AOB: No idea, but if i had to guess i would say it is because gold is so heavy, but i doubt im right. What is the real reason?
mepal: The same way a gallon in the USA is a diffrent amount than the gallon in Canada, when measuring the weight of gold you use a diffrent scale than you would use for feathers so what we call a pound of gold weighed on the scale that is used for gold and took that same amount and put it on a scale used for feathers it would not be a pound of gold.