Those rates depend primarily upon temperature. By plotting the absorption rates of the two, the scientists believe they can read the ancient climate patterns where the artifact was found. That's possibly as significant a contribution as dating it, because changes in local climate have had profound influences on many ancient cultures. Points of Comparison All of that depends on whether the concept can be proven. To do that, the scientists are comparing their findings with artifacts that have been reliably dated by other means.
Most obsidian is black, but pachuca is green.
It was so prized and widely traded that it's been found throughout Mexico and South America. The Mexican National Institute of Anthropology and History has aided the scientists in collecting artifacts of known age from a wide range of areas, and those samples will be analyzed at the lab in Tennessee. Those samples will be subjected to various temperatures and conditions back in the lab to see how they absorb water, and what the absorption rate can tell about past weather. By melding those two data sets, the scientists hope to tell precisely how old each artifact is, and how the weather changed since a hunter long ago crafted a chunk of obsidian into a tool sharper than a modern scalpel. A former science writer for the Los Angeles Times , he now lives in Juneau, Alaska.