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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 ...
Obsidian hydration dating is a method that allows for the absolute or relative dating of an obsidian sample. The degree of hydration (i.e., water absorbed into the material) observed indicates how long it has been since the obsidian surface was exposed (i.e., through flaking). Obsidian hydration dating is at times, however, unreliable.
The presence or absence of an obsidian hydration band has been used to distinguish prehistoric obsidian debitage from obsidian debitage produced by modern flintknappers. This distinction can be made because it takes about 70 years for a band to enlarge sufficiently so that it is readily detectable on a freshly flaked surface of a piece of obsidian.
Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently.
Bentonite layers from an ancient deposit of weathered volcanic ash tuff in Wyoming Gray shale and bentonites (Benton Shale; Colorado Springs, Colorado). Bentonite (/ ˈ b ɛ n t ə n aɪ t / BEN-tə-nyte) [1] [2] is an absorbent swelling clay consisting mostly of montmorillonite (a type of smectite) which can either be Na-montmorillonite or Ca-montmorillonite.
The source of obsidian for cultures inhabiting the territory of and around Greece was the island of Milos; the Starčevo–Körös–Criș culture obtained obsidian from sources in Hungary and Slovakia, while the Cardium-Impresso cultural complex acquired obsidian from the island outcrops of the central Mediterranean.
The pozzolanic activity is a measure for the degree of reaction over time or the reaction rate between a pozzolan and Ca 2+ or calcium hydroxide (Ca(OH) 2) in the presence of water.
Rock salt (halite) In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt.