Urancalcarite is a rare secondary uranium mineral that typically forms as delicate, radiating tufts of acicular crystals. It is primarily found in the oxidized zones of uranium deposits and is highly prized by collectors for its brilliant neon-yellow fluorescence under UV light.

Hardness

2-3

Mohs

Luster

Vitreous

Streak

Light yellow

Transparency

Transparent

mineralrare

Urancalcarite

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

No image

Is this urancalcarite?

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 urancalcarite with a known reference. Urancalcarite 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: light 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: bright yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: acicular, aggregates, radial.

Often confused with

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

mineral

Uranophane

Mohs 2.5

How to tell apart: Streak differs, so Urancalcarite leaves light yellow, Uranophane leaves yellowish white.

How to tell apart: Streak differs, so Urancalcarite leaves light yellow, Liebigite leaves yellow white.

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Often found alongside urancalcarite

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

All properties

Chemical formula: Ca(UO₂)₃CO₃(OH)₆·3H₂O
Mohs hardness: 2-3
Density: 4.03 g/cm³
Colors: Bright yellow
Streak: Light yellow
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Acicular, aggregates, radial
Cleavage: None
Fluorescence: Bright yellow-green under UV light
Rarity: Rare
Uses: Collector
Host rock: In the oxidation zone of uranium deposits

Where rockhounds find urancalcarite

Classic worldwide localities

Found at an undisclosed locality in Hunan Province, China

Field-hunting tip

Where it forms: In the oxidation zone of uranium deposits. If you start seeing uraninite, uranophane, wyartite in float, you are in the right ground. Typical habit: acicular, aggregates, radial. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify urancalcarite?+

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

Where is urancalcarite found?+

Notable localities include Found at an undisclosed locality in Hunan Province, China.

Is urancalcarite safe to handle?+

Urancalcarite contains uranium or thorium and calls for real care. Contains uranium and is highly radioactive. Always store in a lead-lined container, avoid inhalation of dust during handling, and wash hands thoroughly after contact.

What rocks look like urancalcarite?+

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

What minerals are found with urancalcarite?+

Urancalcarite commonly co-occurs with Uraninite, Uranophane, Wyartite, Masuyite, Fourmarierite, Vandendriesscheite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does urancalcarite form in?+

Where it forms: In the oxidation zone of uranium deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is urancalcarite used for?+

Urancalcarite is used in collector.

Find urancalcarite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.