Bog iron, also known as limonite, is a natural mineral that is commonly found in wetlands. It is a type of iron ore that is formed through the precipitation of iron and mineral deposits in acidic environments. Bog iron is an important source of iron and has been used for thousands of years in the production of tools, weapons, and other metal objects. Some synonyms for bog iron include iron oxide, iron hydroxide, and rust. Other similar minerals that can be found in bogs and wetlands include pyrite, marcasite, and siderite. Bog iron is also sometimes referred to as swamp ore or marsh ore. Despite its importance in the past, the use of bog iron has largely been replaced by more efficient methods of iron production.