Plášilite is a rare secondary uranium mineral typically found as small, greenish yellow tabular crystals in oxidized hydrothermal veins. It is known primarily from the Jáchymov district in the Czech Republic and is highly sought after by collectors specializing in rare uranyl minerals.

Hardness

~2-3

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Plášilite

Hardness: ~2-3
Luster: Vitreous
Streak: White
Transparency: Transparent

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Is this plášilite?

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 plášilite with a known reference. Plášilite sits at Mohs ~2-3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: greenish yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, crusts.

Often confused with

Plášilite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Liebigite

Mohs 2-3

How to tell apart: Streak differs, so Plášilite leaves white, Liebigite leaves yellow white.

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Often found alongside plášilite

Minerals reported to co-occur with plášilite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Na(UO₂)(SO₄)(OH)(H₂O)₂
Mohs hardness: ~2-3
Density: 3.726 g/cm³
Colors: Greenish yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular crystals, crusts
Cleavage: Perfect on {010} and {001}
Rarity: Rare
Uses: Collector
Host rock: Of low-temperature secondary origin related to the post-mining oxidation of uraninite, pyrite, chalcopyrite, bornite, and covellite disseminated in lenses of organic matter in sandstone

Where rockhounds find plášilite

Classic worldwide localities

Blue Lizard mine, Red Canyon, White Canyon District, San Juan County, Utah, USA

Field-hunting tip

Where it forms: Of low-temperature secondary origin related to the post-mining oxidation of uraninite, pyrite, chalcopyrite, bornite, and covellite disseminated in lenses of organic matter in sandstone. If you start seeing atacamite, blödite, brochantite 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

How do you identify plášilite?+

Mohs hardness is ~2-3. Luster: vitreous. The streak is white. Common colors include greenish yellow.

Where is plášilite found?+

Notable localities include Blue Lizard mine, Red Canyon, White Canyon District, San Juan County, Utah, USA.

Is plášilite safe to handle?+

Plášilite contains uranium or thorium and calls for real care. Contains uranium and selenium; handle with care using gloves, avoid inhalation of dust, and store in a sealed container away from living areas.

What rocks look like plášilite?+

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

What minerals are found with plášilite?+

Plášilite commonly co-occurs with Atacamite, Blödite, Brochantite, Chalcanthite, Dickite, Gerhardtite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does plášilite form in?+

Where it forms: Of low-temperature secondary origin related to the post-mining oxidation of uraninite, pyrite, chalcopyrite, bornite, and covellite disseminated in lenses of organic matter in sandstone. Working float back to the host body is the standard way to chase a fresh occurrence.

What is plášilite used for?+

Plášilite is used in collector.

Find plášilite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.