Chemically, Obsidian closely resembles granite and rhyolite but the processes which lead to the formation of Obsidian are different to those which shape granite. Indeed, Obsidian is not a true mineral because it lacks crystal structure. Probably a better description, and that most often used for Obsidian, is a that it is a naturally occurring form of glass. While pure Obsidian is dark in appearance, the colour varies depending on the presence of impurities.
Obsidian hydration dating - Wikipedia
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Obsidian hydration dating
Absolute dating techniques attempt to pinpoint a discrete, known interval in time such as a day, year, century, or millennia. Very few artifacts recovered from an archeological site can be absolutely dated. Archeologists use several methods to establish absolute chronology including radiocarbon dating , obsidian hydration , thermoluminescence , dendrochronology , historical records, mean ceramic dating , and pipe stem dating.
Obsidian hydration dating OHD is a geochemical method of determining age in either absolute or relative terms of an artifact made of obsidian. Obsidian is a volcanic glass that was used by prehistoric people as a raw material in the manufacture of stone tools such as projectile points, knives, or other cutting tools through knapping , or breaking off pieces in a controlled manner, such as pressure flaking. Obsidian obeys the property of mineral hydration , and absorbs water , when exposed to air, at well defined rate.