Opal belongs to golden emerald, also known as cat's eye, cat's eye and oriental cat's eye. It is a rare and precious variety of stone cat's eye in jewelry. Opal is one of the most precious emeralds, which is valuable and produced in Sri Lanka. Opal is named because it is similar to cat's eye and can change with the change of light.
Opal needs to be cleaned regularly with warm salt water during wearing to avoid soaking in acid substances such as sweat to avoid discoloration. Opal should avoid the influence of high temperature and external force. When wearing opal at ordinary times, it is necessary to avoid being close to naked flames, so as to avoid the internal structure of the cat's eye book being destroyed and bursting. In swimming, fitness and other sports, opal should be removed to avoid opal loss caused by excessive exercise.
The curved top of natural opal has only one bright band, while the curved top of artificial opal has two or three. The specific gravity of real cat's eye book is 3.72, and that of artificial cat's eye stone is 2.264. If they are put into an iodomethane solution with a specific gravity of 3.32, the real opal will sink and the fake one will float. The Mohs hardness of true opal is 7, and that of false opal is 5.