Fluorescent Clam Fossil from Ruck's Pit, Fort Drum, Florida

This is a fluorescent, Pleistocene age (approx. 1-2 mya) Mercenaria permagna clam fossil from the famous Rucks' Pit site in Fort Drum, Florida. During the fossilization process of these clams, the calcium carbonate from the original shell material dissolved and recrystalized as beautiful, honey-colored, scalenohedral, calcite crystals on the interior of the shell. The resulting calcite is brightly fluorescent under all wavelengths of UV, and also displays a short-lived green phosphorescence. The exterior of the shell is encrusted with the coquina from which it was removed. The size of this specimen is 94.2 x 79.5 x 47.9 mm, and it weighs 164 grams.

Fluorescence under short wave UV (254 nm).

Fluorescence under long wave UV (365 nm).

Pale green phosphorescence is seen following exposure to long wave UV.


Photograph taken under visible light. Note the numerous honey-colored, scalenohedral, calcite crystals on the inner surface of the shell.

Reverse side of same specimen shown under short wave UV (254 nm).

Reverse side of same specimen shown under long wave UV (365 nm).

Green phosphorescence is seen following exposure to long wave UV.

Reverse side of same specimen shown under visible light.

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