Datolite

specimen number:
2062321

location:
Copper Falls Mine, Keweenaw Co., Michigan, USA

description:
Colorless crystals of datolite measuring to 0.6 cm in size across the top of matrix. In good condition. Collected in 1999.

The Copper Falls mine, located near Eagle Harbor in Keweenaw County, Michigan, was an early and prominent underground mining operation situated within the historic Lake Superior native copper district. Geologically, the mine targeted copper mineralization hosted in the basaltic lava flows and interbedded conglomerates of the Portage Lake Volcanics, with production focused on both amygdaloidal stratabound layers and cross-cutting mineralized fissures like the Copper Falls vein, where native copper precipitated alongside calcite, prehnite, and datolite. Organized mining began at the site in 1845 under the Copper Falls Mining Company, making it one of the earliest systematic mining ventures on the Keweenaw Peninsula. Over its lengthy tenure, operators sank numerous shafts, drove the extensive Spencer adit, and erected advanced stamp mills to process the copper-bearing rock, despite facing frequent financial reorganizations and challenging underground structural faults. Active commercial mining and milling operations continued with varying levels of success until 1893, when low copper prices and declining ore grades forced the permanent closure of the mine.

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