Sodalite Tenebrescense - Some brief Observations

Green sodalite exhibits dramatically strong tenebrescense - but most people don’t see the initial color of the mineral when it is broken from the matrix. Almost all of the rocks within the Illimaussaq complex show a strange coloration when initially broken (first exposed to daylight). This color is always darker than the piece normally is (on exposure to light). Once the color fades on most of the minerals, it cannot be brought back by UV exposure.

The green sodalite does respond strongly to UV light and is highly tenebrescent. But in the following animation note that the tenebrescense caused by UV light is not the same return to the initial color pattern when the mineral is first broken. The complete piece darkens to a deep purple, where only certain areas were purple when the mineral was first broken from the matrix.

For more on this unusual property, check out the animations - but watch out, large images, high-bandwidth area ahead:

Theory: All of this sodalite is somewhat translucent. After eons of exposure to sunlight (while still just a great big rock) the UV rays penetrated the outer layers and faded the purple. Only the innermost portions of the boulder still retain the purple coloration.

Any other opinions? Radioactivity?

Tenebrescense - Brief Overview

A piece of green sodalite placed under UV light will fluoresce bright orange, followed by a deep purple tenebrescense. To date we have discovered only this one variety of sodalite from Greenland exhibiting this dramatically deep tenebrescense.

Top Right - Longwave UV
Middle - Natural Light
Bottom Right - Tenebrescent

Bottom Left - Animation showing
progressive color change
under Shortwave UV lighting.

How long does it last?

The top image on the right was taken immediately after exposure to 5 minutes of shortwave UV. The bottom image was taken after 8 hours in the dark. The deep purple has changed hue to a rich burgundy. This color changed occurred in a virtually light-proof box, with the flash of the camera being the only light on this specimen.