The hydration layer is caused by absorption of water on exposed surfaces of the rock.The surface of obsidian starts to absorb water as soon as it is exposed by flaking during manufacture of an artifact.The layer of hydrated obsidian is visible when a slice of the artifact is examined under an optical microscope at a magnification of x 500. The land was poor for agriculture, but marine resources were exploited and the small center was quite wealthy.
The area was an important center in the Neolithic and Chalcolithic, with sites like Catal Huyuk and .
Timber-framed huts consisted of shallow mud-walled pits that were likely roofed with branches.
Obsidian was already being traded and flint tools were made.
SYNONYMS OR RELATED TERMS: hyalopsite, Iceland agate, mountain mahogany CATEGORY: geology DEFINITION: A jet-black to gray, naturally occurring volcanic glass, formed by rapid cooling of viscous lava.
It was often used as raw material for the manufacture of stone tools and was very popular as a superior form of flint for flaking or as it is easily chipped to form extremely sharp edges.
Obsidian breaks with a and is easily chipped into precise and delicate forms.
It was very widely traded from the anciently exploited sources in Hungary, Sardinia, Lipari of Sicily, Melos in the Aegean, central and eastern Anatolia, Mexico, etc.
Chemical analysis of their trace elements now allows most of the sources to be distinguished (especially by neutron activation and x-ray fluorescence spectrometry), so that the pattern of trade spreading out from each can be traced.
Two dating methods have been applied to obsidian: it generally went out of favor for everyday purposes (perhaps as a result of competition from metal tools) but it continued to be used for prestige objects in some areas, especially by the Minoans and Mycenaeans.
Obsidian has been quarried and traded by western Melanesians since at least 19,000 bp, with the earliest-used and most important source being that at Talasea on CATEGORY: geology DEFINITION: The absorption of water on exposed surfaces of obsidian.
In each specific environment, the surface of an obsidian artifact absorbs water at a steady rate, forming the hydration layer. If the local hydration rate is known and constant, this phenomenon can be used as an SYNONYMS OR RELATED TERMS: obsidian hydration layer dating, obsidian dating CATEGORY: technique DEFINITION: A method of dating in which the age of an obsidian artifact is established by measuring the thickness of its (layer of water penetration) and comparing that to a known local hydration rate.