4 1/4" Hammerstone found in Brookings Co., South Dakota by Harlan Olson.

4 1/4" Hammerstone found in Brookings Co. South Dakota by Harlan Olson. Pictured in Lar Hothem's rare and unusual artifacts on page 107. Hothem says in his description this is a rare triple-grooved example . From the collection of the late Harlan Olson.