Sphalerite and Fluorite from the Sweet Home Mine, Colorado
Contributed by: Michael Crawford
Date: Sep 6th, 2025
Locality: Sweet Home Mine, Detroit City Claim Block, Mount Bross, Alma Mining District, Park County, Colorado, USA (See on Mindat)
Size: 7 x 7 cm
Description:
Sphalerite (ZnS), fluorite (CaF2), and quartz specimen from the Sweet Home Mine, Park County, Colorado. The sphalerite fluoresces bright orange under longwave UV light. It is non-fluorescent under midwave and shortwave light. It has no afterglow. The fluorite fluoresces blue under longwave UV light. It is dimmer under midwave and shortwave light. An interesting feature is the quartz disappears in the longwave fluorescent image. The quartz is transparent to UV light, and the light makes the sphalerite and fluorite behind it to fluoresce. The fluorescent light also passes through the quartz.
The longwave emission spectra are shown in the last image. The fluorite spectrum has a peak at 422 nm and it is activated by europium (Eu2+) replacing calcium. The sphalerite spectrum has a peak at 583 nm and it is activated by manganese replacing zinc.
Summary of luminescence responses:
Sphalerite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Orange
- Fluorescence under Longwave (365nm LED) UV light: Blue