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St. Croix Co., Wisconsin, USA
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St. Croix County is underlain by Cambrian and Ordovician sedimentary rocks. The Cambrian sediments are largely sandstones, often glauconitic. The Ordovician section tends to be carbonate dominated, with the notable exception of the super-mature St. Peter Sandstone. The carbonates are quarried for crushed stone. Calcite and drusy quartz can be found in these rocks.

Several faults originally of Keweenawan age, but reactived in post-Ordovician time, shift Cambrian and Ordovician strata. The most notable is the Hastings - Hudson Fault, traceable near Hudson and through Willow River State Park.

The Wisconsinan St. Croix moraine cuts through the county near the Interstate 94 corridor. The landscape south of there is bedrock dominated with only thin older glacial drift. North of the interstate the terrain is dominated by glacial landforms. Interesting materials can be found in the glacial drift including iron formation, float copper, jasper and "Lake Superior" agates.

Mineral List

Mineral list contains entries from the region specified including sub-localities
var: Agate

11 entries listed. 8 valid minerals.

Localities in this Region


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Dott, R. & J. Attig (2004) Roadside Geology of Wisconsin: Mountain Press, 346 p.

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Copyright © Jolyon Ralph and Ida Chau 1993-2014. Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them. Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of thousands of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register.
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