Structural Water Content and Hydration Rates for Mount Hicks, Truman-Queen, Eureka Dunes Unknown-1, and Saline Obsidians

Obsidian hydration dating (OHD) has become a commonly employed method for establishing chronology at archaeological sites containing obsidian flaked-stone components. Since its initial archaeological application, methodological advancements have refined the OHD process increasing its accuracy and precision. It is now well established that intrinsic water content coupled with temperature account for most of the observed variation in the rate of hydration (Rogers, Alexander K., and Christopher M. Stevenson. 2022. “An Equation Relating Obsidian Hydration Rate to Temperature and Structural Water Content.” Bulletin of the International Association for Obsidian Studies 69:3–15; Stevenson, Christopher M., M. Gottesman, and M. Macko. 2000. “Redefining the Working Assumptions of Obsidian Hydration Dating.” Journal of California and Great Basin Anthropology 22 (2): 223–236). Consequently, an equation has been published relating obsidian hydration rate to structural (intrinsic) water content and temperature (Rogers, Alexander K. 2015. “An Equation for Estimating Hydration Rate of Obsidian from Intrinsic Water Concentration.” Bulletin of the International Association for Obsidian Studies 53:5–13; Rogers, Alexander K., and Christopher M. Stevenson. 2022. “An Equation Relating Obsidian Hydration Rate to Temperature and Structural Water Content.” Bulletin of the International Association for Obsidian Studies 69:3–15). Following that methodology, this paper advances structural water content-based obsidian hydration rates for four obsidians, two eastern Californian obsidians and two sources from western Nevada. Obsidians from these sources are widely distributed within archaeological assemblages from eastern California and western Nevada.