Iron(II) sulfide

sulphide) is one of a family of chemical compounds and minerals with the approximate formula FeS.

As organic matter decays under low-oxygen (or hypoxic) conditions such as in swamps or dead zones of lakes and oceans, sulfate-reducing bacteria reduce various sulfates present in the water, producing hydrogen sulfide.

When eggs are cooked for a long time, the yolk's surface may turn green.

[4] The presence of ferrous sulfide as a visible black precipitate in the growth medium peptone iron agar can be used to distinguish between microorganisms that produce the cysteine metabolizing enzyme cysteine desulfhydrase and those that do not.

Peptone iron agar contains the amino acid cysteine and a chemical indicator, ferric citrate.

Sample of iron(II) sulfide
Sample of iron(II) sulfide
NFPA 704 four-colored diamond Health 1: Exposure would cause irritation but only minor residual injury. E.g. turpentine Flammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuel Instability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorus Special hazards (white): no code
An overcooked hard-boiled egg , showing the distinctive green coating on the yolk caused by the presence of iron(II) sulfide