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 (repeating unit) | FeS |
IMA symbol | Py[1] |
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 |
Fusibility | 2.5–3 to a magnetic globule |
Solubility | Insoluble in water |
Other characteristics | paramagnetic |
References | [2][3][4][5] |
The mineral pyrite (/ˈpaɪraɪt/ PY-ryte),[6] 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.[7]
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.[8][9]
The name pyrite is derived from the Greek πυρίτης λίθος (pyritēs lithos), 'stone or mineral which strikes fire',[10] in turn from πῦρ (pŷr), 'fire'.[11] In ancient Roman times, this name was applied to several types of stone that would create sparks when struck against steel; Pliny the Elder described one of them as being brassy, almost certainly a reference to what is now called pyrite.[12]
By Georgius Agricola's time, c. 1550, the term had become a generic term for all of the sulfide minerals.[13]
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.[14] Despite being nicknamed "fool's gold", pyrite is sometimes found in association with small quantities of gold. A substantial proportion of the gold is "invisible gold" incorporated into the pyrite (see Carlin-type gold deposit). It has been suggested that the presence of both gold and arsenic is a case of coupled substitution but as of 1997 the chemical state of the gold remained controversial.[15]