Chinese Name： 紫方鈉石 (屬方鈉石的品種)
English Name： Hackmanite、belong to Sodalite's varieties
Optical Effect：Tenebrescence
Chemical: Na8Al6Si6O24(Cl2,S)  (Chloric Sodium Aluminium Silicate)
Crystal System：Cubic
Hardness：5.5 - 6.0
SG：2.14 to 2.40
RI：1.48
Related Chakra：Throat, third-eye and crown
Astrological Sign: Sagittarius
Locality： Afghanistan, Burma, Russia and Canada
Colour：Pink to grey white to white photochrome variety of sodalite containing some Sulfur. Occasionally not enough S to be detectable with EDS (<1%). The S content can give sodalite reversible photochromism or tenebrescence. The fluorescent community reserve the name hackmanite for tenebrescent sodalites.

Special Optical Effect：Tenebrescence: Hackmanite appears pale to deep violet when first mined, but once exposed to sunlight, the color quickly fades to grayish or greeenish-white. When placed back into a dark place or when exposed to ultraviolet light (UV Light), the violet colour returns. The change in violet color can be seen within seconds of being exposed to UV light, but the return of the grayish or greeenish-white color can sometimes take up to a week. The tenebrescence effect can be repeated indefinitely, but is detroyed by heating.

Hackmanite is exceptionally rare. It is considered a collector's stone.

Source of Name：It was first discovered in Greenland in 1896 by L.C. Boergstroem, and was later named after Victor Axel Hackman (1866-1941), a Finnish geologist. However, it wasn't until recently (1991) that the first gem-quality hackmanite deposit was discovered in Quebec, Canada.