“Space casino” is gone from Factorio 2.1 as asteroid reprocessors don't take quality items anymore. Motivated by devs that it was 'just too easy' to get legendary items this way.
Michael Hendricks: Next time ...
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.
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.