Autunite is a secondary uranium mineral characterized by its striking neon-green fluorescence under UV light. It typically occurs as thin, square-shaped tabular crystals or micaceous crusts in the oxidized zones of uranium deposits.
Is this 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 autunite with a known reference. 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. Autunite leaves a pale yellow streak.
- 3Read the lusterHold the specimen under a strong light. Autunite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-green, lemon-yellow.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular crystals, micaceous aggregates, crusts.
Often confused with
Autunite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Autunite leaves pale yellow, Torbernite leaves pale green; luster reads pearly on Autunite and vitreous on Torbernite.
How to tell apart: Streak differs, so Autunite leaves pale yellow, Meta-autunite leaves yellow.
How to tell apart: Streak differs, so Autunite leaves pale yellow, Uranocircite leaves yellow.
Often found alongside autunite
Minerals reported to co-occur with 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)₂·10-12H₂O
- Mohs hardness
- 2-2.5
- Density
- 3.1-3.2 g/cm³
- Streak
- Pale Yellow
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Tabular Crystals, Micaceous Aggregates, Crusts
- Cleavage
- Perfect Basal
- Fluorescence
- Bright Neon Yellow-green Under UV Light
- Rarity
- Common
- Uses
- Collector
- Host rock
- Oxidized Zones of Uranium-bearing Hydrothermal Deposits
- Typical price
- $20-150 thumbnail to cabinet specimen
Where rockhounds find autunite
17 mapped spotsClassic worldwide localities
- Autun, France
- Mount Spokane, USA
- Portugal
- Australia
- Democratic Republic of the Congo
U.S. states with autunite
Each link opens a state-specific list of mapped rockhounding spots that produce autunite.
Field-hunting tip
Look in oxidized zones of uranium-bearing hydrothermal deposits country, the host setting where autunite typically forms. If you start seeing torbernite, uraninite, meta-autunite in float, you are in the right ground. Field specimens usually show a tabular crystals, micaceous aggregates, crusts habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, North Carolina, Connecticut. Start trip planning there.
Common questions
How do you identify autunite?+
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Find autunite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
