Originally posted by The Phoenix:

Something I dont understand.
So you get say Copper Ore. Copper Ore Weighs 10 pounds
You put it into the thing to melt it down and remove the Impure parts
of the Ore. SO your taking away some Weigh of the Ore.
BUT As soon as it becomes a Bar. It Gains 2 pound making it 12 pounds
Where the 2 extra pounds come from?
it should not be heavier. It should be Lighter if not , then the same weight.

Because it is a magical world is the answer you are looking for.

Secondly, impure metals is why on a magical planet.