Běhounekite is a rare secondary uranyl sulfate mineral typically found as a result of the oxidation of uraninite. It manifests as delicate yellow crusts or small tabular crystals and is primarily known from the historic mining districts of the Czech Republic.
Is this běhounekite?
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 běhounekite with a known reference. Běhounekite 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. Běhounekite leaves a pale yellow streak.
- 3Read the lusterHold the specimen under a strong light. Běhounekite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, greenish-yellow.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular crystals, crusts, pulverulent aggregates.
Often confused with
Běhounekite vs. its common look-alikes — and how to tell them apart in the field.

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

How to tell apart: Streak differs — Běhounekite leaves pale yellow, Zippeite leaves yellow; luster reads vitreous on Běhounekite and pearly on Zippeite.
Often found alongside běhounekite
Minerals reported to co-occur with běhounekite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- UO₂(SO₄)·4H₂O
- Mohs hardness
- 2
- Density
- 3.5 g/cm³
- Colors
- Streak
- Pale Yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Tabular Crystals, Crusts, Pulverulent Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Uranium-bearing Veins
- Typical price
- $50-300 per specimen
Where rockhounds find běhounekite
Classic worldwide localities
- Jáchymov, Czech Republic
Field-hunting tip
Look in hydrothermal uranium-bearing veins country — that is the host setting where běhounekite typically forms. If you start seeing johannite, jáchymovite, uranyl sulfates in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, pulverulent aggregates habit, so train your eye for that shape before scanning the outcrop.
