18-karat gold is a popular choice for fine jewelry, including neckpieces, due to its higher gold content and durability. As mentioned earlier, 18K gold contains 75% pure gold and 25% other metals, making it more resistant to tarnishing and scratches compared to higher-purity gold.Overall, an 18CT gold neckpiece with American diamonds can be an attractive and budget-friendly choice for those who desire the look of diamond jewelry without the higher price tag associated with natural diamonds.