Pyrite

The mineral pyrite,^[1] or iron pyrite, is an iron sulfide with the formula FeS₂. This mineral's metallic lustre and pale-to-normal, brass-yellow colour have earned it the nickname fool's gold because of its resemblance to gold.^{[2][3][4][5][6][7]} The term pyrite may also be used for some other sulphides such as copper sulphide.

Pyrite
General
Category	Sulphide mineral
Formula (repeating unit)	iron disulfide (FeS2)
Identification
Color	Pale brass-yellow, tarnishes darker and iridescent
Crystal habit	Cubic
Crystal system	Isometric Diploidal, Space group Pa3
Mohs scale hardness	6–6.5
Luster	Metallic, glistening
Streak	Greenish-black to brownish-black; smells of sulphur
Specific gravity	4.95–5.10
Solubility	Insoluble in water
Other characteristics	paramagnetic

Uses

In the 16th and 17th centuries, pyrite was used to create sparks in early firearms called wheellocks. The Kaurna people of South Australia also used pyrite with flintstone and bark to start fires in their traditional way.^[8][9]

Since ancient times, pyrite helped make copperas (ferrous sulfate) by letting it weather in big heaps. By the 19th century, this method replaced burning sulfur to produce sulfuric acid. Even today, pyrite is used to make sulfur dioxide for the paper industry and to manufacture sulfuric acid. Heating pyrite also gives iron sulfide (FeS) and elemental sulfur.^[10][11]

In modern times, pyrite has new uses. It works as the cathode material in some Energizer lithium batteries. Pyrite is also a natural semiconductor with a band gap of 0.95 eV and is naturally n-type because of tiny sulfur gaps in its structure.^[12][13][14]

In the early 1900s, pyrite was used in crystal radios as a detector. Some hobbyists still use it today, and it can work as well as modern germanium diodes.^[15]

History

Pyrite is the most common sulphide mineral. In ancient Roman times, the name was applied to several types of stone that would create sparks when it was struck against steel. Pliny the Elder described one of them as being brassy, which was almost certainly a reference to what is now called pyrite.^[16]

By Georgius Agricola's time, the term had become a generic term for all sulphide minerals.^[17]

Pyrite is usually found associated with other sulphides 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 amounts of gold.

Gallery

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  Pyrite cubic crystals
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  Pyrite mine in Slovakia
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  Crystals from Italy
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  Ammonite with Pyrite