Fluornatromicrolite is a rare member of the pyrochlore supergroup characterized by high sodium and fluorine content in its structure. It typically occurs as small, sharp octahedral crystals in rare alkaline igneous environments. Collectors should be aware of its inherent radioactivity due to common substitution of radioactive elements within the crystal lattice.

Hardness

Mohs

Luster

Adamantine

Streak

White

Transparency

Transparent

mineralrarePyrochlore Supergroup family

Fluornatromicrolite

Hardness: 5
Luster: Adamantine
Streak: White
Transparency: Transparent

Is this fluornatromicrolite?

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 fluornatromicrolite with a known reference. Fluornatromicrolite sits at Mohs 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: white.
3
Read the luster
Hold the specimen under a strong light. Luster: adamantine.
4
Match the color range
Compare against the expected color range: green.
5
Look at form & habit
Crystal system: cubic. Typical habit: octahedral crystals.

Often confused with

Fluornatromicrolite 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 Fluornatromicrolite leaves white, Pyrochlore leaves brown; luster reads adamantine on Fluornatromicrolite and vitreous to resinous on Pyrochlore.

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Often found alongside fluornatromicrolite

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

All properties

Chemical formula: (Na₁.₅Bi₀.₅)Ta₂O₆F
Mohs hardness: 5
Density: 6.49 g/cm³
Colors: Green
Streak: White
Luster: Adamantine
Transparency: Transparent
Crystal system: Cubic
Crystal habit: Octahedral crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In a granitic pegmatite

Where rockhounds find fluornatromicrolite

Classic worldwide localities

Alto Quixaba pegmatite, Frei Martinho municipality, Paraíba State, northeastern Brazil
Altai Mounains, Russia and the Borborema pegmatitic province, northeastern Brazil

Field-hunting tip

Where it forms: In a granitic pegmatite. If you start seeing perthitic microcline, albite, amblygonite in float, you are in the right ground. Typical habit: octahedral crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify fluornatromicrolite?+

Mohs hardness is 5. Luster: adamantine. The streak is white. Common colors include green.

Where is fluornatromicrolite found?+

Notable localities include Alto Quixaba pegmatite, Frei Martinho municipality, Paraíba State, northeastern Brazil; Altai Mounains, Russia and the Borborema pegmatitic province, northeastern Brazil.

Is fluornatromicrolite safe to handle?+

Fluornatromicrolite contains trace uranium or thorium. Due to its uranium and thorium content, this mineral is radioactive. Handle with care, wash hands after handling, and store in a shielded container away from living areas.

What rocks look like fluornatromicrolite?+

Fluornatromicrolite 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 fluornatromicrolite?+

Fluornatromicrolite commonly co-occurs with Perthitic microcline, Albite, Amblygonite, Muscovite, Quartz, Elbaite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does fluornatromicrolite form in?+

Where it forms: In a granitic pegmatite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is fluornatromicrolite used for?+

Fluornatromicrolite is used in collector.

Find fluornatromicrolite on the map

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