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Thomsonite was created from lava flows of the Keweenawan Period, over 600 million years ago. Gases trapped within the lava and seams between the lava flows turned into hollow pockets when the lava hardened. Over hundreds of thousands of years, these hollow openings filled and solidified, forming Thomsonite.

The unique combination of volcanic activity and certain chemicals and minerals is responsible for why the gemstone formed in this location along the North Shore.

Thomsonite is found in the Kilpatrick Hills of Scotland; in the north of Ireland; Saxony, Germany; the Faroe Islands; Kern County, California; Cape Lookout, Oregon; and in the Lake Superior region.

Thomsonite can be found locally on the beaches between Tofte and Grand Marais, on the Cook-Lake County line, on Isle Royal, Michigan and near Saxon Falls and the Montreal River Gorge on the Keweenaw Peninsula in Michigan. The color and texture of Minnesota’s Thomsonite makes it unique as gem-quality stones are found only in a limited area of Lake Superior’s shoreline about 5 ½ miles southwest of Grand Marais.

Thomsonite is a mineral belonging to the zeolite group of minerals, which has over 35 different recognized members. Thomsonite is one of the rarer zeolites. It forms tight acicular radiating clusters and sphericules as well as some blockier crystals and is found in the vesicles or bubbles of volcanic rock, as are most other zeolites.

Dr. Thomas Thomson, for whom Thomsonite is named, first described the mineral in 1840, after finding it in the Kilpatrick Hills of Scotland.

The Minnesota Geological Survey was established in 1873 and headed by Newton Winchell, who taught in the winter and conducted surveys during the summer months. Two of his students, young professors from the University of Minnesota, S.F. Peckman and C.W. Hall, spent their vacation in 1879 along the north shore of Lake Superior studying rocks. A report they published in 1888 is the first printed reference to Thomsonite.

Pure Thomsonite is snow-white and sometimes translucent. Other compounds such as ferric and / or ferrous iron or copper are responsible for the various colorations within the gemstone. Commonly found colors are pink, tan, white, red and brown. Those with green, gray or black backgrounds or green eyes are the most highly prized and least frequently found.

During the turn of the century, Hans Bernard Larsen, a Norwegian immigrant who came to Grand Marais in 1888, sold Thomsonite in a summer tent along Good Harbor Bay. By 1924, the American Exploration Company owned much of the Thomsonite-laden property.

In 1942, Harlow Tyschen bought Lake Superior shoreline and began to mine Thomsonite. He sold his property in 1974 to Anita and Jack Brust and formed Tybrus Gems to mine the stones.

Maurice and Tania Feigal bought 500 feet of shoreline to build the Thomsonite Beach resort in 1961, where they mined and sold Thomsonite jewelry until 1998.