Andersonite is a rare uranyl carbonate mineral known for its striking bright yellow-green fluorescence under ultraviolet light. It typically occurs as small rhombohedral crystals or efflorescent crusts in the oxidized zones of uranium mines. Collectors prize it for its vibrant reaction under UV lighting, though it must be kept in a climate-controlled environment as it is sensitive to humidity.
Is this andersonite?
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 andersonite with a known reference. Andersonite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Andersonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Andersonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: bright yellow, yellow-green.
- 5Look at form & habitCrystal system: trigonal. Typical habit: rhombohedral crystals, crusts, radial aggregates.
Often confused with
Andersonite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside andersonite
Minerals reported to co-occur with andersonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Ca(UO₂)(CO₃)₃·6H₂O
- Mohs hardness
- 2.5
- Density
- 2.8 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Rhombohedral Crystals, Crusts, Radial Aggregates
- Cleavage
- Perfect On {0001}
- Fluorescence
- Bright Yellow-green Under SW and LW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Uranium-vanadium Deposits
- Typical price
- $30-150 per specimen
Where rockhounds find andersonite
Classic worldwide localities
- Mohave County, Arizona
- San Juan County, Utah
- Grand County, Utah
Field-hunting tip
Look in oxidized zones of uranium-vanadium deposits country — that is the host setting where andersonite typically forms. If you start seeing schroeckingerite, liebigite, gypsum in float, you are in the right ground. Field specimens usually show a rhombohedral crystals, crusts, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify andersonite?+
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How much is andersonite worth?+
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What rocks look like andersonite?+
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Find andersonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
