Potassic-magnesio-fluoro-arfvedsonite

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.

Potassic-magnesio-fluoro-arfvedsonite
General
Category	Silicate
Formula (repeating unit)	[(K,Na)][Na2][Mg4Fe3+][Si8O22][(F,OH)2]
IMA symbol	Pmfarf
Crystal system	Monoclinic
Crystal class	2/m - Prismatic
Space group	C2/m
Identification
Color	Bluish-Gray
Twinning	Common on TL, as simple or lamellar (ll57A) on {100}
Cleavage	Perfect on {110}
Fracture	Splintery
Tenacity	Brittle
Mohs scale hardness	6
Lustre	Vitreous
Streak	White
Specific gravity	3.174 g/cm3
Optical properties	Biaxial Negative
Ultraviolet fluorescence	None
References

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 {110} 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.

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) ų, 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.