Explained below are the most common and accepted treatments for different types of colored gemstones. Oiling Oiling is an ancient process that is used to enhance the clarity of emeralds. Oil is applied to the emerald and seeps into naturally caused fissures that reach the stone's surface. Aside from improving clarity, this process may prevent brittleness. Generally, oil treatment does not provide permanent results, and oil may need to be reapplied every few years.
Special care is required for cleaning, repairing, or mounting oiled stones.
Heating Heating is a widely accepted enhancement process that is used to treat rubies, sapphires, amber, aquamarine, amethyst, citrine, tiger eye, tanzanite, topaz and tourmaline. This treatment improves the transparency of the stone and enhances its color. Since heat generally produces permanent results, heated stones do not require repeated special treatments. Diffusion Diffusion is a method that is occasionally used on sapphires. During treatment, a colorless sapphire is coated with a compound of titanium and oxide and is exposed to heat.