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.
Is this plavnoite?
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 plavnoite with a known reference. Plavnoite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Plavnoite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Plavnoite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, golden yellow.
- 5Look at form & habitCrystal 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.
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
- 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, 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
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Find plavnoite on the map
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