White Gold is a metal alloy, consisting of a mixture of gold and one or more white metals-- usually nickel, manganese or palladium. In the Chronicles of Thomas Covenant the Unbeliever, white gold can be used to channel Wild Magic.
During the First Chronicles and Second Chronicles, the only article of white gold in the Land is Thomas Covenant's wedding ring. At the end of the Second Chronicles, it passed to Linden Avery. During the Last Chronicles, Linden Avery has it with her, and uses it several times. However, Joan Covenant was also translated to the Land in the Last Chronicles, and she had her ring with her.