Which gem is frequently subjected to heat treatment?

Sapphire is frequently subjected to heat treatment to enhance its color and clarity. This process involves heating the gem to high temperatures, which can improve its appearance by removing inclusions and altering its color. Heat treatment is a well-established practice in the gemstone industry and is commonly applied to various colored sapphires, particularly those that exhibit less than optimal hues or clarity.

In the case of sapphires, heat treatment can transform light-colored stones into deeper, more desirable shades, significantly increasing their market value. This method is considered an accepted enhancement that is often disclosed in the sale of sapphires, as it is an integral part of their treatment history.

While other gemstones listed, such as topaz and emerald, may undergo various treatments, heat treatment is not as prevalent or standard as it is for sapphires. Amber, being an organic gemstone, typically does not undergo such processes, as its appeal lies in its natural coloration and inclusions. Therefore, sapphire stands out as the gem most commonly associated with heat treatment.