Erbium is one of the lanthanide or 'rare earth' metals, and is one of four elements named after the town of Ytterby in Sweden. Although the lanthanides aren't the most well known of the elements, they play an important role in modern life. Erbium is mostly used within fibre optics to amplify the signal - without erbium, there'd be no global communications as we know it. Although in its pure metallic form erbium is a typical shiny grey metal, its ions are pink in solution and form pink salts. Erbium oxide may be added to glass or zircona crystals to give them a tint. This Elemental cat is all done up with metallic thread and beads to trace a looping fibre optic pattern across its body, with pink beads to show off its colours, all finished off with a silver bow.