Were you aware that the gold in jewelry is not pure gold? Pure gold is called 24 Karat (24K) gold. 24K gold is much too soft to make any durable jewelry! So, pure gold is alloyed (mixed) with other, stronger metals. So, if 24K gold is 100% gold, 14K is 50% gold, and 18K is 75% gold.
Gold is alloyed with copper and silver for strength. Rose gold is an alloy of gold and copper. White gold is an alloy of gold, silver, and palladium, nickel, zinc or other white metal. Green gold is an alloy of gold and silver.
Below: 14K solid gold bead ring. Ring & photo by Emily Wiser.