Malad obsidian

Malad is a heavily used and widely traded obsidian from the Idaho-Utah border country, about 30 km north of Malad, Idaho. It crops out as angular pieces of banded black to clear glass in pumice at the base of a rhyolite dome complex of the Hawkins Basin Volcanic Center, across more than 50 square kilometers of woods, farms and perlite mines. The rocks are Late Miocene, and a biotite-bearing flow above them dates to about 6.6 million years. Many labs have sampled it. In Wyoming, a 1999 study of 18 excavated sites found Malad, Obsidian Cliff and Bear Gulch to be the most important obsidians, and Malad dominated several early-to-late components. Skinner ranks it sixth among sources represented in the artifacts his lab has characterized from Utah.

Upper Miocene rhyolite and dacite flows of the Hawkins Basin Volcanic Center (Salt Lake Formation), unrelated to the Snake River Plain hotspot. The earliest flow is a 60 m thick, flow-banded, non-biotite rhyolite partly blanketed in obsidian cobbles; pumice deposits more than 30 m thick with obsidian clasts are exposed in perlite mine pit walls. A biotite-bearing flow is dated at 6.63 million years. At Arbon Gap the glass occurs with a metamorphosed lakebed tuff.