Park exhibits explain how the diamonds got here. During the Age of Reptiles 95 million years ago, a volcanic eruption blasted this lode of minerals from 70 miles below the earth's surface. It formed a 35-acre crater filled with volcanic rock that quickly broke down into the sticky greenish soil studded with minerals, including garnets, amethysts, and diamonds. Park workers often plow the crater floor to churn up fresh soil and rocks. Exhibits also show uncut diamonds of various colors and qualities and describe how to tell them from quartz, calcite, and glittery mica.
Diamonds are usually small and well-rounded with an average size about that of a kitchen match head.
A diamond will be shiny, and you cannot scratch its surface with a key or other metal object as you can a piece of quartz. Park staff will identify, weigh, and certify diamonds, as well as demonstrate digging techniques. A 3.3-carat diamond that Arkansan Shirley Strawn found in 1993 may be the finest stone turned up here. The rest of the crater was owned by M.M. Mauney, the first to charge visitors a fee to hunt diamonds. Through the decades, the property changed hands with various attempts at commercial mining, marked by a weathered wooden mine shaft built by Austin Millar in the 1910s.