Pargasite and Spinel from Vietnam
Contributed by: Michael Crawford
Date: Jun 19th, 2025
Locality: L?c Yên District, Yên Bái Province, Vietnam (See on Mindat)
Size: 9.5 x 12 cm
Description:
This is a specimen of spinel (MgAl2O4) and pargasite (NaCa2(Mg4Al)(Si6Al2)O22(OH)2) in marble matrix from Luc Yen, Yen Bai Province, Vietnam. The red spinel fluoresces bright red in longwave UV illumination. The green pargasite fluoresces pale green in longwave and shortwave UV illumination.
The emission spectra show the characteristic signature for spinel activated by chromium (Cr3+). It has five sharp peaks at 673 nm, 685 nm, 696 nm, 705 nm, and 715 nm; three are in the visible red and two are in the near infrared.
Summary of luminescence responses:
Pargasite
- Fluorescence under Longwave (365nm LED) UV light: Green
- Fluorescence under Shortwave (255nm LED) UV light: Green
- Fluorescence under Longwave (365nm Lamp/Mercury) UV light: Red
- Fluorescence under Longwave (365nm LED) UV light: Blue