Chamosite

specimen number:
2062224

location:
Champion Mine, Marquette Co., Michigan, USA

description:
Choice thumbnail for the species, a radiating crystal grouping of deep green chamosite. There is little attached matrix.

The Champion mine, situated at the town of Champion within Marquette County, Michigan, United States, is a historic and deeply significant underground iron operation noted by mineralogists for producing fine, distinct specimens of the iron-rich chlorite group mineral chamosite. Geologically, this major deposit is located within the Paleoproterozoic-age Negaunee Iron Formation of the Marquette Range, where highly deformed, cherty iron-formations underwent intense, high-grade regional metamorphism and localized hydrothermal alteration during the Penokean Orogeny. This intense metamorphic environment stimulated the recrystallization of massive magnetite and specular hematite ores, while late-stage magmatic fluids circulating through localized quartz veins and fracture zones allowed well-formed, dark green to nearly black platy crystals and fine-grained scaly aggregates of chamosite to precipitate cleanly inside open solution pockets alongside quartz, tourmaline, and chloritoid. Historically, organized industrial development and shaft-sinking at the site commenced in 1867 under the Champion Iron Company, with the complex quickly evolving into one of the deepest and most productive underground operations on the range, utilizing multiple deep shafts to extract high-grade hard ores for American steel manufacturing. Continuous large-scale corporate mining ran for several decades until changing economic conditions and the exhaustion of easily accessible underground reserves led to the permanent cessation of regular ore extraction around 1912, followed by sporadic dump-reclamation projects in the mid-twentieth century.

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