Siderite

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Rich cleavage masses of siderite throughout a calcite matrix. Collected around the year 1950.The Commonwealth Mine, located in Florence County, Wisconsin, was discovered in 1876 by H.D. Fisher and formally opened by the Commonwealth Iron Company around 1880, operating initially for about 11 years before intermittent and related regional mining activities wound down by approximately 1920. Geologically, the deposit sits within the Menominee Iron Range, where high-grade soft hematite and limonite iron ores formed via secondary enrichment, specifically through the oxidation and leaching of Precambrian sedimentary iron formations and interlayered iron-bearing carbonate and silicate strata.