Bornhardtite is a rare cobalt selenide mineral typically occurring as microscopic inclusions in other selenide minerals. It is best identified in laboratory settings via X-ray diffraction or electron microprobe analysis due to its visual similarity to other metallic sulfides and selenides.

Hardness

4.5-5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrareLinnaeite Group family

Bornhardtite

Hardness: 4.5-5
Luster: Metallic
Streak: Black
Transparency: Opaque

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Is this bornhardtite?

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 bornhardtite with a known reference. Bornhardtite sits at Mohs 4.5-5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Bornhardtite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Bornhardtite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: pinkish-white, gray.
5
Look at form & habit
Crystal system: cubic. Typical habit: massive, granular, rarely octahedral.

Often confused with

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

Often found alongside bornhardtite

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

All properties

Chemical formula: Co₃Se₄
Mohs hardness: 4.5-5
Density: 5.65 g/cm³
Colors: Pinkish-white Gray
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Massive, Granular, Rarely Octahedral
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Selenide Deposits
Typical price: $50-300 per specimen depending on size and rarity

Where rockhounds find bornhardtite

Classic worldwide localities

Tropicana mine, Australia
Tilkerode, Germany
Hope's Nose, England
Skrikerum, Sweden

Field-hunting tip

Look in hydrothermal selenide deposits country — that is the host setting where bornhardtite typically forms. If you start seeing clausthalite, tiemannite, berzelianite in float, you are in the right ground. Field specimens usually show a massive, granular, rarely octahedral habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify bornhardtite?+

Mohs hardness is 4.5-5. It typically shows a metallic luster. The streak is black. Common colors include pinkish-white, gray.

Where is bornhardtite found?+

Notable localities include Tropicana mine, Australia; Tilkerode, Germany; Hope's Nose, England; Skrikerum, Sweden.

How much is bornhardtite worth?+

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

Is bornhardtite safe to handle?+

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

What rocks look like bornhardtite?+

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

What minerals are found with bornhardtite?+

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

What kind of rock does bornhardtite form in?+

Bornhardtite typically forms in hydrothermal selenide deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is bornhardtite used for?+

Bornhardtite is used in collector.

Find bornhardtite on the map

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