest costs in an underground mine is typically ventilation, which uses power. The amount of  ventilation required is largely related to how much diesel equipment you've got running around. As the existing resources are accessed from horizontal tunnels we believe that battery electric vehicles will work very well for a future mining operation at Oracle Ridge. This leads to much fewer emissions, less ventilation and therefore much less power required. Less power reduces mining costs as well," Mason said.

"At this stage, what we want to do is grow our resources. That can underpin a long life production profile with some decent throughput rates for a reasonable length of time, and it will get our unit costs down.

"We're setting the basis for a strong business going forward, with a view to get into production. Underpinned by solid foundations, we believe Eagle Mountain has the projects, resources and expertise to build a sustainable copper mining company."