RocksdayCobaltite vs Pyrite
How to tell them apart
A silvery cobalt arsenic sulfide with a pinkish tint, forming pyrite-like crystals.
Photo: User Tor Svensson, CC BY-SA 3.0
Brassy iron sulfide famous as 'fool's gold'. It often forms startlingly perfect cubes with fine parallel lines on the faces.
Photo: Ivar Leidus, CC BY-SA 4.0
Quick tests
- Streak (rub on unglazed porcelain): Cobaltite leaves a grayish black streak; Pyrite leaves greenish black.
Key differences
- Pyrite is brass-yellow.
Side by side
| Property | Cobaltite | Pyrite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 5.5 | 6–6.5 |
| Luster | Metallic | Metallic |
| Streak | Grayish black | Greenish black |
| Colors | Silver, Pink | Gold |
| Crystal system | Orthorhombic (pseudo-cubic) | Cubic |
| Specific gravity | 6.3 | 4.95–5.1 |
| Formula | CoAsS | FeS₂ |
| Found in | Tunaberg, Sweden; Cobalt, Ontario | Navajún, Spain; Huanzala, Peru |
Properties that are the same for both are grayed out.
How to identify cobaltite
- Silver-white with a reddish tint.
- Cubes and pyritohedrons like pyrite.
- Pink 'cobalt bloom' crust on weathered pieces.
Crystal system: Orthorhombic (pseudo-cubic)
Full Cobaltite guide →How to identify pyrite
- Pale brass-yellow metallic color.
- Streak is greenish black, not gold.
- Hard and brittle — it shatters rather than flattens when struck.
- Cubes with striated faces, or twelve-sided pyritohedrons.
Crystal system: Cubic
Full Pyrite guide →More comparisons
Could you tell them apart from a blurry close-up?
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