Rhenium oxide is a chemical compound composed of rhenium and oxygen atoms. Its chemical formula is ReO3, and it is a black or dark gray solid with a crystalline structure. Rhenium oxide is a highly refractory material with a very high melting point and excellent thermal stability, which makes it useful in high-temperature applications such as furnace linings and electrical contacts. It is also used as a catalyst in various chemical reactions, including the production of synthetic ammonia and in the dehydrogenation of alcohols. Rhenium oxide is a relatively rare material and is generally produced as a byproduct of other mining and refining processes. It has a number of unique properties that make it valuable in a variety of industrial and scientific applications.