Masuyite is a rare secondary uranium mineral often found as attractive orange to reddish-orange platy crystal aggregates. It typically forms through the alteration of uraninite in the oxidation zones of uranium deposits and requires careful handling due to its radioactive nature.

Hardness

3-4

Mohs

Luster

Vitreous

Streak

Orange-yellow

Transparency

Transparent

mineralrare

Masuyite

Hardness: 3-4
Luster: Vitreous
Streak: Orange-yellow
Transparency: Transparent

Is this masuyite?

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 masuyite with a known reference. Masuyite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: orange-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: brown orange, carmine red, red, red orange.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: pseudo hexagonal, twinning common.

Often confused with

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

mineral

Curite

Mohs 4-5

How to tell apart: Streak differs, so Masuyite leaves orange-yellow, Curite leaves orange; luster reads vitreous on Masuyite and adamantine on Curite.

How to tell apart: Streak differs, so Masuyite leaves orange-yellow, Vandenbrandeite leaves green.

How to tell apart: Streak differs, so Masuyite leaves orange-yellow, Fourmarierite leaves orange; luster reads vitreous on Masuyite and adamantine to subadamantine on Fourmarierite.

Compare →

Often found alongside masuyite

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

All properties

Chemical formula: Pb(UO₂)₃O₃(OH)₂·3H₂O
Mohs hardness: 3-4
Density: 5.08 g/cm³
Colors: Brown orange Carmine red Red Red orange
Streak: Orange-yellow
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Pseudo hexagonal, twinning common
Cleavage: {001}, perfect; {010}, good
Rarity: Rare
Uses: Collector
Host rock: A secondary mineral formed in the oxidized zone of uranium-bearing deposits

Where rockhounds find masuyite

Classic worldwide localities

Shinkolobwe, and the Kamoto mine, near Kolwezi, Katanga Province, Congo (Shaba Province, Zaire)
El Sharana mine, South Alligator Valley, Northern Territory, Australia
Found at the Rabéjac uranium deposit, seven km south-southwest of Lodève, Hérault, France

Field-hunting tip

Where it forms: A secondary mineral formed in the oxidized zone of uranium-bearing deposits. If you start seeing uraninite, rutherfordine, becquerelite in float, you are in the right ground. Typical habit: pseudo hexagonal, twinning common. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify masuyite?+

Mohs hardness is 3-4. Luster: vitreous. The streak is orange-yellow. Common colors include brown orange, carmine red, red, red orange.

Where is masuyite found?+

Notable localities include Shinkolobwe, and the Kamoto mine, near Kolwezi, Katanga Province, Congo (Shaba Province, Zaire); El Sharana mine, South Alligator Valley, Northern Territory, Australia; Found at the Rabéjac uranium deposit, seven km south-southwest of Lodève, Hérault, France.

Is masuyite safe to handle?+

Masuyite contains lead and uranium or thorium and calls for real care. This mineral is radioactive and contains lead and uranium. Handle with gloves, avoid inhalation of dust, wash hands thoroughly after contact, and store in a lead-lined container away from living areas.

What rocks look like masuyite?+

Masuyite is most often confused with Curite, Vandenbrandeite, Fourmarierite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with masuyite?+

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

What kind of rock does masuyite form in?+

Where it forms: A secondary mineral formed in the oxidized zone of uranium-bearing deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is masuyite used for?+

Masuyite is used in collector.

Find masuyite on the map

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