can provide a general idea. Sourcing is assumed to provide information about trade, or travel routes. Dating Some debitage material has been examined in an effort to obtain dates. Since debitage is plentiful, and individual specimens are usually not diagnostic, they can often undergo destructive analysis that would not be suitable for other artifacts. Results have been promising, but not spectacular. Obsidian and cryptocrystalline silicates appear to be the most promising materials for destructive analysis. Obsidian, as a natural glass material, is peculiar because when it is exposed to water, the surface develops a patinated layer of hydrated perlite. Old fractures therefore have thicker layers of patina than more recent flake scars. As the rate of hydration is determined by factors such as moisture content, temperature, and the chemical composition of the obsidian, this method cannot provide absolute dates. However, this method has the major advantage of relying on obsidian flaking as the activating cause in this dating scheme. Cryptocrystalline silicates, such as flint and chert, are sometimes heat-treated in order to improve the flaking properties of the material. This heating can be used as a zeroing point, and the date since the material was last heated can be established through fission track counts, thermoluminescence, or, in some rare cases, paleomagnetism. These provide absolute dates. Unfortunately, not all such tool stones were heat-treated, and not all heat-treatment is due to human agency. Forest fires are one way that stones can be heat-treated without human action. See also Hammerstone Midden References Lithics