Carrollite is a rare copper-cobalt sulfide that typically forms distinct, metallic octahedral crystals. Collectors prize it for its bright luster and classic isometric crystal habits found primarily in the Copperbelt region of the Congo.
Is this carrollite?
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 carrollite with a known reference. Carrollite sits at Mohs 4.5-5.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Carrollite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Carrollite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: light steel-gray, white, iron-black.
- 5Look at form & habitCrystal system: cubic. Typical habit: octahedral crystals, often with curved faces, or massive.
Often confused with
Carrollite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside carrollite
Minerals reported to co-occur with carrollite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuCo₂S₄
- Mohs hardness
- 4.5-5.5
- Density
- 4.85 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Octahedral Crystals, Often with Curved Faces, Or Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins and Sedimentary Copper-cobalt Deposits
- Typical price
- $50-500 depending on crystal size and provenance
Where rockhounds find carrollite
Classic worldwide localities
- Kamoto Mine, Democratic Republic of the Congo
- Shinkolobwe, Democratic Republic of the Congo
- Carroll County, Maryland, USA
- Siegen, Germany
Field-hunting tip
Look in hydrothermal veins and sedimentary copper-cobalt deposits country — that is the host setting where carrollite typically forms. If you start seeing chalcocite, bornite, dolomite in float, you are in the right ground. Field specimens usually show a octahedral crystals, often with curved faces, or massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find carrollite on the map
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