I picked up a gold ring and took it to the gold shop for consultation. It said it was hard gold. What is hard gold, please

Gold has a characteristic that its texture is relatively soft. Of course, this characteristic is also a standard for distinguishing the authenticity of gold. Hard gold is "hard" gold made by new methods. Its texture makes ordinary gold harder. Therefore, it is called "hard gold" in the industry. Hard gold is actually an alloy. Although it contains gold, its color is not as bright as gold. After all, it is mixed with some other metal substances. And those with a gold content of not less than 999 are called thousand gold, which is the highest value in the naming of jewelry fineness.