From Earth Science Picture Of The Day; February 6, 2014:
Photographer and Summary Author: Dave Lynch
Sulfur is easily recognized by its bright yellow color. In its native form elemental sulfur is usually associated with volcanic activity. These chunks came from Isola Vulcano, a small island north of Sicily in the Tyrrhenian Sea. All volcanoes derive their names from this Mediterranean island. Sulfur is one of 13 elements known to ancient people and is the 10th most common element in the Universe. Jupiter’s moon Io is yellowish because volcanoes continuously erupt sulfur – bottom photo [NASA image]
Sulfur’s chemical abbreviation is S, but its room- temperature crystalline structure is a cluster of eight atoms, or S8. Most sulfur on Earth is in the form of sulfates and sulfides like gypsum (CaSO4) and pyrite (iron sulfide, FeS2).
Sulfur is a necessary element for life, being essential for metabolism and respiration. It’s found in proteins, vitamins and amino acids. Many sulfur compounds are smelly. Odors from skunks, grapefruit, rotten eggs and garlic derive from sulfur compounds.