Hackmanite is a very special and rare variety of sodalite. This amazing mineral possesses the ability to change color when exposed to ultraviolet radiation (both UV from a UV lamp and UV from the direct sun). This phenomenon, known as tenebrescence, is a reversible photochroism. In other words, the color change is not permanent and can be repeated indefinitely. However if the stones is heated, its ability to change color is destroyed. Typical color changes for rare Burmese hackmanites specimens are from colorless, light pink, blue or purple to intense blue or deep purple. According to the quality - i.e. purity - of the hackmanite specimen, the color change is naked eye visible in few seconds, whereas the return of the initial color may take between hours and one week when stored in a complete dark area. The most sought after specimens are those with a color change from colorless or very light color to intense deep purple.