Neodymium Oxide or Neodymium Sesquioxide is the chemical compound composed of neodymium and oxygen with the formula Nd2O3. It forms very light grayish blue hexagonal crystals. The rare earth mixture didymium, previously believed to be an element, partially consists of Neodymium Oxide.
Neodymium Oxide is used to dope glass, including sunglasses, make solid-state lasers, and to color glasses and enamels. Neodymium-doped glass turns purple due to the absorbance of yellow and green light, and is used in welding goggles. Some Neodymium-doped glass is dichroic; that is, it changes color depending on the lighting. One kind of glass named for the mineral alexandrite appears blue in sunlight and red in artificial light. 7000 tonnes of Neodymium Oxide are produced worldwide each year. Neodymium Oxide is also used as a polymerization catalyst.