Mule Creek obsidian

Mule Creek is probably the geographically largest obsidian source in the Southwest. The glass lies in a huge late Tertiary ash-flow sheet across Greenlee County, Arizona, and Catron and Grant counties, New Mexico (as the lab page lists them). It occurs as marekanites (small nodules, up to 10 cm) in perlitic lava, and erodes into the San Francisco and Gila rivers. The glass is aphyric, from opaque black to translucent smoky gray with some gray banding, and a few pieces are mahogany-brown banded with black. Some nodules have a silver sheen on the cortex. At one locality it is only a fair medium and very brittle, but it takes pressure flaking very well. At least four chemical groups exist, including Antelope Creek, Mule Mountains and North Sawmill Creek. Paleoindian points rarely used it because the nodules are small.

A very extensive late Tertiary ash-flow sheet and perlitic lava of the Mule Creek caldera area, Mogollon-Datil volcanic field. Perlitic lava at the Antelope Creek East locality is dated at about 19.56 million years. Nodule density can reach 100 per 5 m2 on ash hills. At least four chemically distinct groups are mixed in the Gila Conglomerate.