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Chameleon Agate from the Granite Mountains, Wyoming

Agate/chalcedony nodule from the Granite Mountains, Fremont County, Wyoming, that shows a unique multi-colored fluorescent response dependent on the UV wavelength of excitation. Under short wave UV (254nm) a bright green response is seen. A less bright green response occurs under mid wave UV (302nm). Things get interesting under long wave UV (365nm) however, as this material fluoresces a beautiful peach/pink color. There are numerous uranium mines in the area where this material occurs, providing confirmation that uranium is the activator responsible for the green fluorescence seen under short and mid wave UV. However, a second activator appears to be at work under long wave UV to produce the pastel orange/pink response; possibly manganese and lead. This is the fluorescent chameleon of the agate world! 39 x 28 x 25 mm, 33 grams.

In the photo montage above, the specimen is shown under visible light (upper left), short wave UV (upper right), mid wave UV (lower left), and long wave UV (lower right). Click on the photograph for larger images taken under each wavelength.

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