Calciouranoite is an extremely rare secondary uranium mineral typically found as an alteration product of uraninite. It occurs most commonly as bright yellow earthy masses or crusts within oxidized zones of uranium ore bodies.
Is this calciouranoite?
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 calciouranoite with a known reference. Calciouranoite 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. Calciouranoite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Calciouranoite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: yellow, orange-yellow.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: fibrous, earthy, massive crusts.
Often confused with
Calciouranoite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Calciouranoite leaves yellow, Uranophane leaves pale yellow; luster reads dull on Calciouranoite and vitreous on Uranophane.
How to tell apart: Luster reads dull on Calciouranoite and pearly on Boltwoodite.
Often found alongside calciouranoite
Minerals reported to co-occur with calciouranoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Ba,Pb)U₂(O,OH)₁₀·5H₂O
- Mohs hardness
- 2-3
- Density
- 4.1 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Hexagonal
- Crystal habit
- Fibrous, Earthy, Massive Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Uranium Deposits
- Typical price
- $50-300 per small specimen
Where rockhounds find calciouranoite
Classic worldwide localities
- Oklo deposit, Gabon
- Tyuya-Muyun District, Kyrgyzstan
Field-hunting tip
Look in oxidized uranium deposits country — that is the host setting where calciouranoite typically forms. If you start seeing uraninite, becquerelite, curite in float, you are in the right ground. Field specimens usually show a fibrous, earthy, massive crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find calciouranoite on the map
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