Indiana Rocks and Minerals

Indiana is mostly sedimentary rock brought by ancient seas and glaciers.

This is great for fossils, but not great for rocks and minerals.

During the past 2 million years, two major glacial advances and retreats crossed the state. Bedrock is exposed only in the south-central part of the state, which was not glaciated.

Up to 75% of all limestone used in North American buildings has been supplied by Indiana. Limestone was first quarried as a building stone in 1827 in Monroe County and continues to be actively quarried, milled, and produced in Monroe and Lawrence Counties. In fact, Salem Limestone was named the state’s official state rock in 1971.

Calcite is common in sedimentary rocks, limestone in particular, and calcite is found throughout Indiana, especially in areas with limestone formations, such as Marengo and Bloomington.

Coal is mined in the southwest corner of the state. Indiana annually is among the top ten coal producing states in the nation averaging 32,000,000 to 35,000,000 tons each year. More than 95% of electricity used in Indiana comes from coal. Pyrite, siderite, and sulfur can be found in and around the coal mines.

Fluorite can be found in southwestern Indiana, particularly in areas near the Illinois border, such as the Cave-in-Rock district.

You can find crinoid, brachiopods, and more fossils at the Falls of the Ohio State Park, in Clarksville, Indiana. The St. Paul Stone Quarry in St. Paul, Indiana quarry allows visitors to search for fossils in the limestone deposits during select times of the year. Also, Glendon Limestone Quarry near Aurora, Indiana, is known for its abundant trilobite fossils.

And if you search the river gravels, especially near the Maumee River near Fort Wayne, you may find agates, jaspers, and even petrified wood.

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.