Margaritasite is a rare cesium-bearing uranyl vanadate mineral that typically forms vibrant yellow crystalline crusts or small platy crystals. It is primarily found in the oxidized zones of uranium-vanadium deposits and is highly prized by advanced radioactive mineral collectors. Due to its radioactive nature, it requires careful storage and handling protocols.
Is this margaritasite?
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 margaritasite with a known reference. Margaritasite sits at Mohs 2, 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: pearly.
- 4Match the color rangeCompare against the expected color range: yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts, coatings.
Often confused with
Margaritasite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Margaritasite leaves light yellow, Carnotite leaves strontian-yellow; luster reads pearly on Margaritasite and dull, earthy; silky when crystalline on Carnotite.
How to tell apart: Luster reads pearly on Margaritasite and adamantine, pearly on {001}, may be dull to waxy if massive on Tyuyamunite.
Often found alongside margaritasite
Minerals reported to co-occur with margaritasite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cs₂(UO₂)₂(VO₄)₂·H₂O
- Mohs hardness
- 2
- Density
- 5.4 g/cm³
- Colors
- Streak
- Light yellow
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, crusts, coatings
- Cleavage
- Perfect
- Fluorescence
- Bright yellow-green under UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As pore fillings and phenocryst casts in felsic volcanic tuffs, which have been altered by high-temperature hydrothermal fluids
Where rockhounds find margaritasite
Classic worldwide localities
- Margaritas uranium deposit, Peña Blanca district, about 70 km north of Chihuahua City, Chihuahua, Mexico
Field-hunting tip
Where it forms: As pore fillings and phenocryst casts in felsic volcanic tuffs, which have been altered by high-temperature hydrothermal fluids. If you start seeing kaolinite, quartz in float, you are in the right ground. Typical habit: platy crystals, crusts, coatings. Train your eye for that shape before scanning the outcrop.
Common questions
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Find margaritasite on the map
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