Because pure gold has low hardness and dark color, and as an inactive metal, its characteristics are very obvious. We use many methods to distinguish it from these aspects. For example, look at the color, or burn it and so on.

1, hardness check

We all know that gold is a soft metal, which is different from other metals. The higher the purity of gold, the higher its softness and the lower its hardness. So we can check the purity of gold by checking the hardness. We can put a bite of gold in our mouth. If you can leave tooth marks, it means that the hardness of this piece of gold is relatively low. In other words, the higher the purity of this piece of gold. But this is a relatively simple method, and we'd better use it when the tools are not so complete.

2. Fire

As the saying goes, real gold is not afraid of fire. As an inactive metal, gold is difficult to react with other substances. On the contrary, if gold is doped with other substances, it can react with oxygen after combustion. So by burning, we can identify the purity of gold. After gold is heated, if the color of gold does not change continuously at high temperature, it shows that its purity is high. If the color of gold changes after heating, such as from blue to green, it means that other metals are doped.

To sum up, the identification of gold is relatively easy, because the activity of gold is not high, and we can detect its purity by chemical means. At the same time, the purity of gold can be identified by the difference of hardness and color in the simplest way.