Umohoite is a rare secondary uranium mineral typically found as small, black, platy crystals or foliated masses with a distinct pearly luster. It is specifically associated with uranium-molybdenum hydrothermal vein systems. Collectors should handle it with care due to its significant radioactive nature.
Is this umohoite?
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 umohoite with a known reference. Umohoite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Umohoite leaves a blue-black streak.
- 3Read the lusterHold the specimen under a strong light. Umohoite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: black, dark blue, bluish-black.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: platy crystals, foliated, massive.
Often confused with
Umohoite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Umohoite leaves blue-black, Molybdenite leaves greenish-gray; luster reads pearly on Umohoite and metallic on Molybdenite.
How to tell apart: Coffinite is the harder of the two (Mohs 5 vs. 2-3); streak differs — Umohoite leaves blue-black, Coffinite leaves brownish-black; luster reads pearly on Umohoite and dull on Coffinite.
Often found alongside umohoite
Minerals reported to co-occur with umohoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (UO₂)(MoO₄)·4H₂O
- Mohs hardness
- 2-3
- Density
- 4.9-5.1 g/cm³
- Streak
- Blue-black
- Luster
- Pearly
- Transparency
- Opaque
- Crystal system
- Hexagonal
- Crystal habit
- Platy Crystals, Foliated, Massive
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector, Scientific Study
- Host rock
- Hydrothermal Uranium-molybdenum Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find umohoite
Classic worldwide localities
- Marysvale, Utah (USA)
- Lucky Mc Mine, Wyoming (USA)
- Schmiedeberg, Germany
Field-hunting tip
Look in hydrothermal uranium-molybdenum deposits country — that is the host setting where umohoite typically forms. If you start seeing uraninite, molybdenite, ilsemannite in float, you are in the right ground. Field specimens usually show a platy crystals, foliated, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find umohoite on the map
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