Wetherillite is a rare secondary uranium sulfate mineral that typically forms as a bright yellow efflorescence or thin platy crusts on sandstone. It is found in arid, uranium-rich mining districts where it occurs as a post-mining alteration product.
Is this wetherillite?
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 wetherillite with a known reference. Wetherillite 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: pale greenish yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, tabular aggregates.
Often confused with
Wetherillite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside wetherillite
Minerals reported to co-occur with wetherillite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Mg(UO₂)₂(SO₄)₄·18H₂O
- Mohs hardness
- ~2
- Density
- 2.626 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, tabular aggregates
- Cleavage
- Perfect on {101̄} and fair on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As efflorescent crusts, on the surfaces of mine walls, derived from the oxidation of primary minerals (uraninite, pyrite, chalcopyrite, bornite and covellite) in a relatively humid underground environment
Where rockhounds find wetherillite
Classic worldwide localities
- Blue Lizard mine, Red Canyon, White Canyon district, San Juan County, Utah, USA
Field-hunting tip
Where it forms: As efflorescent crusts, on the surfaces of mine walls, derived from the oxidation of primary minerals (uraninite, pyrite, chalcopyrite, bornite and covellite) in a relatively humid underground environment. If you start seeing bobcookite, boyleite, chalcanthite in float, you are in the right ground. Typical habit: platy crystals, tabular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify wetherillite?+
Where is wetherillite found?+
Is wetherillite safe to handle?+
What rocks look like wetherillite?+
What minerals are found with wetherillite?+
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Find wetherillite on the map
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