Gold jewelry is typically measured in karats (K), which indicates the purity of the gold. 24K gold is considered pure gold,  18K gold is made by mixing 75% gold with 25% other metals. 14K gold is made by mixing 58.3% pure gold with 41.7% other metals. The other metals used in the alloy can vary, but commonly include copper, silver, or zinc. These additions define the color of the gold.  The purpose of adding these metals is to enhance the durability and strength of the gold, as pure gold (24K) is relatively soft and may not be suitable for certain types of jewelry that require more resilience. 14K gold is a popular choice for jewelry as it offers a good balance between purity, durability, and affordability.