A metallic yellow iron sulphide (FeS2) mineral, common and widespread, often occurring as well-formed cubic crystals; also termed fool's gold because of its colour. It is used as a source of sulphur and in the manufacture of sulphuric acid.
| Pyrite | |
|---|---|
|
A mass of intergrown, striated pyrite crystals |
|
|
Euhedral cubic 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. |
| Crystal system | Isometric; bar 3 2/m |
| Melting Point | 1,177-1,188°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 | paramagnetic |
The mineral pyrite, or iron pyrite, is iron sulfide, FeS2.
Pyrite exposed to the environment during mining and excavation reacts with oxygen and water to form sulfuric acid, resulting in acid mine drainage.
Pyrite and marcasite
Pyrite is often confused with the mineral marcasite, a name derived from the Arabic word for pyrite, due to their similar characteristics. Marcasite is a polymorph of pyrite, which means it has the same formula as pyrite but a different structure and, therefore, different symmetry and crystal shapes.
Marcasite is metastable relative to pyrite and will slowly be changed to pyrite if heated or given enough time.
Formal oxidation states for pyrite, marcasite, and arsenopyrite
From the perspective of classical inorganic chemistry, which assigns formal oxidation states to each atom, pyrite is probably best described as Fe.
Related minerals and varieties
Bravoite is a nickeloan variety of pyrite, with >50% substitution of Ni within pyrite.
User Comments Add a comment…