Before the 1970’s, most topaz in jewelry was yellow, brown, or clear to barely lightly colored. Natural topaz with an attractive, light blue color was rare and very expensive; the only places sourced being from Texas, U.S.A. and the Ural Mountains in Russia. In today’s market, blue topaz is one of the most popular gemstones. Over 95% of all blue topaz have been treated to create their beautiful blue tones and saturation.
Conversion to Blue
In the early 1970’s, gem treatment experiments revealed that colorless topaz could be converted into a stable blue topaz utilizing high-energy electron or gamma radiation, and then heated to the desired blue color. The radiation treatment uses a beam of subatomic particles that enters the topaz at a high velocity. The speed knocks electrons out of their orbits, or can cause other damage to crystal lattices within the topaz. Those defects change the way light travels through the topaz, and changes the wavelengths of light being absorbed. This results in a change of color perceived by our eyes, and we see beautiful hues of blue.
Irradiated and Safe
Any company that treats gemstones with radiation has to be licensed by the Nuclear Regulatory Commission (N.R.C.). The N.R.C. requires that irradiated gemstones are stored in a secure location after treatment. While they are in storage, they are monitored until the residual radiation declines to acceptable levels safe for jewelry and close contact to humans. It usually takes approximately two to three years to decay below the exemption level after irradiation. For example, a six-carat blue topaz gemstone could release 0.03 millirem dose of radiation in one year, while an x-ray gives 60 millirem or a porcelain crown or false teeth give 0.07 millirem. The level of radiation from a blue topaz gemstone, once released from N.R.C. licensing, is extremely safe.
The radiation and heat treatment are permanent, so no risk of fading from exposure to sunlight. However, topaz has one direction of cleavage that might separate if exposed to rough handling, like a hard impact. It can also have liquid inclusions in them that can cause a gem to fracture when heated. Topaz is best cleaned with warm water and soap, not steam or ultrasonic cleaning.
Shades of Blue
Two colors of topaz have dominated the market by popularity; “Swiss Blue” and “London Blue”. Swiss Blue is a light blue tone and light to moderate saturation. London Blue is a dark blue to blue-green tone with a moderate to dark saturation. Both these popular colors are the result of clear topaz gemstone treatment to obtain these sought-after colors. While blue topaz is the main gemstone utilizing radiation and heat treatment, other limited/smaller scale gemstones have also been treated to create a better color-saturation; diamonds, pearls, beryl, yellow sapphire, amethyst and tourmaline.