The volcanic glass called obsidian was highly prized in prehistory where ever it was found. The glassy material comes in a range of colors from black to green to bright orange, and it is found everywhere rhyolite-rich volcanic deposits are found.
Obsidian Qualities
The qualities that made obsidian a favorite trade item are its shiny beauty, its easily worked fine texture, and the sharpness of its flaked edges. Archaeologists are fond of it because of obsidian hydration---a relatively secure (and relatively low cost) way to date the period an obsidian tool was last flaked.
Sources
For information on dating obsidian see the article on obsidian hydration. See the History of Glass Making, if that's what interests you. For more rock science on the substance, see About.com's Geology entry for obsidian.
For the heck of it, try the Obsidian Trivia Quiz.
Here are a few recent studies on obsidian:
Negash, Agazi, M. S. Shackley , and Mulugeta Alene 2006 Source provenance of obsidian artifacts from the Early Stone Age (ESA) site of Melka Konture, Ethiopia. Journal of Archaeological Science 33:1647-1650.
Rogers, Alexander K. 2006 Induced hydration of obsidian: a simulation study of accuracy requirements. Journal of Archaeological Science 33:1696-1705.
Vogel, Nadia, Sebastien Nomade, Agazi Negash, and Paul R. Renne 2006 Forensic 40Ar/39Ar dating: a provenance study of Middle Stone Age obsidian artifacts from Ethiopia. Journal of Archaeological Science 33:1749-1765.
This glossary entry is part of the Dictionary of Archaeology. Any mistakes are the responsibility of Kris Hirst.
