If you must know whether the gem has been burned, it is better for non-professionals to see the certificate. The certificates of domestic testing institutions, such as NGTC (National Jewelry Quality Testing Center) and GIC (Jewelry Testing Center of China Geo University), do not indicate whether the sapphire is fired. Only Swiss Gubyrin and GRS, American AGL and GIA, Sri Lankan EGL and other certificates will have the distinguishing sign of "burning and not burning".

If the natural gemstone is heated or the color is unnatural, the letters H, E, LIBS:H, commonly known as "old burn" or "old burn", and H (heating) means that there is no residue after heat treatment, and it is regarded as permanent treatment, only simple heat treatment and no coloring.