Uramarsite is a rare secondary uranium mineral typically found in oxidized zones of uranium deposits. It usually appears as bright yellow to yellow-green platy crystals that resemble mica, often found as coatings or clusters on matrix rock.
Is this uramarsite?
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 uramarsite with a known reference. Uramarsite 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: pale green.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: platy.
Often confused with
Uramarsite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Uramarsite leaves white, Autunite leaves pale yellow.
How to tell apart: Streak differs, so Uramarsite leaves white, Meta-autunite leaves yellow; luster reads vitreous on Uramarsite and pearly to dull on Meta-autunite.
How to tell apart: Streak differs, so Uramarsite leaves white, Torbernite leaves pale green.
Often found alongside uramarsite
Minerals reported to co-occur with uramarsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NH₄(UO₂)AsO₄·3H₂O
- Mohs hardness
- 2.5
- Density
- 3.22 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Platy
- Cleavage
- Perfect {001}, imperfect {010}
- Fluorescence
- Green under SW and LW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the oxidized zone of pitchblende-sulfide mineralization in highly-fractured, hydrothermally-altered felsite porphyry and tuff breccia
Where rockhounds find uramarsite
Classic worldwide localities
- Bota-Burum deposit, south of Alakol’ Lake, southwestern Balkhash area, Southern Kazakhstan Region, Kazakhstan
Field-hunting tip
Where it forms: In the oxidized zone of pitchblende-sulfide mineralization in highly-fractured, hydrothermally-altered felsite porphyry and tuff breccia. If you start seeing calcite, arsenopyrite, pyrite in float, you are in the right ground. Typical habit: platy. Train your eye for that shape before scanning the outcrop.
Common questions
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Find uramarsite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
