The most common and most useful metallic element, being of
   almost universal occurrence, usually in the form of an oxide (as
   hematite, magnetite, etc.), or a hydrous oxide (as limonite, turgite,
   etc.). It is reduced on an enormous scale in three principal forms;
   viz., cast iron, steel, and wrought iron. Iron usually appears dark
   brown, from oxidation or impurity, but when pure, or on a fresh
   surface, is a gray or white metal. It is easily oxidized (rusted) by
   moisture, and is attacked by many corrosive agents. Symbol Fe (Latin
   Ferrum). Atomic weight 55.9. Specific gravity, pure iron, 7.86; cast
   iron, 7.1. In magnetic properties, it is superior to all other
   substances.