Baumoite is a rare uranyl molybdate mineral typically found as small, bright yellow to orange-yellow platy crystals. It is primarily known from the Bauserach area in Germany, where it forms in oxidized hydrothermal uranium deposits. Due to its radioactive nature, it is strictly a mineral for advanced collectors and should be stored properly.
Is this baumoite?
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 baumoite with a known reference. Baumoite 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. Baumoite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Baumoite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-orange.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, tabular, clusters.
Often confused with
Baumoite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Baumoite leaves yellow, Autunite leaves pale yellow; luster reads vitreous on Baumoite and pearly on Autunite.
How to tell apart: Uraninite is the harder of the two (Mohs 5-6 vs. 2); streak differs — Baumoite leaves yellow, Uraninite leaves brownish-black to greenish-black; luster reads vitreous on Baumoite and submetallic to dull on Uraninite.
How to tell apart: Wulfenite is the harder of the two (Mohs 3 vs. 2); streak differs — Baumoite leaves yellow, Wulfenite leaves white; luster reads vitreous on Baumoite and resinous on Wulfenite.
Often found alongside baumoite
Minerals reported to co-occur with baumoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- BaU₄(MoO₄)O₁₀(OH)₂·11H₂O
- Mohs hardness
- 2
- Density
- 4.95 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Tabular, Clusters
- Cleavage
- Perfect in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $50-500 depending on specimen quality
Where rockhounds find baumoite
Classic worldwide localities
- Hesse, Germany
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where baumoite typically forms. If you start seeing uraninite, wulfenite, cerussite in float, you are in the right ground. Field specimens usually show a platy crystals, tabular, clusters habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find baumoite on the map
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