Thomsonite

specimen number:
2062323

location:
Grand Marais, Minnesota, USA

description:
A set of crystallized thomsonite from this famous area for the species. These are partially polished. The size provided is the size of the box from which these are displayed.

The Grand Marais region, located along the North Shore of Lake Superior in Cook County, Minnesota, is a well-known locality for the distinct, nodular variety of zeolite known as thomsonite. Geologically, these mineral formations are hosted within the Mesoproterozoic North Shore Volcanic Group, specifically inside the vesicular gas pockets of ancient basaltic lava flows where low-temperature hydrothermal fluids precipitated secondary zeolites over time. Unlike a traditional industrial mine or commercial aggregate quarry, this shoreline locality has no history of corporate subterranean mining or formal commercial dates of operation. Instead, small-scale quarrying has been conducted by local lapidaries, property owners, and beachcombers who have extracted the rounded, concentric-banded nodules directly from the basalt cliffs and shoreline gravels since the late nineteenth century, with the most active periods of organized surface digging and extraction occurring along Thomsonite Beach from the 1920s through the late twentieth century.

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