Vulture obsidian

Vulture obsidian comes from the Vulture Mountains region of northwestern Maricopa County, Arizona. It is a mid-Tertiary source: bedded ash-flow tuffs punctuated with rhyolite domes that grade into perlite or vitrophyre, now largely buried by later andesite volcanoes. Marekanites up to 10 cm lie in the alluvium and have washed at least 20 km south and east. The glass is aphyric, from nearly opaque brown-green to nearly transparent, and some nodules are banded or cloudy. Thin black cortex feels velvety or water-worn. Shackley calls it an excellent medium for small bifaces. Vulture glass dominates Sacaton-period Hohokam sites on the Lower Salt River, where Superior glass dominates the Middle Gila, so the two are separated by chemistry.

Mid-Tertiary rhyolite domes and bedded ash-flow tuffs, largely subsumed by andesitic Vulture and Diamond Mountains volcanism. Marekanites sit in tuff and perlite along Jackrabbit Wash and erode into the alluvium; nodule density near the source reaches 5 to 10 per square meter. A large lithic procurement site (AZ T:5:5) covers part of the source.