Strontianite

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Snow white crystallized grouping of strontianite. In great condition. Good miniature for the species.The Minerva Number 1 Mine, located in the Cave-in-Rock District of Hardin County, Illinois, was one of the largest and most significant underground operations within the Illinois-Kentucky Fluorspar District. Geologically, the mine exploited Mississippi Valley-Type (MVT) bedded replacement deposits primarily within the Mississippian-aged Ste. Genevieve and Renault Formations, where fluorine-rich hydrothermal fluids replaced limestone with massive fluorite ore. While the mine is famous for its multicolored fluorite and exceptional crystallized barite, it is also a premier locality for strontianite, which typically occurs as white to cream-colored, acicular or radiating fibrous tufts within vugs. These strontianite crystals often formed as a late-stage mineral during the waning phases of hydrothermal activity, sometimes perching on fluorite or calcite. Historically, the mine was opened in 1942 by the Minerva Oil Company and was later operated by the Ozark-Mahoning Company and the Seaforth Mineral and Ore Company. It remained a vital producer of acid-grade fluorspar for over fifty years until its closure in 1996, marking the end of major commercial fluorspar mining in the United States.