Witherite with Alstonite, Fluorite

specimen number:
2312311

location:
Minerva Mine #1, Hardin Co., Illinois, USA

description:
Classic specimen for this locality, lustrous slightly translucent crystals of witherite in a cluster with micro alstonite. Minor fluorite present as well. This is in excellent condition.

The Minerva Mine Number 1, located near Cave-in-Rock in Hardin County, Illinois, was a premier producer within the famous Illinois-Kentucky fluorspar district. Geologically, the mine exploited massive Mississippi Valley-type deposits, featuring extensive bedding-replacement orebodies and hydrothermal vein systems hosted in Paleozoic limestone. Hot mineral-rich fluids deposited large quantities of fluorite, sphalerite, calcite, and other prized minerals along structural faults and fractures. Historically, the deposit was discovered around 1940, with surface and underground facilities established in 1941. It operated under various owners—producing fluorspar, zinc, and lead—with active mining continuing intermittently until final closure in 1995.

Witherite is a barium carbonate mineral that was discovered in 1784 by English physician and naturalist William Withering, who proved it was chemically distinct from barite. It was officially named in his honor by German geologist Abraham Gottlob Werner in 1790. Geologically, witherite typically forms in low-temperature hydrothermal veins, frequently associated with lead ores, fluorite, and barite. Mineralogically, it belongs to the aragonite group and is well known for its characteristic pseudohexagonal crystal twinning, high specific gravity, and strong bluish-white ultraviolet fluorescence.

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