18K

18K refers to an alloy of gold containing 75% gold by weight. In the karat system, pure gold is 24K, so 18K equals 18/24. The remaining 25% consists of other metals such as copper, silver, nickel, or palladium, added to adjust color, hardness, and durability. The exact composition varies by manufacturer and region.

Color and alloys: Yellow 18K is the traditional color, while white 18K uses white metals and is often plated with rhodium to enhance whiteness. Rose 18K contains more copper, giving a reddish hue. The specific mix determines hardness and workability as well as color.

Properties and uses: Higher gold content yields richer color but softer metal. 18K is harder and more resistant to bending than 24K gold, yet less durable than 14K or 10K for heavy wear. It is widely used in fine jewelry—rings, bracelets, necklaces—and in luxury watches. White gold can contain nickel, which may provoke allergies; many pieces are rhodium-plated to maintain light color.

Care, value, and standards: 18K gold is more expensive than lower-karat gold due to its gold content. Hallmarks include 18K or 750 in many markets; 750 denotes 75% gold by weight. Prices fluctuate with gold markets and craftsmanship. While gold itself does not tarnish, alloy metals can affect appearance and durability over time.