Genthelvite from Mt. St. Hiliare, Canada
Contributed by: Michael Crawford
minID: 6MU-4C3
Date: Jun 13th, 2025
Locality: Poudrette quarry (De-Mix quarry; Demix quarry; Uni-Mix quarry; Carrière Mont Saint-Hilaire; MSH), Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada (See on Mindat)
Size: 0.9 x 1.4 cm
Description:
These genthelvite (Be3Zn4(SiO4)3S) crystals from the Poudrette Quarry, Mont Saint-Hilaire (MSH), La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada have different fluorescent response in different illumination wavelengths. The fluorescence is green in longwave and shortwave UV illumination and red orange in midwave UV illumination. Spectra of the green longwave and shortwave fluorescence are nearly identical. They peak around 508 nm. These peaks are shifted towards blue light compared to willemite fluorescence (peak at 525 nm). The midwave emission spectrum has two peaks, a large broad peak with a maximum around 670 nm and a smaller peak at 518 nm. Czaja and others (2021) found that the green fluorescence in MSH genthelvite is activated by Mn2+ replacing Zn2+. Their specimens did not contain any iron. The red-orange midwave fluorescence is likely caused by Mn2+ activation as well, but no explanation was found to explain why midwave fluorescence is red-orange and not green like the LW and SW fluorescence.
Czaja, M., Lisiecki, R., Juroszek, R., and Krzykawski, T., 2021, Luminescence Properties of Tetrahedral Coordinated Mn2+; Genthelvite and Willemite Examples, Minerals, V.11, 1215.
Summary of luminescence responses:
Genthelvite
- Fluorescence under Longwave (365nm LED) UV light: Green
- Fluorescence under Midwave (305nm LED) UV light: Orange
- Fluorescence under Shortwave (255nm LED) UV light: Green