Françoisite-(Nd) is a very rare secondary uranium mineral typically found in the oxidized zones of uranium-rich ore bodies. It usually occurs as small, yellow, platy crystals or thin crusts, often associated with other uranium-bearing minerals.
Is this françoisite-(nd)?
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-(nd) with a known reference. Françoisite-(Nd) 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: aggregates, platy.
Often confused with
Françoisite-(Nd) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Françoisite-(Nd) leaves white, Françoisite-(Ce) leaves pale yellow.
How to tell apart: Streak differs, so Françoisite-(Nd) leaves white, Meta-autunite leaves yellow; luster reads vitreous on Françoisite-(Nd) and pearly to dull on Meta-autunite.
Often found alongside françoisite-(nd)
Minerals reported to co-occur with françoisite-(nd). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Nd(UO₂)₃(PO₄)₂O(OH)·6H₂O
- Mohs hardness
- 3
- Density
- 4.06 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent to opaque
- Crystal system
- Monoclinic
- Crystal habit
- Aggregates, platy
- Cleavage
- On {010}, good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare alteration product of uraninite in a sedimentary Cu–Co deposit (Kamoto-East mine, Congo)
Where rockhounds find françoisite-(nd)
Classic worldwide localities
- Kamoto-East Cu–Co mine, five km east of Kolwezi, Katanga Province, Congo (Shaba Province, Zaire)
- Bangombé natural fission reactor, Gabon
Field-hunting tip
Where it forms: A rare alteration product of uraninite in a sedimentary Cu–Co deposit (Kamoto-East mine, Congo). If you start seeing uraninite, schoepite, uranophane in float, you are in the right ground. Typical habit: aggregates, platy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify françoisite-(nd)?+
Where is françoisite-(nd) found?+
Is françoisite-(nd) safe to handle?+
What rocks look like françoisite-(nd)?+
What minerals are found with françoisite-(nd)?+
What kind of rock does françoisite-(nd) form in?+
What is françoisite-(nd) used for?+
Find françoisite-(nd) on the map
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