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Douglas Co., Wisconsin, USA

Douglas County is underlain entirely by Precambrian (Keweenawan) volcanic and sedimentary rocks associated with the Mid-Continent Rift System. These are liberally covered by Pleistocene sediments, including thick deposits of lake clays from previous high stands of Lake Superior. The best exposures are in Pattison and Amnicon Falls State Parks where one can see the volcanic rocks juxtaposed on little metamorphosed Precambrian sandstones along the Douglas Fault. This juxtaposition forms waterfalls, such as Big Manitou Falls, the state's highest, in Pattison State Park. Although never a significant copper produced, the county's volcanic rocks do yield minerals suites similar to those found in Michigan's more famous Keweenaw Peninsula. Coarse glacial drift can yield interesting minerals such as banded iron formation, jasper, float copper and "Lake Superior" agates.

Mineral List

Mineral list contains entries from the region specified including sub-localities
'Albite-Anorthite Series'
Analcime
Ankerite
'Apophyllite'
Augite
Azurite
Baryte
Bornite
Calcite
Chalcocite
Chalcopyrite
'Chlorite Group'
Copper
Cuprite
Datolite
Epidote
Hematite
Ilmenite
'K Feldspar'
'var: Adularia'
Laumontite
Malachite
Marcasite
Natrolite
Prehnite
'Pumpellyite'
Quartz
var: Agate
var: Chalcedony
Saponite
Silver


31 entries listed. 23 valid minerals.

Localities in this Region

USA
USA

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References

Grant, U. S. (1901), Preliminary report on the copper-bearing rocks of Douglas County, Wisconsin, 2nd Ed.: Wisconsin Geological and Natural History Survey Bull. VI Economic Series #3, 83 p.

Dutton, C. E. (1972) Sampling of Copper-bearing Keweenawan Rocks of Northwestern Wisconsin: U.S. Geological Survey Open File Report 9.1267, 13p.

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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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