Pyrite
| Pyrite | |
|---|---|
 Intergrowth of lustrous, cubic crystals of pyrite, with some surfaces showing characteristic striations, from Huanzala mine, Ancash, Peru. Specimen size: 7.0 × 5.0 × 2.5 cm | |
| General | |
| Category | Sulfide mineral |
| Formula | FeS2 |
| IMA symbol | Py |
| Strunz classification | 2.EB.05a |
| Dana classification | 2.12.1.1 |
| Crystal system | Cubic |
| Crystal class | Diploidal (m3) H-M symbol: (2/m 3) |
| Space group | Pa3 |
| Unit cell | a = 5.417 Å, Z = 4 |
| Identification | |
| Formula mass | 119.98 g/mol |
| Color | Pale brass-yellow reflective; tarnishes darker and iridescent |
| Crystal habit | Cubic, faces may be striated, but also frequently octahedral and pyritohedral. Often inter-grown, massive, radiated, granular, globular, and stalactitic. |
| Twinning | Penetration and contact twinning |
| Cleavage | Indistinct on {001}; partings on {011} and {111} |
| Fracture | Very uneven, sometimes conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 6–6.5 |
| Luster | Metallic, glistening |
| Streak | Greenish-black to brownish-black |
| Diaphaneity | Opaque |
| Specific gravity | 4.95–5.10 |
| Density | 4.8–5 g/cm3 (0.17–0.18 lb/cu in) |
| Fusibility | 2.5–3 to a magnetic globule |
| Solubility | Insoluble in water |
| Other characteristics | Diamagnetic to paramagnetic A semiconductor with bandgap of 0.72 to 3.26 eV. |
| References | |
The mineral pyrite (/ˈpaɪraɪt/ PY-ryte), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula FeS2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of fool's gold. The color has also led to the nicknames brass, brazzle, and brazil, primarily used to refer to pyrite found in coal.
Pyrite 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 a replacement mineral in fossils, but has also been identified in the sclerites of scaly-foot gastropods. Despite being nicknamed "fool's gold", pyrite is sometimes found in association with small quantities of actual gold. A substantial proportion of this is "invisible gold" incorporated into the pyrite. It has been suggested that the presence of both gold and arsenic is a case of coupled substitution. However, as of 1997, the chemical state of the gold remained controversial.