White gold is actually yellow gold that has been alloyed with different metals to make it whiter. 18k (18ct carat) gold is made up of 18 parts out of 24 parts gold. (24 carat being pure gold). The other 25% of the mixture is used to colour the metal or give it specific working properties. White gold is white, but with a hint of greyish yellow. Platinum on the other hand is purely white. White gold is plated with a white metal called rhodium (basically platinum), which makes a white gold and a platinum ring look identical at point-of-sale. But, the plating does rub away with wear. Depending on how rough the wearer is on the ring it normally takes 6 months to 18 months to be very noticeable. Some people don’t mind, but it definitely makes the ring look better and the diamond sparkle more when the ring is polished and rhodium plated. Platinum doesn’t have this problem.