The geochemistry of obsidian provides a unique tool for both archaeologists and geologists. Geochemical data from archaeological artifacts can be matched with those from known obsidian sources to indicate the parent source of origin for each artifact, and they also may indicate the presence of unknown geological sources for obsidian. Archaeologists are interested in locating all sources of artifact-quality obsidian and in identifying geochemical types on a scale that separates geographic obsidian sources and matches them with artifacts. Archaeologists then use geochemical data to reconstruct prehistoric trade/exchange relationships and group mobility patterns through time. Geologists are interested in obsidian geochemistry...