Oswaldpeetersite is a rare uranyl carbonate mineral typically found as delicate, vibrant yellow lath-like crystals. It is primarily known from the Musonoi Mine in the Congo and is highly sought after by collectors specializing in secondary uranium minerals due to its intense fluorescence under UV light.

Hardness

2-3

Mohs

Luster

Vitreous

Streak

Pale yellow

Transparency

Transparent

mineralrareUranyl Carbonate Group family

Oswaldpeetersite

Hardness: 2-3
Luster: Vitreous
Streak: Pale yellow
Transparency: Transparent

No image

Is this oswaldpeetersite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch oswaldpeetersite with a known reference. Oswaldpeetersite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: pale yellow.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: canary yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: microscopic crystals, prismatic.

Often confused with

Oswaldpeetersite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Rutherfordine

Mohs 2.5

How to tell apart: Streak differs, so Oswaldpeetersite leaves pale yellow, Rutherfordine leaves yellow; luster reads vitreous on Oswaldpeetersite and dull to earthy, silky if fibrous on Rutherfordine.

Often found alongside oswaldpeetersite

Minerals reported to co-occur with oswaldpeetersite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: (UO₂)₂CO₃(OH)₂·4H₂O
Mohs hardness: 2-3
Density: 4.54 g/cm³
Colors: Canary yellow
Streak: Pale yellow
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Microscopic crystals, prismatic
Cleavage: Parallel elongation
Fluorescence: Bright green under SW UV
Rarity: Rare
Uses: Collector
Host rock: In a sedimentary Colorado-Plateau-type U–V deposit

Where rockhounds find oswaldpeetersite

Classic worldwide localities

Jomac uranium mine, Brown’s Rim, White Canyon district, San Juan Co., Utah, USA

Field-hunting tip

Where it forms: In a sedimentary Colorado-Plateau-type U–V deposit. If you start seeing gypsum, cuprite, antlerite in float, you are in the right ground. Typical habit: microscopic crystals, prismatic. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify oswaldpeetersite?+

Mohs hardness is 2-3. Luster: vitreous. The streak is pale yellow. Common colors include canary yellow.

Where is oswaldpeetersite found?+

Notable localities include Jomac uranium mine, Brown’s Rim, White Canyon district, San Juan Co., Utah, USA.

Is oswaldpeetersite safe to handle?+

Oswaldpeetersite contains uranium or thorium and calls for real care. This mineral is radioactive and contains uranyl ions. Handle with appropriate protective gear, minimize skin contact, do not inhale dust, and store in a lead-lined container away from living areas.

What rocks look like oswaldpeetersite?+

Oswaldpeetersite is most often confused with Rutherfordine, Grimselite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with oswaldpeetersite?+

Oswaldpeetersite commonly co-occurs with Gypsum, Cuprite, Antlerite, Goethite, Lepidocrocite, Mbobomkulite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does oswaldpeetersite form in?+

Where it forms: In a sedimentary Colorado-Plateau-type U–V deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is oswaldpeetersite used for?+

Oswaldpeetersite is used in collector.

Find oswaldpeetersite on the map

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