Cross-dating determines the age of undated wood by directly matching ring patterns with trees of known age. Greatly simplified, the process samples living and dead trees in a given area. The tree-ring patterns are matched, and laid down in series, building a continuous timeline of known dates.

Is petrified wood worth any money?

Small samples of low-quality petrified wood may not be worth anything, while a high-quality petrified wood log can sell for several hundred dollars. And large items that have been manufactured out of polished petrified wood, such as tabletops, can sell for thousands of dollars.