How to Heat Treat Tourmalines

Screen tourmalines from the mining process for color and brilliance. Set aside any gems that exhibit a good quality appearance or satisfactory color. You want to use gems that require enhancement of color and brilliance. Tourmalines appear in a variety of colors including reds, pinks, purples and blues and greens of dark and light hues.

Place the rest of the tourmalines into the chamber of a high-temperature furnace and slowly raise the temperature. The temperature must be high enough that the tourmalines' crystal lattice is able to rearrange. Depending on the color of the tourmaline, the temperature required to yield color change is between 157 degrees Celsius and 1,900 degrees Celsius. Rearrangement of the color of the tourmaline can lighten, deepen, or intensify the observed color.

Lower the temperature of the furnace and allow the gemstones to cool to the point where you can handle them. Sort through the gems and remove those that have reached a satisfactory level of color and brilliance.

Reseal the furnace and cycle the temperature one more time to a temperature near the melting point of the tourmalines to promote rearrangement of the crystal lattice and allow time for the atoms to rearrange.

Lower the furnace temperature and allow all the remaining tourmalines to cool. Gemstones are not usually temperature-cycled more than two times. Select the gemstones for sale or use after the last heating.