Mianningite is a rare, complex uranium-bearing oxide mineral discovered in the Maoniuping carbonatite deposit in Sichuan, China. It is typically found as dark, submetallic grains associated with rare-earth element minerals and must be handled with appropriate radiation safety precautions due to its uranium content.

Hardness

Mohs

Luster

Submetallic

Streak

Black

Transparency

Opaque

mineralrarePyrochlore Supergroup family

Mianningite

Hardness: ~6
Luster: Submetallic
Streak: Black
Transparency: Opaque

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Is this mianningite?

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 mianningite with a known reference. Mianningite sits at Mohs ~6, 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: submetallic.
4
Match the color range
Compare against the expected color range: black.
5
Look at form & habit
Crystal system: trigonal. Typical habit: anhedral to subhedral grains.

Often confused with

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

mineral

Pyrochlore

Mohs 5-5.5

How to tell apart: Streak differs, so Mianningite leaves black, Pyrochlore leaves brown; luster reads submetallic on Mianningite and vitreous to resinous on Pyrochlore.

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Often found alongside mianningite

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

All properties

Chemical formula: (□,Pb,Ce,Na)(U,Mn,U)Fe₂(Ti,Fe)₁₈O₃₈
Mohs hardness: ~6
Density: 4.62 g/cm³
Colors: Black
Streak: Black
Luster: Submetallic
Transparency: Opaque
Crystal system: Trigonal
Crystal habit: Anhedral to subhedral grains
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In fractures within lamprophyre veins and their contacts with a later quartz-alkali feldspar syenite dike containing REE, U, and Th mineralization

Where rockhounds find mianningite

Classic worldwide localities

Baozi Hill, near the Maoniuping REE mine, Mianning county, Sichuan province, China

Field-hunting tip

Where it forms: In fractures within lamprophyre veins and their contacts with a later quartz-alkali feldspar syenite dike containing REE, U, and Th mineralization. If you start seeing microcline, albite, quartz in float, you are in the right ground. Typical habit: anhedral to subhedral grains. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify mianningite?+

Mohs hardness is ~6. Luster: submetallic. The streak is black. Common colors include black.

Where is mianningite found?+

Notable localities include Baozi Hill, near the Maoniuping REE mine, Mianning county, Sichuan province, China.

Is mianningite safe to handle?+

Mianningite contains lead and uranium or thorium and calls for real care. Mianningite contains uranium, thorium, and lead. Handle with care, wear gloves, store in a sealed container, and keep away from living spaces to avoid dust inhalation and radon exposure.

What rocks look like mianningite?+

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

What minerals are found with mianningite?+

Mianningite commonly co-occurs with Microcline, Albite, Quartz, Iron-rich phlogopite, Augite, Muscovite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does mianningite form in?+

Where it forms: In fractures within lamprophyre veins and their contacts with a later quartz-alkali feldspar syenite dike containing REE, U, and Th mineralization. Working float back to the host body is the standard way to chase a fresh occurrence.

What is mianningite used for?+

Mianningite is used in collector.

Find mianningite on the map

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