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New Mexico Mineral Symposium — Abstracts

The Fissure Veins of Keweenaw County, Michigan

Christopher J. Stefano and Phillip Persson

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Figure 1. Copper, adularia, epidote, 6.8 cm. Dana Mine, Central, Keweenaw Co., MI. Scott Rudolf specimen. Jeff Scovil photo

Michigan’s Keweenaw Peninsula is well known to mineral collectors for producing the world’s finest specimens of native copper, along with world-class specimens of native silver, calcite, analcime, and many other species. The district has a rich history dating back to prehistoric times, and its development has contributed significantly to the course of US and therefore world history. Despite this, specimen mineralogical literature on the region has been largely confined to discussions of recent discoveries in a series of articles in Rocks & Minerals by Tom Rosemeyer. The only really in-depth historical dive was done by Marc Wilson and Stan Dyl in their 1992 Mineralogical Record special issue (Wilson and Dyl 1992). While outstanding as far as it goes, this coverage only scratches the surface of the deep and rich history and mineralogy of the region.

The present authors have begun the process of digging deeper with the recently released Michigan Copper Country II issue of the Mineralogical Record, which covers the so-called fissure mines of Keweenaw County, Michigan (Vol.54, No.1, 2023). Additional special issues are planned to cover the rest of the district with the same level of detail. We chose to start with the fissure veins because these were among the very first mines opened in the district. Conveniently, those early mines were among the most prolific producers of fine specimens for the collector, and most are familiar with the likes of the Phoenix, Central, Copper Falls, and Cliff mines. This talk will briefly summarize the history and mineralogy of these mines as laid out in our recent Mineralogical Record special issue.


  1. Wilson, M.L. and Dyl, S.J. II (1992) The Michigan Copper Country. Mineralogical Record, V.23(#2), 1-76.


Fissures, mines

pp. 13

43rd New Mexico Mineral Symposium
November 10-12, 2023, Macey Center, Socorro, NM
Print ISSN: 2836-7294
Online ISSN: 2836-7308