Oursinite is a very rare secondary uranium mineral that typically forms as delicate, needle-like yellow crystals or radial sprays. It is almost exclusively found in association with other rare uranyl minerals in oxidized deposits, making it a highly sought-after but difficult-to-acquire species for radioactive mineral collectors.
Is this oursinite?
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 oursinite with a known reference. Oursinite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Oursinite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Oursinite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular or fibrous radial aggregates.
Often confused with
Oursinite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside oursinite
Minerals reported to co-occur with oursinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Co(UO₂)₂(SiO₃OH)₂·6H₂O
- Mohs hardness
- 2-3
- Density
- 3.8 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular or Fibrous Radial Aggregates
- Cleavage
- None
- Fluorescence
- Yellow-green Under UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Uranium Deposits
- Typical price
- $50-500 depending on specimen quality
Where rockhounds find oursinite
Classic worldwide localities
- Shinkolobwe Mine, DR Congo
Field-hunting tip
Look in oxidized zones of uranium deposits country — that is the host setting where oursinite typically forms. If you start seeing sklodowskite, curite, vandenbrandeite in float, you are in the right ground. Field specimens usually show a acicular or fibrous radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify oursinite?+
Where is oursinite found?+
How much is oursinite worth?+
Is oursinite safe to handle?+
What rocks look like oursinite?+
What minerals are found with oursinite?+
What kind of rock does oursinite form in?+
What is oursinite used for?+
Find oursinite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
