Arfvedsonite

Arfvedsonite

Arfvedsonite from New Hampshire, USA
General
Category Inosilicates
Amphiboles
Formula
(repeating unit)		 [Na][Na2][(Fe2+)4Fe3+][(OH)2|Si8O22]
Strunz classification 09.DE.25
VIII/F.08-100
Dana classification 66.1.3c.9
Identification
Color Black, deep green on thin edges
Crystal habit Fibrous, radial prismatic aggregates
Crystal system Monoclinic – Prismatic
Twinning Simple or lamellar parallel to [100]
Cleavage Perfect on [110]
Fracture Uneven
Tenacity Brittle
Mohs scale hardness 5–6
Luster Vitreous
Streak Deep bluish gray, gray-green
Diaphaneity Translucent to opaque
Specific gravity 3.3–3.5
Optical properties Biaxial (-)
Refractive index nα = 1.652–1.699
nβ = 1.660–1.705
nγ = 1.666–1.708
Birefringence δ = 0.014
Pleochroism Strong: Blue-greens, yellow-browns, gray-violets
Dispersion r > v strong
References [1][2][3][4]

Arfvedsonite is a sodium amphibole mineral with composition: [Na][Na2][(Fe2+)4Fe3+][(OH)2|Si8O22]. It crystallizes in the monoclinic prismatic crystal system and typically occurs as greenish black to bluish grey fibrous to radiating or stellate prisms.

It is a rather rare mineral occurring in nepheline syenite intrusions and agpaitic (peralkaline) pegmatites and granites as the Golden Horn batholith in Okanogan County, Washington (type locality for zektzerite). Occurrences include Mont Saint-Hilaire, Quebec, Canada; the Ilímaussaq complex in Southern Greenland; and in pegmatites of the Kola Peninsula, Russia. Its mineral association includes nepheline, albite, aegirine, riebeckite, katophorite and quartz.[1]

Arfvedsonite was discovered in 1823 and named for the Swedish chemist Johan August Arfwedson (1792–1841).[3]

See also

Arfvedsonite, Poudrette quarry, Mont Saint-Hilaire, Montérégie, Quebec


References

Wikimedia Commons has media related to Arfvedsonite.
  1. ↑ 1.0 1.1 Arfvedsonite. Handbook of Mineralogy
  2. ↑ Arfvedsonite. Mindat.org
  3. ↑ 3.0 3.1 Arfvedsonite. Webmineral
  4. ↑ IMA Master List