Skutterudite is a metallic arsenide mineral often found as distinct, sharp cubic crystals or dense granular masses. It is a significant ore of cobalt and is typically identified by its high specific gravity and association with other cobalt-nickel minerals in hydrothermal veins.
Is this skutterudite?
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 skutterudite with a known reference. Skutterudite sits at Mohs 5.5-6, 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.
- 4Match the color rangeCompare against the expected color range: white, light steel gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: colloform, granular, massive.
Often confused with
Skutterudite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Skutterudite leaves black, Cobaltite leaves grayish black.
How to tell apart: Streak differs, so Skutterudite leaves black, Gersdorffite leaves grayish black.
Often found alongside skutterudite
Minerals reported to co-occur with skutterudite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CoAs₃
- Mohs hardness
- 5.5-6
- Density
- 6.5 g/cm³
- Colors
- WhiteLight steel gray
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Colloform, granular, massive
- Cleavage
- Distinct on {001} and {111}; in traces on {011}
- Rarity
- Uncommon
- Uses
- Collector, Ore of cobalt, Ore of nickel
- Host rock
- Typically in medium- to high-temperature hydrothermal veins with other Ni–Co sulfide minerals
Where rockhounds find skutterudite
Classic worldwide localities
- Chatham, Middlesex Co., Connecticut, USA
- Mine la Motte, Madison Co., Missouri, USA
- Skutterud, Modum (type locality), Norway
- Schneeberg, Annaberg, and Freiberg, Saxony, Germany
- Lölling, Carinthia, Austria
- Valley of Gistain, Huesca Province, Spain
Field-hunting tip
Where it forms: Typically in medium- to high-temperature hydrothermal veins with other Ni–Co sulfide minerals. If you start seeing nickeline, cobaltite, arsenopyrite in float, you are in the right ground. Typical habit: colloform, granular, massive. Train your eye for that shape before scanning the outcrop.
Common questions
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Find skutterudite on the map
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