Hackmanite is a rare form of sodalite and it is a true oddity in the mineral world due to its displaying tenebrescence. This property can also be described as reversible photochromism, and it’s incredibly rare in natural materials.
This quality means that the stone will change colors in light, but it’s also reversible. This is different than the color change effect in stones like alexandrite since the stone doesn’t immediately change color.
Instead, hackmanite will slowly change color in sunlight. The variety found in Greenland is a strong violet when pulled from the earth, fading to a pale green-white after prolonged sun exposure. It then changes back when kept out of the sun for some time.
There is another variety found in Burma that is clear when mined but ends up being purple after sun exposure. This variety is also reversible!
Hackmanite is a strange form of sodalite which changes colors back and forth depending on sun exposure. This quality is found in few other gemstones or even man-made materials. Of the latter, the only commonly known use is in glasses that darken when exposed to light.
History of Hackmanite
Hackmanite was first discovered in Greenland by L.H. Borgstroem in 1901. He named it after the famed Finnish Geologist, Victor Axel Hackman. Important deposits of Hackmanite are located in Afghanistan, Myanmar, Canada, Norway and Russia.
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