Klockmannite is a rare copper selenide mineral typically found as metallic, slate-gray masses in hydrothermal veins. It is often identified by its association with other rare selenide minerals and its distinct lack of crystal faces in hand samples. Collectors should treat it with caution due to the presence of selenium.
Is this klockmannite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch klockmannite with a known reference. Klockmannite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic when freshly broken, soon becoming dull.
- 4Match the color rangeCompare against the expected color range: blue black, grayish black, dark gray.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: aggregates, granular.
Often confused with
Klockmannite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Klockmannite leaves black, Chalcocite leaves blackish lead-gray.
How to tell apart: Streak differs, so Klockmannite leaves black, Covellite leaves lead-gray, shining; luster reads metallic when freshly broken, soon becoming dull on Klockmannite and submetallic, inclining to resinous, somewhat pearly on cleavage; subresinous to dull when massive on Covellite.
Often found alongside klockmannite
Minerals reported to co-occur with klockmannite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₅.₂Se₆
- Mohs hardness
- 2-3
- Density
- 5.99 g/cm³
- Streak
- Black
- Luster
- Metallic when freshly broken, soon becoming dull
- Transparency
- Opaque
- Crystal system
- Hexagonal
- Crystal habit
- Aggregates, granular
- Cleavage
- Perfect on {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Of hydrothermal origin, in deposits rich in copper and tellurium
Where rockhounds find klockmannite
Classic worldwide localities
- Sierra de Umango (type locality), and in the Santa Brigida mine and at Tuminico, Sierra de Cacho, La Rioja Province, Argentina
- Cerro de Cacheuta, Mendoza Province, Argentina
- Lerbach, Tilkerode, and Zorge, Harz Mountains, Germany
- Skrikerum, Kalmar, Sweden
- Bukov, near Tisnova, Czech Republic
- Petrovice uranium deposit, near Ždǎr, Czech Republic
Field-hunting tip
Where it forms: Of hydrothermal origin, in deposits rich in copper and tellurium. If you start seeing clausthalite, umangite, eucairite in float, you are in the right ground. Typical habit: aggregates, granular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find klockmannite on the map
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