Where it forms, where it's found
- Geological setting
Fumarole at ~230ºC.
- Type locality
- Hekla
- Rangárþing ytra
- Southern Region
- Iceland
63.9926°, -19.6658°
5recorded occurrences
Physical
- Transparency
- Transparent
- Colour
- White
- Streak
- White
- Density
- 2.89 g/cm³
Optical
- UV response
- Does not fluoresce in LW UV
Crystallography
- Space group
- C2/c
- Cell parameters
- a = 8.601(1) Å · b = 6.2903(6) Å · c = 7.2190(7) Å
- Cell angles
- β = 114.61(1) °
- Ratio a:b:c
- 1 : 0.731 : 0.839
- Unit cell volume
- 355.09 ų
- Z
- 4
- Morphology
Acicular crystals which are probably elongated along [100]; fragile crusts.
- Type-locality form
Acicular crystals up to 50 µm long. Also as a white overgrowth on a yellowish base of massive ralstonite, anhydrite and jarosite which together form a 2-3 cm thick crust on altered scoria.
Crystal structure
Chemical composition
Synonyms
- IMA2011-036
- Jakobssoniet
- UM2010-01-F:AlCa
- Unnamed (Ca-Al Fluoride)
In other languages
- German
- IMA 2011-036 · Jakobssonit
- Italian
- jakobssonite
Classification
Strunz
10th ed.3.CD.15
- 3HalidesClass
- 3.CComplex halidesDivision
- 3.CDIno-aluminofluoridesGroup
- 3.CD.15JakobssoniteSpecies
Group, growth & confusion
Literature, links & citation
Citations
- 1991Hemon, A., Courbion, G. (1991) Refinement of a room-temperature structure of α-CaAlF5. Acta Crystallographica Section C Crystal Structure Communications, 47 (6) 1302-1303 doi:10.1107/s0108270190013956DOI: 10.1107/s0108270190013956
- 2008Jakobsson, S.P., Leonardsen, E.S., Balić-Žunić, T., Jonsson, S.S. (2008) Encrustations from three recent volcanic eruptions in Iceland: the 1963-1967 Surtsey, the 1973 Eldfell and the 1991 Hekla eruptions. Fjölrit Náttúrufraedistofnunar:. p.1-65.
- 2011Williams, P. A., Hatert, F., Pasero, M., Mills, S. J. (2011) New minerals and nomenclature modifications approved in 2011, CNMNC Newsletter No. 10. Mineralogical Magazine, 75 (5) 2549-2561 doi:10.1180/minmag.2011.075.5.2549 DOI: 10.1180/minmag.2011.075.5.2549
- 2012Balić-Žunić, T., Garavelli, A., Mitolo, D., Acquafredda, P., Leonardsen, E. (2012) Jakobssonite, CaAlF5, a new mineral from fumaroles at the Eldfell and Hekla volcanoes, Iceland. Mineralogical Magazine, 76 (3) 751-760 doi:10.1180/minmag.2012.076.3.22 DOI: 10.1180/minmag.2012.076.3.22
- 2015(2015) Jakobssonite. Handbook of Mineralogy. Mineralogical Society of America
Cite this entry
@misc{mineral2026,
author = {Mineral Index editorial board},
title = {Jakobssonite — Mineral Index},
year = {2026},
url = {https://mineralindex.org/minerals/jakobssonite-42796},
note = {Accessed 2026-05-11}
}