Karat is the unit of measurement that expresses how pure the gold in a piece of jewelry actually is. Pure gold is rated at 24 karats, meaning it contains no other metals mixed in. Every step down from 24k represents a proportionally smaller share of actual gold: 18 karat gold is 18 parts gold and 6 parts other metal, 14 karat is 14 parts gold and 10 parts other metal, and 10 karat sits just above 41% pure gold, which is the legal minimum for gold jewelry sold in the United States. The remaining percentage in each alloy is made up of metals such as silver, copper, zinc, or nickel, depending on the piece's intended color and durability.
Karat stamps appear on the inner surface of rings, on the clasps of necklaces and bracelets, and on the posts of earrings. Common marks include 10k, 14k, 18k, and 24k, along with European hallmarks like 417 (10k), 585 (14k), and 750 (18k) – those three-digit numbers represent the parts-per-thousand gold content. The lower the karat, the more alloy metal is present in the mix. That ratio directly affects the metal's hardness, color, tarnish resistance, and overall durability. Higher-karat gold tends to have a richer, more saturated color; lower-karat pieces are harder and more scratch-resistant because the alloy content stiffens the metal.
Karat is the first thing a bench jeweler needs to know before starting any repair. Higher-karat gold is softer and shapes more easily but requires careful heat management. Lower-karat pieces are more resilient but need solder that exactly matches the metal's composition – using mismatched solder creates visible discoloration and weak joints. At QJR, every piece is tested before work begins to confirm the karat, ensuring the right solder is used, sizing is done safely, and the finished repair holds up exactly as it should.