Roubaultite is a rare copper uranyl hydroxy-hydrate mineral primarily found in the oxidized zones of uranium deposits. It typically forms as delicate, orange, 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 pearly luster.
- 4Match the color rangeCompare against the expected color range: orange, red-orange.
- 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 — Roubaultite leaves yellow, Masuyite leaves orange-yellow; luster reads pearly on Roubaultite and adamantine on Masuyite.
How to tell apart: Luster reads pearly 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
- Pearly
- 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
- Typical price
- $50-300+ depending on crystal size and quality
Where rockhounds find roubaultite
Classic worldwide localities
- Shinkolobwe mine, DR Congo
Field-hunting tip
Look in oxidized zones of uranium-bearing hydrothermal deposits country — that is 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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