Obsidian Hydration Dating

A method of dating artefacts of Obsidian.

Principles
Surface layers of obsidian artefacts undergo a gradual chemical change as a result of the inward diffusion of water. This 'hydration' commences as soon as the artefact is made and has surfaces exposed to the atmosphere. If the rate of hydration is known, then the thickness of the hydrated layer can be used to date the object. Rate of hydration, however, is also controlled by temperature and the chemical composition of the obsidian. Information about hydration rate must be built up for each region and can be calibrated by fission track dating.

Range
Dates have been obtained in Japan extending back as far as c25,000 BC. Range and applicability depends on the extent to which it has been possible to investigate hydration rate in the area. The technique is therefore limited to those regions of the world which are rich in obsidian.

A method of dating artefacts of obsidian. Principles. Surface layers of obsidian artefacts undergo a gradual chemical change as a result of the inward diffusion of water. This ‘hydration’ commences as soon as the artefact is made and has surfaces exposed to the atmosphere. If the rate of hydration is known, then the thickness of the hydrated layer can be used to date the object. Rate of hydration, however, is also controlled by temperature and the chemical composition of the obsidian. Information about hydration rate must be built up for each region and can be calibrated by Range. Dates have been obtained in Japan extending back as far as c25,000 bc. Range and applicability depends on the extent to which it has been possible to investigate hydration rate in the area. The technique is therefore limited to those regions of the world which are rich in obsidian.