system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why gold is referred to when we are speaking of wealth, even though platinum is rarer, less reactive and more expensive?
gpt
Gold, as a metal independent of other metals, has been known since the dawn of history, named and readily identifiable. It has a melting point when pure of about 1000°C — which is pretty high for a metal. It occurs unalloyed in nature fairly often.

Platinum was unknown as an independent metal in Western society until the 1500's — and then solely because *conquistadores* discovered (stole) Native Central American artifacts made from it. It is often alloyed naturally with other silver-white metals, and often mistaken for other silver-white metals. It melts at about 1700°C, higher than what most refineries operated at until they understood what platinum is.

Gold is rare, but readily identifiable — of all the metals, it and copper are the only ones that are not naturally some sort of silvery-white in their unoxidised states. So until fairly recently, platinum was unknown or unidentified or mistaken for silver.

There are any number of other rare — and therefore precious — silver-white metals; platinum today is fairly valuable specifically because it is useful, as a rapid catalyst of a number of chemical reactions. That is generally why it is more expensive — there's a high utility demand for it. Gold is so expensive today primarily because there is a high utility demand for it — in electronics.