Spinel, Pargasite and Chondrodite from Vietnam
Contributed by: Michael Crawford
Date: Jun 18th, 2025
Locality: L?c Yên District, Yên Bái Province, Vietnam (See on Mindat)
Size: 9.5 x 12 cm
Description:
This is a multi-color fluorescent specimen from Luc Yen, Yen Bai Province, Vietnam. The specimen has the fluorescent minerals spinel (MgAl2O4), pargasite (NaCa2(Mg4Al)(Si6Al2)O22(OH)2), and chondrodite (Mg5(SiO4)2F2) in a marble matrix. The red spinel fluoresces bright red in longwave UV illumination. The green pargasite fluoresces greenish white in shortwave UV illumination and the orange chondrodite fluoresces a modest orange is shortwave UV light.
The last image shows the emission spectra of the minerals in the specimen. The sharp peaks of the spinel longwave emission are caused by a chromium activator. Pargasite shortwave emission has a broad peak with a maximum at 460 nm. There are no references that describe the activator for pargasite fluorescence. My spectrometer was only able to collect a noisy spectrum of chondrodite shortwave fluorescence. The brightness of chondrodite fluorescence is considerably less bright than spinel and pargasite fluorescence.
Summary of luminescence responses:
Spinel
- Fluorescence under Longwave (365nm LED) UV light: Red
- Fluorescence under Shortwave (255nm LED) UV light: Green
- Fluorescence under Shortwave (255nm LED) UV light: Orange