Ottohahnite is a rare secondary uranium phosphate mineral that typically forms as a dehydration product of higher-hydrate uranium minerals. Collectors generally find it as small, yellowish platy crystals or crusts associated with other uranium secondary species in oxidized zones of ore deposits.
Is this ottohahnite?
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 ottohahnite with a known reference. Ottohahnite 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. Ottohahnite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Ottohahnite typically shows a resinous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-orange.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts, aggregates.
Often confused with
Ottohahnite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Ottohahnite leaves yellow, Autunite leaves pale yellow; luster reads resinous on Ottohahnite and pearly on Autunite.
How to tell apart: Streak differs — Ottohahnite leaves yellow, Torbernite leaves pale green; luster reads resinous on Ottohahnite and vitreous on Torbernite.
Often found alongside ottohahnite
Minerals reported to co-occur with ottohahnite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Mg(UO₂)₂(PO₄)₂·10H₂O
- Mohs hardness
- 2
- Density
- 4.67 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Crusts, Aggregates
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Uranium-bearing Hydrothermal Veins
- Typical price
- $50-500 depending on specimen quality
Where rockhounds find ottohahnite
Classic worldwide localities
- Grube Johanngeorgenstadt, Saxony, Germany
Field-hunting tip
Look in uranium-bearing hydrothermal veins country — that is the host setting where ottohahnite typically forms. If you start seeing uraninite, meta-autunite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts, aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ottohahnite?+
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Find ottohahnite on the map
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