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Sauk Co., Wisconsin, USA
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The oldest rocks in this county are the Proterozoic rocks of the Baraboo syncline, ranging from 1.75 billion year old granite and rhyolite, through the famous 1.65 billion year old Baraboo quartzite to a poorly exposed iron formation that was once mined. The quartzite stood as resistant bluffs, pounded by Cambrian storm waves. It is a classic area, with many outcrops visited by thousands of geologists and geology students because many basic principles of structural geology can be illustrated. Cambrian storm wave debris is also beautifully exposed in several places, most notably Parfery's Glen. Quartz crystals and hematite clusters are known where the quartzite is quarried for crushed and building stone.

Much of the county is underlain by Cambrian sandstone. These are well exposed along the Dells of the Wisconsin River, a popular tourist attraction. In thew western part of the county, hills are capped by Early Ordovician dolostones, which are also widely quarried, and can yield interesting specimens of drusy quartz, calcite, dolomite and goethite pseudomorphs after pyrite and marcasite. A few sulfide deposits fringing the Upper Mississippi Valley Zinc-Lead district are known.

On the eastern edge of the county, the Johnstown moraine covers the landscape. To the west, the landscape is carved into hills and glens (or "coulees") with significant bedrock outcrop. Gravel in the drift and along bars in the Wisconsin River and its tributaries can yield interesting transported materials such as float copper, granites and other glacial erratics.

Mineral List

Mineral list contains entries from the region specified including sub-localities
var: Cleavelandite
'Chlorite Group'
'Feldspar Group'
'K Feldspar'
var: Sericite
var: Lake Superior Agate

40 entries listed. 26 valid minerals.

Localities in this Region


The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


Dalziel, I. W. D. & R. H. Dott, R. Jr. (1970) Geology of The Baraboo District, Wisconsin: Wisconsin Geological and Natural History Survey Information Circular 14: 164 p.

Clayton, L. (1990) Geology of Sauk County: Wisconsin Geological and Natural History Survey Information Circular 67: 68 p. with map.

Medaris, L. & J. Fournelle (1998) Svanbergite in the Baraboo Quartzite: significance for diagenetic processes and phosphorus flux in Precambrian ocean: Institute on Lake Superior Geology,:44th Annual Meeting: Pt. 1: Programs and Abstracts: p. 91-92.

External Links

Wisconsin Mineral index - Wisconsin Geological and Natural History Survey http://wgnhs.uwex.edu/wisconsin-geology/minerals-wisconsin/

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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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