Agrinierite is a rare, vibrant orange uranyl oxide mineral that typically forms as a secondary mineral in the oxidized zones of uranium deposits. Collectors should look for its distinctive platy, orange crystals that often occur as thin crusts on uranium-bearing host rocks.

Hardness

Mohs

Luster

Resinous to greasy

Streak

Yellow

Transparency

Transparent to translucent

mineralrare

Agrinierite

Hardness: 3
Luster: Resinous to greasy
Streak: Yellow
Transparency: Transparent to translucent

Is this agrinierite?

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 agrinierite with a known reference. Agrinierite sits at Mohs 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: yellow.
3
Read the luster
Hold the specimen under a strong light. Luster: resinous to greasy.
4
Match the color range
Compare against the expected color range: orange.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: lamellar, pseudo hexagonal.

Often confused with

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

mineral

Becquerelite

Mohs 2.5

How to tell apart: Luster reads resinous to greasy on Agrinierite and adamantine to greasy on Becquerelite.

How to tell apart: Luster reads resinous to greasy on Agrinierite and adamantine on Billietite.

Compare →

Often found alongside agrinierite

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

Uranophane
mineral · Mohs 2.5

All properties

Chemical formula: K₂Ca[(UO₂)₃O₃(OH)₂]₂·5H₂O
Mohs hardness: 3
Density: 5.7 g/cm³
Colors: Orange
Streak: Yellow
Luster: Resinous to greasy
Transparency: Transparent to translucent
Crystal system: Orthorhombic
Crystal habit: Lamellar, pseudo hexagonal
Cleavage: {001}, good
Rarity: Rare
Uses: Collector
Host rock: In the oxidation zone of a uranium deposit

Where rockhounds find agrinierite

Classic worldwide localities

Margnac mine, Compreignac, Haute-Vienne, France

Field-hunting tip

Where it forms: In the oxidation zone of a uranium deposit. If you start seeing uranophane, gummite in float, you are in the right ground. Typical habit: lamellar, pseudo hexagonal. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify agrinierite?+

Mohs hardness is 3. Luster: resinous to greasy. The streak is yellow. Common colors include orange.

Where is agrinierite found?+

Notable localities include Margnac mine, Compreignac, Haute-Vienne, France.

Is agrinierite safe to handle?+

Agrinierite contains uranium or thorium and calls for real care. Contains uranium and is significantly radioactive; handle with gloves and store in a lead-lined container. Do not inhale dust or allow skin contact.

What rocks look like agrinierite?+

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

What minerals are found with agrinierite?+

Agrinierite commonly co-occurs with Uranophane, Gummite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does agrinierite form in?+

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

What is agrinierite used for?+

Agrinierite is used in collector.

Find agrinierite on the map

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