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Arfvedsonite
Arfvedsonite is inosilicate (sodium amphibole), Na₃(Fe,Mg)₄FeSi₈O₂₂(OH)₂. In the hand, it rates 5.5 to 6 on the Mohs scale, and it runs black with silver-blue flash and blue-gray starbursts in pale matrix. Black bladed crystals in starburst sprays that flash silvery-blue, the 'fireworks' stone usually mislabeled astrophyllite.
The geology.
Arfvedsonite carries the formula Na₃(Fe,Mg)₄FeSi₈O₂₂(OH)₂. It belongs to the monoclinic system. On paper it is inosilicate (sodium amphibole).
It sits at 5.5 to 6 on the Mohs scale. The surface reads vitreous to silky. Light behaviour is opaque. Specific gravity runs 3.4 to 3.5. The streak is bluish gray. It breaks with two perfect cleavages at ~56°/124°; splintery.
Black bladed crystals in starburst sprays that flash silvery-blue, the 'fireworks' stone usually mislabeled astrophyllite.
Expect to see it as radiating starburst sprays in matrix, polished palm stones, spheres or tumbled.
The origins.
Alkaline intrusions; commercial material from Khibiny/Lovozero (Kola, Russia), Greenland, Malawi.
On value, the database notes: common and affordable; sharp starbursts are mid-range.
Traditional associations.
In energy work traditions, associated with clearing scattered thoughts and night-sky perspective.
Recorded here because it is part of how this material is sold, not because it is a property of the material.
Spotting the real thing.
Black bladed crystals in starburst sprays that flash silvery-blue, the 'fireworks' stone usually mislabeled astrophyllite.
Sold as astrophyllite constantly; blue flash = arfvedsonite, gold flash = astrophyllite.
| Looks like | How to tell them apart |
|---|---|
| Astrophyllite | True astrophyllite flashes bronze-GOLD starbursts; arfvedsonite flashes silver-BLUE |
| Nuummite | Nuummite shows golden lath-shaped flashes in charcoal rock and is far rarer |
| Black tourmaline | Schorl has no directional silvery flash |
At-home tests.
None of these need a lab. A 10x loupe, good daylight and a steady hand cover most of what a buyer needs to know about arfvedsonite.
| Test | What you should see |
|---|---|
| By eye | Silver-blue (never gold) flash from bladed sprays |
| By eye | Splintery amphibole cleavage |
| Scratch check | Knife barely scratches it |
Destructive tests belong to a gemologist, not a kitchen table. If a piece matters to you, pay for an appraisal before you take a file to it.
Care & handling.
At 5.5 to 6 on the Mohs scale it handles careful wear but scratches against quartz and dust. Store it separately and take rings off before rough work.
It breaks with two perfect cleavages at ~56°/124°; splintery, which is worth knowing before you set it or drop it.
Clean it by hand, dry it properly, and keep it away from ultrasonic cleaners and hot steam.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is Na₃(Fe,Mg)₄FeSi₈O₂₂(OH)₂. Crystal system: Monoclinic. Specific gravity: 3.4 to 3.5. Streak: Bluish gray. Cleavage and fracture: Two perfect cleavages at ~56°/124°; splintery.
How it reaches the market
Alkaline intrusions; commercial material from Khibiny/Lovozero (Kola, Russia), Greenland, Malawi.
What it gets confused with
Astrophyllite: True astrophyllite flashes bronze-GOLD starbursts; arfvedsonite flashes silver-BLUE. Nuummite: Nuummite shows golden lath-shaped flashes in charcoal rock and is far rarer. Black tourmaline: Schorl has no directional silvery flash.
What it is worth
Common and affordable; sharp starbursts are mid-range.
Where buyers get caught
Sold as astrophyllite constantly; blue flash = arfvedsonite, gold flash = astrophyllite.
One more thing
Most 'astrophyllite' palm stones on the market are actually arfvedsonite, the blue flash gives the swap away in seconds.
An education-first guide.
We do not stock arfvedsonite. Writing it up regardless is the point of a reference library.
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