Wikipedia
Iron(II) sulfide or ferrous sulfide (Br.E. sulphide) is a chemical compound with the formula . In practice, iron sulfides are often iron-deficient non-stoichiometric. Powdered iron sulfide is pyrophoric (ignites spontaneously in air).
Iron sulfide or Iron sulphide can refer to a range of chemical compounds composed of iron and sulfur.
Iron(III) sulfide, also known as ferric sulfide or sesquisulfide, is one of the three iron sulfides besides FeS and FeS. It is a solid, black powder but decays at ambient temperature into a yellow-green powder.
This is a relatively unstable artificial product that does not occur in nature.
Iron(II,III) sulfide is a blue-black (sometimes pinkish) chemical compound of iron and sulfur with formula FeS or FeS·FeS, which is much similar to iron(II,III) oxide. It occurs naturally as the sulfide mineral greigite and is magnetic. It is a bio-mineral produced by and found in magnetotactic bacteria. It is a mixed valence compound, featuring both Fe and Fe centers, in 1:2 ratio.
Usage examples of "iron sulfide".
It might be any of a number of things, but he would have bet on its being some variety of impure iron sulfide.
This process has accelerated here in the rainy season due to the high iron oxide and iron sulfide content in the soil.