One of the prominent features of gold is flexibility, which makes it hard to produce various exquisite patterns and styles, in particular, pearl, stone and jade set on gold jewelry are likely to lose.
For this reason, it’s a common practice of jewelry makers to add traces of Ag, Cu, Zn and like metals in gold jewelry for additional strength and toughness, gold jewelry produced in this way is also called K gold jewelry.
K gold jewelry can be custom-made in various colors. Internationally popular K gold jewelry is available in various colors, of which most common varieties are yellow and white. Adding Pd or Ni in 25% gold will make white gold, of which gold is the main composition, and which is called white K gold jewelry.
With current level of scientific and technological development, it’s impossible to refine gold material of 100% purity. Therefore, in marked gold products, gold content is indicated by standard gold karats, and pure gold is generally called 24K gold, which means 100% gold content in theory, but it does not exist in reality. Thus, no gold content of gold jewelry is allowed to be marked as “24K gold” in a nonstandard way according to national standard currently in force. Since pure gold is marked as 24K gold, i.e. 100% gold content in theory, 1K gold represents 1/24 gold content in gold products, approximately 4.16%. 18K gold represents gold content of 18/24, equal to 75% gold content, with remaining impurities such as Ag or Cu.
It’s said that “gold can’t be hundred percent pure”, generally, gold jewelry contains less than 1% of other metal(s). Express criteria are set out in national standard for the purity of gold content in gold products, that the dealer must tag each piece of gold jewelry, clearly indicating its gold content and count of karats. The count of karats of all gold jewelries must be calculated according to national legal unit of measurement. The gold content should be marked with “K gold” (24K gold not included), “gold” (Gold content not less than 99%) or “pure gold” (Gold content not less than 99.9%), nonstandard tagging like “99.99% pure gold”, “pure gold”,”24K gold” and “9999 gold” are not allowed.