Walpurgite is a rare secondary uranium-bismuth mineral typically found as thin, yellow, tabular crystals or radiating sprays in oxidized hydrothermal veins. It is highly prized by collectors for its brilliant yellow fluorescence under UV light, though it requires careful handling due to its uranium content.
Is this walpurgite?
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 walpurgite with a known reference. Walpurgite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale brownish yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine to greasy.
- 4Match the color rangeCompare against the expected color range: colorless, straw yellow, wax yellow.
- 5Look at form & habitCrystal system: triclinic. Typical habit: lath, radial.
Often confused with
Walpurgite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Walpurgite is noticeably harder (Mohs 3.5 vs. 2-2.5); luster reads adamantine to greasy on Walpurgite and vitreous, subadamantine, waxy, pearly on cleavages; becoming dull on dehydration to metatorbernite on Torbernite.
How to tell apart: Walpurgite is noticeably harder (Mohs 3.5 vs. 2-2.5); luster reads adamantine to greasy on Walpurgite and vitreous, pearly on {001} on Autunite.
How to tell apart: Luster reads adamantine to greasy on Walpurgite and vitreous, silky in aggregates on Mixite.
Often found alongside walpurgite
Minerals reported to co-occur with walpurgite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (BiO)₄(UO₂)(AsO₄)₂·2H₂O
- Mohs hardness
- 3.5
- Density
- 5.95 g/cm³
- Colors
- Streak
- Pale brownish yellow
- Luster
- Adamantine to greasy
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Lath, radial
- Cleavage
- On {010}, perfect
- Fluorescence
- Bright yellow under SW and LW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in the oxidized zone of Bi–U–As-bearing hydrothermal mineral deposits
Where rockhounds find walpurgite
Classic worldwide localities
- Found in the Walpurgis vein, Weisser Hirsch mine, and on the dump of the Ritterzeche, Neustädtel-Schneeberg, Saxony, Germany
- Schmiedestollen, near Wittichen, and at Nussbach, near Triberg, Black Forest, Germany
- Geister vein, Eliáš mine, Jáchymov (Joachimsthal), Czech Republic
- Southwick Cliffs, near Dalbeattie, Kirkcudbrightshire, Scotland
Field-hunting tip
Where it forms: A rare secondary mineral in the oxidized zone of Bi–U–As-bearing hydrothermal mineral deposits. If you start seeing trögerite, zeunerite, uranosphaerite in float, you are in the right ground. Typical habit: lath, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify walpurgite?+
Where is walpurgite found?+
Is walpurgite safe to handle?+
What rocks look like walpurgite?+
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Find walpurgite on the map
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