Datolite

specimen number:
1791257

location:
Ridge Mine, Ontonagon Co., Michigan, USA

description:
A cut and polished portion of a datolite nodule. The color due to the presence of copper.

The Ridge Mine, located in Ontonagon County within Michigan's Upper Peninsula, was established in the mid-19th century during the region's historic copper mining boom. Geologically, the site is situated within the Portage Lake Volcanics of the Midcontinent Rift System, consisting of tilted Precambrian basalt flows and interbedded sedimentary rocks. Its mineralogy is defined by hydrothermal native copper mineralization, which filled ancient vesicles, amygdules, and fissures alongside associated gangue minerals like quartz, calcite, and epidote. After operating independently for decades, the property was eventually consolidated into the Mass Consolidated Mining Company around the turn of the twentieth century.

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