saf-ahyuh r

Discovered in Greenland in the late 1890's, hackmanite is named for Finnish geologist Victor Hackman. It is a rare occurrence to find gem-grade hackmanite; at best, most crystals are translucent. Hackmanite is the light pink to pale violet variety of sodalite. It is a particularly unusual gem because it exhibits a special optical property known as "tenebrescence," a type of reversible photochromism. This feature allows the gems to temporarily change color when exposed to different light forms. While hackmanite gems are usually pink to violet, the color quickly fades to gray or greenish-white in sunlight, and will slowly return to the original color after changing the light. Its tenebrescent property makes hackmanite a prized mineral for collectors.

Hackmanite Polished
Hackmanite Classification
Common Name Hackmanite
Species Sodalite
Hackmanite Optical Properties
Transparency Transparent - Translucent
Dispersion Strength: Moderate Fire Value: 0.018
Refractive Index 1.479-1.487
Optic Character NA
Optic Sign NA
Polariscope Reaction Aggregate (AGG), Singly Refractive (SR)
Fluorescence SWUV: Typically orangish yellow but can be bluish white or orange
LWUV: moderate to strong orange to yellowish orange
Pleochroism None
Hackmanite Characteristic Physical Properties
Hardness 5.5-6
Streak White
Specific Gravity 2.140-2.400 Typical:2.250
Toughness Poor
Inclusions Hackmanite can contain small black inclusions.
Luster Vitreous, Greasy
Fracture Uneven, conchoidal
Cleavage Poor, in one direction
Hackmanite Chemistry & Crystallography
Chemical Name chloric sodium aluminum silicate
Chemical Formula Na8Al6Si6O24Cl2
Crystal System Cubic
Chemistry Classification Silicate

Hackmanite Colors

  • Gray Hackmanite Gray
  • Purple Hackmanite Purple
  • Pink Hackmanite Pink
  • White Hackmanite White

Countries of Origin

Canada; Myanmar; Afghanistan; United States of America (the); Guinea; Norway; Russian Federation (the); Greenland


When exposed to sunlight the color will fade to white. Color will return if stones are stored in darkness for several days or when exposed to shortwave ultraviolet light.

Sisk Gemology Reference

Showcasing 200 gemstones in over 1,000 pages and accompanied by more than 2,000 photos, The Sisk Gemology Reference is a must-have in every collector’s library. Each comprehensive, three-volume set features state-of-the-art photography, detailed illustrations, and scientifically precise descriptions to create an entrancing experience for gemstone amateurs and afficionados alike.

Shop Now

Tim Matthews


Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.