Sulfur
Sulfur is a byproduct of cooling down Sour Gas into Methane.
Usage
Its softness and low melting point makes it an interesting material to generate "natural" tiles for Pip farms.
Grubfruit Plants requires 10 kg per cycle of Sulfur as fertilizer.
Sweetles eat 20 kg per cycle of Sulfur.
Molecular Forge produces Fullerene from Sulfur, Aluminum, and Graphite:
Production
When cooling down Sour Gas to -163.5 °C (condensation point -2 °C), it will turn into Methane (67% mass) and Sulfur (33% mass).
Sulfur does not occur naturally on most Vanilla asteroids, except for the Aridio Asteroid where it spawns in the Rust Biome.
In the Spaced Out DLC it appears in the Wasteland Biome, the Radioactive Biome, and is produced in liquid form by Sulfur Geysers.
It can be harvested on rocket missions from renewable Radioactive Asteroid Fields.