Sale of Gold and Silver against Gold and Silver

2127. If gold is sold against gold or silver is sold against silver, whether it is in the form of coins or otherwise, in case the weight of one of them is more than that of the other, the transaction is Haraam and void. 

2128. If gold is sold against silver or silver is sold against gold, the transaction is valid and it is not necessary that the weight of both the commodity should be equal.