Miller, the owner of Yax Tun Minerals, a dealer in Chiapas, Mexico, that specializes in Guatemalan jade, took a strand of blue-green beads from around his neck and held it to the light.

Jade processing was in full swing by the middle of the Jomon period. People made tools, beads, pendants and magatama (comma-shaped stones). Jade wasn’t just a material; it became a symbol of ...