Sodalite with Sulfur / Hackmanite "eyes-chain" from Afghanistan.

The mineral sodalite is a chlorine-containing sodium aluminum silicate with the chemical formula Na8Al6Si6O24Cl2. It belongs to the feldspathoids tectosilicaat. The white, gray, pink, green or deep blue sodalite is a glass to oily shine, a white stripe color and cleavage is poor according to the crystal surface [110]. The average density is 2.29 and the hardness is 6. The crystal system is cubic and the mineral is not radioactive. The name of the mineral sodalite is derived from the chemical composition; English sodium means "sodium." Sodalite is mainly found in nepheline syenieten, phonolite and other felsic silica-poor igneous and metamorphic rocks. The type locality is situated in the Ilimaussaq massif on Greenland.

Hackmanite is an important variety of sodalite exhibiting tenebrescence. When hackmanite from Mont Saint-Hilaire (Quebec) or Ilímaussaq (Greenland) is freshly quarried, it is generally pale to deep violet but the color fades quickly to greyish or greenish white. Conversely, hackmanite from Afghanistan and the Myanmar Republic (Burma) starts off creamy white but develops a violet to pink-red color in sunlight. If left in a dark environment for some time, the violet will fade again. Tenebrescence is accelerated by the use of longwave or, particularly, shortwave ultraviolet light. Much sodalite will also fluoresce a patchy orange under UV light.