Potassic-magnesio-fluoro-arfvedsonite

KNa2(Mg4Fe3+)Si8O22F2
IMA status
  • Approved
IMA symbol
Pmfarf
IMA approved
1985
Also known as
  • Fluoro-potassic-magnesio-arfvedsonite
  • IMA1985-023
  • Potassic-magnesio-fluoro-arfvedsoniet
  • +1 more

Where it forms, where it's found

Geological setting

Narrow dolomite-amphibole veins cutting mesoproterozoic alkali feldspar trachyte,

Type locality
Highway 366 roadcut
  1. Val-des-Monts
  2. Les Collines-de-l'Outaouais RCM
  3. Outaouais
  4. Québec
  5. Canada

45.6066°, -75.6253°

8recorded occurrences
Source · OpenStreetMap

Physical

Cleavage
Perfect

on (110)

Crystallography

Crystal system
Monoclinic
Space group
B2/m
Morphology

Elongated crystals with striations parallel to <em>c</em>

Twinning

Common on TL, as simple or lamellar (ll57A) on (100)

Parting
On (001)
Comment

By analogy to other Arfvedsonites

Crystal structure

Chemical composition

Constituent elements
Mass composition breakdown
ElementAtoms At. mass g/mol Mass g/molMass share
8OOxygenOxygen2215.999351.978
41.27%
14SiSiliconSilicon828.085224.680
26.35%
12MgMagnesiumMagnesium424.30597.220
11.40%
26FeIronIron155.84555.845
6.55%
11NaSodiumSodium222.99045.980
5.39%
19KPotassiumPotassium139.09839.098
4.58%
9FFluorineFluorine218.99837.996
4.46%
Total852.797100.00%

Mass share = atoms × atomic mass ÷ molar mass × 100

From IMA formula

Synonyms

  • Fluoro-potassic-magnesio-arfvedsonite
  • IMA1985-023
  • Potassic-magnesio-fluoro-arfvedsoniet
  • Potassium fluor-magnesio-arfvedsonite

In other languages

German
IMA 1985-023 · Kalium-Magnesio-Fluoro-Arfvedsonit
Italian
potassic-magnesio-fluoro-arfvedsonite

Classification

Strunz
10th ed.

9.DE.25

  • 9SilicatesClass
  • 9.DInosilicatesDivision
  • 9.DEInosilicates with 2-periodic double chains, Si4O11; ClinoamphibolesGroup
  • 9.DE.25Potassic-magnesio-fluoro-arfvedsoniteSpecies

Group, growth & confusion

Literature, links & citation

Citations
  1. 1984Donald D. Hogarth, Pierre LaPointe (1984) Amphibole and pyroxene development in fenite from the Gatineau area, Quebec. The Canadian Mineralogist, 22. 281-295
  2. 1987Hogarth, D.D., Chao, G.Y., Townsend, M.G. (1987) Potassium- and fluorine-rich amphiboles from the Gatineau area, Quebec. The Canadian Mineralogist, 25. 739-753
  3. 2006Hawthorne, F. C., Oberti, R. (2006) On the classification of amphiboles. The Canadian Mineralogist, 44 (1) 1-21 doi:10.2113/gscanmin.44.1.1DOI: 10.2113/gscanmin.44.1.1
  4. 2006Hogarth, D. D. (2006) FLUORO-POTASSIC-MAGNESIO-ARFVEDSONITE, KNa2Mg5Si8O22F2, FROM THE OUTAOUAIS REGION, QUEBEC, CANADA. The Canadian Mineralogist, 44 (1) 289 doi:10.2113/gscanmin.44.1.289DOI: 10.2113/gscanmin.44.1.289
  5. 2012Hawthorne, F. C., Oberti, R., Harlow, G. E., Maresch, W. V., Martin, R. F., Schumacher, J. C., Welch, M. D. (2012) Nomenclature of the amphibole supergroup. American Mineralogist, 97 (11) 2031-2048 doi:10.2138/am.2012.4276 DOI: 10.2138/am.2012.4276
Cite this entry
@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Potassic-magnesio-fluoro-arfvedsonite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/potassic-magnesio-fluoro-arfvedsonite-29104},
  note      = {Accessed 2026-05-11}
}