Carnotite is a bright yellow, radioactive secondary mineral commonly found as earthy or powdery crusts in sandstone formations. It serves as an important secondary ore for uranium and vanadium, often replacing organic materials like fossilized wood within its host rock.
Is this carnotite?
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 carnotite with a known reference. Carnotite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: strontian-yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: dull, earthy; silky when crystalline.
- 4Match the color rangeCompare against the expected color range: yellow, golden yellow, greenish yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: earthy, encrustations, platy.
Often confused with
Carnotite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Carnotite leaves strontian-yellow, Tyuyamunite leaves light yellow; luster reads dull, earthy; silky when crystalline on Carnotite and adamantine, pearly on {001}, may be dull to waxy if massive on Tyuyamunite.
How to tell apart: Streak differs, so Carnotite leaves strontian-yellow, Autunite leaves pale yellow; luster reads dull, earthy; silky when crystalline on Carnotite and vitreous, pearly on {001} on Autunite.
How to tell apart: Streak differs, so Carnotite leaves strontian-yellow, Uranophane leaves yellowish white; luster reads dull, earthy; silky when crystalline on Carnotite and vitreous on Uranophane.
Often found alongside carnotite
Minerals reported to co-occur with carnotite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₂(UO₂)₂(VO₄)₂·3H₂O
- Mohs hardness
- 2
- Density
- 4.70 g/cm³
- Streak
- Strontian-yellow
- Luster
- Dull, earthy; silky when crystalline
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Earthy, encrustations, platy
- Cleavage
- Perfect on {001}, micaceous
- Rarity
- Common
- Uses
- Ore of uranium, Ore of vanadium, Collector mineral
- Host rock
- An important ore mineral of uranium, typically in paleochannels in sandstone Colorado Plateau-type U–V deposits, found near fossil carbonaceous matter, and in calcretes and near playas
Where rockhounds find carnotite
26 mapped spotsClassic worldwide localities
- San Rafael Swell, Emery Co., around Thompsons and Richardson, Grand Co., Utah, USA
- Mines in the Grants district, McKinley Co., New Mexico, USA
- Anderson mine, Yavapai Co., and an ore mineral in Monument Valley, Apache and Navajo Cos., Arizona, USA
- El Sherana, Northern Territories, Australia
- A Yeelirrie, Western Australia
- Radium Hill mine, near Olary, South Australia
U.S. states with carnotite
Each link opens a state-specific list of mapped rockhounding spots that produce carnotite.
Field-hunting tip
Where it forms: An important ore mineral of uranium, typically in paleochannels in sandstone Colorado Plateau-type U–V deposits, found near fossil carbonaceous matter, and in calcretes and near playas. If you start seeing tyuyamunite, metatyuyamunite, volborthite in float, you are in the right ground. Typical habit: earthy, encrustations, platy. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, Pennsylvania. Start trip planning there.
More carnotite photos
Common questions
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Find carnotite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
