Metacalciouranoite is an extremely rare secondary uranium mineral typically found as an alteration product in oxidized uranium-rich deposits. It is best identified by its distinct yellowish color, greasy luster, and characteristic radioactive nature, often appearing as platy crusts or earthy masses.
Is this metacalciouranoite?
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 metacalciouranoite with a known reference. Metacalciouranoite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: greasy.
- 4Match the color rangeCompare against the expected color range: orange.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: aggregates.
Often confused with
Metacalciouranoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Metacalciouranoite leaves yellow, Uranophane leaves yellowish white; luster reads greasy on Metacalciouranoite and vitreous on Uranophane.
How to tell apart: Streak differs, so Metacalciouranoite leaves yellow, Autunite leaves pale yellow; luster reads greasy on Metacalciouranoite and vitreous, pearly on {001} on Autunite.
How to tell apart: Luster reads greasy on Metacalciouranoite and adamantine to greasy on Becquerelite.
Often found alongside metacalciouranoite
Minerals reported to co-occur with metacalciouranoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Na,Ba)U₂O₇·2H₂O
- Mohs hardness
- 3-4
- Density
- 4.9 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Greasy
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the oxidation zone of a U-Mo deposit, replacing "pitchblende", and being replaced by uranophane
Where rockhounds find metacalciouranoite
Classic worldwide localities
- U-Mo deposit in Russia (type locality)
Field-hunting tip
Where it forms: In the oxidation zone of a U-Mo deposit, replacing "pitchblende", and being replaced by uranophane. If you start seeing uraninite, uranophane, bauranoite in float, you are in the right ground. Typical habit: aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify metacalciouranoite?+
Where is metacalciouranoite found?+
Is metacalciouranoite safe to handle?+
What rocks look like metacalciouranoite?+
What minerals are found with metacalciouranoite?+
What kind of rock does metacalciouranoite form in?+
What is metacalciouranoite used for?+
Find metacalciouranoite on the map
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