Ferrosulfur – one of the most abundant   sulphide in the Earth crust.  Large deposits of it concentrated in the fields of hydrothermal origin, pyrites deposits, sedimentary and metamorphic rocks. In addition  ferrosulfur  formed in small quantities in magmatic processes. In  ferrosulfur  sedimentary rocks formed in a closed sea basins like the Black Sea, as a result of the deposition of hydrogen sulfide.
In Russia, pyrite deposits are located in the Urals (Degtyarskoe, Kalatinskoe, Berezovskoye gold, etc.), in Altai, the Caucasus and elsewhere. In the world - in Kazakhstan, Norway, Spain (Rio Tinto), Italy, on the island of Cyprus, the United States, Canada and Japan.
Ferrosulfur  is the raw material for sulfuric acid, sulfur and iron sulfate, but recently, rarely used for these purposes. In large amounts, it is extracted in the development of the hydrothermal deposits of copper, lead, zinc, tin and other nonferrous metals. But the processing of  ferrosulfur  into useful components are usually inefficient, and it is sent to dumps.