Note: This story has been updated to include comments from Knife River and the South Dakota Department of Transportation.

SIOUX FALLS, S.D. (KELO) — It’s not gold but it’s valuable in terms of streets and roads.

The stuff under the W. H. Lyon Fairgrounds is likely similar to what’s in the Knife River quarry near Interstate 29 in Sioux Falls. Knife River has offered Minnehaha County $65 million with several contingencies, or steps, for the fairgrounds property. The county commissioners heard the offer on July 5. The offer is preliminary and county officials indicated that it may not be considered in the near future.

“The fairgrounds property happens to be a great fit for a couple of reasons – its proximity to our operations and the quality of rock we believe to be there,” Tony Spilde said in an email on behalf of Knife River and the Sioux Falls location. The remaining lifespan of the quarry along I-29 is about five years of quartzite, Spilde said.

There are several quarries in eastern South Dakota from which aggregate rocks, gravel, sand and quartzite are being removed each week.

The mining of quartzite is a multi-million dollar business in eastern South Dakota.

The geological make-up of the state differs from the west to the east.

“The eastern half of the state had more glaciers,” said Emily Berry, the assistant director of the Museum of Geology at the South Dakota School of Mines and Technology in Rapid City. “You will find more gravel and stone and also quartzite.

A 1986 research paper published online by the Geological Society of America said “The Sioux (Quartzite of inferred Early Proterozoic age (1,760−1,630 m.y.) occurs in southwestern Minnesota, eastern South Dakota, and adjoining parts of Iowa and Nebraska…”

The rocks, sand, gravel and quartzite found in quarries is crushed and meshed into material that is used for roadbeds and in the making of concrete and asphalt. Rock is also used for riprap in river beds and shorelines and along culverts.

“Everybody uses the gravel and sand,” Minnehaha County Highway Superintendent Steve Groen said of material from a quarry.

Rock County, Minnesota, gets some of its road construction material from quarries in eastern South Dakota, said assistant county engineer Andy Haakenson.

The county also gets material from a quarry near Hardwick in southwestern Minnesota.

The South Dakota Department of Transportation also uses quarry material.

“Quarry material is used on DOT projects comes from multiple suppliers in the eastern half of the state where quartzite is available,” said Craig Smith of the SD DOT. “This includes material from Knife River in Sioux Falls.”

Contractors that work on DOT projects are response for selecting sources of project materials, Smith said.

That’s true for counties and cities as well but municipal or state entities may also buy sand and gravel from sources/suppliers for year-round use.

“Majority of the market is in the Sioux Falls metro area, but we do reach out to about a 90-mile radius,” Spilde said of Knife River’s customer base.

The access to nearby quarry material across eastern South Dakota and southwestern Minnesota benefits local governments and contractors.

“It reduces the trucking costs. It makes it more competitive for (buying) materials,” Groen said.

But how would a company know there is valuable material under the fairgrounds’ property?

Berry said geological maps of the state show the rock and other formations in the state. A company can also hire a business to do a geological survey of a specific location, she said.

“We estimate the fairgrounds could be 75 more years of reserves, but have not been able to access the property to verify this,” Spilde said in the email.

Before any material is dug from a quarry, the owner needs a license. According to the South Dakota Department of Agriculture and Natural Resources, “A mine license is required to mine sand, gravel, rock to be crushed and used in construction, pegmatite minerals; and limestone, iron ore, sand, gypsum, or shale used to make cement or lime; or dredging for commercial resale. Mining of all other minerals requires a mining permit.”