This is a video of heating amethyst with a halogen point heater to change its color.

Please check the following site for more information.

Related page:

Heating, melting and vitrification of rocks series 30 – Amethyst Heat dissolution of black lava No.53 Heat test of the color filter Shrinkage of heat shrink tube with heat resistance of 200℃ Heating of emerald (Nanosital) Proven by heating paper : Emissivity difference by color Heat dissolution of nylon yarn Heat dissolution of acrylic beads