Infrared light is similar to normal light, but its wavelength is too long for our eyes to detect. Far infrared light has an even longer wavelength and transfers heat very efficiently. It is why sunlight feels warm. It can penetrate 6-8 inches into the body, and because of this, these rays not only benefit the surface, but all cells including blood vessels, lymph glands and nerves in the deepest parts of our body. This deeply penetrating heat speeds cellular metabolism, reduces pain and quickly heals injuries. In comparison, heat transferred merely by conduction (contact) or convection (airflow) does not heat an object deeply or evenly throughout. Amethyst was found to be ideal for the purpose of converting conductive heat into far infrared light.