Sphalerite and Fluorite from Sweet Home Mine, Colorado
Contributed by: Michael Crawford
Date: Oct 14th, 2025
Locality: Detroit City Mine, Detroit City Claim Block, Mount Bross, Alma Mining District, Park County, Colorado, USA (See on Mindat)
Size: 10 x 18 cm
Description:
A sphalerite and fluorite specimen from the Detroit City Mine, Park County, Colorado. The Detroit City mine was started in 2016 and is a new mine approximately 60 meters vertically above the former Sweet Home Mine that is famous for its rhodocrosite specimens. This specimen was split along a narrow vein of sphalerite and fluorite with a trace amount of pink rhodocrosite. The sphalerite and fluorite have bright fluorescence under longwave UV illumination. The sphalerite fluoresces yellow-orange and the fluorite fluoresces blue. The fluorescence is dimmer under midwave and shortwave light. The fluorite has brief afterglow from exposure to UV light.
The longwave emission spectrum of the sphalerite is a broad peak with a maximum at 569 nm. The fluorescence is activated by manganese replacing zinc. The fluorite exhibits the typical blue fluorescence activated by europium that replaces calcium. The fluorite emission has a peak with a maximum at 422 nm. The shortwave emission spectrum of fluorite has a second peak in the ultraviolet at 314 nm. The peak is likely activated by yttrium. This ultraviolet peak differs from many blue, fluorescent fluorite specimens that have ultraviolet fluorescence activated by cerium that causes a double peak at 319 nm and 341 nm.
Summary of luminescence responses:
Sphalerite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Yellow
- Fluorescence under Longwave (365nm LED) UV light: Blue