Moluranite is a rare secondary uranium-molybdenum mineral typically found as soft, yellow fibrous crusts or powdery coatings in oxidized ore zones. It is highly radioactive and primarily sought after by advanced collectors of rare uranium minerals for its distinct chemical composition.
Is this moluranite?
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 moluranite with a known reference. Moluranite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous.
- 4Match the color rangeCompare against the expected color range: black, brown.
- 5Look at form & habitCrystal system: amorphous. Typical habit: fibrous, powdery, crusts.
Often confused with
Moluranite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Ilsemannite is the harder of the two (Mohs 5.5-6 vs. 3-4); streak differs, so Moluranite leaves brown, Ilsemannite leaves pale blue; luster reads resinous on Moluranite and dull on Ilsemannite.
How to tell apart: Moluranite is noticeably harder (Mohs 3-4 vs. 1-2); streak differs, so Moluranite leaves brown, Ferrimolybdite leaves pale yellow; luster reads resinous on Moluranite and adamantine to silky, earthy on Ferrimolybdite.
Often found alongside moluranite
Minerals reported to co-occur with moluranite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- H₄U(UO₂)₃(MoO₄)₇·18H₂O
- Mohs hardness
- 3-4
- Density
- 4 g/cm³
- Streak
- Brown
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Amorphous
- Crystal habit
- Fibrous, powdery, crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In fine fissures in granulated albite, in part replacing brannerite
Where rockhounds find moluranite
Classic worldwide localities
- Aleksandrovskii Golets Mo–U deposit, upper Chetkanda River, Udokan Range, Chara region, northern Transbaikal, Russia
Field-hunting tip
Where it forms: In fine fissures in granulated albite, in part replacing brannerite. If you start seeing brannerite, molybdenite, chalcopyrite in float, you are in the right ground. Typical habit: fibrous, powdery, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
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Find moluranite on the map
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