Iriginite is a rare secondary uranium molybdenum mineral that typically forms as bright yellow earthy crusts or powdery coatings. It is an alteration product of primary ores and is highly sought after by radioactive mineral specialists for its distinct coloration and aesthetic occurrences in oxidation zones.
Is this iriginite?
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 iriginite with a known reference. Iriginite sits at Mohs 4-5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to dull.
- 4Match the color rangeCompare against the expected color range: canary yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: aggregates, crystalline.
Often confused with
Iriginite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Iriginite is noticeably harder (Mohs 4-5 vs. 1-2); streak differs, so Iriginite leaves light yellow, Ferrimolybdite leaves pale yellow; luster reads vitreous to dull on Iriginite and adamantine to silky, earthy on Ferrimolybdite.
How to tell apart: Iriginite is noticeably harder (Mohs 4-5 vs. 2.5); streak differs, so Iriginite leaves light yellow, Uranophane leaves yellowish white.
Often found alongside iriginite
Minerals reported to co-occur with iriginite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (UO₂)Mo₂O₇·3H₂O
- Mohs hardness
- 4-5
- Density
- 3.84 g/cm³
- Colors
- Streak
- Light yellow
- Luster
- Vitreous to dull
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Aggregates, crystalline
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In granulated albite, in part replacing brannerite (Aleksandrovskii Golets deposit, Russia); in a stream channel in sandstone (Hart Table, South Dakota, USA); may be of post-mining origin
Where rockhounds find iriginite
Classic worldwide localities
- Hart Table, southwest of Scenic, Pennington Co., South Dakota, USA
- East of Cameron, Coconino Co., Arizona, USA
- Clyde Long property, Elk Park area, San Juan Co., Colorado, USA
- Aleksandrovskii Golets Mo–U deposit, upper Chetkanda River, Chara district, Udokan Range, northern Transbaikal, Russia
- Found in the Shunak Mountains, 60 km west of the Mointy railroad station, and at the Kyzylsai Mo–U deposit, Chu-Ili Mountains, southwestern Balkhash region, Kazakhstan
- Rabéjac uranium deposit, seven km south-southeast of Lodève, Hérault, France
Field-hunting tip
Where it forms: In granulated albite, in part replacing brannerite (Aleksandrovskii Golets deposit, Russia); in a stream channel in sandstone (Hart Table, South Dakota, USA); may be of post-mining origin. If you start seeing ferrimolybdite, ilsemannite, metauranocircite in float, you are in the right ground. Typical habit: aggregates, crystalline. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify iriginite?+
Where is iriginite found?+
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What rocks look like iriginite?+
What minerals are found with iriginite?+
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Find iriginite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
