Uses
Pyrite enjoyed brief popularity in the 16th and 17th centuries as a source of ignition in early firearms, most notably the wheellock, where the cock held a lump of pyrite against a circular file to strike the sparks needed to fire the gun.
Pyrite has been used since classical times to manufacture copperas, that is, iron(II) sulfate. Iron pyrite was heaped up and allowed to weather as described above (an early form of heap leaching). The acidic runoff from the heap was then boiled with iron to produce iron sulfate. In the 15th century, such leaching began to replace the burning of sulfur as a source of sulfuric acid. By the 19th century, it had become the dominant method.
Pyrite remains in commercial use for the production of sulfur dioxide, for use in such applications as the paper industry, and in the manufacture of sulfuric acid. Thermal decomposition of pyrite into FeS (iron(II) sulfide) and elemental sulfur starts at 550 °C; at around 700 °C pS2 is about 1 atm.
Pyrite is a semiconductor material with band gap of 0.95 eV.
During the early years of the 20th century, pyrite was used as a mineral detector in radio receivers, and is still used by 'crystal radio' hobbyists. Until the vacuum tube matured, the crystal detector was the most sensitive and dependable detector available- with considerable variation between mineral types and even individual samples within a particular type of mineral. Pyrite detectors occupied a midway point between galena detectors and the more mechanically complicated perikon mineral pairs. Pyrite detectors can be as sensitive as a modern 1N34A diode detector.
Pyrite has been proposed as an abundant, inexpensive material in low cost photovoltaic solar panels. Synthetic iron sulfide is used with copper sulfide to create the experimental photovoltaic material.
Pyrite is used to make marcasite jewelry (incorrectly termed marcasite). Marcasite jewelry, made from small faceted pieces of pyrite, often set in silver, was popular in the Victorian era.
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