Hackmanite

Hackmanite is an extremely rare, sulfur-rich variety of sodalite that shows tenebrescence. It was first discovered in Greenland in 1896 by L. C. Boergstroem and was later named after Victor Axel Hackman, a Finnish geologist. However, it escaped the interest of jewelers until recently (1991), when the first high-quality abrasive hackmanite was found to be discovered in Quebec, Canada. Hackmanite has a light to dark purple color just after mining, but as soon as it is exposed to sunlight, the color quickly disappears and changes to gray or green-white. When placed back in a dark room or when exposed to shortwave UV light, the purple color slowly returns. A color change can occur within a few seconds when exposed to sunlight, but it can sometimes take up to a week to return to the original color. This effect can be repeated continuously, but is permanently destroyed by high heat. Some hackmanites (from Afghanistan and Burma), on the other hand, initially have a creamy white color, but in sunlight they turn purple to pinkish-red, which can fade again if left in a dark environment for some time. Under UV light, it changes color to bright pink-orange.