This scarce metal is much in use by artists for jewelry due to the gorgeous colors it sports when anodized. Anodization is the application of an electrical current of two metals in opposite charges through an electrolyte. In this case, niobium acts goes on the positive side of the current acting as cathode. As electricity passes through it, pure oxygen forms on the surface from the breakdown of water into hydrogen and oxygen (hydrogen forms at the sacrificial anode). This oxygen immediately oxidizes a microscopically thin layer of niobium. This changes the properties of light being reflected off the bulk of the metal underneath as it absorbs different wavelengths. By varying the voltage of the electricity the oxide layer's depth varies accordingly and reflects different wavelengths of light thus allowing for the possibility for several different hues. As it's not paint it won't discolor or wash off unless physically gouged out.

CAS 7440-03-1