By Renée Newman

Blue topaz is one of the most popular gems today, but do not expect to find it in antique jewellery. The landscape of the blue topaz market underwent a significant shift following mineralogist Frederick Pough’s report of irradiated blue topaz in 1957. Natural-colour blue topaz—found in Brazil, Russia, Australia, and central Texas—is relatively rare. In the 1970s, decades after Pough’s discovery, large amounts of undisclosed irradiated blue material entered the market.

Colourless topaz, which is widely available, had been converted to brown or yellow topaz with irradiation and then turned blue with heat treatment. While natural blue topaz typically has a light blue colour (see Figure 1), the depth and stability of the irradiated stone’s colour depended on the type of irradiation.

In 1974, some experienced gem dealers in Idar-Oberstein paid high prices for deep coloured topaz that faded in a few days. After this was reported, and hundreds of thousands of carats of treated blue topaz entered the world market, the prices of blue topaz plummeted.

Today, blue topaz is a relatively low-priced gem and is assumed to be irradiated unless it is identified as natural-colour topaz and their blue colour is stable as long as the stone is not heated. Nevertheless, sellers are required to disclose the treatment.

Types and trade names

“Blue topaz” is the gemmological variety name for topaz that is blue. However, depending on the types of radiation used to alter its colour—e.g., x-rays, gamma rays, neutrons, and high energy-charged particles such as electrons and protons—its colour ranges across shades of blue. Gem dealers often identify the three basic colours and types of blue topaz by the following trade names:

(1) Sky blue topaz

Characterized by a light to medium-light blue or greenish blue, like the colour of the sky on a clear day (see Figure 2). The signature colour can be produced by electron treatment followed by heat treatment, it only takes a few days to a few weeks to turn colourless topaz with this method. This stone provides the look of aquamarine at a very affordable price.

(2) Swiss blue topaz  

This medium blue topaz has a vibrant, electric blue colour resembling some Paraiba tourmaline. Terms such as “super blue” and “American blue” have also been used to describe it. Swiss blue topaz is produced using a combination of neutrons followed by electrons in a process patented by R. Fournier (see Figure 3).

(3) London blue topaz

This stone’s medium dark to dark blue colour, resembling that of a sapphire (see Figure 5), is produced by neutrons in a nuclear reactor. The origin of the name “London blue” is debatable. One theory suggests that, as London blue is the richest and deepest colour of topaz available on the market, it has been named to evoke the prestige associated with the city of London, U.K.

Is irradiated blue topaz safe?

Worldwide regulations control the release of gems from irradiation facilities to ensure they meet safety standards. Blue topaz is monitored until its residual radiation declines to a level that is safe. Its safety can be verified with a Geiger counter.

Showcasing the beauty of blue topaz

The affordability and versatility of blue topaz allow it to be used in:

• Statement pieces. Bold and unique jewelry pieces (like the necklace in Figure 4) allow men and women to express their individuality.
• Replicated jewellery. Treated blue topaz is a jewellery manufacturer’s dream because it has a high clarity and the colour can be produced consistently, allowing exact copies of pieces to be made for collections. In addition, enhanced blue topaz comes in various shades of blue.

Caring for blue topaz

Blue topaz has a hardness of 8 on the Mohs scale, making it more resistant to scratches than other gems. However, it has one direction of perfect cleavage (a plane of weakness) which makes it susceptible to chipping and cracking if dropped or exposed to rough handling.

The colour of blue topaz does not fade with exposure to light, but high heat can change its colour and rapid heating and cooling can cause internal breaks even at temperatures as low as 200 C. Therefore, blue topaz should not be steam cleaned or exposed to a jeweller’s torch.

According to the GIA Gem Reference Guide, ultrasonic cleaners should never be used for topaz. The safest method is warm soapy water.

Based on many studies, blue is the world’s favourite colour. It is not too bright or too dark and it is easy to match it with other colours. Blue can make people feel calm and secure and even has the psychological effect of lowering blood pressure and reducing stress. Colour is not the only feature that makes blue topaz so popular. Thanks to gem treatments, it is readily available in a variety of blue shades. Considering the beauty, availability, and affordability of blue topaz, it is no wonder that blue topaz has become a popular option for both casual and formal jewellery.

Renée Newman, GG, is a gemmologist and the author of Gold, Platinum, Palladium, Silver & Other Jewelry Metals and 13 other books on jewellery and gems. She became interested in jewellery metals while overseeing jewellery quality control at the Josam Diamond Corporation in downtown Los Angeles. Her metals book is used as a textbook at the Texas Institute of Jewelry Technology. For more information about Newman and her books, visit ReneeNewman.com.