One of the characteristics of gold is its softness, so when setting gems, it is easy to fall off because of insufficient strength. Therefore, people add silver, copper, zinc and other metals to gold to increase its strength and toughness. The gold ornaments made in this way are also called K gold. In jewelry inlaying, almost all gems are inlaid with K gold with different K numbers. This not only makes gold noble, but also makes up for its shortcomings, and can be made into various colors as needed. K gold is the most commonly used and diverse material in jewelry.

The relationship between k number and gold content: Au wt% = K/24 × 100%.

According to the national standard GB 1 1887-89, the gold content per k is 4. 166%, and the purity range is as follows:

The minimum value of the purity of K gold, in units of one thousandth.

8K 333

9K 375

10K 4 17

12K 500

14K 585

18K 750

20K 833

2 1K 875

22K 9 16

Note: 24 is theoretical purity, and its gold content is 100%.

The weight of gold ornaments shall use the national legal unit of measurement. Its gold content should use "K gold" (excluding 24K gold), pure gold (with a gold content of not less than 99%) and thousands of gold (with a gold content of not less than 99.9%), and non-standard methods such as "thousands of gold", "pure gold" and "24K gold" that do not actually exist should not be used.