Pseudojohannite is a rare secondary uranium sulfate mineral typically found as small, bright yellow tabular crystals in oxidized uranium deposits. It is frequently associated with johannite, from which it can be distinguished by specific optical properties and its triclinic structure. Collectors should treat it with caution due to its high radioactivity and solubility.

Hardness

2-3

Mohs

Luster

Vitreous

Streak

Yellow

Transparency

Translucent

mineralrare

Pseudojohannite

Hardness: 2-3
Luster: Vitreous
Streak: Yellow
Transparency: Translucent

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Is this pseudojohannite?

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 pseudojohannite with a known reference. Pseudojohannite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Pseudojohannite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Pseudojohannite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, greenish-yellow.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals, crusts, coatings.

Often confused with

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

mineral

Johannite

Mohs 2

How to tell apart: Streak differs — Pseudojohannite leaves yellow, Johannite leaves pale green.

How to tell apart: Luster reads vitreous on Pseudojohannite and pearly on Meta-autunite.

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Often found alongside pseudojohannite

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

All properties

Chemical formula: Cu(UO₂)₂(SO₄)₂(OH)₂·12H₂O
Mohs hardness: 2-3
Density: 4.15 g/cm³
Colors: Yellow Greenish-yellow
Streak: Yellow
Luster: Vitreous
Transparency: Translucent
Crystal system: Triclinic
Crystal habit: Tabular Crystals, Crusts, Coatings
Cleavage: Perfect
Fluorescence: Bright Yellow-green Under UV
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Uranium-bearing Veins
Typical price: $50-500 thumbnail depending on matrix and crystal quality

Where rockhounds find pseudojohannite

Classic worldwide localities

Jáchymov, Czech Republic
Wölsendorf, Germany
Great Bear Lake, Canada

Field-hunting tip

Look in hydrothermal uranium-bearing veins country — that is the host setting where pseudojohannite typically forms. If you start seeing uraninite, johannite, gypsum in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, coatings habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify pseudojohannite?+

Mohs hardness is 2-3. It typically shows a vitreous luster. The streak is yellow. Common colors include yellow, greenish-yellow.

Where is pseudojohannite found?+

Notable localities include Jáchymov, Czech Republic; Wölsendorf, Germany; Great Bear Lake, Canada.

How much is pseudojohannite worth?+

Typical asking prices fall in the range of $50-500 thumbnail depending on matrix and crystal quality. Quality, size, and provenance can move individual specimens well outside that range.

Is pseudojohannite safe to handle?+

This mineral is radioactive. It contains toxic constituents. Radioactive material; keep shielded, store in sealed containers, and wash hands thoroughly after handling. Avoid dust inhalation. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like pseudojohannite?+

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

What minerals are found with pseudojohannite?+

Pseudojohannite commonly co-occurs with Uraninite, Johannite, Gypsum, Brochantite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does pseudojohannite form in?+

Pseudojohannite typically forms in hydrothermal uranium-bearing veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is pseudojohannite used for?+

Pseudojohannite is used in collector.

Find pseudojohannite on the map

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