igneous

Arfvedsonite in Quartz

Arfvedsonite [Na3(Fe2+4Fe3+)Si8O22(OH)2] often hosted in Quartz or Feldspar

Hardness: 5.5-6 (Arfvedsonite) / 7 (Quartz); Color: Black fibers/streaks in a white or light gray matrix; Luster: Vitreous to sub-metallic; Crystal Structure: Monoclinic; Specific Gravity: 3.44 (Arfvedsonite)

Hardness: 5
Color: Black fibers/streaks in a white or light gray matrix
Luster: Vitreous to sub-metallic

Identified April 2, 2026More igneous →

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Physical properties

Formation & geological history

Formed in highly alkaline igneous rocks such as syenite and granite pegmatites. It crystallizes from late-stage magmatic fluids rich in sodium and iron.

Uses & applications

Primarily used as a metaphysical stone, for lapidary work (towers, spheres), and as a collector's specimen.

Geological facts

Arfvedsonite is often mistaken for Astrophyllite or Nuummite due to its dark, bladed appearance, but it is distinctively an amphibole mineral. It was named after the Swedish chemist Johan August Arfwedson.

Field identification & locations

Identify by its dark blue-black to black needle-like or bladed crystals often showing a slight blue flash when polished. Found commonly in Greenland, Russia (Kola Peninsula), and Canada.

Other igneous specimens

See all

Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral