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  3. Hackmanite Vs Sodalite

Hackmanite vs Sodalite: One Mineral, One Reversible Color Change

By Digital Towns Crystals · Last reviewed October 8, 2026

Short answer: yes, hackmanite is sodalite. Both are the same sodium aluminum silicate with chlorine, Na8Al6Si6O24Cl2, with the same hardness and density. "Hackmanite" is the variety name for sodalite that is tenebrescent: ultraviolet light shifts its color toward pink or purple, and visible light or darkness returns it to its starting color. Ordinary blue sodalite keeps its color under the same lamp. The only test that separates them is to charge the stone with UV, then look at it under white light.

If hackmanite is sodalite, why does it get its own name?

Because of one behavior collectors can see and the rest of the species does not show. The Fluorescent Mineral Society puts it simply: sodalite which exhibits tenebrescence has been given the variety name hackmanite (Fluorescent Mineral Society). Minerals.net describes hackmanite as a sulfur-rich form of the mineral, prized for its pink or purple color and strong fluorescence (Minerals.net). The name honors Victor Axel Hackman of the Finnish Geological Survey.

Definitions vary a little by source. A 2023 study presented at the International Gemmological Conference cites Jackson's definition of hackmanite as a sulfur-bearing sodalite that exhibits fluorescence (IGC 2023). In the trade, though, the word means the color change. A stone that glows but does not change color is sold as sodalite by careful dealers, and that is the line this page uses.

What is the same and what differs?

Feature Sodalite (common blue) Hackmanite
Formula Na8Al6Si6O24Cl2 Same, with sulfur-related defects
Crystal system Isometric (cubic) Isometric (cubic)
Mohs hardness 5.5 to 6 5.5 to 6
Specific gravity 2.14 to 2.40 Same range
Refractive index 1.483 to 1.487 Same range
Daylight color Royal blue, often with white veins White, gray, pale pink, violet, sometimes blue
After UV No change Pink, violet or deep purple, then fades
Color cause Trisulfide ions, absorption near 595 nm Electrons trapped at chlorine vacancies, band near 530 nm
Typical fluorescence Weak orange, often Usually stronger orange; Afghan stones often creamy white

The physical rows come from webmineral, Minerals.net and the International Gem Society. Every row a refractometer, a scale or a scratch test can measure is identical. That is why no density, hardness or refractive index reading will ever tell them apart.

How do you test a stone in five minutes?

You need a UV torch (365 nm longwave works for most stones; a shortwave lamp is stronger on many), a white light, and a dark corner.

  1. Record the starting color. Photograph the stone under ordinary white light, next to a white card.
  2. Charge it. Hold the UV torch close for 30 to 60 seconds. For Afghan material, allow several minutes.
  3. Switch off the UV and look under white light. This step matters. Under the UV lamp you see fluorescence, which most sodalite shows to some degree. Only under white light, after the UV is off, can you see whether the body color has changed.
  4. Compare with the photo. A pink, raspberry or purple shift that was not there before means tenebrescence, so the stone is hackmanite.
  5. Watch it fade. Leave it under a bright lamp. The Fluorescent Mineral Society reports that most pieces fade in direct sunlight within seconds, while some Afghan hackmanite keeps its color for weeks or months.

A blue sodalite run through the same steps comes back the same blue. The IGC researchers found the spectrum of their blue sodalite was identical before and after UV, which they took to mean it had no photochromism at all.

Why is a glow under the lamp not proof?

Fluorescence and tenebrescence are separate effects, and sodalite often shows the first without the second. Geology.com notes that sodalite often produces a weak orange fluorescence under shortwave or longwave UV (Geology.com). The Fluorescent Mineral Society adds that sodalite from Kola, Bancroft, Mont Saint-Hilaire and Greenland all fluoresce the same color, peaking between 625 and 635 nm under 365 nm light, while their color change varies widely. An orange glow under the lamp therefore says "sodalite group", not "hackmanite". Our fluorescence guide explains why the two effects are different physics, and the UV testing guide covers choosing a torch.

What else can fool a buyer?

  • The fresh-break flash. Collectors in Greenland crack sodalite open and watch the new surface turn purple for a moment. The Fluorescent Mineral Society warns that most sodalite from Ilímaussaq shows this when broken but is not necessarily tenebrescent under UV.
  • Blue hackmanite. Not all hackmanite starts pale. The same society describes naturally blue Greenland sodalite that darkens to deep purple in seconds under shortwave UV. A blue stone that turns purple after charging is hackmanite, however ordinary it looks in daylight.
  • Heat. Heating destroys the effect: Greenland hackmanite held at 500 F for 10 minutes faded completely and would no longer change color, though it still fluoresced. A heated stone cannot be identified as hackmanite by its behavior anymore.
  • Dye. IGS notes that white sodalite may be dyed to give it the popular blue color. Dye adds nothing to the UV test, but it is worth knowing when a blue stone looks unusually even.
  • Tugtupite. Sometimes sold beside hackmanite, this is a different, rarer mineral. It was discovered in 1957 at Tugtup agtakôrfia in the Ilímaussaq Complex and was first called beryllium sodalite. It also deepens in color under UV.

