Obsidian Hydration Dating
Obsidian hydration dating was introduced in 1960 by Irving Friedman and Robert Smith of
the U.
S.
Geological Survey.
Their initial work focused on obsidians from archaeological sites in
western North America (http://en....
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Obsidian Hydration Dating
Obsidian hydration dating was introduced in 1960 by Irving Friedman and Robert Smith of
the U.
S.
Geological Survey.
Their initial work focused on obsidians from archaeological sites in
western North America (http://en.
wikipedia.
org/wiki/Obsidian_hydration_dating).
Obsidian is a naturally occurring volcanic glass of rhyolitic composition.
As soon as a fresh
sur- face of obsidian is exposed to the atmosphere, water begins to diffuse slowly from the
surface into the body of the obsidian.
When the layer has reached a thickness of about 1/2
micrometer or more it is detectable and measurable by conventional microscopic examination of
a thin section in the laboratory.
The measured thickness of hydration is usually then converted
into age terms (Friedman, Trembour 1983).
To measure the hydration band, a small slice of material is typically cut from an artifact.
This sample is ground down to about 30 micrometres thick and mounted on a petrographic slide.
Th
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