The use of iron ore in modern industry is second only to the use of petroleum, as a raw natural resource. Iron ore is found naturally occuring in the Earth and has many widespread applications. The natural element iron is smelted from the ore itself. The first stage most iron goes through in processing is to make what is known as pig iron, which is one of the precursors to making steel. Iron ore comes in lots of different colors, ranging from brown, to purple, to dark rusty red. Most iron ores are iron oxides; depending on the ratio of iron atoms to oxygen atoms, the color of the compound can fluctuate. Many appliances are still made principally from steel; steel is still an important component used by the automotive industry. As far as I can see, iron doesn't have too many limitations. It occurs naturally within the Earth, there seems to be no end in sight.