Gauthierite is an exceptionally rare potassium-lead uranyl oxide mineral discovered in the oxidized zones of uranium mines. It typically occurs as delicate, bright yellow tabular crystals that are highly sought after by collectors of radioactive minerals due to its distinct crystallography.
Is this gauthierite?
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 gauthierite with a known reference. Gauthierite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Gauthierite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Gauthierite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, orange-yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, clusters.
Often confused with
Gauthierite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Gauthierite and adamantine on Becquerelite.
How to tell apart: Curite is the harder of the two (Mohs 4-5 vs. 2-3); streak differs — Gauthierite leaves yellow, Curite leaves orange; luster reads vitreous on Gauthierite and adamantine on Curite.
How to tell apart: Streak differs — Gauthierite leaves yellow, Masuyite leaves orange-yellow; luster reads vitreous on Gauthierite and adamantine on Masuyite.
Often found alongside gauthierite
Minerals reported to co-occur with gauthierite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₄Pb₆(UO₂)₈O₆(OH)₆·20H₂O
- Mohs hardness
- 2-3
- Density
- 5.5-6.0 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular Crystals, Clusters
- Cleavage
- Perfect
- Fluorescence
- Bright Yellow-green Under UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Uranium Deposits
- Typical price
- $200-2000+ for rare micro-specimens
Where rockhounds find gauthierite
Classic worldwide localities
- Shinkolobwe Mine, DR Congo
Field-hunting tip
Look in oxidized uranium deposits country — that is the host setting where gauthierite typically forms. If you start seeing curite, becquerelite, masuyite in float, you are in the right ground. Field specimens usually show a tabular crystals, clusters habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find gauthierite on the map
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