Changchengite is an extremely rare iridium bismuth telluride mineral first discovered in the Changcheng gold mine in China. It typically occurs as minute, steel-black grains embedded within massive sulfide ore, requiring advanced mineralogical analysis for identification.

Hardness

3.7

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrareSulfosalt family

Changchengite

Hardness: 3.7
Luster: Metallic
Streak: Black
Transparency: Opaque

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Is this changchengite?

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 changchengite with a known reference. Changchengite sits at Mohs 3.7, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: black.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: gray, black.
5
Look at form & habit
Crystal system: cubic. Typical habit: granular.

Often confused with

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

mineral

Froodite

Mohs 2.5

How to tell apart: Changchengite is noticeably harder (Mohs 3.7 vs. 2.5).

Often found alongside changchengite

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

All properties

Chemical formula: Ir(BiS)
Mohs hardness: 3.7
Density: 11.96-12.27 g/cm³
Colors: Gray Black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Granular
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Of hydrothermal origin in chromite bodies in dunites and placers derived therefrom

Where rockhounds find changchengite

Classic worldwide localities

Along a branch of the Luanhe River in Hebei Province, about 200 km ENE of Beijing, China (type locality)

Field-hunting tip

Where it forms: Of hydrothermal origin in chromite bodies in dunites and placers derived therefrom. If you start seeing iridium, ferrian platinum, laurite in float, you are in the right ground. Typical habit: granular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify changchengite?+

Mohs hardness is 3.7. Luster: metallic. The streak is black. Common colors include gray, black.

Where is changchengite found?+

Notable localities include Along a branch of the Luanhe River in Hebei Province, about 200 km ENE of Beijing, China (type locality).

Is changchengite safe to handle?+

Contains tellurium and bismuth; avoid inhaling dust or ingesting. Handle with care and wash hands thoroughly after contact.

What rocks look like changchengite?+

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

What minerals are found with changchengite?+

Changchengite commonly co-occurs with Iridium, Ferrian platinum, Laurite, Sperrylite, Cooperite, Irarsite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does changchengite form in?+

Where it forms: Of hydrothermal origin in chromite bodies in dunites and placers derived therefrom. Working float back to the host body is the standard way to chase a fresh occurrence.

What is changchengite used for?+

Changchengite is used in collector.

Find changchengite on the map

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