Hackmanite is a rare, semi-precious mineral with a number of unique properties:

Color

Hackmanite is typically pink to violet in color, but can also be white, blue, gray, or purple. When exposed to sunlight or UV light, it can temporarily change color to gray or greenish-white. This is known as tenebrescence, or reversible photochromism, and is the rarest optical phenomenon in gemstones.

Formation

Hackmanite is usually formed in alkaline magmas with low silica, such as nepheline syenites, phonolites, and metasomatized calcareous rocks.

Discovery

Hackmanite was discovered in Greenland in the late 1890s and named after Finnish geologist Victor Hackman.

Uses

Hackmanite is used in jewelry and as an energy crystal, but it also has potential for high-tech applications. For example, researchers at the University of Turku are developing hackmanite plates to measure radiation levels on the International Space Station.

Other names

Hackmanite is a variety of sodalite, a sodium aluminosilicate containing chloride. The International Mineralogical Association no longer considers hackmanite an official mineral name, so some say that photochromic or tenebrescent sodalite would be a more appropriate name.