TOPAZ IN THE WILD AND TOPAZ IN THE LAB
With several excellent examples of topaz in our August Unmounted Gemstones auction, we thought you’d enjoy a primer on all things topaz.
In nature, topaz is abundant in its most common form, which is colourless. Other shades include yellow, orange and brown, with the rarest hues being blue, pale green, pink and red.
Before 1970, mainstream topaz jewellery was typically yellow to brown in colour, with the rarer shades being very expensive and seldom seen. In the early 1970s, it was discovered that the colourless stones could be transformed into brilliant blue hued gems by a process of targeted high-energy electron or gamma radiation followed by a period of heat.
With this method, a beam of subatomic particles is directed towards the stones: the tiny particles that enter the topaz crystals are able to knock electrons out of their orbits, causing damage to the crystal lattice. These “defects” alter the way that light travels through the stone, influencing the way that the human eye perceives its colour—in this case, transforming a seemingly “colourless” rock into a brilliant blue gemstone. The resulting colour is permanent and stable, so wearers need not worry about further exposure to light.
Interestingly, naturally occurring blue topaz has gone through a similar chemical process and there is no way to differentiate a stone that has been created “in the wild” from one which has been irradiated artificially. That being said, a very intensely saturated blue topaz has never been discovered outside of the lab, so it can be assumed that any topaz that hits those ultra-deep shades has been treated.
Lighter shades of blue topaz are known as “sky blue,” while medium shades are termed “Swiss blue,” and the darkest are referred to as “London blue.” The latter two are more sought after, with “London Blue” being the most popular and commanding a slightly higher price.
Blue topaz has surpassed other topaz colours to dominate the marketplace, perhaps due to its brilliant colours, abundance and accessible price point. Another factor contributing to its dominance is consistency—a large retailer looking for a sizeable batch of identically-hued and faceted stones need look no further than treated blue topaz.
View examples of Topaz in this auction
Lot 308 – Pair of Cushion Cut Blue Topaz
Lot 309 – 3 Blue Topaz
Lot 319 – 3 Oval Cut Topaz
Lot 320 – 4 Oval Cut Topaz
Lot 321 – 3 Blue Topaz
Lot 358 – Various Cut Blue Topaz and Zircon
Lot 371 – 69 Various Cut Blue Topaz
TOPAZ THROUGHOUT THE AGES
Humankind is no stranger to this beautiful stone, with some of the earliest extant examples dating back to Ancient Egypt. In his writings, Pliny mentions a large topaz gifted to Ptolemy I’s wife Berenice I, and examples of topaz ornaments have been recovered in Egyptian tombs and Roman ruins. The name “topaz” comes from the island of Topazus, the largest in a group of islands located in Foul Bay, slightly north of the Tropic of Cancer, off the coast of Egypt. Topazus Island is known today as Geziret El Zabargad in Arabic or St. John’s Island in English, and has historically been a source of some of the best peridots. It has been speculated that Bronze Age societies were also highly aware of topaz, as it is commonly found near tin deposits—tin being integral to the making of bronze, which is an alloy of copper and tin.
Topaz seems to have lost its appeal during the Middle Ages, thought it was used sometimes in ecclesiastical ornamentation. When large caches of topaz were discovered in Brazil in the 18th century, the stone’s popularity skyrocketed in Europe, with yellow and pink shades being the most sought-after. Like blue topaz, pink topaz is very rare and often quite pale when naturally occurring. In the 18th century, it was discovered that yellow topaz could be slowly heated up to temperatures of around 500 degrees Celsius and then slowly cooled to bring out pink tones, in a process known as “pinking.” As such, it can be assumed that most pink topaz on the market has undergone this treatment.
By the Victorian era, topaz was one of the most commonly used gemstones. During this period, demand for affordable jewellery was so high that “gold-filled” pieces began to flood the market. “Gold-filled” denotes jewellery composed of a solid layer of gold bonded to base of silver or another base metal, which could easily mimic the styles worn by the upper classes at a fraction of the cost. Sparkly gemstones like diamonds were also very much in fashion, however use of genuine stones would have moved gold-filled jewellery outside of that affordable price range. Thus for the masses, the dazzling diamond look was imitated with—you guessed it—topaz.
It is worth noting that until the mid-18th century, the term “topaz” was used to refer to any and all yellow, orange and brown gemstones, including yellow sapphire, quartz and citrine. This misnomer actually continued well into the 1960s as older retailers referred to citrine as “topaz quartz.” Donald McLean, Senior Specialist in Waddington’s Jewellery Department, explains that over his career, 95% of topaz rings he examines are actually citrines that have been misidentified by generation after generation. He also notes that apart from blue topaz, he rarely sees the stone at all.
As illustrated by blue and pink topaz, humans have long been fascinated with enhancing this highly adaptive gemstone. In the late 1990s, an eye-popping stone named “mystic topaz” was debuted in Hong Kong. Using a patented technique known as CVD (Chemical Vapours Disposition) an infinitesimally thin layer of titanium or a similar metal is deposited onto the exterior of a colourless topaz, resulting in a vivid rainbow of colours definitely not found in nature. This coating is somewhat analogous to that found on iridescent sunglasses. Mystic topaz can last a lifetime, though it must be cared for like a pearl—very gently.
Topaz has one direction of “perfect cleavage,” (along the basal plane for any students of gemology reading this) meaning that it can be damaged through rough handling. “Cleavage” refers to the tendency of certain crystals to break along certain planes if the atomic bonds are weaker in those areas—analogous to wood splitting with its grain. While this in no way means that topaz is “fragile,” it should be handled with care: a sharp tap in the wrong direction will break the stone. Topaz shares this quality with diamonds, which are also prone to directional cleavage. Make sure to clean these stones with warm soap and water rather than with steam or ultrasonic methods, as heat can damage the crystals.
FIND OUT MORE about this auction
Our Unmounted Gemstones auction is offered online August 15 – 20. Please view the gallery.
We are always delighted to provide additional photographs, condition notes and/or more detail.
Please contact Donald McLean for more information.