Sphalerite and Fluorite Make for a Beautiful 2-Color Rock from the Sweet Home Mine, Alma, Colorado

To mineral collectors, the Sweet Home Mine in Alma, Colorado is best known as a producer of some of the finest rhodochrosite specimens in the world. During the process of trimming these rhodochrosites to remove excess matrix, waste material is produced which sometimes contains fluorescent sphalerite and fluorite, both of which show a bright two-color response under long wave UV. The specimen featured here is an excellent example of such material and contains a combination of brightly fluorescent sphalerite (orange) and fluorite (blue/purple), and minor amounts of non-fluorescent pyrite and rhodochrosite. The size of this piece is 33 x 27 x 27 mm, and it weighs 28 grams.

The image above shows the specimen at its brightest under long wave UV (365 nm). The bright orange fluorescence of the sphalerite dominates the response, with blue/purple accents provided by the fluorite.

As shown above, this specimen is also fluorescent under short wave UV (254 nm). The response is similar to what is seen under long wave UV, but is less bright and the colors are more muted.

Same specimen shown under visible light. Note the minor flecks of brassy pyrite and patches of red/pink rhodochrosite.

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