Sphalerite and Calcite from the Sterling Mine, Ogdensburg, Sussex County, New Jersey
Contributed by: Michael Crawford
Date: Oct 2nd, 2025
Locality: Sterling Mine, Sterling Hill, Ogdensburg, Sussex County, New Jersey, USA (See on Mindat)
Size: 6.5 x 10.5 cm
Description:
A sphalerite and calcite specimen from the Sterling Hill, Ogdensburg, Sussex County, New Jersey. The sphalerite fluoresces blue and orange under longwave and midwave UV illumination. It is non-fluorescent under shortwave light. It has afterglow from exposure to longwave light, but no afterglow from midwave light exposure. The calcite fluoresces red under all wavelengths of UV light. It is brightest under shortwave light. There is also a small amount of willemite that fluoresces green under shortwave light,
Sphalerite is a semi-conductor. The band gap between the valance band and the conduction band is narrow enough that electrons can move to the conduction band when sphalerite is exposed to UV light. When the electrons return to the valance band, blue photons are emitted. The emission spectrum of this blue fluorescence peaks at 449 nm. For more details on semiconducting minerals and band transitions see the article by Glenn Waychunas, in the 2020 FMS Journal.
Manganese replacing zinc activates the orange fluorescence. It takes less energy to create this manganese activated fluorescence, so the light emitted is at a longer wavelength. Emission spectra of this orange fluorescence is a broad peak with maximum at 605 nm. The 449 nm peak is still present in the emission of the orange, fluorescent sphalerite.
The shortwave emission spectrum of calcite has a broad peak with a maximum at 619 nm. This peak is activated by manganese replacing calcium. The spectrum also has a small broad peak in the ultraviolet with a maximum around 319 nm. This peak may be activated by lead. The peak of the longwave emission spectrum of calcite is at 611 nm. I do not know the cause of this shift or why the emission rises in the blue portion of the spectrum.
Summary of luminescence responses:
Sphalerite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Blue
- Fluorescence under Midwave (305nm LED) UV light: Blue
- Fluorescence under Longwave (365nm LED) UV light: Orange
- Fluorescence under Midwave (305nm LED) UV light: Orange
- Fluorescence under Shortwave (255nm LED) UV light: Red