Platinum
Platinum exists in higher abundances on the Moon and in meteorites. Correspondingly, platinum is found in slightly higher abundances at sites of bolide impact on Earth that are associated with resulting post-impact volcanism, and can be mined economically; the Sudbury Basin is one such example.
Platinum as an investment
Other ways of investing in platinum include spread betting or contracts for difference on the price of the metal, owning shares in mining companies with substantial platinum assets or exposure, owning traded options in platinum (only available in the US market).