An 18K gold necklace is valuable because it contains 75% pure gold, making it a popular choice for both luxury and long-term value. Its worth at a pawn shop depends mainly on the necklace's weight, current gold market price, purity, condition, and brand. Most pawn shops typically offer 55–75% of the necklace's melt value, while designer pieces or certified jewelry may receive higher offers. Before selling or pawning, check the live gold price, weigh your necklace, compare offers from multiple buyers, and verify its authenticity to ensure you receive the best possible value.