The pale yellow element that commonly occurs in nature is sulfur. Sulfur is a nonmetallic element that belongs to Group 16 (the chalcogens) of the periodic table. It is the 10th most abundant element in the universe and the 16th most abundant element in the Earth's crust. Sulfur is found in a variety of forms, including elemental sulfur, sulfide minerals, and sulfate minerals. Elemental sulfur is a yellow, brittle solid that is insoluble in water. It is found in volcanic deposits and in certain sedimentary rocks. Sulfide minerals are compounds that contain sulfur and a metal. Some common sulfide minerals include pyrite (iron sulfide), galena (lead sulfide), and sphalerite (zinc sulfide). Sulfate minerals are compounds that contain sulfur and oxygen. Some common sulfate minerals include gypsum (calcium sulfate), barite (barium sulfate), and celestite (strontium sulfate).