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Formula: KNa2(Fe2+4Fe3+)Si8O22(OH)2
Inosilicate, arfvedsonite root name group,
amphibole
Crystal System: Monoclinic
Specific gravity: 3.39 measured, 3.43 calculated
Hardness: 5½ to 6
Streak: Pale blue
Colour: Black or dark blue-green
Environments
Localities
There are three co-type localities:
The Potassic-Arfvedsonite occurrence, Pegmatite Valley, Lilleelv, Head of Kangerluarsuk, Kangerluarsuk Fjord,
Ilímaussaq complex, Kujalleq, Greenland
The Hilairitovoye pegmatite, Kirovskii apatite mine, Kukisvumchorr Mt, Khibiny Massif, Murmansk Oblast, Russia
The Palitra pegmatite, Karnasurt mine, Karnasurt Mountain, Lovozersky District, Murmansk Oblast, Russia
At the type localities, potassic-arfvedsonite occurs as euhedral, prismatic to acicular crystals from
a few centimeters to 15 x 0.8 cm in agpaitic complexes.
Associated minerals include villiaumite,
titanite,
steenstrupine-(Ce),
sodalite, rinkite-(Ce),
nepheline, natrolite,
microcline,
lorenzenite,
lomonosovite,
lamprophyllite,
fluorite, fluorapatite,
eudialyte, epistolite,
arfvedsonite, analcime
and aegirine
(Mindat).
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