Platinum in the United States is usually 90 - 95 % pure platinum. Compared to 18K gold, which is 75 % pure gold, or 14K gold, which is 58.5 % pure gold, the purity of platinum is much higher. The higher degree of purity in platinum also makes it hypoallergenic. To ensure that a piece of platinum jewelry meets the highest standards, look for Platinum, PLAT, PT950 or PT900 stamped inside the jewelry.