Erbium

                  

• A Chemical Element in the Lanthanide Series with Symbol Er and atomic number 68.
• A Silvery White solid metal and it is always naturally found in chemical combination with other elements on earth. Erbium metal is readily oxidize in air and burns to form Erbium Oxide.
• Its salts are rose coloured and it has a sharp adsorption spectra in visible, ultraviolet & infrared light.
• The wavelength of erbium-emitted light at 1530nm falls very close to the ideal wavelength (1550nm) for minimal signal loss in optical fibers. 
• As a Photographic Filter and because of its resilience it is useful as a metallurgical additive.