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Wisconsin Rocks and Minerals
Wisconsin is one of the best states in the U.S. for finding a variety of rocks, crystals and minerals.
Wisconsin is a rolling plain laid down on sedimentary rocks and broken in places by uplifted igneous and metamorphic rocks, such as the Baraboo Hills in the south-central region, the granite exposures in Waushara and Marathon counties, and the gneisses of the northeastern part of the state. Wisconsin’s extensive glaciation is shown in its many lakes and the famous moraine district west of Milwaukee. The glaciers flattened mountains, carved bedrock, and deposited sand and gravel in many areas of the state.
The Western Upland is part of the Driftless Area, it was not covered by glaciers during the most recent ice age. This area contains many of the caves in Wisconsin, including the Natural Landmark Cave of the Mounds. In the Driftless Area copper was produced. The Mineral Point Copper Deposits are located in Mineral Point, Wisconsin. This area has a significant historical association with the Upper Mississippi Valley Mining District. Coper gemstones, such as azurite, malachite, cuprite, chrysocolla and even covellite have been found here.
Wausau Red Granite was declared the official state rock of Wisconsin in 1971.
Also in 1971, Galena was declared the state's mineral. Galena is the primary ore of lead, which has played a big role in the mining history in Wisconsin. The mining of lead ore was the main occupation of the settlers of early Wisconsin, mostly in the southwest corner of the state in what are now the counties of Iowa, LaFayette and Grant. The area around Dodgeville in old mines and quarries is the best spot to find galena, but there’s galena spread throughout most parts of the state in smaller amounts. Lead is also associated with zinc, and often sphalerite, the primary ore of zinc, as well as pyrite can be found in this area too.
Fossils are found along the coast of Lake Michigan. They are mostly Paleozoic, from 385 to 485 million years ago. The trilobite Calymene celebra is Wisconsin's official state fossil in 1986 Calymene specimens are frequently found in limestones and dolomites in the southern part of the state.
Gravel beds of streams and rivers, as well as quarries and old mining dumps are great places to look for pretty rocks. The local quarries around Racine are particularly notable for their gem-quality specimens. Many interesting specimens can be found in this area including calcite crystals, hematite, rhyolite, crinoids, trilobites, geodes, and even diamonds.
The Great Lakes region has the largest diamond fields found in the United States. These were carried down long ago by great glaciers that advanced and retreated from Canada. As the glaciers retreated, they left behind boulders, gravel and clay the ice had carried down. The diamonds were found at the outer limits these glaciers reached in Milwaukee, Wisconsin to Cincinnati, Ohio. Wisconsin diamonds have a characteristic dodecahedral shape, as opposed to the more common Africa ones that are octahedral in shape.
The Great Lakes is also known for agates and jaspers, including the world-famous Lake Superior Agates, but agates can be found in waterways throughout the state.
Wisconsin is also even known for its rocks not of this world-meteorites! The Mifflin Meteorite, named after Mifflin Township, near the center of the area in southwest Wisconsin showered by the meteorite on Apr. 14, 2010, is one of 14 meteorites known to have landed in Wisconsin.
Before venturing out-do some research on where and what you can collect. Remember you must have permission to collect on private property.
See my page on Rockhounding Rules for general information on the rules of collecting rocks on various lands.