Shigaite

specimen number:
2062330

location:
Homer Mine, Iron Co., Michigan, USA

description:
A small but choice cluster for this species of shigaite Crystals. In good condition. These were never common in the district.

The Homer mine, located near Iron River in Iron County, Michigan, was a prominent underground iron mine operated by the M.A. Hanna Company. Geologically, the deposit is situated within the complexly folded Paleoproterozoic Riverton Iron-Formation, where secondary hydrothermal alteration enriched the cherty iron strata into dense bodies of hematite and goethite ore. Shaft sinking began in 1914, and the mine entered regular production in 1915, later integrating its underground workings with the adjacent Cardiff and Wauseca properties to form the Homer-Wauseca group. The mine remained an important regional producer of direct-shipping iron ore until underground operations finally ceased in 1969 due to the depletion of commercial reserves and changing steel manufacturing demands.

Shigaite is a complex, hydrous aluminum manganese sulfate mineral that typically forms small, tabular hexagonal crystals or platy aggregates with a distinct vitreous to pearly luster. Geologically, it is a secondary mineral that precipitates from low-temperature hydrothermal fluids or oxidizes within highly altered manganese-bearing iron-formations and stratiform zinc-manganese deposits.

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