One of the most abundant non-metallic elements on the planet, sulfur is a multivalent material that is typically found in bright yellow crystals that remain solid at room temperature. Additionally, sulfur is reactive with all other elements on the periodic table with the exception of iridium, gold, tellurium, platinum and all of the noble gases. Though naturally occurring deposits of sulfur do exist, sulfur is more typically found in the form of sulfide and sulfate minerals. As one of the oldest known chemical elements, it is mentioned in the earliest histories of India, China, Greece, and Egypt, wherein it was often referred to as brimstone. Today, nearly all sulfur produced industrially is a byproduct of extracting sulfur-containing contaminants from petroleum and natural gas during the refining process. The industrial process that consumes the most sulfur is the manufacturing of sulfuric acid for use in phosphate and sulfate fertilizers, as well as commercial products such as insecticides and fungicides.