Ag2S, or silver sulfide, is a chemical compound made up of silver and sulfur. It appears as a black solid and is commonly found in nature as the mineral argentite. Silver sulfide is known for its low solubility in water and is often used in various applications, including electronics and photography. In addition to its industrial uses, Ag2S plays a role in the tarnishing of silver objects. When silver is exposed to sulfur compounds in the air, it can form a layer of silver sulfide, resulting in the characteristic black tarnish seen on silverware and jewelry.