Judging quality
Flash is generally blue and appears in broad streaks along cleavage rather than nuummite's fine needles. Crystals are prismatic with a resinous black lustre.
Amphibole
Arfvedsonite
A dark sodium amphibole that carries a startling blue-to-gold flash along its cleavage — sold widely and inaccurately as 'nuummite', which it superficially resembles.
Care
Moderate hardness; the polish scratches. Store apart from quartz.
History & lore
Named for the Swedish chemist Johan August Arfwedson, who discovered lithium.
Cultural history, recorded as tradition rather than as medical or scientific claim.
Common questions about Arfvedsonite
- What is Arfvedsonite?
- A dark sodium amphibole that carries a startling blue-to-gold flash along its cleavage — sold widely and inaccurately as 'nuummite', which it superficially resembles.
- How hard is Arfvedsonite and what is it made of?
- Arfvedsonite is a Amphibole-family mineral with the composition Na3Fe4FeSi8O22(OH)2. It crystallizes in the monoclinic system and rates 5-6 on the Mohs hardness scale. It occurs in black, iridescent, blue.
- Where does Arfvedsonite come from?
- Notable localities for Arfvedsonite include Greenland, Norway, Russia, Malawi.
- How do you tell good Arfvedsonite from filler?
- Flash is generally blue and appears in broad streaks along cleavage rather than nuummite's fine needles. Crystals are prismatic with a resinous black lustre.
- How do you care for Arfvedsonite?
- Moderate hardness; the polish scratches. Store apart from quartz.
See it in person
Photographs only go so far
Both rooms are open six days a week, and there is always someone happy to pull pieces out of the case so you can compare them under the light.