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. Françoisite-(Ce) leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Françoisite-(Ce) typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: yellow, orange-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: Luster reads pearly on Françoisite-(Ce) and earthy on Phosphuranylite.
How to tell apart: Streak differs — Françoisite-(Ce) leaves yellow, Torbernite leaves pale green; luster reads pearly on Françoisite-(Ce) and vitreous on Torbernite.
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,Ca,Nd)(UO₂)₃(PO₄)₂(OH)₃·8H₂O
- Mohs hardness
- 3
- Density
- 4.1-4.2 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Crusts, Lamellar Aggregates
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Uranium Ore Zones
- Typical price
- $50-300 per thumbnail specimen
Where rockhounds find françoisite-(ce)
Classic worldwide localities
- Kamoto East Mine, Democratic Republic of the Congo
- Shinkolobwe Mine, Democratic Republic of the Congo
Field-hunting tip
Look in oxidized uranium ore zones country — that is the host setting where françoisite-(ce) typically forms. If you start seeing uraninite, metatorbernite, studtite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts, lamellar aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify françoisite-(ce)?+
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What rocks look like françoisite-(ce)?+
What minerals are found with françoisite-(ce)?+
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Find françoisite-(ce) on the map
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