Marialite from Sar-e-Sang, Badakhshan Province, Afghanistan
Contributed by: Michael Crawford
Date: Nov 16th, 2025
Locality: Pitwak Mine, Sar-e-Sang River, Sar-e-Sang, Kuran wa Munjan District, Badakhshan, Afghanistan (See on Mindat)
Size: 6.5 x 8 cm
Description:
A well-formed tetragonal marialite (Na4Al3(/sub>Si9O24Cl) crystal from Sar-e-sang, Badakhshan Province, Afghanistan. The 3 cm tall crystal is glassy and translucent. The marialite crystals are in a gypsum matrix that comes from a gypsum diapir in the Pitwak Mine.
The marialite fluoresces different colors under different wavelengths of UV illumination. Under longwave light, the marialite fluoresces bright yellow. It fluoresces a peach color under midwave light, and it fluoresces red under shortwave light.
The longwave emission spectrum of the marialite has nine vibronic peaks ranging from 540 nm to 712 nm. The maximum peak is at 573 nm. These peaks are activated by disulfide ions (S2-) replacing chlorine in the marialite structure. The spectrum also has a peak at 418 nm. The activator for this peak is unknown at this time. It might be dioxide replacing chlorine, crystal defects, a rare earth element impurity.
The shortwave emission spectrum shows that the red fluorescent color is a single broad peak that extends into the near infrared and has a maximum at 690 nm. This red fluorescence is likely activated by ferric iron (Fe3+) replacing aluminum. The spectrum also has a peak in the ultraviolet with a maximum at 338 nm. This peak may be caused by cerium or another rare earth impurity.
The midwave emission spectrum of marialite is a combination of the longwave and shortwave spectra. The midwave spectrum is dominated by a broad peak with a maximum at 696 nm that is caused by a ferric ion activator. There is also some yellow emission from the disulfide activator.
Summary of luminescence responses:
Marialite (Mindat) (RRUFF)
- Fluorescence under Longwave (365nm LED) UV light: Yellow
- Fluorescence under Midwave (305nm LED) UV light: Orange
- Fluorescence under Shortwave (255nm LED) UV light: Red