Roubaultite is a rare copper uranyl hydroxy-hydrate mineral primarily found in the oxidized zones of uranium deposits. It typically forms as delicate, grass-green to apple-green, platy crystals or radiating sprays that are highly prized by radioactive mineral collectors. Due to its significant uranium content, it requires specialized handling and secure storage protocols.
Is this roubaultite?
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 roubaultite with a known reference. Roubaultite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to slightly greasy.
- 4Match the color rangeCompare against the expected color range: grass green, apple green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy, rosette.
Often confused with
Roubaultite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Roubaultite leaves green, Masuyite leaves orange-yellow.
How to tell apart: Streak differs, so Roubaultite leaves green, Becquerelite leaves yellow; luster reads vitreous to slightly greasy on Roubaultite and adamantine to greasy on Becquerelite.
Often found alongside roubaultite
Minerals reported to co-occur with roubaultite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₂O₂(UO₂)₃(CO₃)₂(OH)₂(H₂O)₄
- Mohs hardness
- ~3
- Density
- 5.02 g/cm³
- Colors
- Streak
- Green
- Luster
- Vitreous to slightly greasy
- Transparency
- Semitransparent
- Crystal system
- Triclinic
- Crystal habit
- Platy, rosette
- Cleavage
- Perfect on {100}; good on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare mineral in the zone of oxidation of copper-bearing uranium deposits, formed by alteration of uraninite
Where rockhounds find roubaultite
Classic worldwide localities
- Shinkolobwe, near Kolwezi, at the Musonoi mine, and in the Kamoto mine, Katanga Province, Congo (Shaba Province, Zaire)
- Komsomol ore field, eastern Siberia, Russia
Field-hunting tip
Where it forms: A rare mineral in the zone of oxidation of copper-bearing uranium deposits, formed by alteration of uraninite. If you start seeing vandenbrandeite, soddyite, becquerelite in float, you are in the right ground. Typical habit: platy, rosette. Train your eye for that shape before scanning the outcrop.
Common questions
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Find roubaultite on the map
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