Unless you SPECIFICALLY...FULLY.....TRUST the source, be VERY careful about buying anything labeled "wrought iron" sight unseen. It is likely one of the most fraudulent things sold when it comes to blacksmithing/forging/metals. As far as I know, there is only ONE modern source of actual wrought iron, and it is out of England. "Old" wrought is still findable, usually in the form of OLD wagon wheels, and one source many overlook are old iron bridges, and RR water towers. I have horded my own "stash" over the years...... and use it only for very special ironwork/ornamental projects.
As it applies to knives, wrought is far overrated for by most knifemakers for use, and unless a client specifies it, I do not use it on knives. Why? Unless anyone looking at the knife specifically knows wrought iron (such as those buyers who are knowledgeable enough to know/understand it, and how it's suppose to look).....they are going to think you have flaws in your work/knife (During my career, I've seen knifemakers get their bubble busted at shows time and again by using wrought, and folks walking up to their table(s) and ask "what happened there?")..... that is unless you "refine" it enough to eliminate the silicon slag...... then you might as well be using mild steel.