Potassic-magnesio-fluoro-arfvedsonite explained

Category:Silicate
Formula:[(K,Na)][Na2][Mg4Fe3+][Si8O22][(F,OH)2]
Imasymbol:Pmfarf
System:Monoclinic
Class:2/m - Prismatic
Symmetry:C2/m
Color:Bluish-Gray
Twinning:Common on TL, as simple or lamellar (ll57A) on
Cleavage:Perfect on
Fracture:Splintery
Tenacity:Brittle
Mohs:6
Opticalprop:Biaxial Negative
Fluorescence:None
Streak:White
Gravity:3.174 g/cm3
Lustre:Vitreous
References:[1] [2] [3] [4]

Potassic-magnesio-fluoro-arfvedsonite is an amphibole mineral first discovered in Quebec, Canada, 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.

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 plane. The calculated density is 3.174 g/cm3.

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. 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

Oxidewt%
SiO254.25
TiO21.08
Al2O30.03
Cr2O3n.a.
Fe2O38.07
FeO13.23tot<14.52
MnO0.32
ZnO0.05
MgO13.99
BaO+SrOn.a.
CaO1.16
Na2O6.33
K2O5.20
H2O0.74
F2.20
–O=F-0.93
Total99.18

X-ray diffraction and Crystallography

!Face!D(Å)
1108.539
1313.412
2403.298
3103.183
312.759
1512.718
2602.551
512.352
3312.269
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.

Notes and References

  1. 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:
  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
  3. Web site: Potassic-Magnesio-Fluoro-Arfvedsonite. Mindat.
  4. Warr. L.N.. 2021. IMA–CNMNC approved mineral symbols. Mineralogical Magazine. 85. 3. 291–320. 10.1180/mgm.2021.43. 2021MinM...85..291W. 235729616. free.
  5. Web site: What is the longest mineral name? – ShortInformer . 2023-12-08 . short-informer.com.