Autunite
Autunite is phosphates (uranyl micas), Ca(UO2)2(PO4)2·10 to 12H2O. In the hand, it rates 2 to 2.5 on the Mohs scale, and it runs lemon yellow and yellow-green. Collector mineral; fine fluorescent plates modest in price, handled with respect.
The geology.
Autunite carries the formula Ca(UO2)2(PO4)2·10 to 12H2O. It belongs to the tetragonal system. On paper it is phosphates (uranyl micas).
It sits at 2 to 2.5 on the Mohs scale. The surface reads vitreous to pearly. Light behaviour is transparent to translucent. Specific gravity runs 3.1 to 3.2. The streak is pale yellow. It breaks with perfect micaceous cleavage; flaky.
Lemon-to-green square flakes that peel like mica, and under longwave UV erupt in blazing green fluorescence; a Geiger counter confirms what the glow suggests: this is a uranium ore mineral.
Expect to see it as square platy crystals, fan-shaped aggregates or crusts on granite.
The origins.
Oxidized uranium deposits, Autun (France, its namesake), Daybreak Mine (Washington State), Portugal, Margnac (France).
On value, the database notes: collector mineral; fine fluorescent plates modest in price, handled with respect.
Traditional associations.
In energy work traditions, autunite is treated as a specimen-shelf curiosity rather than a handling stone, its lesson being respect for hidden power.
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.
Lemon-to-green square flakes that peel like mica, and under longwave UV erupt in blazing green fluorescence; a Geiger counter confirms what the glow suggests: this is a uranium ore mineral.
Not faked, the radioactivity is unprofitable to counterfeit; the real risk is buying it unlabeled in old collections.
| Looks like | How to tell them apart |
|---|---|
| Torbernite | Its copper twin, emerald green squares that do NOT fluoresce (copper quenches the glow) |
| Yellow mica | Mica neither fluoresces vividly green nor clicks a counter |
| Sulfur crusts | Sulfur smells on warming, no square plates, no radioactivity |
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 autunite.
| Test | What you should see |
|---|---|
| Under UV | Brilliant yellow-green UV fluorescence |
| By eye | Geiger counter responds clearly |
| By eye | Square plates with perfect flaky cleavage |
Anything that scratches, burns or dissolves the piece is a lab job. Get it appraised rather than testing it apart.
Care & handling.
At 2 to 2.5 on the Mohs scale this is a soft material. Keep it as a display piece, store it apart from harder stones, and skip daily-wear settings.
It breaks with perfect micaceous cleavage; flaky, which is worth knowing before you set it or drop it.
Warm water and a soft cloth clean almost everything. Ultrasonic tanks, steamers and household cleaners are where pieces get ruined.
RADIOACTIVE uranium mineral: store sealed and labeled away from living and sleeping areas, never carry in pockets or make elixirs, wash hands after any contact, and avoid inhaling flakes or dust.
A deeper look.
Extended detail on composition, sourcing, authentication and market value.
The physical record
The formula on record is Ca(UO2)2(PO4)2·10 to 12H2O. Crystal system: Tetragonal. Specific gravity: 3.1 to 3.2. Streak: Pale yellow. Cleavage and fracture: Perfect micaceous cleavage; flaky.
How it reaches the market
Oxidized uranium deposits, Autun (France, its namesake), Daybreak Mine (Washington State), Portugal, Margnac (France).
What it gets confused with
Torbernite: Its copper twin, emerald green squares that do NOT fluoresce (copper quenches the glow). Yellow mica: Mica neither fluoresces vividly green nor clicks a counter. Sulfur crusts: Sulfur smells on warming, no square plates, no radioactivity.
What it is worth
Collector mineral; fine fluorescent plates modest in price, handled with respect.
Where buyers get caught
Not faked, the radioactivity is unprofitable to counterfeit; the real risk is buying it unlabeled in old collections.
One more thing
Specimens slowly dehydrate into dull meta-autunite, so collectors keep prized pieces in sealed humid containers, a mineral you literally have to keep watered like a houseplant.
An education-first guide.
No product links here. We do not sell autunite, and a guide that only covers our own shelves would not be much of a guide.
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