Domeykite, Algodonite, Quartz
specimen number:
2262189
location:
Delaware Mine, Keweenaw Co., Michigan, USA
description: The Delaware mine, located in Keweenaw County on Michigan's Keweenaw Peninsula, is a historic underground copper operation that exemplifies the region's famous native copper deposits. Geologically, the mine is hosted within the Portage Lake Volcanics, a thick sequence of Neoproterozoic basaltic lava flows where hydrothermal solutions deposited native copper within the porous, vesicular tops of the flows (amygdaloids) and associated conglomerates, alongside secondary minerals like calcite, prehnite, and epidote. Historically, organized mining began at the site in 1847 under the Northwest Mining Company, and despite multiple reorganizations under different names like the Delaware Mining Company, the property struggled with profitability before final commercial operations ceased around 1887. In the late 20th century, the site was preserved and converted into a popular tourist attraction, which continues to offer guided underground tours through 2026. While the Delaware mine itself focused on native copper, the broader Keweenaw district, particularly the nearby Mohawk mine, is famous for a material known as "mohawkite," which is a rare local mixture of copper arsenide minerals, primarily algodonite and domeykite, often including nickel and cobalt. This material occurs in narrow, late-stage hydrothermal veins that cut across the basalt beds, presenting as a heavy, metallic, brassy-yellow aggregate that rapidly tarnishes to dark brown or iridescent shades, making it a highly prized curiosity among regional mineral collectors.
A good rich example of what is known as mohawkite, basically a mixture of domeykite and algodonite. This is throughout a massive quartz with minor copper. The specimen comes with an antique data card as shown at the end of the video with an acquisition date shown of 1961.
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