I do like this idea. Iron and gold chunks/dust/nuggets (what have you) gives the player a more satisfying source for obtaining copious amounts of iron and gold without farming, large scale piston related builds, large scale rail systems, and full size beacon construction demand tons of iron and/or gold. It also coincides more with the rest of the mechanics of the game, specifically referring to the inability to obtain blocks in their "Organic" state without silk touch.
The Meaning of Life, the Universe, and Everything.
With gold nuggets and iron nuggets you will not need to smelt them, so no I prefer two new items, dust or chunk, it depends.
And my arguments are : coal are really frequent and can be obtained with tree, so why Fortune would no work with iron and gold? Especialy when I need a lot of gold without go in the nether to farm pigmen. In my games I have often more diamonds than golds, and I need gold to make subways. ^^
I forgot, I said "your right" in order to say "your authorization" in the sence of "you have the right". ^^
I would like this for gold. Even though it is "useless" it can be hard to come by at times. Iron, however, is very plentiful and easy to find. I feel like this should only be for gold, however, making dust for only one ore seems a bit strange... Possibly have it affect both iron and gold, but make it minimal. Even if you have fortune, you don't end up with a ton more of the ingots than you would have without fortune. Basically I am trying to say that it would need to be balanced.