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.

Hardness

Mohs

Luster

Vitreous

Streak

Pale Yellow

Transparency

Transparent

mineralrare

Leószilárdite

Hardness: 2
Luster: Vitreous
Streak: Pale Yellow
Transparency: Transparent

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Is this leószilárdite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch leószilárdite with a known reference. Leószilárdite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Leószilárdite leaves a pale yellow streak.
3
Read the luster
Hold the specimen under a strong light. Leószilárdite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow.
5
Look at form & habit
Crystal 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: Luster reads vitreous on Leószilárdite and pearly on Schröckingerite.

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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: 2.98 g/cm³
Colors: Yellow
Streak: Pale Yellow
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals, Crusts
Cleavage: Good
Rarity: Rare
Uses: Collector
Host rock: Sedimentary Sandstone
Typical price: $50-300 thumbnail

Where rockhounds find leószilárdite

Classic worldwide localities

San Rafael Swell, Utah, USA

Field-hunting tip

Look in sedimentary sandstone country, the host setting where leószilárdite typically forms. If you start seeing uraninite, gypsum in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify leószilárdite?+

Mohs hardness is 2. It typically shows a vitreous luster. The streak is pale yellow. Common colors include yellow.

Where is leószilárdite found?+

Notable localities include San Rafael Swell, Utah, USA.

How much is leószilárdite worth?+

Typical asking prices fall in the range of $50-300 thumbnail. Quality, size, and provenance can move individual specimens well outside that range.

Is leószilárdite safe to handle?+

This mineral is radioactive. It contains toxic constituents. This mineral contains uranium and is radioactive; handle with gloves and store in a sealed lead-lined container away from living areas. Avoid inhaling dust or ingestion. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like leószilárdite?+

Leószilárdite is most often confused with Liebigite, Schröckingerite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with leószilárdite?+

Leószilárdite commonly co-occurs with uraninite, gypsum. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does leószilárdite form in?+

Leószilárdite typically forms in sedimentary sandstone. Working float back to the host body is the standard way to chase a fresh occurrence.

What is leószilárdite used for?+

Leószilárdite is used in collector.

Find leószilárdite on the map

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