Sulfur

One of the most valuable and sought after resources in rust, sulfur is useful to almost all players (with the exception of freshspawns) due to it being required to craft gunpowder, a resource necessary to create ammo as well as any explosive. It can be found in its ore form in sulfur nodes, identifiable by their distinct yellow colouring. This then needs to be smelted in a furnace in order to obtain its purified form seen here.