Platinum. Because platinum is rarer than gold; Platinum's qualities are more outstanding than gold's; Refining platinum is more difficult than gold and requires a higher level of craftsmanship, so platinum is more expensive than gold.
Platinum is more expensive than gold because it is the rarest precious metal in the world and can only be mined in very few places around the world (mainly in South Africa and Russia). If all the platinum in the world were poured into an Olympic-sized swimming pool, it would not be deep enough to cover the instep.
Platinum has outstanding qualities that no other metal can match: it is extremely dense, tough and durable, and it can remain stable in a variety of extreme environments, so that it can remain white as before and never fade.
Moreover, platinum is more difficult to refine than gold and requires a lot of energy: ten tonnes of ore can be refined into just one ounce of platinum in eight weeks; By comparison, one ounce of gold takes five tons of ore in five days. At the same time, processing platinum requires a higher level of craftsmanship than processing gold, and each step of the process technology needs to be very precise.