Originally posted by Cooperal:

Yes. And copper ore somehow gets 20% heavier when you smelt them down to bars. The devs are under no obligation to make the game realistic but I see where you are coming from.

Metal usually is denser than the waste rock from which it is extracted. Depending on how much waste is in the ore, ingots could be more or less heavy.

Smelting scrap iron should have no effect on weight. I was smelting on site for about ten hours before this thought crossed my mind. :)