Prehistoric Obsidian Utilization in the Beartooth Mountains of Montana and Wyoming

X-ray fluorescence spectroscopy was used to determine the source of 107 obsidian projectile points in surface collections from the Beartooth Mountains of south-central Montana and northwest Wyoming. Seventy-two percent of the points were from Obsidian Cliff in Yellowstone National Park, Wyoming. Evidence was found for change of source usage when the artifacts were grouped into cultural affiliation periods.