What does a gem lab see that the eye cannot?

The IGC study measured 13 Myanmar cabochons, eight hackmanites and five sodalites, weighing 0.45 to 1.67 carats. After 365 nm exposure, the hackmanites showed a broad absorption band centered at 530 nm, which faded over minutes to hours in the dark or under visible light. The blue sodalites instead showed bands near 600 and 660 nm that did not move.

Their chemistry result is the surprise. Sulfur was present in every sample at levels below about 0.4 percent by weight, and the highest value came from a sodalite, not a hackmanite. The authors concluded that the color change is not proportional to sulfur content and depends instead on trace sulfur defects, disulfide ions next to chlorine vacancies. In plain terms, a chemical analysis showing sulfur does not make a stone hackmanite. The UV behavior does.

Where does each one come from?

Both form in rare, silica-poor igneous rocks. Webmineral lists sodalite's environment as nepheline syenites, phonolites and related rock types, plus metasomatized calcareous rocks and ejected volcanic blocks.

Sodalite. Geology.com lists Litchfield, Maine; Magnet Cove, Arkansas; northern Namibia; Golden, British Columbia; Bancroft, Ontario; the Kola Peninsula; and the Ilimaussaq complex of Greenland. Minerals.net singles out the Princess Mine in Dungannon Township, Ontario, for deep blue gem sodalite. IGS describes Ohopoho, Namibia, as producing extremely intense blue material that is sometimes nearly transparent.

Hackmanite. The Fluorescent Mineral Society lists the Ilímaussaq Complex in Greenland, the Kola Peninsula, Mont Saint-Hilaire and Bancroft in Canada, Afghanistan and Myanmar. Minerals.net names the Davis Quarry in Dungannon, Ontario, for highly fluorescent hackmanite. The hackmanite we stock is Afghan, which suits a buyer who wants to admire the change: the Fluorescent Mineral Society reports that Afghan stones can keep their charged color for weeks or months.

How do prices compare, and which should you buy?

Massive blue sodalite is a common lapidary material. IGS notes that Canadian and Namibian blocks are large enough for carvings and spheres of almost any size, so a 50 to 60 mm sodalite sphere is a modest purchase. Hackmanite tends to cost more than plain sodalite of the same size, because fewer localities produce it and the color change, not the stone, is what you are paying for.

  • Choose sodalite for a deep blue sphere, palm stone or carving, or as the starting point for the lapis versus sodalite question.
  • Choose hackmanite to see a mineral change color in your hand. Buy from a seller who states "UV reactive" or shows before-and-after photos.
  • Own both as a pair: run the same torch over each and the difference between glow and color change is obvious. The hackmanite guide explains the mechanism in depth, and the sodalite guide covers the blue stone itself.

In crystal traditions both are counted among stones of clear thinking and expression. These are beliefs, not measurable properties. Care is the same for both: at Mohs 5.5 to 6 they scratch easily, so store them apart from quartz.

Shopping hackmanite and sodalite we stock

Ask any hackmanite seller three questions: the locality, whether the stone is UV reactive, and whether there are photos taken right after charging. For sodalite, look for saturated blue with crisp white veins and check that the color is not suspiciously uniform.

Digital Towns Market

Hackmanite and sodalite in stock

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Frequently asked questions

Is all sodalite hackmanite?

No. Hackmanite is only the sodalite that changes color under ultraviolet light and fades back in visible light. Most blue sodalite sold as spheres and palm stones shows no color change at all, even though many pieces fluoresce a weak orange under a UV lamp.

Can blue sodalite be hackmanite?

Yes. Some naturally blue sodalite from Greenland darkens to deep purple within seconds under shortwave UV and then bleaches back in bright light. Daylight color does not decide the name. If the body color changes after UV and returns, the stone is hackmanite.

Why does my hackmanite stay purple for days?

Fade speed depends on the locality and the stone. Greenland and Canadian hackmanite usually bleaches in seconds of bright light, while some Afghan hackmanite holds its charged color for weeks or months, even under lamps. A bright, UV-free white light speeds the return.

Does hackmanite wear out after many UV charges?

Collectors report no loss of the effect from repeated charging and fading, and the published literature does not describe one. Heat is the real risk: a Greenland piece heated to 500 F for ten minutes lost its color change permanently while keeping its fluorescence.

Is hackmanite harder or more fragile than sodalite?

Neither. They are the same mineral with the same hardness of 5.5 to 6 and the same density. Both scratch against quartz and dust, so store them separately and clean them with a soft damp cloth.

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