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

No image

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, 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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