Karat, or K, refers to the percentage of gold in jewelry. Items labeled 18K, 14K, or 10K contain gold mixed with another metal, and items falling below 10K cannot be called gold. 24K indicates 100 percent gold; also referred to as solid gold. 18K indicates 75 percent gold. 14K indicates 58.3 percent gold. 10K indicates 41.7 percent gold.