The largest reservoir of sulphur in the biosphere is the

The largest reservoir of sulphur in the biosphere is the Rocks.
Sulphur may be found by itself and historically was usually obtained in this form; pyrite has also been a source of sulphur. Sulphur deposits were piled and stacked in brick kilns built on sloping hillsides, with airspaces between them.
Mining was unmechanized and labor-intensive, with pickmen freeing the ore from the rock, and mine-boys carrying baskets of ore to the surface, often through a mile or more of tunnels.