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 — Autunite leaves pale yellow, Torbernite leaves pale green; luster reads pearly on Autunite and vitreous on Torbernite.
How to tell apart: Streak differs — Autunite leaves pale yellow, Meta-autunite leaves yellow.
How to tell apart: Streak differs — 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 — that is 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, Maine — 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.
