Sulfur

Sulfur (S), element 16. A highly reactive nonmetal useful for chemistry, especially the production of acids, and an essential element for life.

Historically known as brimstone, with applications in medication and fertilizer.

Some organisms use sulfur in their metabolism, even in the absence of oxygen. These sulfur-reducing organisms can form the base of a food web in deep sea habitats.

Assessment: search for elemental sulfur deposits near thermal vents or volcanic activity.