Thomsenolite
A valid IMA mineral species - grandfathered
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About Thomsenolite
Hans Peter JĂžrgen Julius Thomsen
Formula:
NaCa[AlF6] · H2O
Colour:
Colourless, white, pale lilac; brownish or reddish tinted due to staining; colourless in transmitted light.
Lustre:
Vitreous, Pearly
Hardness:
3 - 3½
Specific Gravity:
2.981
Crystal System:
Monoclinic
Name:
Named after Hans Peter JĂžrgen Julius Thomsen (16 February 1826, Copenhagen, Denmark - 13 February 1909, Copenhagen, Denmark), Professor of Chemistry, University of Copenhagen (Denmark), and founder of the Greenland cryolite industry.
Dimorph of:
This page provides mineralogical data about Thomsenolite.
Unique Identifiers
Mindat ID:
3940
Long-form identifier:
mindat:1:1:3940:2
IMA Classification of Thomsenolite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
NaCaAlF6·H2O
First published:
1866
Type description reference:
Classification of Thomsenolite
3.CB.40
3 : HALIDES
C : Complex halides
B : Neso-aluminofluorides
3 : HALIDES
C : Complex halides
B : Neso-aluminofluorides
11.6.6.1
11 : HALIDE COMPLEXES
6 : Aluminofluorides - Isolated Octahedra
11 : HALIDE COMPLEXES
6 : Aluminofluorides - Isolated Octahedra
8.6.17
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
6 : Halides of Al
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
6 : Halides of Al
Mineral Symbols
As of 2021 there are now IMAâCNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Tse | IMAâCNMNC | Warr, L.N. (2021). IMAâCNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Thomsenolite
Vitreous, Pearly
Transparency:
Transparent, Translucent
Comment:
Pearly on cleavages
Colour:
Colourless, white, pale lilac; brownish or reddish tinted due to staining; colourless in transmitted light.
Streak:
White
Hardness:
3 - 3½ on Mohs scale
Hardness:
VHN25=220 - 320 kg/mm2 - Vickers
Comment:
Typically given as Mohs 2. Modern measurement and discussion by Pauly (1985).
Tenacity:
Brittle
Cleavage:
Perfect
On {001}; {110} distinct.
On {001}; {110} distinct.
Fracture:
Irregular/Uneven
Density:
2.981 g/cm3 (Measured) 2.986(3) g/cm3 (Calculated)
Optical Data of Thomsenolite
Type:
Biaxial (-)
RI values:
nα = 1.4072 nβ = 1.4136 nγ = 1.415
Max. Birefringence:
δ = 0.008
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 ”m thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 ”m thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Very High (negative)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
No measured or calculated 2V is on file for this mineral, so the value used here (50°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
No measured or calculated 2V is on file for this mineral, so the value used here (50°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
r > v
Optical Extinction:
X ⧠c = â52°; Z = b.
Chemistry of Thomsenolite
Mindat Formula:
NaCa[AlF6] · H2O
Element Weights:
Crystallography of Thomsenolite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Cell Parameters:
a = 5.563(2) Å, b = 5.541(2) Å, c = 16.115(1) Å
β = 96.35(3)°
β = 96.35(3)°
Ratio:
a:b:c = 1.004 : 1 : 2.908
Unit Cell V:
493.69 Ă
Âł (Calculated from Unit Cell)
Morphology:
Crystals commonly prismatic [001]; cubic in aspect with equal development of {001} and {110}. Grouped in parallel aggregates. Also tabular {001}. {110} and terminal prisms strongly striated parallel to the intersection with {001}. {h0l} often curved. Opaline or chalcedony-like crusts and stalactitic masses.
Twinning:
None observed.
Crystallographic forms of Thomsenolite
Crystal Atlas:
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Thomsenolite no.1 - {110} - Goldschmidt (1913-1926)
Thomsenolite no.7 - {110} - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by
www.smorf.nl.
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Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0009312 | Thomsenolite | Cocco G, Castiglione P C, Vagliasindi G (1967) The crystal structure of thomsenolite Acta Crystallographica 23 162-166 |  | 1967 | Ivigtut, Greenland | 0 | 293 |
| 0012167 | Thomsenolite | Adhikesavalu D, Cameron T S, Knop O (1985) Thomsenolite, NaCaAlF6*H2O: hydrogen bonding and comparison with pachnolite Canadian Journal of Chemistry 63 3322-3327 | 1985 | 0 | 293 |
CIF Raw Data - click here to close
Epitaxial Relationships of Thomsenolite
Epitaxial Minerals:
| 'Pachnolite' | NaCa[AlF6] · H2O |
Epitaxy Comments:
Oriented growths of thomsenolite on pachnolite, with thomsenolite (001) and (110) quasi-parallel to pachnolite (110) and (001). Also with thomsenolite (110) and (110) quasi-parallel to pachnolite (110) and (001).
X-Ray Powder Diffraction
Loading XRD data...
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.02 Ă | (100) |
| 1.963 Ă | (90) |
| 1.996 Ă | (80) |
| 2.92 Ă | (50) |
| 1.761 Ă | (30) |
| 2.16 Ă | (20) |
| 1.640 Ă | (20) |
Comments:
Ivigtut, Greenland.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 22 : Hydration and low-đ subsurface aqueous alteration (see also #23) | |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 56 : Slag and smelter minerals (see also #51 and #55) |
Geological Setting:
Granitic pegmatites
Type Occurrence of Thomsenolite
Place of Conservation of Type Material:
University of Copenhagen, Copenhagen, Denmark, 1868.1499.
