WGNHS
Wisconsin Geological and Natural History Survey

Mining in Wisconsin

Mining has long been part of Wisconsin’s economy and history and even precedes our statehood. On this page, you will find information about two types of mining in Wisconsin: iron mining and frac sand mining. There are also links to additional information about mining in Wisconsin at the bottom of this page.

Iron mining

Types of iron ore

Iron ore is present in a number of places and geologic settings within Wisconsin. Iron ore can be defined on the basis of its iron content into low-grade ore (taconite), which commonly contains 25 to 35% iron, and high-grade ore, which contains 50 to 70% iron.

Iron-bearing ore minerals include oxides, carbonates, silicates, and, in some cases, sulfides. In Wisconsin, the most important iron ore minerals are oxides: magnetite (Fe3O4), hematite (Fe2O3), and goethite/limonite (Fe2O3•H2O).

A large chunk of rock with a striped pattern. A penny is leaned against the rock for scale; the penny is much smaller than the rock.
Banded iron formation with alternating layers of silvery gray hematite and reddish fine-grained silica (chert).

Brief overview of Wisconsin’s iron mining history

Limited amounts of high-grade iron ore were first mined in Wisconsin in the 1850s in the Black River Falls District of Jackson County and the Ironton area of Sauk County. More substantial iron mining of high-grade ore began in the Gogebic and Florence Districts in the 1880s and continued into the 1960s. Mining in the Baraboo District took place between 1904 and 1925. The Jackson County Iron Company re-opened mining in the Black River Falls District in 1969 when they began extracting low-grade taconite ore that was beneficiated (concentrated) and pelletized on site. The mine ceased operations in 1983 and was reclaimed.

Map of Wisconsin showing the locations of important iron ore deposits in the state. The base map only shows the county lines with the county names labeled. Below the map is text reading "Modified from Mineral and Water Resources of Wisconsin, 1976."

Development opportunities

Significant remaining tonnages of lower-grade ore have been identified by magnetic surveys and limited core drilling in several of the aforementioned districts, most notably the Gogebic District in Iron and Ashland counties. Future development will depend on economic and environmental considerations.

For more information

For more details about iron mining in Wisconsin, please contact:

Esther K. Stewart
Bedrock Geologist
phone: (608) 263-3201
email: esther.stewart@wisc.edu

Background on metallic mining regulations and resources

Frac sand mining

Wisconsin’s sandstones, especially the Cambrian- and Ordovician-age formations, are prized for their uniform grain size and high silica content. These formations are excellent sources of the raw material needed for many industrial products and processes, including hydraulic fracturing (fracking) for fossil fuel extraction.

Frac sand primer

Wisconsin has abundant resources of sand that have been mined for more than 100 years. Wisconsin’s sand is used for glass manufacture, foundry molds, and even golf course traps. It has been mined for the petroleum industry for many years. Advances in extracting oil and gas using a process called “fracking” (short for hydraulic fracturing) have greatly increased the demand for Wisconsin’s sand in recent years.

A man's hand holding a palmful of light yellow sand against a backdrop of even more sand. The sand he's holding is fine-grained with a few tiny pebbles.
Handful of silica sand. (Photo credit: Mike Parsen)

What is frac sand?

Frac sand is quartz sand of a specific grain size and shape that is suspended in fluid and injected into oil and gas wells under very high pressure. The fluid pressure opens and enlarges fractures as well as creates new ones. Sand grains are carried into these fractures and prop them open after the fluid is pumped out.

The type of sand used in this process must be nearly pure quartz, very well rounded, extremely hard, and of uniform size. Before shipment, frac sand is washed, sorted to ensure uniformity, and dried.

Wisconsin has some of the best frac sand in the country because several of our geologic formations meet these specifications and are found near the surface.

Where is frac sand found?

Frac sand is currently being mined from sandstone formations in much of western and central Wisconsin. The same formations are less well exposed and generally more fine-grained in the eastern and southern parts of the state. Sand from younger glacial deposits as well as most beach and riverbank sand is too impure and too angular to be used as frac sand.

A sand mine with sandstone outcrops, large piles of golden sand, and sand covering the ground. A yellow construction truck sits in the middle with its bed full of sand and sandstone chunks. The truck is much smaller than the mine pit.
An active frac sand mine pit.
Map of Wisconsin showing that sandstone formations and frac sand mines and processing plants are all primarily concentrated in the western parts of the state, with a few in central Wisconsin.
Locations of sandstone formations and frac sand mines and processing plants in Wisconsin (as of October 2013).

Where is fracking performed?

Fracking has been used by our domestic oil and gas industry for more than 75 years. In recent years, the development of new horizontal drilling technology using hydraulic fracturing has made possible the production of previously unrecoverable natural gas resources in the eastern, western, and southwestern United States.

In Wisconsin, a different kind of fracking is used to increase the productivity of water supply wells in relatively impermeable rocks, such as the granite in the central part of the state. In these cases, only pressurized water is injected into the well—no sand is added.

Permits and regulations

Concerns have been raised regarding environmental and nuisance problems as sand mines proliferate. Mine siting is regulated at the local zoning level. Mine reclamation plans, required by NR 135, must be in place before mining begins. The Department of Natural Resources provides technical assistance to local authorities for these plans. For a summary of Wisconsin’s nonmetallic mining regulations, visit the DNR website.

For more information

Contact the following staff at the Wisconsin Geological and Natural History Survey for more details about frac sand in Wisconsin:

Eric Stewart
Bedrock Geologist
phone: (608) 262-9403
email: eric.stewart@wisc.edu

Other resources

Mine locations map: Wisconsin Department of Natural Resources—Industrial Sand Mining
Interactive map shows locations and types of frac sand mining operations

Background information

Economics: The Federal Reserve Bank of Minneapolis—Regional Business & Economics Newspaper
Article outlines the economic evaluation of frac sand mining (PDF)

Mining statistics: U.S. Geological Survey—Silica Statistics
Annual reports for national silica mining statistics

Planning and zoning: Center for Land Use Education (UW–Stevens Point)—Mining Publications and Resources
Four-part series on planning, zoning, and evaluating county nonmetallic mining plans

Regulations

Silica dust: Occupational Safety and Health Administration—Crystalline Silica
Occupational health hazards and symptoms of exposure to silica dust

Back to top