Aegirine
Image: <a href="//commons.wikimedia.org/wiki/User:Iifar" title="User:Iifar">Ivar Leidus</a> (CC BY-SA 4.0)
Mineral NameAegirine
Chemical FormulaNaFe³⁺Si₂O₆
Mohs Hardness6
Crystal Systemmonoclinic
Lustervitreous
Streak Coloryellowish-gray to brownish-green
Cleavagegood on {110}
Fractureuneven to conchoidal
Specific Gravity3.5
Colorsdark green, greenish-black, black
Transparencytranslucent to opaque
Type LocalityMt Malosa, Zomba, Malawi
Mineral GroupSilicates
Usescollector, minor industrial
Associated Mineralsfeldspar, nepheline, arfvedsonite, eudialyte
Rarityuncommon
Description
This specimen features a prominent, dark, prismatic aegirine crystal standing upright, surrounded by smaller, radiating crystals and minor white to cream-colored feldspar. The crystals exhibit a vitreous luster and a deep, dark green to black color.
Geological Context
Aegirine is a sodium-iron silicate mineral typically found in alkaline igneous rocks such as nepheline syenites, phonolites, and carbonatites. It forms under conditions of high sodium and iron content, often in pegmatites or hydrothermal veins associated with these rock types.
