Platinum
In the early 2000s to 2008, the price of platinum was much higher than the prices of gold and palladium. Its price today is historically low, leading to the closure of mining sites.
Platinum is even more limited than gold and according to some analysts, the exploitation of this resource would dry up around 2065.
The only available sector would be recycling, but it has shown that the returns were very low. Many mints have started to strike coins with a face value. Some are already speculating on a future bull market.