mineral

Arfvedsonite (often mistakenly sold as Astrophyllite)

Arfvedsonite [Na3(Fe2+)4Fe3+Si8O22(OH)2]

Hardness: 5-6 Mohs. Color: Deep black to dark blue-gray with needle-like blue or silver flashes. Luster: Vitreous to submetallic. Crystal structure: Monoclinic, often found in fibrous or radiating aggregates.

Hardness: 5-6 Mohs
Luster: Vitreous to submetallic

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed in highly alkaline igneous rocks such as syenites and pegmatites. It forms as a primary mineral during the late stages of magmatic crystallization.

Uses & applications

Primarily used as a collector’s stone, or tumbled for use in jewelry and metaphysical practices. It is not used in industrial applications due to its brittleness.

Geological facts

Arfvedsonite is famous for its 'fire' or blue flash when tilted under light, which causes it to be frequently confused with Astrophyllite or Nuummite by novice collectors.

Field identification & locations

Identify in the field by its dark color and the characteristic radiating fan-like pattern of its crystals. It is commonly found in Russia (Kola Peninsula), Greenland, and Canada. Look for the distinct blue chatoyancy to distinguish it from similar black minerals.

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