Silver
From Tolkien Gateway
Silver is a highly reflective gray or white metal referenced often by Tolkien in his legendarium. One of the Two Trees, Telperion, was silver in color if not in material. Mithril is said to highly resemble silver. Several examples of objects made of silver are the crown of Elu Thingol of Doriath, the silver harp of the House of the Harp in Gondolin, the Tree of Gondor, according to Bilbo the habergeon of Eärendil the Mariner (which, if true, suggests that silver was stronger in Middle-earth than in the real world), and one of the gates of Gondolin. As well, it was often referenced in titles and names (for example Celeborn, silver-tree, Celebrimbor, silver-hand, and Celebrindal, silver-foot).