What does the jewelry mark 14K Cu mean?

The jewelry mark "14K Cu" indicates that the piece is made of 14-karat gold that contains copper as part of its alloy. In this case, "14K" signifies that the gold is 58.3% pure gold, while "Cu" denotes that copper is one of the metals mixed with the gold, likely to enhance its durability and color. This combination is common in gold jewelry, as copper can give a warm hue and improve the metal's strength.