no. 1949 for the year 2007 which includes the following:
If a person borrows gold from another intending to return it in kind and in its original weight, how should he repay it if the creditor agrees to take its value instead? Is it calculated according to its weight at the time it was borrowed or at the time it is returned?
 

The principle is that borrowed gold must be returned in kind and in its original weight. If the creditor accepts to take the value of the gold, then it must be calculated according to its value at the time it is returned and not at the time it was loaned. This is because the principle is that gold must be returned as gold. Allah Almighty knows best.