One particularly promising biosignature is the iron-sulfur mineral pyrite—"fool's gold"—which is abundant in hydrothermal vents on the ocean floor. Pyrite can either be formed directly or ...

sulfur can take many forms (or oxidation states)—elemental sulfur ions, mineral sulfate and sulfide gas. It does that by changing its valence, or the number of negative charges, during the ...

A different water-bearing layer may or may not be sulfur-free. Generally, the deeper the well, the higher the mineral and sulfur content. Clark, G. Douglas, ed., The Indiana Water Resource, ...