Fools gold Pyrite

Pyrite

A mass of intergrown pyrite crystals
General
Category Sulfide mineral
Chemical formula iron disulfide (FeS2)
Strunz classification II/D.17-30
Dana classification 2.12.1.1
Crystal symmetry 2/m3
Unit cell a = 5.417 Å, Z=4
Identification
Color Pale brass-yellow, tarnishes darker and iridescent
Crystal habit Cubic, faces may be striated, but also frequently octahedral and pyritohedron. Often inter-grown, massive, radiated, granular, globular and stalactitic.
Crystal system Isometric Diploidal, Space group Pa3
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; smells of sulfur
Diaphaneity Opaque
Specific gravity 4.95–5.10
Fusibility 2.5–3 to a magnetic globule
Solubility Insoluble in water
Other characteristics paramagnetic
References [1][2][3][4]

The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic lustre and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold. The color has also led to the nicknames brass, brazzle and Brazil, primarily used to refer to pyrite found in coal.[5][6]

Pyrite is the most common of the sulfide minerals. The name pyrite is derived from the Greek πυρίτης (puritēs), "of fire" or "in fire", from πύρ (pur), "fire". 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 we now call pyrite.[7] By Georgius Agricola's time, the term had become a generic term for all of the sulfide minerals.[8]

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. Despite being nicknamed fool's gold, pyrite is sometimes found in association with small quantities of gold. Gold and arsenic occur as a coupled substitution in the pyrite structure. In the Carlin, Nevada, gold deposit, arsenian pyrite contains up to 0.37 wt% gold.[9] Auriferous pyrite is a valuable ore of gold.