Sioux Quartzite

Near Jeffers, Minnesota; Saturday, July 25, 2009:  As I was heading toward New Ulm on US 71, I saw a sign for the Jeffers Petroglyphs, and decided to see what it was all about. Turns out that it's a site operated by the Minnesota Historical Society, and preserves rock carvings done before European settlement of the region. The carvings are done on a type of rock called Sioux Quartzite, which is part of a 1.6-billion-year-old formation.