Previously published data suggest that this range is due to hydration rate variations caused by variability in the concentration of intrinsic water, and specifically hydroxyl ions, in the obsidian.
Such variability exists within any given obsidian source, and even within any particular specimen.
In order to calculate dates, we will need obsidian source information and the location of the site where the specimens were obtained.
allow for comparison of the amount of hydration that develops on single source specimens as well as comparison of the amount of hydration developed on several obsidian sources processed simultaneously.
Induced hydration studies are especially valuable in that they reveal variation or homogeneity in hydration band development within and between obsidian sources.
Comparison constants from induced studies are particularly useful in establishing hydration rates for an obsidian source with no known hydration rate when it is compared to the hydration rate of a control source - for example, Napa Glass Mountain which has a well established rate.
Suggested guidelines for obsidian hydration dating are developed using a case study.
These findings do not invalidate obsidian hydration as a chronometric technique, but they do suggest limits to the temporal resolution achievable.
- If you desire that a specific portion of the specimen be analyzed, we suggest that your photograph the item, scan it, or photocopy it, and mark with an arrow the location you want analyzed.To measure the hydration band, a small slice of material is typically cut from an artifact.Obsidian hydration dating typically yields a range of ages for a single chronometric measurement, even after controlling for source chemistry and effective hydration temperature.The ability of the intrinsic water model to produce age determinations compatible with other chronometric methods is examined with a case example from Xaltocan, Mexico.Twenty years after cofounding and directing the obsidian laboratory at Sonoma State University, Tom established Origer's Obsidian Laboratories in 2002.When an unworked nodule of obsidian is initially fractured, there is typically less than 1% water present.