Is it permissible to consider the fineness of gold in lending and exchanging gold, such that 5 grams of 21-carat gold are exchanged for 5 grams of 24-carat gold with a cash payment for the difference in fineness, or that 7 grams of 21-carat gold are exchanged for 5 grams of 24-carat gold, so that the difference in weight compensates for the difference in fineness?

Gold is one of the usurious commodities (amwal ribawiya). When selling it or exchanging it for the same kind, two conditions must be met: immediate possession (al-taqabud) at the time of the contract, and equality in quantity according to Islamic law, meaning no increase or decrease in weight is permissible. Equality is not achieved when exchanging mixed gold, such as 21-karat gold, for pure 24-karat gold, due to the known difference in their value. The Shariah Standards stipulate that when selling mixed gold containing non-essential additives (for calibration or coloring), it is obligatory to ensure immediate possession and verify the equality of the net weight of pure gold in both exchanged items.

Therefore, whoever wishes to exchange gold for another kind must observe equality in weight and karat. Alternatively, they can sell their gold for banknotes and then use the proceeds to purchase the gold they desire.