The primary difference between 18ct and 9ct gold is percentage composition of gold, where 18ct means 75 percent pure, or 18 parts pure gold and 9ct means 37.5 percent pure, or 9 parts pure gold. A 750 mark is typically stamped on 18ct pieces, while a 375 mark is branded on 9ct pieces.
Gold is a valuable metal that is commonly used in jewelry making. Twenty-four carat gold, designated as 24ct, is 100 percent pure gold. Due to its inherent malleability, gold is typically alloyed with other metals to increase its hardness. However, when gold is combined with other metals, its durability is decreased. The durability of 18ct gold is higher compared to 9ct gold. Although 9ct gold is harder than 18ct gold, it does not last as long as 18ct gold.