Leószilárdite is a rare uranyl carbonate mineral typically found as small, bright yellow tabular crystals or crusts in uranium-bearing sandstone. It was discovered in the San Rafael Swell of Utah and is highly prized by advanced collectors for its rarity and complex chemical composition.
Is this leószilárdite?
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 leószilárdite with a known reference. Leószilárdite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous (crystals); pearly (aggregates).
- 4Match the color rangeCompare against the expected color range: pale yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, crusts.
Often confused with
Leószilárdite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Leószilárdite leaves white, Liebigite leaves yellow white.
How to tell apart: Streak differs, so Leószilárdite leaves white, Schröckingerite leaves pale yellow; luster reads vitreous (crystals); pearly (aggregates) on Leószilárdite and subvitreous, pearly on {001} on Schröckingerite.
Often found alongside leószilárdite
Minerals reported to co-occur with leószilárdite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₆Mg(UO₂)₂(CO₃)₆·6H₂O
- Mohs hardness
- ~2
- Density
- 3.256 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous (crystals); pearly (aggregates)
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, crusts
- Cleavage
- Perfect on {001}
- Fluorescence
- Weak green fluorescence in LW and SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A product of post-mining oxidation of primary minerals (uraninite) in the humid underground environment of a sandstone roll-front uranium deposit
Where rockhounds find leószilárdite
Classic worldwide localities
- Markey Mine, Red Canyon, White Canyon District, San Juan County, Utah, USA
Field-hunting tip
Where it forms: A product of post-mining oxidation of primary minerals (uraninite) in the humid underground environment of a sandstone roll-front uranium deposit. If you start seeing andersonite, natrozippeite, gypsum in float, you are in the right ground. Typical habit: tabular crystals, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
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Find leószilárdite on the map
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