Francevillite is a rare secondary uranium vanadate mineral that typically forms vibrant yellow platy or tabular crystals. It is found in the oxidized zones of uranium deposits and is highly sought after by radioactive mineral collectors.
Is this francevillite?
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 francevillite with a known reference. Francevillite 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: light yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine to pearly.
- 4Match the color rangeCompare against the expected color range: yellow, brownish yellow, yellow green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, tabular aggregates, crusts.
Often confused with
Francevillite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Francevillite is noticeably harder (Mohs 3 vs. 2); streak differs, so Francevillite leaves light yellow, Carnotite leaves strontian-yellow; luster reads adamantine to pearly on Francevillite and dull, earthy; silky when crystalline on Carnotite.
How to tell apart: Francevillite is noticeably harder (Mohs 3 vs. ~2).
Often found alongside francevillite
Minerals reported to co-occur with francevillite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ba(UO₂)₂(VO₄)₂·5H₂O
- Mohs hardness
- 3
- Density
- 4.55 g/cm³
- Streak
- Light yellow
- Luster
- Adamantine to pearly
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy crystals, tabular aggregates, crusts
- Cleavage
- On {001}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the oxidized zone of a Pb-bearing U–V deposit (Mounana mine, Gabon)
Where rockhounds find francevillite
Classic worldwide localities
- Jim Thorpe, Carbon Co., Pennsylvania, USA
- Mounana uranium mine, Franceville, Gabon
- Kambove and in the Musonoi mine, near Kolwezi, Katanga Province, Congo (Shaba Province, Zaire)
- Southwest edge of the Chimeja Range, about four km north of Lubimbi Spring, Zimbabwe
- Bertholène and Lussagues, Aveyron, and Saint-Pierre, Cantal, France
- Donnersberg, near Imsbach, Rhineland-Palatinate, Germany
Field-hunting tip
Where it forms: In the oxidized zone of a Pb-bearing U–V deposit (Mounana mine, Gabon). If you start seeing curienite, duttonite, vanuralite in float, you are in the right ground. Typical habit: platy crystals, tabular aggregates, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
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Find francevillite on the map
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