Obsidian hydration dating
Obsidian contains water trapped in it during its formation.In its natural state, it has a thick rind formed by the diffusion of the water into the atmosphere when it first cooled--the technical term is "hydrated layer".
Temperature fluctuates daily, seasonally and over longer time scales in every region on the planet.But OHD is troublesome in regions like the Andes mountains of South America, where people brought their obsidian artifacts across enormous ranges in altitudes, from the sea level coastal regions to the 4,000 meters (12,000 foot) high mountains and higher.Even more difficult to account for is differential glass chemistry in obsidians.Prehistoric rinds can vary from less than 1 micron (µm) to more than 50 µm, depending on the length of time of exposure.By measuring the thickness you can easily determine if one artifact is older than another (relative age).► New approaches of hydrated surface layer by using Fick's law of diffusion.
► New approach for measuring hydration layer with Secondary Ion Mass Spectrometry.
Obsidian hydration dating (or OHD) is a scientific dating technique, which uses the understanding of the geochemical nature of the volcanic glass (a silicate) called obsidian to provide both relative and absolute dates on artifacts.
Obsidian outcrops all over the world, and was preferentially used by stone tool makers because it is very easy to work with, it is very sharp when broken, and it comes in a variety of vivid colors, black, orange, red, green and clear.
different from that of the remainder of the obsidian.
The thickness of the layer can be determined by microscopic examination of a thin section of the sample cut at right angles to the surface.
They and subsequent researchers developed distinct versions of obsidian hydration method consisting of both empirical rate and intrinsic rate development, thus refining the method.