Pure iron is barely harder  and stronger than copper. Impurities are to iron, what paint is to an artist’s canvas.

Red Ochre is Iron

The problem with iron at this level of purity is that it is too soft and too ductile for most commercial uses.

This means that the iron products that we know and recognize are relatively and deliberately impure.
Iron also has three allotropes or crystal forms,  delta iron (body centered cubic) gamma (face centered cubic) and alpha, body centered cubic. I was originally taught* that delta and alpha iron were the same allottrope, a distinction that now appears to be a chrming sign of old age… and the addition of impurities (alloying elements) have different solubilities based on these forms.
It is the addition of carbon and other elemental impurities which alter these allotropic forms that gives commercial iron and steel products their diverse properties.
When we look on the material certs that accompany our steel products , the first element that is reported is carbon. Carbon is ubiquitous, and has the dominant effect on the behavior of the iron based product to which it is part, even in the presence of large amounts of alloying elements.
What is implied by the certs is that after adding up all of the elements reported, the balance of the material is “iron.”
In 2009 world Iron and steel production was estimated to be 1,219.7 million metric tonnes.

Physics trivia: Iron is the heaviest atom that can be made by the fusion of stars. Iron is is the ‘ash’ of stellar nuclear fusion. Iron is abundant- the fifth most abundant element on earth, and sixth most abundant in the universe. Our blood is red because of iron, and since iron is an essential part of our bodies, we can truly  claim that we are “Stardust.”  

"We are Stardust, We are golden, We are billion year old carbon, and we got to get ourselves, back to the garden."

Iron is essential  to almost all living things indeed it is key to the working of hemoglobin and oxygen transfer in humans, as well as in enzymes that are involved in the creation of DNA.
Our bodies store surplus iron in the liver, to cover for those days when we do not get our required 7 to 11 milligrams of daily iron.

When properly contaminated with carbon, manganese, a sprinkle of sulfur or phosphorous, iron makes some damn fine precision machined parts too!

Mostly iron, but the cert doesn't say so

  *I was originally taught= Alloying Elements in Steel by Edgar C Bain and Harold W Paxton, 2nd edition:
“The metal iron, as shown in figure 1., exists in two isometric allotropic crystal forms: (1) alpha  and delta iron, whose solid solutions are called ferrite (or delta ferrite) and (2) gamma iron whose solid solution is is austenite.”

Cave painting
Lyrics by Jodi Mitchell, performed by Crosby, Stills, and Nash.