| Pyrite | |
|---|---|
| [image] A mass of interwoven pyrite crystals | |
| General | |
| Category | Mineral |
| Chemical formula | Iron disulfide (FeS2) |
| Identification | |
| Colour | Pale, dull gold |
| Crystal habit | Cubic, faces may be striated, but also frequently octahedral and pyritohedron. Often intergrown, massive, radiated, granular, globular and stalactitic. |
| Crystal system | Isometric; bar 3 2/m |
| Melting point | 2140°C |
| Cleavage | Poor |
| Fracture | Very uneven, sometimes conchoidal |
| Mohs Scale hardness | 6 - 6.5 |
| Luster | Metallic, glistening |
| Refractive index | Opaque |
| Streak | Greenish-black to brownish-black |
| Specific gravity | 4.95 - 5.10 |
| Fusibility | 2.5-3 |
| Solubility | insoluble in water |
| Magnetism | magnetic after heating |
The Mineral pyrite, or iron pyrite, is iron disulfide, FeS2. It has isometric crystals that usually appear as cubes, faces may be striated (parallel lines on crystal surface or cleavage face) as a result of twinning, but is also frequently octahedral and occurs as pyritohedrons (a dodecahedron with pentagonal faces). It has a slightly uneven and conchoidal fracture, a hardness of 6-6.5, and a specific gravity of 4.95-5.10. Its metallic luster and pale-to-normal Brass-yellow hue have earned it the nickname fool's gold, but ironically enough, small quantities of actual Gold can sometimes be found in pyrite. In fact, some auriferous pyrite is a very valuable Ore of gold.
Pyrite is the most common of the sulfide minerals. It is usually found associated with other sulfides or oxides in Quartz veins, Sedimentary rock and Metamorphic rock, as well as in Coal beds, and as the replacement mineral in fossils. Pyrites, interestingly, can show Negative resistance, acting as Radio detectors and have been used in oscillator circuits.
Pyrite exposed to the environment during Mining and excavation can react with Oxygen and Water to form Acid mine drainage in the form of Sulfuric acid. Similarly, the paper industry often uses pyrite for the production of Sulfur dioxide and in the manufacture of sulfuric acid, though not as much as it used to.
The name pyrite is from the Greek word "Pyr" meaning "fire". This is likely due to the sparks that result when pyrite is struck against Steel. This capacity made it popular for use in early firearms such as the Wheellock.
Pyrite is often used in Jewellery (jewelry) such as necklaces and bracelets, but although the two are similar, marcasite cannot be used in jewellery as it has a tendency to crumble and turn into powder. Adding to the confusion between marcasite and pyrite is the use of the word marcasite as a jewellery trade name. The term is applied to small polished and faceted stones that are inlaid in Sterling silver, but even though they are called marcasite, they are actually pyrite.