Aegirine
Image: Didier Descouens (CC BY-SA 3.0)
Mineral NameAegirine
Chemical FormulaNaFeSi2O6
Mohs Hardness5
Crystal Systemmonoclinic
Lustervitreous
Streak Coloryellowish-gray
Cleavagegood on {110} at 87° and 93°
Fractureuneven
Specific Gravity3.55
Colorsblack, dark green, greenish-black
Transparencytranslucent
Type LocalityMont Saint-Hilaire, Rouville Co., Montérégie, Québec, Canada
Mineral GroupSilicates
Usescollector, minor industrial
Associated Mineralsanalcime, nepheline, feldspar, arfvedsonite
Rarityuncommon
Description
This specimen features a cluster of dark, elongated, prismatic aegirine crystals, partially covered by lighter, blocky, well-formed analcime crystals.
Geological Context
Aegirine is a sodium-iron rich pyroxene typically found in alkali-rich igneous rocks such as nepheline syenites and phonolites, and their associated pegmatites and hydrothermal veins. Mont Saint-Hilaire is a classic locality for such alkaline intrusive complexes.
