Chapter 10: Obsidian Hydration Dating

Abstract

A freshly-made surface of obsidian (volcanic glass of rhyloitic composition) will absorb water which slowly penetrates by diffusion into the body of the artifact. Although the depth of penetration can be measured by various methods, it is generally determined by microscopic examination on thin sections of the artifact cut normal to the surface. The rate of penetration of water is dependent upon several factors, primarily the chemical composition of the glass and the temperature at which the hydration occurred. Discussions are given of techniques for measuring the hydration thickness, measurement (or estimates ) of ambient hydration temperature, chemical composition of the obsidian and the ocnversion of hydration thickness to dating the time of manufacture of the artifact. Comparisons are made between the results of obsidain hydration and other dating methods.