Oppenheimerite is a rare copper sodium sulfate mineral first identified at the Rowley Mine in Arizona. It typically appears as small, vibrant yellow tabular crystals formed in the oxidation zones of ore deposits.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Oppenheimerite

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

No image

Is this oppenheimerite?

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 oppenheimerite with a known reference. Oppenheimerite 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: pale greenish yellow.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals.

Often confused with

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

How to tell apart: Brochantite is the harder of the two (Mohs 3.5-4 vs. 2.5); streak differs, so Oppenheimerite leaves white, Brochantite leaves pale green.

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Often found alongside oppenheimerite

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

All properties

Chemical formula: Na₂(UO₂)(SO₄)₂·3H₂O
Mohs hardness: 2.5
Density: 3.360 g/cm³
Colors: Pale greenish yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Tabular crystals
Cleavage: Good on {11̄0}, {011} and {101}
Fluorescence: Bright yellow-green under UV
Rarity: Rare
Uses: Collector
Host rock: oxidized mine dumps and hydrothermal veins

Where rockhounds find oppenheimerite

Classic worldwide localities

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

Field-hunting tip

Where it forms: oxidized mine dumps and hydrothermal veins. If you start seeing fermiite, blödite, bluelizardite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify oppenheimerite?+

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

Where is oppenheimerite found?+

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

Is oppenheimerite safe to handle?+

Oppenheimerite contains uranium or thorium and calls for real care. Contains copper; handle with care and wash hands after contact. Dust inhalation should be avoided.

What rocks look like oppenheimerite?+

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

What minerals are found with oppenheimerite?+

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

What kind of rock does oppenheimerite form in?+

Where it forms: oxidized mine dumps and hydrothermal veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is oppenheimerite used for?+

Oppenheimerite is used in collector.

Find oppenheimerite on the map

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