Tengchongite is an exceptionally rare uranium-molybdenum mineral discovered in the oxidized zones of uranium deposits. It typically forms delicate orange to yellow platy crystals or crusts and is highly sought after by radioactive mineral specialists.

Hardness

2-2.5

Mohs

Luster

Vitreous

Streak

Light yellow

Transparency

Transparent to translucent

mineralrare

Tengchongite

Hardness: 2-2.5
Luster: Vitreous
Streak: Light yellow
Transparency: Transparent to translucent

Is this tengchongite?

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 tengchongite with a known reference. Tengchongite sits at Mohs 2-2.5, 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: yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: platy crystals, crusts, aggregates.

Often confused with

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

mineral

Autunite

Mohs 2-2.5

How to tell apart: Streak differs, so Tengchongite leaves light yellow, Autunite leaves pale yellow.

How to tell apart: Streak differs, so Tengchongite leaves light yellow, Torbernite leaves pale green.

Compare →

Often found alongside tengchongite

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

All properties

Chemical formula: Ca(UO₂)₆(MoO₄OH)₂O₂(OH)₄·9H₂O
Mohs hardness: 2-2.5
Density: 4.25 g/cm³
Colors: Yellow
Streak: Light yellow
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Orthorhombic
Crystal habit: Platy crystals, crusts, aggregates
Cleavage: On {001}, perfect
Rarity: Rare
Uses: Collector
Host rock: In the oxidized portions of a uranium deposit in migmatite and gneiss

Where rockhounds find tengchongite

Classic worldwide localities

Tongbiguan village, Tengchong Co., Yunnan Province, China

Field-hunting tip

Where it forms: In the oxidized portions of a uranium deposit in migmatite and gneiss. If you start seeing studtite, calcurmolite in float, you are in the right ground. Typical habit: platy crystals, crusts, aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tengchongite?+

Mohs hardness is 2-2.5. Luster: vitreous. The streak is light yellow. Common colors include yellow.

Where is tengchongite found?+

Notable localities include Tongbiguan village, Tengchong Co., Yunnan Province, China.

Is tengchongite safe to handle?+

Tengchongite contains uranium or thorium and calls for real care. Contains uranium and is highly radioactive; handle with gloves and keep in a sealed, labeled container. Do not ingest, inhale dust, or touch without washing hands thoroughly.

What rocks look like tengchongite?+

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

What minerals are found with tengchongite?+

Tengchongite commonly co-occurs with Studtite, Calcurmolite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tengchongite form in?+

Where it forms: In the oxidized portions of a uranium deposit in migmatite and gneiss. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tengchongite used for?+

Tengchongite is used in collector.

Find tengchongite on the map

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