Opal and green/purple tantalum earrings, 1976.
© Science Museum / Science & Society Picture Library
Tantalum was first isolated pure in 1903 by the German scientist Werner von Bolton. A heavy blue-grey transition metal, it is particularly useful as a material for surgical implants because of its lack of reaction to body fluids. Tantalum is also used in alloys because of its hardnes and resistance to corrosion. The colour of these pieces of jewellery is obtained by heating the metal.