Znucalite is a very rare secondary uranium-zinc carbonate mineral that forms as thin, pearly crusts or small platy crystals in oxidized zones. It is highly valued by mineral collectors for its distinct bright green fluorescence under shortwave ultraviolet light.

Hardness

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrare

Znucalite

Hardness: 2
Luster: Pearly
Streak: White
Transparency: Translucent

Is this znucalite?

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 znucalite with a known reference. Znucalite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Znucalite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Znucalite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: white, colorless, pale yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: platy crystals, crusts, aggregates.

Often confused with

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

mineral

Autunite

Mohs 2-2.5

How to tell apart: Streak differs — Znucalite leaves white, Autunite leaves pale yellow.

How to tell apart: Adamite is the harder of the two (Mohs 3.5 vs. 2); luster reads pearly on Znucalite and vitreous on Adamite.

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Often found alongside znucalite

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

All properties

Chemical formula: CaZn₁₁(UO₂)₂(CO₃)₃(OH)₂₂·4H₂O
Mohs hardness: 2
Density: 2.8 g/cm³
Colors: White Colorless Pale Yellow
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Platy Crystals, Crusts, Aggregates
Cleavage: Perfect in One Direction
Fluorescence: Bright Green Under SW UV
Rarity: Rare
Uses: Collector, Scientific Study
Host rock: Oxidized Zones of Uranium-zinc Hydrothermal Deposits
Typical price: $50-300 per specimen

Where rockhounds find znucalite

Classic worldwide localities

Jachymov, Czech Republic
Schneeberg, Germany
Rum Jungle, Australia

Field-hunting tip

Look in oxidized zones of uranium-zinc hydrothermal deposits country — that is the host setting where znucalite typically forms. If you start seeing adamite, smithsonite, uraninite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts, aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify znucalite?+

Mohs hardness is 2. It typically shows a pearly luster. The streak is white. Common colors include white, colorless, pale yellow.

Where is znucalite found?+

Notable localities include Jachymov, Czech Republic; Schneeberg, Germany; Rum Jungle, Australia.

How much is znucalite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is znucalite safe to handle?+

This mineral is radioactive. It contains toxic constituents. Contains uranium and zinc; handle with care using gloves and store in a sealed container away from living areas to avoid ingesting radioactive dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like znucalite?+

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

What minerals are found with znucalite?+

Znucalite commonly co-occurs with Adamite, Smithsonite, Uraninite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does znucalite form in?+

Znucalite typically forms in oxidized zones of uranium-zinc hydrothermal deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is znucalite used for?+

Znucalite is used in collector, scientific study.

Find znucalite on the map

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