The first obsidian implements were reported from Ohio Hopewell mounds in 1848. Since that time five different regions have been suggested as the source area. Neutron activation analysis of the elemental composition of Hopewellian obsidian indicates two separate element groups with a sodium to manganese ratio of about 150 in one case and 90 in the other. The first group has its source at Obsidian Cliff in Yellowstone National Park and the second source is also located in Yellowstone but the exact flow has not yet been discovered. -- AATA