Lead Hammer

Lead and iron sit on the same rung, so the only question is which ore your world handed you. Coming up from the copper tier, the difference shows up when you are stripping background walls out of a cave or squaring off a room, which is what hammers spend most of their working life doing.

Keep it away from the reforge anvil. The mining speed bonus rounds to an identical number across most of the good modifiers, and you will replace the tool outright the moment you reach the gold tier anyway.