Stone? Definitely the volcano. With the right tools and the right attributes, you can get approx. 21k in 15-20 minutes. There are many areas where stone nodes are clumped in such a way that one swing hits 2-4 nodes. If you know the volcano well, you can get 100k or more in less than two hours – a long slog, but that way you don’t have to do it too often.
If you need some stone really quickly, you can get something like 4k from the landslide inside the abandoned mine near the Jawbone. It’ll take you less than a minute to get those 4k, but that’s it – then you have to wait for it to respawn.
As for the iron, the two best locations are the Godsclaw Passage and the area around the Tower of Bats. You’ll get a slightly lower yield around the Tower of Bats, but it’s somewhat safer and less popular.
EDIT: I forgot to specify that all these figures are for official PVE(-C) servers. If your server has harvesting multipliers – and I’m not sure, but I think official PVP servers do – then apply those multipliers to what I wrote.