IDENTIFICATION OF POTENTIAL INDUSTRIAL MINERAL RESOURCES IN OLMSTED COUNTY, MINNESOTA

In 1984, the Minnesota Legislature passed Statute 84.94, entitled “Aggregate Planning and Protection”, which mandated the MN/DNR to map and classify the state's aggregate resources. The purpose of the statute is to supply local and county governments with the necessary information to make informed planning, zoning, and land-use decisions regarding aggregate resources. Due to continued land use conflicts and increased demand for aggregate resources, Olmsted County passed a resolution in 2002, requesting aggregate resource mapping for future planning.

The aggregate resources in Olmsted County consist of both sand and gravel and crushed stone. These resources were mapped and classified based on their textural and quality characteristics. These characteristics determine the final end-use of the material; the higher end-uses include concrete and asphalt products, whereas the lower quality aggregate is typically used for road base or class 5 material (gravel roads). Other industrial minerals within Olmsted County include dimension stone and industrial sand. The potential of dimension stone depends on the thickness, durability, strength, and aesthetic qualities of the bedrock material. Olmsted County has potential carbonate units that exhibit these characteristics, which are desirable for construction and monumental applications. Industrial sand potential depends on the purity of the silica and textural qualities, such as grain size and sphericity. Olmsted County has two potential sandstone units that meet the criteria for glassmaking, foundry sand, hydraulic fracturing, or abrasive applications.

Crushed stone potential in Olmstead County can be found in the carbonate units of the Maquoketa Formation, Dubuque Formation, Galena Group, Platteville Formation, and Prairie du Chien Group. The primary dimension stone possibility exists within the Oneota Dolomite of the Prairie du Chien Group and to a lesser extent in the other carbonate units. The potential industrial sand deposits are primarily included within the Jordan and St. Peter Sandstones. Also present within Olmsted County is shale from the Decorah and Glenwood Formations and the relatively inaccessible St. Lawrence Formation dolomite and Franconia Formation sandstone. Potential sand and gravel resources are found within the surficial alluvial and glacial deposits.