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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 ...
The rate at which the obsidian hydration band forms increases with temperature. Second, the rate of hydration and obsidian hydration band formation varies with the geochemistry of the obsidian, including the intrinsic water content, seems to affect the rate of hydration. Finally, water vapor pressure may also affect the rate of obsidian hydration.
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.
Perlite boulders with fireweed in foreground. Perlite softens when it reaches temperatures of 850–900 °C (1,560–1,650 °F). Water trapped in the structure of the material vaporises and escapes, and this causes the expansion of the material to 7–16 times its original volume.
In inorganic chemistry, mineral hydration is a reaction which adds water to the crystal structure of a mineral, usually creating a new mineral, commonly called a hydrate. In geological terms, the process of mineral hydration is known as retrograde alteration and is a process occurring in retrograde metamorphism .
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.
Wheels with Asanti 28 in (710 mm) rims on a police Hummer H2 car. The wheel size is the size designation of a wheel given by its diameter, width, and offset. The diameter of the wheel is the diameter of the cylindrical surface on which the tire bead rides. The width is the inside distance between the bead seat faces.
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.