Still easy enough on Vulcanus though, thanks to infinite resources from infinite lava.
legendary coal -> plastic - > low density structures.
Coal is the only solid ingredient needed in this whole chain. Then that can be recycled to make legendary copper and steel.
legendary calcite -> stone (lava to molten copper recipe) -> concrete
Then that concrete can be recycled to make legendary iron ore.
Or, if energy/space isn't of huge concern to you: a lot of foundries with quality, and just dump anything that's not legendary into the lava.