Ranunculite is a rare secondary uranium mineral typically found as bright yellow botryoidal crusts. It is named for its buttercup-yellow color and is primarily collected by specialized radioactive mineral enthusiasts.
Is this ranunculite?
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 ranunculite with a known reference. Ranunculite 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: dull.
- 4Match the color rangeCompare against the expected color range: golden yellow, canary yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: botryoidal, nodular, platy.
Often confused with
Ranunculite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ranunculite leaves light yellow, Autunite leaves pale yellow; luster reads dull on Ranunculite and vitreous, pearly on {001} on Autunite.
How to tell apart: Streak differs, so Ranunculite leaves light yellow, Torbernite leaves pale green; luster reads dull on Ranunculite and vitreous, subadamantine, waxy, pearly on cleavages; becoming dull on dehydration to metatorbernite on Torbernite.
Often found alongside ranunculite
Minerals reported to co-occur with ranunculite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al(UO₂)(PO₃OH)(OH)₃·4H₂O
- Mohs hardness
- 3
- Density
- 3.4 g/cm³
- Streak
- Light yellow
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Botryoidal, nodular, platy
- Cleavage
- Perfect on {001}; perfect on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In U-rich portions of a pegmatite with other Al-U phosphates
Where rockhounds find ranunculite
Classic worldwide localities
- Kobokobo, Kivu, Zaire (type locality)
Field-hunting tip
Where it forms: In U-rich portions of a pegmatite with other Al-U phosphates. If you start seeing variscite, meta-autunite, uraninite in float, you are in the right ground. Typical habit: botryoidal, nodular, platy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ranunculite?+
Where is ranunculite found?+
Is ranunculite safe to handle?+
What rocks look like ranunculite?+
What minerals are found with ranunculite?+
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Find ranunculite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
