Sodalite var. Hackmanite from Greenland
Contributed by: Michael Crawford
Date: Jun 8th, 2025
Locality: Ilímaussaq complex, Kujalleq, Greenland (See on Mindat)
Size: 8 x 7 x 12 cm
Description:
This is a sodalite var. hackmanite specimen from the Ilimaussaq Complex, Greenland. The longwave fluorescence is activated by the disulfide ion (S2-) replacing chlorine in the sodalite structure. The spectrum of longwave fluorescence contains a broad peak with smaller peaks superimposed on it. The smaller peaks are referred to as vibronic peaks and are caused by the vibration of the two sulfur atoms in the disulfide ion. The longwave emission spectrum of this hackmanite is shifted towards longer wavelengths compared to the typical spectrum of sodalite. This shift is expressed as a redder hue of the longwave fluorescence of hackmanite compared to sodalite.
Hackmanite is the tenebrescent variety of sodalite and this specimen exhibits strong tenebrescence. Tenebrescence is caused by a defect where some chlorine ions are missing from the sodalite crystal lattice. Tenebrescence also requires that an adjacent chlorine ion is replaced by an ion that can donate an electron when exposed to UV light. The disulfide ion is the most common donor replacing chlorine to activate tenebrescence.
The red fluorescence in midwave and shortwave illumination is activated by Fe3+ replacing aluminum in the sodalite structure.
Summary of luminescence responses:
- Fluorescence under Longwave (365nm LED) UV light: Blue