Have you ever picked up a rock that just seemed to fit in your hand? Archaeologists are often asked about interesting things found by the public that may not be cultural artifacts. While we typically study artifacts, features, and landscapes that were intentionally altered by humans we also don’t mind answering questions about the naturally occurring items that people often come across in the Midwest. Here are a couple eye-catching examples we are commonly asked about:
Many stones found in Illinois farm fields have been struck repeatedly by metal plow blades. Over time the scars left by farm machinery can form random crisscross patterns. While plow-scarred rocks are unintentionally caused by humans, they were not made by the original indigenous inhabitants of Illinois.
Omarolluks are naturally occurring sedimentary rocks, with round features, or holes, that are usually between a half-inch and three inches in diameter. The holes are caused by water eroding away softer material embedded in the rock over tens of thousands of years. Omarolluks aren’t common but they were scattered over many parts of Illinois by glaciers during the last Ice Age. Geological finds like Omarolluks and other oddly shaped rocks caused by differential erosion are often misidentified as Native American artifacts.