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Sweetwater Agate, Agate Flats, Wyoming

This is a nodule of Sweetwater Agate, a translucent grey/blue dendritic agate found in the Agate Flats area, north of the Sweetwater River, near Jeffrey City, Freemont County, WY. This agate is a regionally popular lapidary material, but it also shows a striking fluorescent response under UV. The bright green short wave UV response is uranyl-activated, confirmed by the presence of numerous uranium mines in the Freemont County area. The orange response seen under long wave UV may be Mn-activated, as suggested by the presence of the manganese oxide dendritic inclusions. This size of this agate nodule is 54 x 40 x 26 mm, and it weighs 67 grams.

In the photo montage above, the Sweetwater agate is shown under visible light (top), short wave UV (middle), and long wave UV (bottom).

As shown in the image above, bright green fluorescence is seen under short wave UV (254 nm).


Under long wave UV (365 nm), a more subdued green and orange response is seen.


Same specimen shown under visible light.

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