Meta-autunite is the dehydrated form of autunite, frequently encountered in the oxidized sections of uranium deposits. It is prized by collectors for its brilliant neon-green fluorescence under UV light, though it requires careful handling due to its radioactivity.
Is this meta-autunite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch meta-autunite with a known reference. Meta-autunite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly to dull.
- 4Match the color rangeCompare against the expected color range: lemon-yellow, greenish yellow, yellowish green, dark green.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular, foliated, micaceous, or crusts.
Often confused with
Meta-autunite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Meta-autunite leaves yellow, Autunite leaves pale yellow; luster reads pearly to dull on Meta-autunite and vitreous, pearly on {001} on Autunite.
How to tell apart: Streak differs, so Meta-autunite leaves yellow, Torbernite leaves pale green; luster reads pearly to dull on Meta-autunite and vitreous, subadamantine, waxy, pearly on cleavages; becoming dull on dehydration to metatorbernite on Torbernite.
How to tell apart: Streak differs, so Meta-autunite leaves yellow, Uranocircite leaves light yellow.
Often found alongside meta-autunite
Minerals reported to co-occur with meta-autunite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca(UO₂)₂(PO₄)₂·2-6H₂O
- Mohs hardness
- 2-2.5
- Density
- 3.35-3.55 g/cm³
- Streak
- Yellow
- Luster
- Pearly to dull
- Transparency
- Translucent to opaque
- Crystal system
- Tetragonal
- Crystal habit
- Tabular, foliated, micaceous, or crusts
- Cleavage
- Perfect on {001}; indistinct on {010}
- Fluorescence
- Fluoresces yellowish green under UV
- Rarity
- Common
- Uses
- Collector
- Host rock
- A secondary mineral, formed as dehydration pseudomorphs after autunite
Where rockhounds find meta-autunite
Classic worldwide localities
- France
- Portugal
- USA (Washington State)
- Australia
- Brazil
Field-hunting tip
Where it forms: A secondary mineral, formed as dehydration pseudomorphs after autunite. If you start seeing autunite in float, you are in the right ground. Typical habit: tabular, foliated, micaceous, or crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify meta-autunite?+
Where is meta-autunite found?+
Is meta-autunite safe to handle?+
What rocks look like meta-autunite?+
What minerals are found with meta-autunite?+
What kind of rock does meta-autunite form in?+
What is meta-autunite used for?+
Find meta-autunite on the map
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