_Hematite_ (sesquioxide of iron) is the ore which supplies three-fourths of the iron of commerce.
_Limonite_ brown (hematite) is a hydrous oxide and furnishes nearly one-fourth of the world’s supply of the metal. Magnetite and siderite are less common ores.
_Pig iron_ is the crude form of the refined metal and is transformed into cast iron, wrought iron and steel in their multitudinous forms.
These three forms of iron differ in hardness, strength, elasticity, malleability, etc., according to the amounts of carbon, sulphur, phosphorus, manganese and other elements.
_Ochers_ and metallic paints are iron oxides. _Prussian blue_ and _copperas_ are iron compounds.
The United States manufactures more iron and steel than any other country. Almost half of the production is in Pennsylvania. _Cast iron_ appears in many articles but is weaker than other forms of iron. _Wrought iron_ contains less impurity and is used for bars, plates, wire, structural material and parts of machinery. _Steel_ (Bessemer, Siemens-Martin, open hearth, etc.) contains more carbon than wrought iron, possesses both strength and hardness, and is used for rails, structural material, machinery, tools, wire rope, sheet steel, etc. Its hardness may be increased by tempering. The United States imports iron ore from Cuba and Spain, pig iron from Great Britain and a little manufactured iron and steel from Europe. We export large quantities of manufactured iron and steel.
=Lead= is the softest, heaviest, most malleable and most easily melted of the common metals. Its ores are found in many countries but the main supply is from the United States, Spain, Germany and Mexico. The chief lead mines of the United States are in Missouri, Idaho, Utah, Colorado and Kansas. Much lead bullion is from smelters where silver ores are reduced.
_Galena_ (lead sulphide) is the only important ore; it often carries a considerable percentage of silver. Carbonates and sulphates of lead are less common. _Solder_ and _type metal_ are alloys of lead with tin and antimony. _White lead_ is a carbonate, _red lead_ and _litharge_ are oxides. _Chrome yellow_ and _orange mineral_ are lead compounds used as pigments.
The chief use of metallic lead is in piping, sheet lead, shot and alloys. Large amounts of ore are transformed not into metallic lead but into white lead for use in paints. Lead ores and lead bullion are imported from Mexico. England is the greatest importer of lead and lead ores.