Cold wrought iron, what is it?

[radferth]

Reading some links off Conaill's bog iron link, one sees that different sources of iron ore have different impurities and may require different processes to make the right mix for good steel. Wanting to stay with the DMG description that cold iron has the exact same properities of regular iron, only it hits some things, I just assumed that only some sources of iron ore had the right mixture that they could be forged at the not-quite-so-hot-temperatures that produced cold iron. The exact explanation would depend on how close to real-world physics your world uses, and what the nature of magic is. Since the average soldier would rarely care if their sword were cold iron, I rule that it my campaign cold iron it not common, but can be "special ordered" from any smith with proper knowledge and access to the right ore.