Obsidian distributions during the Late Prehispanic period reflect the dramatic changes in economy and ideology imposed by powerful states in the region. In the Tiwanaku and Wari spheres of influence obsidian circulation achieved its largest known extent. Particularly intriguing are the examples of non-local obsidian consumption in close proximity to rival obsidian sources, a phenomenon that occurs twice during the Middle Horizon. Three samples of Chivay obsidian were found close to the Sora Sora obsidian source in western Bolivia in a possibly Tiwanaku context (Burger, et al. 2000: 340), and Quispisisa and Alca obsidian were found at the Wari-influenced site of Achachiwa, only 46 km downstream of the Chivay source, in the lower Colca valley (Brooks 1998: 447). During the LIP this pattern of high mobility and sprawling interregional contact is reversed as regional circulation of obsidian is curtailed and the Chivay regional pattern returns to a distribution confined to the Colca region and the North Titicaca Basin. Finally, during the Inka period, obsidian appears to have had a largely diminished significance, particularly in contrast to other materials that were circulated prodigious distances by the Inka. This discussion of the spatial distributions of prehispanic obsidian will be complemented by a review of the uses and forms that obsidian artifacts assume in the archaeological and ethnohistoric record.