Magnesio-arfvedsonite
Magnesio-arfvedsonite is an IMA-recognized mineral species in the silicate class, with the chemical formula NaNa₂(Mg₄Fe³⁺)Si₈O₂₂(OH)₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Amphibole structural group.
Key properties: Mohs hardness 6; specific gravity 3.1–3.3; Vitreous luster; optically biaxial.
IMA symbol Marf, IMA status: approved, named in 1957.
Occurs as exsolution lamellae in cummingtonite from metamorphosed iron formation; in felsic pegmatites; from so dium metasomatism (fenitization) around some carbonatites.
It is found associated with Aegirine, braunite, winchite, cummingtonite, albite, biotite.
The name refers to its high magnesium content and similarity to arfvedsonite.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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