Aegyrine - Encyclopedia

    Class : Silicates
    Subclass : Inosilicates
    Crystal system : Monoclinic
    Chemistry : NaFeSi2O6
    Rarity : Common

Aegyrine is a sodium pyroxene characteristic of alkaline rocks, mainly nepheline syenites, carbonatites and associated pegmatites, where it is a faithful companion of sodium amphiboles. It is also an accessory component of rocks that have undergone extensive metamorphism (blue schists, granulites). It takes its name from Aegir the Scandinavian god of the sea. Its crystals are prismatic to acicular, with the faces of the prism striped vertically and the endings very sharp ; they can reach 35 cm and are commonly arranged in crested or rayed aggregates. The color is usually greenish black, dark green, more rarely reddish brown. It is a mineral that does not have a specific use, some crystals could be cut into faceted gems for the collection (photo below).

Aegyrine in the World

The most beautiful specimens come from massive alkaline rocks. The alkaline pegmatites from Mont St-Hilaire (Quebec, Canada) yield superb lanceolate prismatic crystals of decimeter size associated with serandite. The nepheline syenite massifs of Kola (Lovozero and Khibiny) and those of Langesundsfjord, in the south of Norway, also contain large crystals. Finally, the alkaline complex of Ilimausaq, in the region of Narsarssuak (Greenland), produces superb rosettes of aegyrine associated with nepheline and eudialyte. Among the largest known crystals, which exceed 20 cm, we must mention the magnificent specimens extracted from pegmatites from Malosa Mount in Malawi (main photo).

Aegyrine in France

In France, aegyrine is known in the granite of Ota, in Southern Corsica as well as in the Bras de Cilaos on Reunion Island as microcrystals.

Twinning and special forms

Twins are known on {100} but very rare.

Fakes and scams

No fake recorded for this species.

Hardness : 6
Density : 3.5 to 3.6
Fracture : Irregular
Streak : Yellow-gray

TP : Opaque to transparent
IR : 1.720 to 1.839
Birefringence : 0.037 to 0.061
Optical character : Baxial -
Pleochroism : Visible
Fluorescence : None

Solubility : weakly attacked by acids

Magnetism : Paramagnetic
Radioactivity : None


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