Cobaltite is a distinctive cobalt-arsenic sulfide mineral often found in brilliant silver-white or reddish-tinted metallic crystals. Collectors typically look for its sharp pseudocubic habit, though it is frequently found in massive or granular forms associated with other metallic sulfides.
Is this cobaltite?
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 cobaltite with a known reference. Cobaltite sits at Mohs 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: grayish black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: silver-white, reddish-white, gray, reddish silver white, violet steel gray, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: granular, massive, striated.
Often confused with
Cobaltite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Cobaltite leaves grayish black, Skutterudite leaves black.
How to tell apart: Streak differs, so Cobaltite leaves grayish black, Arsenopyrite leaves black.
How to tell apart: Streak differs, so Cobaltite leaves grayish black, Pyrite leaves greenish black to brownish black.
Often found alongside cobaltite
Minerals reported to co-occur with cobaltite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CoAsS
- Mohs hardness
- 5.5
- Density
- 6.33 g/cm³
- Colors
- Streak
- Grayish black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Granular, massive, striated
- Cleavage
- Perfect on {001}
- Rarity
- Uncommon
- Uses
- Collector, Ore of cobalt
- Host rock
- In high-temperature hydrothermal deposits, as disseminations, and as veins in contact metamorphosed rocks
Where rockhounds find cobaltite
1 mapped spotsClassic worldwide localities
- Tunaberg, Södermanland, Sweden
- Riddarhyttan and Håkansboda, Västmanland, Sweden
- Vena mines, near Askersund, Örebro, Sweden
- Skutterud, Modum, Norway
- Bieber, near Hanau, Hesse, Germany
- Crown’s Engine House, Wheal Cock, and the Botallack mine, St. Just, Cornwall, England
Field-hunting tip
Where it forms: In high-temperature hydrothermal deposits, as disseminations, and as veins in contact metamorphosed rocks. If you start seeing magnetite, sphalerite, chalcopyrite in float, you are in the right ground. Typical habit: granular, massive, striated. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Wyoming. Start trip planning there.
Common questions
How do you identify cobaltite?+
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Can I find cobaltite in the United States?+
Is cobaltite safe to handle?+
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Find cobaltite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
