Tugtupite
Tugtupite, Na4AlBeSi4O12Cl: pink to carmine beryllium silicate from Greenland and Russia, hardness about 4, density 2.33; it fluoresces red to rose-pink.
Tugtupite is a sodium aluminium beryllium silicate chloride, Na4AlBeSi4O12Cl on its Handbook sheet, named for Tugtup agtakôrfia in Greenland’s Ilímaussaq intrusion. It is white to pink and carmine, hardness about 4, density 2.33, and the sheet calls it fluorescent and phosphorescent red to rose-pink under UV, and photochromic: pale colours turn pink in sunlight.
In short
- A beryllium cousin of sodalite. The Handbook of Mineralogy sheet writes Na4AlBeSi4O12Cl; sodalite is Na4Al3Si3O12Cl on the same twelve oxygens and one chlorine. Two aluminium become one beryllium and one more silicon. The sheet names Ilímaussaq, Lovozero and Mont Saint-Hilaire, all three also on the sodalite sheet.
- The four-silicon check. The September 2026 IMA-CNMNC Master List prints Na4BeAl(SiO4)3Cl, three silicons; we read the same on the rendered PDF row. Worked on the usual charges, the Handbook’s four-silicon formula balances, +25 against −25; the IMA string as printed gives +21 against −25. The four-silicon formula reproduces the sheet’s ideal column (SiO2 51.38, BeO 5.35, Cl 7.58) and gives 2.345 on the sheet’s cell, against D(calc.) 2.34 to 2.35. Both analyses carry 1.01 Be per 4 Si.
- Under UV and in sunlight. The sheet’s line: fluorescent and phosphorescent red to rose-pink under UV; photochromic, pale colors become pink on exposure to sunlight or X-rays. The International Gem Society tugtupite article calls the colour change tenebrescence, says darkness fades the red, says the effects are reversible, and says the glow is generally redder under shortwave than longwave.
- Documented failure: the balance. A 20.00 g piece reads 11.42 g in water at the measured 2.33, exactly sodalite’s upper figure (11.19 to 11.42 g). The refractometer separates them: tugtupite is uniaxial (+) with ε 1.499 to 1.502, sodalite isotropic at n 1.483 to 1.487. IGS’s own panel widens tugtupite to SG 2.11 to 2.57 and hardness 4 to 6.5, against the sheet’s 2.33 and about 4.
- Where. In Greenland, the sheet lists Tugtup agtakôrfia, the Tunugdliarfik Fjord, the Kangerdluarssuk Plateau, Qeqertaussaq Island, the Gletscherelv Valley and the Kvanefjeld and Taseq Plateaus, all in the Ilímaussaq intrusion; then Lovozero on the Kola Peninsula and Mont Saint-Hilaire, Quebec. It marks no type locality.
| Line | Tugtupite, Handbook Na4AlBeSi4O12Cl | Tugtupite, IMA string Na4BeAl(SiO4)3Cl | Sodalite, Na4Al3Si3O12Cl |
|---|---|---|---|
| Si : Al : Be per 12 O | 4 : 1 : 1 | 3 : 1 : 1 | 3 : 3 : 0 |
| Charge balance | +25 / −25 | +21 / −25 | +25 / −25 |
| Formula mass | 467.73 | 439.65 | 484.60 |
| Ideal SiO2 / BeO / Cl wt% | 51.38 / 5.35 / 7.58 (sheet column (3): 51.38 / 5.35 / 7.58) | — | — |
| Cell density, Z = 2 | 2.345 (sheet D(calc.) 2.34–2.35) | 2.204 | 2.31 (sheet D(calc.)) |
| Be per 4 Si in the sheet’s analyses | 1.01 (Ilímaussaq); 1.01 (Lovozero) | — | — |
| Density measured; 20.00 g in water | 2.33(1); 11.42 g | — | 2.27–2.33; 11.19–11.42 g |
| System; optics | Tetragonal, pseudocubic; uniaxial (+), ω 1.492–1.496, ε 1.499–1.502 | — | Cubic; isotropic, n 1.483–1.487 |
| Hardness; cleavage | About 4; distinct {101}, fair {110} | — | 5.5–6; {110} poor |
| Under UV (sheet wording) | Fluorescent and phosphorescent red to rose-pink; photochromic, pale colours become pink in sunlight or X-rays | — | Bright red-orange under LW and SW, yellowish phosphorescence; may be photochromic in magentas |
What is tugtupite? Formula and the four-silicon check
Two formulas in print. The Handbook of Mineralogy tugtupite sheet writes Na4AlBeSi4O12Cl. The September 2026 IMA list writes Na4BeAl(SiO4)3Cl, status A, 1967 s.p., country Denmark (Greenland), first reference Meddelelser om Grønland 167 (1962). The text layer and the rendered PDF row agree, so this is how the list prints it. The two differ by one silicon.
