Hackmanite – a mineral with fascinating optical properties

Hackmanite is a rare variety of sodalite (Na₈Al₆Si₆O₂₄Cl₂), which is known for its unique ability to change color and fluoresce. This phenomenon, known as tenebrescence, means that hackmanite darkens after exposure to UV light and then gradually returns to its original color. This makes it one of the minerals that fascinates geologists, collectors and lovers of natural curiosities.

Hackmanite deposits

Hackmanite is mined mainly in Afghanistan, Myanmar, Canada, Russia and Greenland. The most prized specimens are those that show pronounced fluorescence and a strong color change effect.

Fluorescence under UV light

Under ultraviolet light, hackmanite glows with an intense pink, red or orange color. This effect is popular among collectors and makes hackmanite one of the most interesting fluorescent minerals ever.

Hackmanite identification

Chemical formula: Na₈Al₆Si₆O₂₄Cl₂

Color: white, pink, purple (with tenebrescence)

Crystal system: cubic

Hardness: 5.5 – 6 (Mohs scale)

Luster: dull to glassy

Density: 2.2–2.4 g/cm³

Each piece of hackmanite is an original and, thanks to its ability to change color, it is a sought-after collector's mineral.

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