Thomsonite set

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A set of thomsonite nodules from this classic area for the species. Some are tumble polished. Size provided for the largest example.Grand Marais, Minnesota, is a historic harbor community along Lake Superior that began developing as a fur trading post and fishing village in the late 18th to mid-19th centuries, eventually incorporating as a village in 1893. Geologically, the region is defined by ancient Precambrian volcanic activity and continental rifting from over one billion years ago, which produced extensive basaltic lava flows. Within the gas vesicles and cavities of these ancient lava rocks, the zeolite mineral thomsonite formed through hydrothermal fluid activity, yielding unique multicolored, eye-patterned gem nodules along the North Shore.