Sodalite
Sodalite is Na4(Si3Al3)O12Cl on the IMA list: cubic, hardness 5.5 to 6, density 2.27 to 2.33, white streak, red-orange under UV. Hackmanite changes colour.
Sodalite is a sodium aluminium silicate chloride, Na4(Si3Al3)O12Cl on the September 2026 IMA list, and the namesake of the sodalite group with haüyne, nosean and lazurite. Its Handbook sheet gives cubic crystals, hardness 5.5 to 6, density 2.27 to 2.33, a white streak and bright red-orange fluorescence under LW and SW UV. Hackmanite is its tenebrescent variety.
In short
- Two ways to write one formula. The September 2026 IMA-CNMNC Master List gives sodalite as Na4(Si3Al3)O12Cl, status G, 1811, with Denmark (Greenland) in the country column. The Handbook of Mineralogy sodalite sheet writes Na8Al6Si6O24Cl2, which is the IMA formula doubled: the same proportions of every element.
- The chlorine check. On standard atomic weights the ideal formula is 7.32% chlorine by mass. The sheet’s one analysis, from Mont Saint-Hilaire, Quebec, has Cl 7.33 and recalculates to 1.99 chlorine atoms of 2. The chloride in the name is not a trace; it is about one fourteenth of the mineral’s weight.
- The group, by script. Of the Handbook sheets cached for this site, read on 14 October 2026, four print Mineral Group: Sodalite group: sodalite, haüyne, nosean and lazurite, the blue mineral of is lapis lazuli a mineral or a rock. The IMA list has no group column. Of the rows a script parses from it, two are made of sodium, aluminium, silicon, oxygen and chlorine alone: sodalite and marialite, the sodium end of scapolite.
- Hackmanite is sodalite that changes colour. Kondo and Beaton (Gems & Gemology, 2009) define hackmanite as a sulfur-bearing variety of sodalite distinguished by tenebrescence, a reversible colour change under UV or white light, and note there are no guidelines clearly separating the two names. The sheet’s own words are may be photochromic in magentas.
- Light on the scale. A 20.00 g piece weighs 11.19 to 11.42 g in water on the sheet’s density; lazurite reads 11.60 to 11.84 g, and lapis lazuli 12.00 g or more on GIA’s range. The separation is set out on is sodalite the same as lapis lazuli.
| Species | IMA formula | IMA status, year, country | Hardness | Density | 20.00 g piece in water | Streak | UV on the sheet |
|---|---|---|---|---|---|---|---|
| Sodalite | Na4(Si3Al3)O12Cl | G, 1811, Denmark (Greenland) | 5.5–6 | 2.27–2.33 | 11.19–11.42 g | White | Bright red-orange, LW and SW; yellowish phosphorescence |
| Haüyne | Na3Ca(Si3Al3)O12(SO4) | G, 1807, Italy | 5.5–6 | 2.44–2.50 | 11.80–12.00 g | Slightly bluish to colourless | May show reddish orange to purplish pink, LW |
| Nosean | Na8(Si6Al6)O24(SO4)·H2O | G, 1815, Germany | 5.5 | 2.30–2.40 | 11.30–11.67 g | Not printed | Nothing recorded |
| Lazurite | Na7Ca(Al6Si6O24)(SO4)(S3)−·H2O | Rd, 2021 s.p., Afghanistan / Russia | 5–5.5 | 2.38–2.45 | 11.60–11.84 g | Bright blue | Nothing recorded |
| Marialite (scapolite, for the chlorine comparison) | Na4Al3Si9O24Cl | G, 1866, Italy | Not read here | Not read here | Not worked | Not read here | Not read here |
What is sodalite? The IMA row and the chlorine check
The row. The September 2026 IMA-CNMNC Master List lists sodalite as Na4(Si3Al3)O12Cl, status G for grandfathered, year 1811, country Denmark (Greenland), with a second reference of American Mineralogist 89 (2004), 359. The brackets mark the framework: three silicon and three aluminium in every twelve oxygens. The Handbook sheet’s Na8Al6Si6O24Cl2 is the same thing written for twice as many atoms.
The chlorine check, worked. Formula mass 484.60 on standard atomic weights; chlorine 35.45 of that is 7.32%. Written as oxides, as analyses are, the ideal is SiO2 37.20, Al2O3 31.56, Na2O 25.58 and Cl 7.32, less 1.65 for the oxygen the chlorine replaces. The sheet’s Mont Saint-Hilaire microprobe analysis reads SiO2 37.95, Al2O3 31.42, Na2O 24.16 and Cl 7.33, and recalculates to Na 7.50, Al 5.93, Si 6.07 and Cl 1.99. In that analysis sodalite’s chlorine runs at the ideal, and its sodium about 6% short of it.
On the sheet. Cubic; crystals rare, typically dodecahedra, to 10 cm, otherwise embedded grains or massive; twinning common, forming pseudohexagonal prisms. Cleavage poor, fracture uneven to conchoidal, brittle, hardness 5.5 to 6. Isotropic, n = 1.483 to 1.487. Colourless, white, yellowish, greenish, light to dark blue or reddish, with a white streak and vitreous to greasy lustre. It may give off the odor of H2S on fracture; the gem society says the same of cutting. The name is in allusion to its sodium content.
