Potassic-magnesio-fluoro-arfvedsonite
General
CategorySilicate
Formula
(repeating unit)
[(K,Na)][Na2][Mg4Fe3+][Si8O22][(F,OH)2]
IMA symbolPmfarf[1]
Crystal systemMonoclinic
Crystal class2/m - Prismatic
Space groupC2/m
Identification
ColorBluish-Gray
TwinningCommon on TL, as simple or lamellar (ll57A) on {100}
CleavagePerfect on {110}
FractureSplintery
TenacityBrittle
Mohs scale hardness6
LustreVitreous
StreakWhite
Specific gravity3.174 g/cm3
Optical propertiesBiaxial Negative
Ultraviolet fluorescenceNone
References[2][3]

[4]

[1]

Potassic-magnesio-fluoro-arfvedsonite is an amphibole mineral first discovered in Quebec, Canada,[2][3] in an area which is part of the Canadian Shield which is where some of the oldest exposed rocks are that can date back to over 4 billion years ago. Potassic-magnesio-fluoro-arfvedsonite is also the mineral with the longest name of any mineral with 34 letters and 37 characters.

Occurrence

Potassic-magnesio-fluoro-arfvedsonite is found in igneous rocks. The rocks it is found in are classified as a complex mafic ultrapotassic peralkaline igneous rock with high silica contents. Most commonly it is found with Lamproite. Potassic-magnesio-fluoro-arfvedsonite is a uniquely rare mineral, as it occurs in small amounts in very few locations around the world.[4]

Physical properties

Potassic-magnesio-fluoro-arfvedsonite is a bluish-gray mineral with a vitreous luster. It exhibits a hardness of 6 on the Mohs hardness scale. It leaves a white streak of powder behind when you rub it against another surface. Potassic-magnesio-fluoro-arfvedsonite shows perfect cleavage along the {110} plane. The calculated density is 3.174 g/cm3.[2]

Age

Potassic-magnesio-fluoro-arfvedsonite has only been found in a handful of regions. These regions are Quebec, Canada, Montepuez District, Mozambique, Troms Og Finnmark, Norway, Dakhla-Oued Ed-Dahab. Morocco, and Las Vegas, USA. One thing all these locations have in common is the rock formations are older rocks that range from the late Archean eon to the Proterozoic. This range goes from around 2.5 billion years ago to 538 million years ago.

Name

When potassic-magnesio-fluoro-arfevdsonite was first discovered in Quebec in 1985 it was named Potassium fluor-magnesio-arfvedsonite. It was seen as a potassium rich fluor-magnesio-arfvedsonite (now renamed magnesio-fluoro-arfvedsonite). In 2006 it was renamed by the IMA as fluoro-potassic-magnesio-arfvedsonite. and later in 2012 it was renamed again as potassic-magnesio-fluoro-arfvedsonite.[4] It has this name as it is an arfvedsonite that has magnesium, potassium, and fluorine. Potassic-magnesio-fluoro-arfvedsonite has 37 characters which is the longest for any approved mineral.[5]

Chemical composition

Oxide wt%
SiO2 54.25
TiO2 1.08
Al2O3 0.03
Cr2O3 n.a.
Fe2O3 8.07
FeO 13.23<FeOtot<14.52
MnO 0.32
ZnO 0.05
MgO 13.99
BaO+SrO n.a.
CaO 1.16
Na2O 6.33
K2O 5.20
H2O 0.74
F 2.20
–O=F -0.93
Total 99.18

X-ray diffraction and Crystallography

Face D(Å)
110 8.539
131 3.412
240 3.298
310 3.183
331 2.759
151 2.718
260 2.551
351 2.352
331 2.269

The X ray diffraction of potassic-magnesio-fluoro-arfevsonite gave values of the chart above. Calculated unit cell dimensions are a = 9.9591(4), b = 17.9529(7), c = 5.2867(2) Å, β = 104.340(1)°, V = 919.73(10) Å3, Z = 2. Potassic-magnesio-fluoro-arfvedsonite is part of the monoclinic crystal system and in the space group C2/m. Potassic-magnesio-fluoro-arfvedsonite is a double chain inosilicate.[4]

References

  1. 1 2 Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. 1 2 3 Donald D. Hogarth, George Y. Chao, Michael G. Townsend; Potassium- and fluorine-rich amphiboles from the Gatineau area, Quebec. The Canadian Mineralogist 1987; 25 (4): 739–753. doi:
  3. 1 2 Donald D. Hogarth; FLUORO-POTASSIC-MAGNESIO-ARFVEDSONITE, KNa2Mg5Si8O22F2, FROM THE OUTAOUAIS REGION, QUEBEC, CANADA. The Canadian Mineralogist 2006;; 44 (1): 289. doi: https://doi.org/10.2113/gscanmin.44.1.289
  4. 1 2 3 4 "Potassic-Magnesio-Fluoro-Arfvedsonite". Mindat.
  5. "What is the longest mineral name? – ShortInformer". short-informer.com. Retrieved 2023-12-08.
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