Associated Minerals at Type Locality:
Synonyms of Thomsenolite
Other Language Names for Thomsenolite
Common Associates
Associations Based on Photo Data:
| 85 photos of Thomsenolite associated with Hydrokenoralstonite | Na0.5(Al,Mg)2(F,OH)6 · H2O |
| 78 photos of Thomsenolite associated with Cryolite | Na2NaAlF6 |
| 53 photos of Thomsenolite associated with Pachnolite | NaCa[AlF6] · H2O |
| 34 photos of Thomsenolite associated with Prosopite | CaAl2F4[(OH)4-xFx] |
| 30 photos of Thomsenolite associated with Siderite | FeCO3 |
| 19 photos of Thomsenolite associated with Quartz | SiO2 |
| 11 photos of Thomsenolite associated with 'Limonite' | |
| 9 photos of Thomsenolite associated with 'Hagemannite' | |
| 9 photos of Thomsenolite associated with Gagarinite-(Y) | NaCaYF6 |
| 9 photos of Thomsenolite associated with Tridymite | SiO2 |
Related Minerals - Strunz-mindat Grouping
| 3.CB.05 | Cryolithionite | Na3Al2(LiF4)3 |
| 3.CB.15 | Elpasolite | K2NaAlF6 |
| 3.CB.15 | Simmonsite | Na2LiAlF6 |
| 3.CB.15 | Cryolite | Na2NaAlF6 |
| 3.CB.20 | Colquiriite | CaLi[AlF6] |
| 3.CB.25 | Leonardsenite | MgAlF5 · 2H2O |
| 3.CB.25 | Weberite | Na2Mg[AlF6]F |
| 3.CB.30 | Karasugite | SrCa[Al(F,OH)7] |
| 3.CB.35 | Usovite | Ba2CaMgAl2F14 |
| 3.CB.40 | Pachnolite | NaCa[AlF6] · H2O |
| 3.CB.45 | Carlhintzeite | Ca2[AlF6]F · H2O |
| 3.CB.50 | Yaroslavite | Ca3Al2F10(OH)2 · H2O |
| 3.CB.55 | Sbacchiite | Ca2AlF7 |
| 3.CB.60 | Verneite | Na2Ca3Al2F14 |
Other Information
Thermal Behaviour:
Heated in a closed tube it yields water with an acid reaction that etches the glass. At a higher temperature it melts to a clear glass, fusing even more easily than cryolite.
Notes:
Readily soluble in H2SO4.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Thomsenolite
mindat.org URL:
https://www.mindat.org/min-3940.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Thomsenolite
Reference List:
Hagemann, G. (1866) On some minerals associated with the cryolite in Greenland. American Journal of Science and Arts, S. 2 Vol. 42 (124) 93-94(as dimetric pachnolite)
Nordenskiöld, A. E. (1874) Kristallografisk och kemisk undersökning af nÄgra fluormineralier frÄn Ivituk i Grönland. Geologiska Föreningen i Stockholm Förhandlingar, 2 (4) 81-88 doi:10.1080/11035897409454001
Des Cloizeaux, Alfred (1882) Notes sur les caractÚres optiques et cristallographiques de la Pachnolite et de la Thomsénolite. Bulletin de Minéralogie, 5 (9) 310-316 doi:10.3406/bulmi.1882.1767
BĂžggild, O. B. (1913) Beobachtungen ĂŒber die Mineralien der Kryolithgruppe. Zeitschrift fĂŒr Kristallographie, 51 (1-6). 591-613 doi:10.1524/zkri.1913.51.1.591p.601
Frondel, Clifford (1948) New data on elpasolite and hagemannite. American Mineralogist, 33 (1-2) 84-87
Adhikesavalu, D., Cameron, T. Stanley, Knop, Osvald (1985) Thomsenolite, NaCaAlF6âąH2O: hydrogen bonding and comparison with pachnolite. Canadian Journal of Chemistry, 63 (12). 3322-3327 doi:10.1139/v85-550
Localities for Thomsenolite
Showing 31 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
â - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Brazil | |
| 7. symposium on volcanism and ... +2 other references |
| Bastos Neto et al. (2026) | |
Canada | |
| HorvĂĄth et al. (1998) |
| HorvĂĄth et al. (1998) | |
Finland | |
| Marttila |
Greece | |
| Schnorrer-Köhler et al. (1988) |
| Gelaude et al. (1996) |
Greenland (TL) | |
| Palache et al. (1951) +2 other references |
Iceland | |
| Mitolo et al. (2008) |
Japan | |
| Kotora Jimboh (1899) |
Kazakhstan | |
| Pavel M. Kartashov (n.d.) +1 other reference |
Nigeria | |
| Am Min 51:299-323 |
| Bailey (1980) | |
Norway | |
| SĂŠbĂž (1966) +1 other reference |
Russia | |
| Bailey (1980) |
| Bailey (1980) +1 other reference |
| Raade et al. (1980) | |
| Bailey (1980) |
| Pavel M. Kartashov (n.d.) +1 other reference | |
| P.M. Karashov data +2 other references |
Saint HelenaïŒ Ascension and Tristan da Cunha | |
| Bailey (1980) | |
Ukraine | |
| Yurk Yu.Yu. et al. (1973) +1 other reference |
USA | |
| Palache et al. (1951) +1 other reference |
| Gross et al. (1966) +1 other reference | |
| Pavel M. Kartashov analytical data | |
| Eckel et al. (1997) | |
| Gross et al. (1966) +1 other reference | |
| Mandarino (2000) |
| O'Neill (2014) |
| Henderson (1981) |
| Kearns (1995) +1 other reference |
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Ivigtut Mine, Ivigtut stock, Arsuk Fjord, Sermersooq, Greenland