10 Francs Elephant, iridium

Iridium is the second-densest naturally occurring element and one of the rarest in the Earth's crust, found primarily as a byproduct of platinum and nickel mining. Rwanda's use of it here places this piece among a very small number of iridium coins ever struck for any issuer — the metal's extreme hardness makes it genuinely difficult to work with at the die stage, and most mints avoid it entirely. The 2014 date aligns with a period when the National Bank of Rwanda was aggressively diversifying its commemorative bullion program into exotic precious metals to attract specialist collectors.