White gold's properties vary depending on the metals and proportions used. As a result, white gold alloys can be used for different purposes; while a nickel alloy is hard and strong, and therefore good for rings and pins, gold-palladium alloys are soft, pliable and good for white gold gemstone settings. The highest quality white gold is usually at least 18 karat, and made up of gold and palladium, sometimes with other metals like copper, silver, and platinum for weight and durability, although this often requires specialized goldsmiths.
While some higher-quality white gold alloys retain their shine and lustre, most will be coated with a very thin layer of rhodium. This gives the naturally more-dull white gold a shine comparable to platinum or silver; however the rhodium may wear off over time.