John Betts - Fine Minerals
Glassy crystals of translucent Sodalite, variety Hackmanite, in
translucent Limonite-stained marble matrix. The crystals are tenebrescent, meaning they fade
to pinkish-gray in daylight, but turn deep purple after prolonged
exposure to UV illumination.
The top pictures shows the Hackmanite with a deeper color after exposure to UV; the bottom one is standard daylight without exposure.
Kiran, Kokcha Valley, Badakhshan, Afghanistan