Pyrite is the most common sulfide mineral. It is found all over the world in reducing (low-oxygen) environments. Pyrite is polymorphic with the mineral marcasite, that is, they have the same chemistry but different structures. Most gemstones sold as marcasite are actually pyrite, since pyrite is less prone to deteoriation. Pyrite is also known as "Fool's Gold" because it is sometimes mistaken for gold. It can be distinguished from gold by its higher hardness, lower specific gravity and black (not golden) streak. Pyrite is also brittle and breaks like glass when struck.
| FeS2 |
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| Sulfide |
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| Isometric |
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| 2/m -3 |
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| 6-6.5 |
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| 5.02 |
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| {100} poor, {110} poor |
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| Conchoidal |
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| Golden yellow |
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| Greenish-black |
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| Metallic |
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| Opaque |
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| Cubic, drusy, stalactitic |
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| Crystals are often striated |
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| Notable Localities: |
Leadville, Colorado; La Libertad, Peru; Spain |
| Uses: |
Ore of sulfur for the production of sulfuric acid, ore of iron (where iron oxides are not found) |
Specimens:
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