The Arizona Geological Survey at the University of Arizona post below on obsidian in the Southwest garnered a lot of attention (~87,800 views, 580 likes, 39 comments and 217 shares).
On the hunt for obsidian.
M. Steven Shackley, Professor Emeritus of Geoarchaeology, Department of Anthropology, University of California, Berkeley, has been documenting sources of archaeological obsidian in the American Southwest since the mid-late 1980s. This map shows sites of obsidian in SE CA, AZ, NM, and northern Mexico.
Visit his site for the interactive map with descriptions of each site noted in the map. Obsidian is a volcanic glass suitable for tool making – knifes, arrow and spear heads, scrapers, and drills.
I sent this to a flintknapper friend and he said friends of his from Georgia, etc travel there yearly for knapping material. He said, there is now a bag limit on obsidian of 100 pounds a year. I was surprised. The frontier is over. LOL