RocksdayPentlandite vs Pyrrhotite
How to tell them apart
The main ore of nickel, a bronze-yellow sulfide usually intergrown with pyrrhotite.
Photo: John Sobolewski (JSS), CC BY 3.0
A bronze iron sulfide that is noticeably magnetic.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Quick tests
- Magnet: A magnet sticks to Pyrrhotite but not to Pentlandite.
- Streak (rub on unglazed porcelain): Pentlandite leaves a bronze-brown streak; Pyrrhotite leaves grayish black.
Key differences
- Pyrrhotite is magnetic.
- Pentlandite is not magnetic.
Side by side
| Property | Pentlandite | Pyrrhotite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 3.5–4 | 3.5–4.5 |
| Luster | Metallic | Metallic |
| Streak | Bronze-brown | Grayish black |
| Colors | Gold, Brown | Gold, Brown |
| Crystal system | Cubic | Monoclinic |
| Specific gravity | 4.6–5 | 4.6–4.7 |
| Formula | (Fe,Ni)₉S₈ | Fe₁₋ₓS |
| Found in | Sudbury, Ontario; Norilsk, Russia | Sudbury, Ontario; Dalnegorsk, Russia |
Properties that are the same for both are grayed out.
How to identify pentlandite
- Light bronze-yellow metallic.
- Not magnetic.
- Usually as grains within pyrrhotite.
Crystal system: Cubic
Full Pentlandite guide →How to identify pyrrhotite
- Bronze-yellow, tarnishing brown.
- Attracted to a magnet.
- Softer than pyrite.
Crystal system: Monoclinic
Full Pyrrhotite guide →More comparisons
Could you tell them apart from a blurry close-up?
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