Fermiite is a rare secondary uranium sulfate mineral discovered in the uranium-bearing sandstones of Utah. It typically forms as delicate, bright yellow platy crystals or laths and is highly prized by collectors for its intense fluorescence under ultraviolet light.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Fermiite

Hardness: 2.5
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this fermiite?

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 fermiite with a known reference. Fermiite sits at Mohs 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: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: greenish yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: platy crystals, lath-like aggregates.

Often confused with

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

mineral

Zippeite

Mohs ~2

How to tell apart: Streak differs, so Fermiite leaves white, Zippeite leaves yellow white.

How to tell apart: Streak differs, so Fermiite leaves white, Johannite leaves pale green.

Compare →

Often found alongside fermiite

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

All properties

Chemical formula: Na₄(UO₂)(SO₄)₃·3H₂O
Mohs hardness: 2.5
Density: 3.23 g/cm³
Colors: Greenish yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Platy crystals, lath-like aggregates
Cleavage: None
Fluorescence: Bright yellow-green under UV light
Rarity: Rare
Uses: Collector
Host rock: uranium-bearing sandstone

Where rockhounds find fermiite

Classic worldwide localities

Blue Lizard mine, Red Canyon, White Canyon district, San Juan County, Utah, USA

Field-hunting tip

Where it forms: uranium-bearing sandstone. If you start seeing oppenheimerite, blödite, bluelizardite in float, you are in the right ground. Typical habit: platy crystals, lath-like aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify fermiite?+

Mohs hardness is 2.5. Luster: vitreous. The streak is white. Common colors include greenish yellow.

Where is fermiite found?+

Notable localities include Blue Lizard mine, Red Canyon, White Canyon district, San Juan County, Utah, USA.

Is fermiite safe to handle?+

Fermiite contains uranium or thorium and calls for real care. Fermiite contains uranium, making it radioactive; handle with care, use gloves, avoid ingestion or inhalation of dust, and store in a shielded container.

What rocks look like fermiite?+

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

What minerals are found with fermiite?+

Fermiite commonly co-occurs with Oppenheimerite, Blödite, Bluelizardite, Chalcanthite, Epsomite, Gypsum. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does fermiite form in?+

Where it forms: uranium-bearing sandstone. Working float back to the host body is the standard way to chase a fresh occurrence.

What is fermiite used for?+

Fermiite is used in collector.

Find fermiite on the map

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