4. A purple stone traded by ancient merchants in eastern Oklahoma was the

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-answer?

A purple stone traded by ancient merchants in eastern Oklahoma was the obsidian.

In ancient times, pre-Columbian civilizations like the Mayans used obsidian for many purposes, including to make tools and weapons (arrowheads, blades, etc.), as well as ritual and ceremonial objects (for burials for example).

There is believed to have been obsidian trade routes all throughout the American continent, even though obsidian does not itself originate in Oklahoma.