8. Heat Treatment
A common treatment applied to certain gemstones to alter the clarity and colour of a precious stone within a controlled environment. Heat treatment or thermal enhancement has been used in the precious stone industry for the past century. It is only within the past few decades that heat treatment has been perfected to produce consistent results as heat, when used incorrectly, can be harmful to gemstones.
There are two variations of the heat treatment one uses a diverse range of additives and conditions, while the other solely uses heat. Gemstones that are usually heated sans additives are blue zircon, tanzanite, aquamarine, green tourmaline and citrine, and the natural heat deepens and alters the colour of these gemstones. In the alternative treatment, solid materials are added to the heating process as the regular heating treatment is not adequate. This works on glass residues, hybrid gems, diffusion and lead glass-filled rubies.
