Françoisite-(Ce) is a rare hydrated uranium-cerium phosphate mineral typically found as secondary crusts or thin, yellow, platy crystals. It is primarily known from the oxidized zones of uranium deposits in the Democratic Republic of the Congo, where it forms in association with other uranium-bearing minerals.
Is this françoisite-(ce)?
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 françoisite-(ce) with a known reference. Françoisite-(Ce) 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: pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: lemon-yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts, lamellar aggregates.
Often confused with
Françoisite-(Ce) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Françoisite-(Ce) leaves pale yellow, Meta-autunite leaves yellow; luster reads vitreous on Françoisite-(Ce) and pearly to dull on Meta-autunite.
How to tell apart: Streak differs, so Françoisite-(Ce) leaves pale yellow, Phosphuranylite leaves light yellow.
Often found alongside françoisite-(ce)
Minerals reported to co-occur with françoisite-(ce). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ce(UO₂)₃(PO₄)₂O(OH)·6H₂O
- Mohs hardness
- ~3
- Density
- 4.71 g/cm³
- Colors
- Streak
- Pale yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, crusts, lamellar aggregates
- Cleavage
- On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral from the alteration under oxidative conditions of REE- and U4+ - bearing primary minerals: allanite-(Ce), monazite-(Ce), ±uraninite at Les Marécottes
Where rockhounds find françoisite-(ce)
Classic worldwide localities
- La Creusaz uranium deposit, near Les Marécottes, Valais, Switzerland, and at the Number 2 Uranium Workings, Radium Ridge, near Mt. Painter, Arkaroola area, Northern Flinders Ranges, South Australia
Field-hunting tip
Where it forms: A secondary mineral from the alteration under oxidative conditions of REE- and U4+ - bearing primary minerals: allanite-(Ce), monazite-(Ce), ±uraninite at Les Marécottes. If you start seeing uranophane, novácěkite-metanovácěkite, jarosite in float, you are in the right ground. Typical habit: platy crystals, crusts, lamellar aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify françoisite-(ce)?+
Where is françoisite-(ce) found?+
Is françoisite-(ce) safe to handle?+
What rocks look like françoisite-(ce)?+
What minerals are found with françoisite-(ce)?+
What kind of rock does françoisite-(ce) form in?+
What is françoisite-(ce) used for?+
Find françoisite-(ce) on the map
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