Iron sulfide (FeS) is a chemical compound formed from iron and sulfur. It occurs naturally as the mineral pyrite and is often found in sedimentary rocks. In food and spice contexts, iron sulfide is not typically present, but it can form during the cooking of certain foods, especially those high in sulfur compounds. It is known for its black color and can impart a metallic taste when present in food. Iron sulfide is also used in various industrial applications, including the production of iron and as a catalyst in chemical reactions. Its presence in food is generally not desirable due to potential toxicity and off-flavors.