RocksdayArsenopyrite vs Pyrite
How to tell them apart
An iron arsenic sulfide and the main ore of arsenic. It smells of garlic when struck.
Photo: Robert M. Lavinsky, 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): Arsenopyrite leaves a dark gray streak; Pyrite leaves greenish black.
Key differences
- Pyrite is brassy yellow and forms cubes.
Side by side
| Property | Arsenopyrite | Pyrite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 5.5–6 | 6–6.5 |
| Luster | Metallic | Metallic |
| Streak | Dark gray | Greenish black |
| Colors | Silver, Gray | Gold |
| Crystal system | Monoclinic | Cubic |
| Specific gravity | 6–6.2 | 4.95–5.1 |
| Formula | FeAsS | FeS₂ |
| Found in | Panasqueira, Portugal; Hunan, China | Navajún, Spain; Huanzala, Peru |
Properties that are the same for both are grayed out.
How to identify arsenopyrite
- Silvery-white metallic, diamond-shaped prisms.
- Garlic smell when hammered.
- Harder than a knife.
Crystal system: Monoclinic
Full Arsenopyrite 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?
Play today's Rocksday