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 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Roubaultite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Roubaultite typically shows a vitreous to greasy luster.
- 4Match the color rangeCompare against the expected color range: grass-green, apple-green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy crystals, radial aggregates.
Often confused with
Roubaultite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Masuyite is the harder of the two (Mohs 3-4 vs. 2); streak differs, so Roubaultite leaves yellow, Masuyite leaves orange-yellow; luster reads vitreous to greasy on Roubaultite and adamantine on Masuyite.
How to tell apart: Luster reads vitreous to greasy on Roubaultite and adamantine 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
- Cu₂(UO₂)₃(OH)₁₀·5H₂O
- Mohs hardness
- 2
- Density
- 4.96 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Vitreous to Greasy
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Platy Crystals, Radial Aggregates
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Uranium-bearing Hydrothermal Deposits
Where rockhounds find roubaultite
Classic worldwide localities
- Shinkolobwe mine, DR Congo
Field-hunting tip
Look in oxidized zones of uranium-bearing hydrothermal deposits country, the host setting where roubaultite typically forms. If you start seeing soddyite, kasolite, curite in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates habit, so 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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