During the past few years there has been an ever increasing demand for obsidian sourcing studies in archaeological research. The reasons for this demand are obvious: accurate and replicable matches between parent geological sources and obsidian artifacts are prerequisite to establishing source-specific obsidian hydration rates and to determining prehistoric trade and exchange relations.

Archaeologists have eagerly submitted artifacts for analysis, and obsidian sourcing studies have generated tremendous quantities of data. Up to this point, however, there has not been a corresponding enthusiasm for critical evaluation ofthe accuracy and replicabilityof these source assignments, and I think it would be fair to say that the results of most sourcing studies are accepted on faith. Uncritical acceptance of the results of sourcing studies occurs, for the most part, because archaeologists typically are unable to evaluate the methods and techniques applied by specialists to assign artifacts to sources. Because of this, incorrect source assignments rarely are detected.