Template:POTD/2015-12-30
Pellets of 99.9% pure argon-arc remelted hafnium, with visible crystalline structures. The colors are a thin-film effect in the oxide layer; this chemical element is generally a lustrous, silvery gray, tetravalent transition metal. Hafnium is widely used in filaments and electrodes, as well as in some superalloys.Photograph: Heinrich Pniok