Plavnoite is a rare secondary uranium sulfate mineral typically found as a yellow crust or powdery coating on weathered uranium-bearing ores. It is primarily known from the Jáchymov region and is of interest primarily to advanced mineral collectors focusing on uranium species.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

Yellow

Transparency

Translucent

mineralrareJohannite Group family

Plavnoite

Hardness: 2.5
Luster: Vitreous
Streak: Yellow
Transparency: Translucent

Is this plavnoite?

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 plavnoite with a known reference. Plavnoite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Plavnoite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Plavnoite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, golden yellow.
5
Look at form & habit
Crystal system: triclinic. Typical habit: microcrystalline crusts, earthy aggregates.

Often confused with

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

mineral

Johannite

Mohs 2

How to tell apart: Streak differs — Plavnoite leaves yellow, Johannite leaves pale green.

How to tell apart: Luster reads vitreous on Plavnoite and pearly on Zippeite.

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Often found alongside plavnoite

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

All properties

Chemical formula: K₂Mn(UO₂)₂(SO₄)₄·8H₂O
Mohs hardness: 2.5
Density: 3.32 g/cm³
Colors: Yellow Golden Yellow
Streak: Yellow
Luster: Vitreous
Transparency: Translucent
Crystal system: Triclinic
Crystal habit: Microcrystalline Crusts, Earthy Aggregates
Cleavage: None Observed
Rarity: Rare
Uses: Collector, Scientific Research
Host rock: Hydrothermal Uranium Deposits
Typical price: $50-300 per specimen depending on size and quality

Where rockhounds find plavnoite

Classic worldwide localities

Jáchymov, Czech Republic
Plavno, Czech Republic

Field-hunting tip

Look in hydrothermal uranium deposits country — that is the host setting where plavnoite typically forms. If you start seeing uraninite, johannite, gypsum in float, you are in the right ground. Field specimens usually show a microcrystalline crusts, earthy aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify plavnoite?+

Mohs hardness is 2.5. It typically shows a vitreous luster. The streak is yellow. Common colors include yellow, golden yellow.

Where is plavnoite found?+

Notable localities include Jáchymov, Czech Republic; Plavno, Czech Republic.

How much is plavnoite worth?+

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

Is plavnoite safe to handle?+

This mineral is radioactive. It contains toxic constituents. This mineral is radioactive due to its uranium content and should be handled with standard radiological precautions. Keep in a sealed container, wash hands after handling, and avoid creating dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like plavnoite?+

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

What minerals are found with plavnoite?+

Plavnoite commonly co-occurs with Uraninite, Johannite, Gypsum, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does plavnoite form in?+

Plavnoite typically forms in hydrothermal uranium deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is plavnoite used for?+

Plavnoite is used in collector, scientific research.

Find plavnoite on the map

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