Haynesite is a rare uranyl selenite mineral typically found as delicate, pale yellow acicular crystal sprays or coatings. It is primarily known from oxidized portions of uranium-bearing deposits, often forming in association with other rare secondary minerals.
Is this haynesite?
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 haynesite with a known reference. Haynesite sits at Mohs 1.5-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: brownish yellow, amber.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular, rosette, tabular.
Often confused with
Haynesite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Cuprosklodowskite is the harder of the two (Mohs 4 vs. 1.5-2); streak differs, so Haynesite leaves white, Cuprosklodowskite leaves greenish yellow; luster reads vitreous on Haynesite and dull to silky in aggregates on Cuprosklodowskite.
How to tell apart: Streak differs, so Haynesite leaves white, Autunite leaves pale yellow.
Often found alongside haynesite
Minerals reported to co-occur with haynesite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (UO₂)₃(SeO₃)₂(OH)₂·5H₂O
- Mohs hardness
- 1.5-2
- Density
- 4.1 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular, rosette, tabular
- Cleavage
- On {010}, good
- Fluorescence
- Yellowish green under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Rare in an oxidized uranium deposit in mudstones and sandstones
Where rockhounds find haynesite
Classic worldwide localities
- Repete mine, 34 km southeast of Blanding, San Juan Co., Utah, USA
Field-hunting tip
Where it forms: Rare in an oxidized uranium deposit in mudstones and sandstones. If you start seeing andersonite, boltwoodite, ferroselite in float, you are in the right ground. Typical habit: acicular, rosette, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find haynesite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
