Baryte

Baryte from the Minerva Mine, Cave-in-Rock, Illinois, U.S.A., measuring 85 × 50 × 34 mm and weighing 166 grams. A solid tabular specimen from the heart of the Illinois-Kentucky Fluorspar District.

Baryte is barium sulfate, BaSO4, and the Cave-in-Rock sub-district is better known worldwide for its Fluorite, but it has also produced excellent Baryte from the same Mississippi Valley-type hydrothermal veins. These veins formed when warm, barium and fluorine-rich brines moved through fractures in the district's limestone country rock, depositing Fluorite, Baryte, Calcite and Sphalerite in open spaces as the fluids cooled. Baryte here typically forms tabular, often blocky crystals, sometimes tinted amber or honey-brown by trace impurities.

The Minerva Mine was one of the significant producers in the Cave-in-Rock sub-district during the twentieth century, worked primarily for its Fluorite but yielding fine Baryte as well. This specimen carries a double provenance, the David Vince Collection and the Jack Nelson Collection, tying it to two established sources of American fluorspar-district material.