Strangely Tenebrescent Sodalite, Unusual Fluorescence - Greenland

Contributed by: Mark Cole
Date: Apr 5th, 2026
Locality: Taseq Slope, Ilímaussaq complex, Kujalleq, Greenland (See on Mindat)
Size: 3 x 3 x 6 inches
Weight: 1.9 lb

Description:
These pieces were discovered around 2012 on the far eastern Taseq Slope. The discoverer (P. Hintz) nicknamed them "Seal Sodalite" in reference to the dark gray colored sodalite (a first for the Ilimaussaq Complex). In this piece the partial sodalite crystal (see closeup) fluoresces a nice bright orange as you would expect, both longwave and shortwave UV light. BUT - strangely, other areas on the rock exhibit tenebrescence! These areas are not at all fluorescent under longwave UV light and dimly fluorescent under shortwave UV light, reminiscent of feldspar. But they are very tenebrescent. EDS testing has confirmed the presence of sodalite in the matrix, but I believe it to be a homogenous mix of feldspar and sodalite. Very unusual and only found in one area (to date).

Originally posted by Mark Cole on Nature's Rainbows in 2016.

Fluorescence under shortwave UV light.

Fluorescence under longwave UV light.

Tenebrescence after exposure to shortwave UV light.

Normal light.

Tenebrescence after exposure to shortwave UV light. Closeup.

Summary of luminescence responses:

Sodalite (Mindat) (RRUFF)

• Fluorescence under Longwave (365nm LED) UV light: Orange
• Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Orange
• Fluorescence under Shortwave (254nm Lamp/Mercury) UV light: Red