First of all, tourmaline is brittle, and baking with fire is easy to cause uneven local heating, and it will be broken when heated and cooled;

Secondly, the color of tourmaline is determined by metal elements, and roasting and heating are easy to change the elements, and the valence increases and decreases, which leads to discoloration, which is also a loss.

Generally speaking, no one will try to bake such expensive things with fire, and try not to wear them when washing, cooking and moving things. Did you see that star wearing jewelry when he was exercising or outdoors?