The check, worked. On the usual charges, the four-silicon formula balances, +25 against −25, and the three-silicon string does not, +21 against −25. The four-silicon formula, 467.73 g/mol, reproduces the sheet’s ideal column (3) exactly: SiO2 51.38, Al2O3 10.90, BeO 5.35, Na2O 26.50, Cl 7.58, less 1.71 for the oxygen the chlorine replaces. On the sheet’s tetragonal cell (a 8.640, c 8.873 Å, Z = 2) it gives 2.345, against the printed 2.34 to 2.35; the three-silicon string would give 2.204, below the measured 2.33. The sheet’s analyses from Ilímaussaq and Lovozero both work out at 1.01 beryllium per four silicons, and the structure papers it cites write Na8Al2Be2Si8O24(Cl,S)2 (Danø 1966) and Na8[Al2Be2Si8O24]Cl2 (Hassan and Grundy 1991).
What this page does with it. It does its arithmetic on the Handbook formula and quotes the IMA string as printed. It does not say why the list prints three silicons; the list’s second reference, American Mineralogist 89 (2004), 492, was not fetched.
Does tugtupite glow or change colour? What the sheet and IGS say
The sheet’s words. Fluorescent and phosphorescent red to rose-pink under UV; photochromic, pale colors become pink on exposure to sunlight or X-rays. It is also piezoelectric. The sheet was searched ligature-aware, because its fl ligature extracts as a stray symbol.
What the International Gem Society adds. IGS calls the colour change tenebrescence: UV, from a lamp or sunlight, intensifies the colour, generally darker and redder; X-rays darken paler colours; darkness fades the red; the effects are reversible. It says the glow is generally redder under shortwave than longwave, and gives two Greenland notes. Taseq: shortwave pastel orange-red, longwave bright orange, phosphorescing bright cream or orange-cream. Kvanefjeld: longwave bright orange to orange-red, shortwave cerise red and very intense, phosphorescing dull red to medium cream white. These are IGS’s observations, not the Handbook’s.
Its neighbour does it too. The sodalite sheet records bright red-orange fluorescence under LW and SW and may be photochromic in magentas; the sodalite case is on is sodalite UV reactive and the general idea on fluorescent minerals explained. UV lamps have exposure limits of their own, set out in the ICNIRP 2004 guidelines on limits of exposure to ultraviolet radiation; that is not advice, and hazard questions route to toxic minerals in a collection.
How do you tell tugtupite from sodalite?
Not by weighing. At its measured 2.33 a 20.00 g piece of tugtupite reads 11.42 g in water, and sodalite’s 2.27 to 2.33 gives 11.19 to 11.42 g. The top of sodalite’s range is the same number. Method on how to measure specific gravity at home.
By optics and hardness. Tugtupite is uniaxial (+), anomalously biaxial, with ε 1.499 to 1.502; sodalite is cubic and isotropic, n 1.483 to 1.487, so tugtupite’s ε sits 0.012 or more above sodalite’s highest index, and its ω 0.005 or more. The sheets give tugtupite hardness about 4 and sodalite 5.5 to 6. Colour overlaps, since both sheets include white, bluish and greenish. Sodalite against lapis is a different question, on is sodalite the same as lapis lazuli.
Documented failure: IGS’s wider numbers. The IGS panel gives SG 2.11 to 2.57 (10.52 to 12.22 g in water for 20.00 g) and hardness 4 to 6.5 reported, both much wider than the sheet’s 2.33(1) and about 4. A reading inside IGS’s range is not evidence on its own.
Where is tugtupite found? Greenland, Kola and Mont Saint-Hilaire
As the sheet prints it. In Greenland, in the Ilímaussaq intrusion: at Tugtup agtakôrfia, around the Tunugdliarfik Fjord and on the Kangerdluarssuk Plateau; on Qeqertaussaq Island; in the Gletscherelv Valley; and on the Kvanefjeld and Taseq Plateaus. From Mts. Sengischorr and Punkaruaiv, Lovozero massif, Kola Peninsula, Russia. At Mont Saint-Hilaire, Quebec, Canada. The name is for the occurrence at Tugtup agtakôrfia; the sheet marks no type locality (see what is a type locality), and gives type material in Copenhagen and London.
How it forms and with what. At Ilímaussaq it replaces chkalovite in hydrothermal veins cutting sodalite syenite and syenite; at Lovozero it is an alteration product in pegmatites. Associates include albite, analcime, aegirine, natrolite, tetranatrolite, chkalovite, epistolite and monazite. IGS calls it the Reindeer Stone, tugtup meaning reindeer in Greenlandic, places it in the helvine group, and dates its discovery to 1960; the sheet prints no group.
Is tugtupite a gemstone? IGS says it is sporadically used in jewellery, more typically cut as cabochons, that faceted pieces are few and small, and that almost all gem-quality material comes from the Taseq and Kvanefjeld areas. More silicates are in the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.