Highly Tenebrescent White Sodalite
Kangerlussaq, Ilimaussaq Complex, Greenland

When initially discovered (first cracked) this appeared to simply be a plain old white rock. We did not even put a lamp to it because it simply did not look to be much . But, after 5 minutes it had changed color (see image at the bottom) just under sunlight. Exposure to UV causes dramatic changes!