Chemistry Reference
In-Depth Information
FIGURE 22
Obsidian in the eastern Mediterranean Sea area.
Studying the relative
concentration of trace elements in obsidian makes it possible to identify the obsidian
and to determine its provenance. Determining the relative amounts of barium and zir-
conium in ancient obsidian tools and in samples from different sources of the natural
glass, for example, made it possible to identify the provenance of obsidian used in
eastern Mediterranean Sea area sites (Renfrew and Dixon 1976).
it contains: the more water in the obsidian, the thicker the hydrated surface
layer becomes. With the passing of time and exposure to humidity, the
exposed surface continues to react with water, the hydration process con-
tinues, and the hydrated surface layer gradually thickens. The thickness of
the layer can be used for dating the time when the obsidian surface was first
exposed to water or humidity (Liritzis et al. 2006; Ambrose 2001).
TEXTBOX
25
THE HYDRATION OF OBSIDIAN
The natural composition of obsidian includes very little water, generally
less than 0.1%. When new obsidian surfaces are created, either by the
natural breakdown of obsidian bulks or by human activity, the exposure
of a new surface to humidity in the air or to water brings about a process
known as
hydration
: the surface
adsorbs
(takes up) water and becomes
