Pyrite, known since antiquity, had at one time a great strategic importance because it was the main raw material for making elemental sulfur for gun powder manufacture and for making SO2 for sulfuric acid production. However, when other sources of cheap elemental sulfur became available, pyrite not only lost its importance but became a nuisance for the metallurgical industry because of problems associated with its disposal. At present only pyrite-containing gold is treated by a variety of methods to recover gold.