Sulfur is a flammable material used to craft various objects, such as PowerCells or Batteries for power storage, or Explosives or MustardGas for weaponery. Sulfur is obtained in mountains either using the Pickaxe or machinery such as Extractors
When set on fire with a fire-starting device (Flint, Igniters, etc) or another burning part, It will burn for a short time with a blue flame.
In-game description
"A yellow flammable solid. Being set on fire gives it a special blue fire. "