An alloy any metal made by combining two or more different metals into something new. Precious metals like silver, gold, platinum and palladium are elemental, meaning they are each their own element and not made of anything else. When referring to jewelry, an alloy is typically one or more of those precious metals combined with another elemental metal to increase durability and/or produce a new color of metal. Silver is often combined with copper to create sterling silver. Gold is combined with different amounts of copper, silver, zinc or palladium. Gold alloys are defined by their color (yellow, white, rose, green) and the number of parts of elemental gold used in the alloy (10k, 14K, etc.). An 18K yellow gold ring is made of 18 parts (75%) pure gold and 6 parts (25%) other metal.