Datolite

specimen number:
8311377

location:
Franklin Mine, Houghton Co., Michigan, USA

description:

A thick cut slab through datolite, one side polished to show the beautiful interior. This is really large for one of these. This one has quite nice color.

The Franklin Mine, situated in the town of Franklin Mine just north of Hancock in Houghton County, Michigan, was a significant producer within the Keweenaw Peninsula copper district. Geologically, the mine exploited the famous Pewabic Lode, a mineralized basaltic amygdaloid flow where native copper precipitated within gas bubbles and fractures of the Precambrian Portage Lake Volcanics. Unlike many neighboring mines that focused on conglomerate ores, the Franklin was noted for its rich amygdaloidal mineralization. Historically, the Franklin Mining Company was organized in 1857, and the mine began steady production shortly thereafter. The operation saw several phases of expansion, including the acquisition of the adjacent Junior Mine property in the late 1890s to access deeper portions of the lode. The mine remained a consistent contributor to the region's copper output for several decades, though it faced increasing challenges as the ore grew deeper and more expensive to extract. Large-scale operations eventually ceased in the early 1920s, around 1922, following the post-World War I decline in copper prices. Today, the Franklin Mine is remembered as a pioneering effort on the Pewabic Lode, leaving behind notable waste rock piles that have yielded fine specimens of native copper and associated secondary minerals to collectors for over a century.

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