Hackmanite

A variety of sodalite showing tenebrescence (reversible photochromism). Hackmanite can be a deep pink, blue or purple but quickly fades to colourless when exposed to sunlight. The original colour can be restored quickly by exposure to short-wave ultraviolet light, or more slowly by storing it in a dark space.

It typically contains some S, but not always enough to be detectable with EDS (<1%). The S content is related to its tenebresence.

Hackmanite shows orange coloured photoluminescence in UV light, exhibits a purple-red colour subsequently to UV irradiation or after cracking, bleaches within minutes to hours in visible light, and usually recovers colour in darkness.

The change in the colour of hackmanite in photochromism is caused by the joint action of the F-center and the oxygen hole centres. The change in the UV-Vis spectra may be caused by the superposition of two peaks. Under 365 nm UV excitation, the peak of fluorescence spectra of 662 nm is related to the 2∏g→2∏u transition of S²⁻, the blue emission at 441 nm is caused by the 3P0.1→1S0 transition of s2 ions (Pb²⁺, T^l+, Sn²⁺ Sb²⁺) , and at 541 nm is caused by the Mn2+ center. The results are helpful in deepening the understanding of photochromism, fluorescence mechanism, and its structure, expanding the application of hackmanite.

Originally described from Tavaiok river (=Tawajok in Ramsey, 1898; Tawa in Borgström 1901 and 1903) valley, Lovozero (Lujavr-Urt in Ramsay, 1898; Lujaur-Urt in Borgström, 1901 and 1903) Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, Russia (Ramsey, 1898; Borgström, 1901 and 1903).