Wispy Hydrocarbon Inclusions in Fluorite from Cave-In-Rock, Illinois

This pair of yellow fluorite cubes from Cave-In-Rock, Hardin County, Illinois, show a very interesting multi-wave fluorescent response due to the presence of wispy hydrocarbon (petroleum) inclusions within the fluorite crystals. Under all wavelengths, the hydrocarbon inclusions show a bright, filamentous, web-like pattern of white fluorescence. Hydrocarbon inclusions are common in fluorite from the Illinois - Kentucky Fluorspar District. The size of this specimen is 63 x 54 x 56 mm, and it weighs 224 grams.

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