Semi-precious stones are usually treated so that their clarity and color could be enhanced. However, the treatments done, depending on their type and extent, could significantly affect the stone's value. There are those treatments which have been used widely as the resulting gemstones are stable and there are those which are not practiced as the color of the stone becomes unstable and could ultimately revert to its original one. Here are some of the most common treatments done.

1. Heat

Heat could improve or enhance the clarity and color of the semi-precious stone. Citrine is usually made through heating amethyst. Partial heating of that gem with a strong gradient would also result in ametrine which is a partial amethyst and partial citrine stone. Another stone that could be heated is aquamarine so that the yellow tones would be removed, ultimately changing the green into a more desirable blue or just enhancing the blue it already has into a purer blue.

2. Radiation

An example would be the blue topaz, which is irradiated so that the color could be changed from white into blue. Another would be greened quartz like the Oro Verde which is irradiated so that a yellow-green color could be achieved.

3. Waxing or Oiling

Emeralds that contain natural fissures are occasionally filled with oil or wax so that they could be disguised or masked. The oil or wax is colored so that the emerald could have a better color, appearance and quality. Also a semi-precious stone which is waxed or oiled would be turquoise.

4. Fracture Filling

This type of treatment has been used with many gemstones like emeralds, diamonds and sapphires.