Multi-color Sphalerite from the Horn Silver Mine, Utah
Contributed by: Michael Crawford
Date: Sep 4th, 2025
Locality: Horn Silver Mine, Frisco, San Francisco Mining District, Beaver County, Utah, USA (See on Mindat)
Size: 6.5 x 9 cm
Description:
A specimen of multi-color fluorescent sphalerite from the Horn Silver Mine, Frisco, Beaver County, Utah. Wurtzite may also be present and may be fluorescent. The Horn Silver ore body, one of the most productive lead-silver deposits in Utah, was formed along the Horn Silver fault. The fault juxtaposes Upper Cambrian limestones and dolomites against Tertiary volcanics. The shallower portions of the deposit have been oxidized and sulfides such as this specimen are found deeper in the mine.
The fluorescent colors in this specimen include orange, yellow, green, blue-green, and purplish white. The longwave emission spectra show these different colors of the sphalerite. The green sphalerite fluorescence is activated by copper (Cu+) and aluminum (Al3+) substituting for two zinc atoms. Manganese activates orange and yellow fluorescence. This sphalerite specimen has two colors (green and orange) of strong afterglow from longwave illumination. The sphalerite is also triboluminescent.
Summary of luminescence responses:
Sphalerite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Orange
- Fluorescence under Longwave (365nm LED) UV light: Yellow
- Fluorescence under Longwave (365nm LED) UV light: Green