These are caused by borax-based substances that are used in the heat treatment process. On rubies, inclusions may be found that are glassy in appearance. For gems that contain rutile needles, the needle margins may become diffuse. The destruction of gas or fluid inclusions or the dissolving of mineral inclusions are clues to heat treatment. These milky white sapphires turn blue, and account for many of the quality sapphires on today's market.ĭetection of heat and diffusion treatment is possible because these treatments modify natural inclusions. The same can apply to a type of sapphire known as gouda sapphire. This allows the chromium in the stone to combine with different atoms, allowing for a better red hue. Ruby is heated almost to its melting point, allowing the aluminum oxide in the stone to reform, creating a new crystal structure. Only the most valuable and expensive rubies possessing the richest colors are not heat-treated. This is a stone that is commonly heat treated. This heat treatment is permanent and irreversible.Īnother example is ruby.
![heat treated amethyst heat treated amethyst](https://www.ethanlazzerini.com/wp-content/uploads/2018/06/Amethyst-cluster.jpg)
An example of this is the dissolving of rutile silk inclusions in blue sapphires, which improves both clarity and color. This color change may result in the stone being darker, lighter, more intense or of a different color. During treatment, the stone is heated to very high temperatures (approximately 1600 Celsius) causing inclusions, chemical elements, and other impurities to reform themselves and change the color of the stone. Heat treatment is considered to be a natural type of enhancement as it is a continuation of the processes that occur in the earth when the stone was originally formed.