Kruťaite is a rare copper selenide mineral typically found as small, metallic grains within hydrothermal veins. It is most famously associated with the uranium deposits at Bukov and Predborice in the Czech Republic, where it occurs alongside other rare selenides.

Hardness

3.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrarePyrite Group family

Kruťaite

Hardness: 3.5
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this kruťaite?

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 kruťaite with a known reference. Kruťaite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Kruťaite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Kruťaite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: gray, silver-white.
5
Look at form & habit
Crystal system: cubic. Typical habit: anhedral grains, disseminated.

Often confused with

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

mineral

Pyrite

Mohs 6-6.5

How to tell apart: Pyrite is the harder of the two (Mohs 6-6.5 vs. 3.5); streak differs — Kruťaite leaves black, Pyrite leaves greenish-black to brownish-black.

How to tell apart: Marcasite is the harder of the two (Mohs 6-6.5 vs. 3.5); streak differs — Kruťaite leaves black, Marcasite leaves greyish-black.

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Often found alongside kruťaite

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

All properties

Chemical formula: CuSe₂
Mohs hardness: 3.5
Density: 6.6 g/cm³
Colors: Gray Silver-white
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Anhedral Grains, Disseminated
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Veins
Typical price: $100-500 for micro-mounts or small specimens

Where rockhounds find kruťaite

Classic worldwide localities

Bukov, Czech Republic
Predborice, Czech Republic

Field-hunting tip

Look in hydrothermal veins country — that is the host setting where kruťaite typically forms. If you start seeing clausthalite, uraninite, berzelianite in float, you are in the right ground. Field specimens usually show a anhedral grains, disseminated habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kruťaite?+

Mohs hardness is 3.5. It typically shows a metallic luster. The streak is black. Common colors include gray, silver-white.

Where is kruťaite found?+

Notable localities include Bukov, Czech Republic; Predborice, Czech Republic.

How much is kruťaite worth?+

Typical asking prices fall in the range of $100-500 for micro-mounts or small specimens. Quality, size, and provenance can move individual specimens well outside that range.

Is kruťaite safe to handle?+

It contains toxic constituents. Contains selenium, which is toxic if ingested or inhaled as dust. Handle with care and wash hands thoroughly after contact. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like kruťaite?+

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

What minerals are found with kruťaite?+

Kruťaite commonly co-occurs with Clausthalite, Uraninite, Berzelianite, Hematite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kruťaite form in?+

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

What is kruťaite used for?+

Kruťaite is used in collector.

Find kruťaite on the map

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