Aegirine

Aegirine properties at a glance

Geology & background

Aegirine forms almost exclusively in sodium-rich, silica-poor igneous environments, especially nepheline syenites, alkaline granites, and their pegmatites, where sodium and iron are abundant enough to stabilize this pyroxene over more common calcium-magnesium varieties. Classic localities include the Larvik region of Norway, the Kola Peninsula in Russia, Mont Saint-Hilaire in Quebec, and the alkaline complexes of Malawi, all of which supply well-formed prismatic crystals to collectors. The mineral is named for Aegir, the Norse god of the sea, a nod to its discovery in Norway.

Rockhounds should note that aegirine forms a solid-solution series with augite, and iron-rich, low-sodium members were once called acmite, a term still seen on older labels. Because it grows in unusual alkaline rock suites, aegirine specimens often come paired with other rare sodium-bearing minerals, making a single matrix piece educational well beyond the pyroxene itself.

How to identify Aegirine

Look for slender, elongated prismatic crystals with a nearly square cross-section, often striated lengthwise and terminated in a wedge. Color ranges from dark green through brown to nearly black, with a vitreous luster and a pale green to grayish streak. Hardness of about 6 separates it from softer amphiboles like hornblende, which shares a similar habit but has different cleavage angles; aegirine's two cleavage planes meet near 87 and 93 degrees, the classic pyroxene angle.

• Compare the specimen's color, luster, crystal habit, grain size, streak, and locality before confirming.
• Use multiple photos when possible, including a fresh surface and a close view of texture.

Full Aegirine identification guide: checklist, home tests and look-alikes →

Aegirine vs similar stones

Not sure it isn't something else? Side-by-side comparisons with the stones most often confused with Aegirine.

Where Aegirine is found

Reported from multiple localities worldwide; verify locality against specimen provenance when available.

How much is Aegirine worth?

Value depends on size, crystal quality, color, locality, rarity, damage, and provenance.

Common uses

• Collector specimens
• Education
• Field identification
• Industrial or lapidary use when suitable

Interesting facts

• Aegirine is named after Aegir, the Norse sea god, because it was first described from Norwegian alkaline rocks.
• It forms a complete solid-solution series with augite, with iron-rich intermediate members historically labeled acmite.
• Well-formed aegirine crystals sometimes float free in cavities within nepheline syenite pegmatites, allowing perfect termination on all sides.

Care & safety

Handle as a collector specimen until hardness, cleavage, and fracture are verified.

Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a proper respirator.

Aegirine FAQ

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