Which minerals are in the sodalite group?
On the Handbook sheets. A script read the Mineral Group field of every Handbook sheet cached for this site on 14 October 2026; four say Sodalite group: sodalite, haüyne, nosean and lazurite. The International Gem Society sodalite article names the same four, and says all are typically blue and are found in lapis lazuli.
On the IMA list, which has no group column. A script parsed 5,821 rows of the 6,239 species the list states. Nineteen of them write an Al6Si6O24-type framework (or a multiple of it) into the formula, including sodalite, haüyne, nosean, lazurite, sapozhnikovite, Na8(Al6Si6O24)(HS)2, and also cancrinite. That token is a way of writing a formula, not a membership list, so this page counts no group members from it. The narrower test is sharper: only two parsed rows contain sodium, aluminium, silicon, oxygen and chlorine and nothing else, sodalite and marialite, Na4Al3Si9O24Cl.
What sits next to it, and what does not. Tugtupite, Na4BeAl(SiO4)3Cl on the IMA list, a sodium beryllium aluminium silicate chloride, also occurs in the Ilímaussaq intrusion; its sheet prints no mineral group, so it is not counted here. Lapis lazuli is not in the group because it is not a mineral: GIA calls it a rock, mainly lazurite, calcite and pyrite.
What is hackmanite? Sodalite that changes colour in light
The definition GIA uses. Kondo and Beaton (Gems & Gemology, 2009) write that hackmanite is a sulfur-bearing variety of sodalite that gemmologists typically distinguish by its tenebrescence, its ability to change colour when certain wavelengths of light are applied or removed. They add that a survey of the literature showed no consistent definition, that some sources define it by fluorescence and others by tenebrescence, and that there are no guidelines clearly separating hackmanite from sodalite; they suggest that only sodalite with noticeable tenebrescence be called hackmanite. The sheet itself cites a 1983 structure paper on hackmanite, a variety of sodalite, from Mont St-Hilaire, and has no separate entry for it; the IMA list has no hackmanite row.
Which way the colour goes depends on the source. Kondo and Beaton say most material turns pink to purple or violet under UV and fades in sunlight or white light, reversibly unless it is heated, and that heating above 500 °C destroys the effect. The gem society says Canadian and Greenland stones start pink to violet and fade in sunlight, while Afghan and Burmese hackmanite starts white and turns pink or violet in sunlight, and that darkness reverses both.
Where hackmanite is recorded. The 2009 paper lists Mont Saint-Hilaire and Bancroft in Canada, Magnet Cove in Arkansas, Libertyville in New Jersey, Minas Gerais, the Kola Peninsula and Greenland, and more recently Mogok, Myanmar, and Badakhshan, Afghanistan. Its 16 Afghan and Burmese stones are tallied on is sodalite UV reactive.
Is sodalite fluorescent? The sheet line
Yes, under both lamps, on its sheet. The line is Bright red-orange cathodoluminescence and fluorescence under LW and SW UV, with yellowish phosphorescence; may be photochromic in magentas. The sheet was typeset with an fl ligature that text extraction turns into a stray symbol, so this page found it with a ligature-aware search, with hemimorphite and willemite as positive controls.
Not every sodalite-group sheet agrees. Of the four, two record fluorescence: sodalite, and haüyne, reddish orange to purplish pink under longwave. The lazurite and nosean sheets record none. The lamp-by-lamp detail, GIA’s results and the exposure guideline are on is sodalite UV reactive; why minerals glow at all is on fluorescent minerals explained.
Where sodalite is found
Setting. The sheet says sodalite forms in nepheline syenites, phonolites and related rocks, in metasomatised calcareous rocks and in cavities in ejected volcanic blocks, with nepheline, cancrinite, titanian andradite, aegirine, microcline, sanidine, albite, calcite, fluorite, ankerite and barite.
Localities the sheet names. The Ilímaussaq intrusion, southern Greenland; the Langesundsfjord, Norway; the Khibiny and Lovozero massifs, Kola Peninsula, Russia; Monte Somma and Vesuvius, Italy; the Bellerberg volcano near Mayen and elsewhere in the Eifel, Germany; Litchfield, Maine, and Magnet Cove, Arkansas; Bancroft, Ontario, Mont Saint-Hilaire, Quebec, and the Ice River at Kicking Horse Pass, British Columbia; and Cerro Sapo, Bolivia. The gem society adds Bancroft’s massive deep blue material with reddish streaks and Ohopoho, Namibia.
Colour that may not be original. The gem society says heating may cause sodalite to lose colour, irradiation can restore it, and white sodalite may be dyed blue; see how to tell if a crystal is dyed. It also says you are more likely to meet sodalite offered as lapis, in error or to mislead, which is why is sodalite the same as lapis lazuli exists. The species pages are listed in the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.