Neotocite

specimen number:
2062222

location:
Taylor Mine, Baraga Co., Michigan, USA

description:
Lustrous black neotocite on matrix. Nice example for the species. Collected in 2000.

The Taylor mine, located near the village of Alberta within L'Anse Township of Baraga County, Michigan, United States, is a historic underground iron operation that stands as one of the few producers on the far western extension of the Marquette Iron Range. Geologically, this isolated deposit is hosted within the Paleoproterozoic-age Negaunee Iron Formation, where intense regional folding and localized structural faulting allowed circulating groundwater solutions to oxidize primary iron silicates and leach away chert, leaving behind concentrated pockets of soft, dark brown to black hematite and goethite iron ores. Historically, exploratory drilling and shaft-sinking commenced at the site in 1880 under the direction of the Taylor Iron Company, which developed a substantial underground facility utilizing multiple shafts and an open pit to extract the high-grade direct-shipping ore. Regular commercial mining and rail shipments ran continuously for several years until the localized depletion of easily accessible ore pockets and the severe economic challenges of the mid-1880s forced the permanent cessation of all operations in 1883, with brief, sporadic exploration attempts occurring in the following decades. Through 2026, while the historic underground workings are completely flooded and the old surface plant has been dismantled.

Neotocite is a complex, poorly crystalline hydrous manganese iron silicate mineral that typically forms as an amorphous or microcrystalline alteration product within manganese-rich iron formations and hydrothermal ore deposits. Geologically, it precipitates as a secondary mineral resulting from the low-temperature alteration or weathering of primary manganese silicates like rhodonite or rhodochrosite, often occurring as dark brown to velvet-black, resinous, or vitreous masses, veinlets, and botryoidal crusts that can closely resemble dark brown opal or jasper. At the Taylor mine, mineral collectors and geologists discovered exceptional, classic occurrences of this mineral where it formed prominent, lustrous black vein fillings and mass aggregates closely associated with barite and secondary manganese oxides within the fractured iron ore.

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