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Rare Fluorite from the Crystal Mine, Cave-In-Rock, Hardin County, Illinois

The Crystal Mine, one of many fluorspar mines in the historic Cave-In-Rock mining district of Southern Illinois, is not a well-known location for the production of fluorescent mineral specimens. The mine itself shut down production in the 1970s, and specimens from this location are generally quite rare. The Crystal Mine specimen featured here found its way into my collection only recently, and represents a very uncommon Southern Illinois mine location, and as an added bonus, shows a pleasing fluorescent response under UV. The size of this plate of fluorite crystals is 109 x 108 x 28 mm and it weighs 333grams. This specimen displays best under mid and long wave UV, and shows only dim fluorescence under short wave UV.

As shown in the photograph above, this specimen shows its brightest fluorescent response under long wave UV (365 nm). The fluorite cubes produce a beautiful blue glow while intermittent calcite crystals and druse show a white to pale orange response.

A similar, but more purple, response is seen under mid wave UV (302 nm).

Same specimen shown under visible light. This piece consists of a double-sided plate of intergrown, translucent, pale purple fluorite cubes with several colorless calcite scalenohedrons and druse.

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