Linnaeite is a rare cobalt sulfide mineral that typically appears as metallic, steel-gray octahedrons. It is primarily found in hydrothermal veins associated with other sulfide minerals and is a historically significant minor ore of cobalt.
Is this linnaeite?
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 linnaeite with a known reference. Linnaeite 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. Streak: grayish black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic, easily tarnished.
- 4Match the color rangeCompare against the expected color range: steel gray, violet gray, copper red, light gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: crystalline, encrustations, granular.
Often confused with
Linnaeite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Linnaeite leaves grayish black, Pentlandite leaves pale bronze-brown.
How to tell apart: Streak differs, so Linnaeite leaves grayish black, Pyrite leaves greenish black to brownish black.
Often found alongside linnaeite
Minerals reported to co-occur with linnaeite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Co₃S₄
- Mohs hardness
- 4.5-5.5
- Density
- 4.5-4.8 g/cm³
- Colors
- Streak
- Grayish black
- Luster
- Metallic, easily tarnished
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Crystalline, encrustations, granular
- Cleavage
- Imperfect on {001}
- Rarity
- Uncommon
- Uses
- Collector, Ore of cobalt
- Host rock
- In hydrothermal veins with other cobalt and nickel sulfides
Where rockhounds find linnaeite
1 mapped spotsClassic worldwide localities
- Springfield and Mineral Hill mines, Carroll Co., Maryland, USA
- Mine La Motte, Madison Co., Missouri, USA
- Bastnäs mine, near Riddarhyttan, Västmanland (type locality), and at Gladhammar, Kalmar, Sweden
- Outokumpu, Finland
- Müsen, North Rhine-Westphalia, Germany
- Altenberg, Saxony, Germany
Field-hunting tip
Where it forms: In hydrothermal veins with other cobalt and nickel sulfides. If you start seeing chalcopyrite, pyrrhotite, millerite in float, you are in the right ground. Typical habit: crystalline, encrustations, granular. 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
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Find linnaeite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
