The finger of the diamond gold ring is black before it is dark. There are also national inspection certificates for regular shopping malls

There are two possibilities of hacking with a silver ring with a finger:
The lap with a silver ring with a finger is a low -lying corner place, which is easy to accumulate dust and is not easy to clean. It is impossible to remove it every time you wash your hands. Clean.
The long -term friction of the metal, there will be metal grinding, most of the trace metal powder that is grinded is black on the hand. The more softened the material, the easier it is to fall off. For example, the keys made of aluminum are easy The same reason.
It Yinji Yi Yi and sulfur and oxygen in the air to produce black silver compounds