Two Minneapolis businessmen prospecting for gold in South Dakota's Black Hills

Rob Bergmann and Brian Lentz are modern-day Minnesota prospectors.

Bergmann, who grew up in Galena, Ill., and Lentz, who grew up in Stillwater, both said they were kids who loved digging in the dirt and finding cool and interesting rocks. But as kids they didn't understand that in those rocks was a science worth studying.

Then at Winona State University, Bergmann, Lentz and other geology students traveled to the Black Hills in South Dakota. The two men became field work partners and fast friends in the historic geographic formations.

Now, they are scouting a potential gold mine in the Black Hills through a company related to their Big Rock Exploration company, F3 Gold.

F3, a private gold exploration and prospecting company, is awaiting approval from the U.S. Forest Service to conduct a test drilling plan outside of Silver City, S.D.

The test drilling plan has a total footprint of less than 4 acres, but if test results reveal gold deposits, it would be a validation of their geographic theories that were inspired by one of their mentors, Stephen Allard, a geology professor at Winona State.

If feasible, a fully functioning commercial gold mine would be years away from production.

"The rocks have a story to tell; you just have to know how to read it," Allard said.

South Dakota is home to the Homestake mine, one of the largest underground gold and silver mines in U.S. history. The mine operated for about 125 years before being shut down in the early 2000s. Many people believe the area has been mined out.

However, Allard, a structural geologist, theorizes that the Black Hills developed differently than how most people believe.

"It was my idea of how the structure might be related to gold mineralization, in that perhaps that is telling us that there is more out there than what they've already taken out of the ground," Allard said. "Man, [Bergmann and Lentz have] run with it. I can't take any credit for what they've done since."

Allard believes his former students have the drive to make the exploration turn into something more.

After graduation, Bergmann and Lentz worked as consulting geologists on different projects in Canada. After both worked on the same contract, they ended up leading a number of others together. While on these remote Canadian work trips, whether working out of tents or cheap motel rooms, they formed their business.

"It was rocks all day and then forming a business around rocks all night," Bergmann said. "We took a really long time to strategically plan how we were going to launch our company and our ideas … and how we could really get into the market as 24-year-olds."

In 2010, the two launched Big Rock Exploration, a geological consulting firm, which now works with clients from small landowners to multibillion-dollar organizations on metal and mineral projects in the United States and Canada. Some of their clients include PolyMet, AngloGold Ashanti N.A. and Rio Tinto. F3 Gold was formed later.

Big Rock now has a full-time staff of 20 headquartered out of modest offices in northeast Minneapolis. The staff includes 18 full-time geologists and 20 to 25 contract geologists.

Big Rock has worked on copper/nickel, uranium, copper, gemstone, industrial mineral, diamond, rare earth element and renewable-energy projects. Currently, the company has 16 to 20 different projects in nine industries.

"Now we are primed and ready to take that to the $10 million mark," Bergmann said.

In addition to F3, Big Rock has two other related early-stage businesses: Relevant Resources, a generative company to address the growing need for more base and precious metals; and Exsolve, which uses recycling technology to effectively mine industrial waste for valuable metals.

As a young company, Bergmann and Lentz have already started giving back to their industry. They give time and resources to support geology programs including those at Winona, Macalester and the University of Minnesota Twin Cities and Duluth campuses. They also have given presentations at high schools and YMCA programs in the Black Hills.

With their ability to support and develop new talent for the industry and their ability to use new technologies, both believe that Big Rock is in a good position for the future of the mineral exploration industry in North America.

The emergence of more wind and solar farms, the growing number of electric and hybrid vehicles and ever-widening adoption of personal consumer electronics demands more industrial metals and minerals. Bergmann and Lentz believe it can be done responsibly here.

Coinciding with the increased demand are corporations increasing awareness of their own environmental, social and good-governance responsibilities, as evidenced by the more than 85% of the companies in the S&P 500 index who produce corporate social responsibility reports.

"A lot of companies want to be more transparent and not just understand where they source their materials from but they ultimately want to stand behind the products they produce," Lentz said.

Patrick Kennedy • 612-673-7926