Piretite is a very rare hydrated calcium selenite mineral found in the oxidation zones of uranium-selenium deposits. It typically forms small, transparent, yellow tabular crystals that are highly sought after by systematic mineral collectors.
Is this piretite?
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 piretite with a known reference. Piretite 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: pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: lemon yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular, prismatic, tabular.
Often confused with
Piretite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Piretite leaves pale yellow, Anglesite leaves white; luster reads pearly on Piretite and adamantine, resinous to vitreous on Anglesite.
How to tell apart: Streak differs, so Piretite leaves pale yellow, Cerussite leaves white; luster reads pearly on Piretite and adamantine, tending toward vitreous, resinous on Cerussite.
Often found alongside piretite
Minerals reported to co-occur with piretite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca(UO₂)₃(SeO₃)₂(OH)₄·4H₂O
- Mohs hardness
- 2.5
- Density
- 4.00 g/cm³
- Colors
- Streak
- Pale yellow
- Luster
- Pearly
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular, prismatic, tabular
- Cleavage
- On {001}, good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in the oxidized zone of a uranium deposit in limestone
Where rockhounds find piretite
Classic worldwide localities
- Shinkolobwe, Katanga Province, Congo (Shaba Province, Zaire)
Field-hunting tip
Where it forms: A rare secondary mineral in the oxidized zone of a uranium deposit in limestone. If you start seeing uraninite in float, you are in the right ground. Typical habit: acicular, prismatic, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify piretite?+
Where is piretite found?+
Is piretite safe to handle?+
What rocks look like piretite?+
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Find piretite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
