Aegirine
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Mineral NameAegirine
Chemical FormulaNaFe³⁺Si₂O₆
Mohs Hardness5
Crystal Systemmonoclinic
Lustervitreous
Streak Coloryellowish-gray to greenish-gray
Cleavagegood on {110} at 87° and 93°
Fractureuneven to subconchoidal
Specific Gravity3.5
Colorsdark green, greenish-black, black
Transparencytranslucent to opaque
Type LocalityKola Peninsula, Khibiny, Russia
Mineral GroupSilicates (Pyroxene Group)
Usescollector, minor source of rare earth elements
Associated Mineralsnepheline, microcline, albite, arfvedsonite
Rarityuncommon
Description
This specimen displays dark greenish-black, acicular to fibrous crystals of aegirine, forming radiating aggregates within a lighter, possibly white or grey matrix. The mineral exhibits a vitreous luster.
Geological Context
Aegirine typically forms in alkaline igneous rocks such as nepheline syenites and phonolites, as well as in associated pegmatites and some metamorphic rocks. It crystallizes from sodium-rich, silica-undersaturated magmas.
