Asselbornite is a extremely rare secondary uranium mineral that appears as tiny yellow crystals. It is best known for its type locality in Asselborn, Luxembourg, where it forms in oxidized hydrothermal veins. Because of its scarcity and composition, it is highly sought after by advanced radioactive mineral collectors.

Hardness

Mohs

Luster

Adamantine

Streak

Yellow

Transparency

Translucent

mineralrare

Asselbornite

Hardness: 3
Luster: Adamantine
Streak: Yellow
Transparency: Translucent

Is this asselbornite?

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 asselbornite with a known reference. Asselbornite 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. Asselbornite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Asselbornite typically shows a adamantine luster.
4
Match the color range
Compare against the expected color range: yellow, brownish-yellow.
5
Look at form & habit
Crystal system: cubic. Typical habit: small cubic or cubo-octahedral crystals.

Often confused with

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

mineral

Uraninite

Mohs 5-6

How to tell apart: Uraninite is the harder of the two (Mohs 5-6 vs. 3); streak differs — Asselbornite leaves yellow, Uraninite leaves brownish-black to greenish-black; luster reads adamantine on Asselbornite and submetallic to dull on Uraninite.

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Often found alongside asselbornite

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

All properties

Chemical formula: Pb(UO₂)₇(BiO)₄(AsO₄)₂(OH)₉·12H₂O
Mohs hardness: 3
Density: 4.8 g/cm³
Colors: Yellow Brownish-yellow
Streak: Yellow
Luster: Adamantine
Transparency: Translucent
Crystal system: Cubic
Crystal habit: Small Cubic or Cubo-octahedral Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Veins
Typical price: $200-800 per specimen

Where rockhounds find asselbornite

Classic worldwide localities

Asselborn, Luxembourg

Field-hunting tip

Look in hydrothermal veins country — that is the host setting where asselbornite typically forms. If you start seeing uraninite, bismuthinite in float, you are in the right ground. Field specimens usually show a small cubic or cubo-octahedral crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify asselbornite?+

Mohs hardness is 3. It typically shows a adamantine luster. The streak is yellow. Common colors include yellow, brownish-yellow.

Where is asselbornite found?+

Notable localities include Asselborn, Luxembourg.

How much is asselbornite worth?+

Typical asking prices fall in the range of $200-800 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is asselbornite safe to handle?+

This mineral is radioactive. It contains toxic constituents. This mineral is both radioactive and contains lead and arsenic. Handle with gloves, store in a sealed container, and wash hands thoroughly after contact. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like asselbornite?+

Asselbornite is most often confused with Uraninite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with asselbornite?+

Asselbornite commonly co-occurs with uraninite, bismuthinite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does asselbornite form in?+

Asselbornite typically forms in hydrothermal veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is asselbornite used for?+

Asselbornite is used in collector.

Find asselbornite on the map

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