Niobium - Wikipedia
Niobium, also known as columbium, is a chemical element with the symbol Nb (formerly Cb) and atomic number 41. Niobium is a light grey, crystalline, and ductile transition metal.Pure niobium has a Mohs hardness rating similar to that of pure titanium, and it has similar ductility to iron.Niobium oxidizes in the earth's atmosphere very slowly, hence its application in jewelry as a ...