damn, started with uranium and always have a shortage of the others, oh well

If you review the discussions you would see this questions has been answered multiple times . Please follow this link for a very detailed explanation with photo.
http://gamersunite.coolchaser.com/topics/67986-empires-allies-change-copper-in-iron-aluminium

Your ore is preselected, at random, when you first start playing the game.  There is at this time no way to change your ore production type.  (I don't think that's going to change.)  Those who have multiple markets for selling more then one type of ore simply have a surplus of more then one type of ore from looting and invading others.