November, the middle month of post-Halloween sugar rushes and the anticipation of Christmas jitters. Traditionally, November has been associated with the golden gemstones of topaz and citrine. This blog will be about the prior, topaz, as I feel too many November babies complain about this gem. Lucky for you I know many things about this gemstone, including the many colours it can be when the conditions are right.
There even are varieties of topaz that deserve enough respect to be labelled as “Imperial”. Aside from the known golden orange colours, topaz can come in colours of wine red, pink, yellow, grey, colourless, blue and even a rare green and violet. Topaz is also an interesting stone as it’s colours can be enhanced with treatments, more so than other stones.
Topaz is a very old gemstone but has a muddled history as the name was used to classify any yellow gemstone, hence it gets mixed up with citrine. Etymologically, the name derives from the same island that peridot was mined in ancient times, Τοπαζος, the ancient name of St. John’s Island in the Red Sea. The word topaz may also be related to the Sanskrit word तपस् “tapas,” meaning “heat” or “fire” due to the burning red and gold colours some of these gemstones display. In the modern era, topazes are fairly abundant compared to their cardinal cousins. Many of the rare and beautiful varieties of topaz come from Brazil, however, the USA, Sri Lanka and Africa are also known to supply excellent examples of this gemstone as well.
Topaz is identified as:
- 1) Orthorhombic Crystal System
- 2) Silicate Category
- 3) Nesosilicate Family
- 4) Mineral = Topaz -Al2SiO4(F,OH)2
- 5) Varieties = Imperial Topaz, Sherry Topaz, (colour) Topaz, Mystic Topaz (man-made).
There are many attractive traits to topaz besides its colour. With a hardness of 8, it produces a bright lustre and is fairly resistant to scratches, however, chipping is a different story. Due to the atomic alignment, the crystal structure has weak points, known as cleavage planes. In topaz, these cleavage planes are very pronounced, as in it makes a clean break, and the stone can easily fracture along this plane. To avoid this, gem cutters cut the gemstone off angled to these planes to minimize the risk of cleaving your stone. Gem cutters also love this stone because it is relatively flawless compared to other stones thus you are able to cut beautiful flawless gems.
Another intriguing quality about topaz is its strong pleochroism, an optical quality in a gemstone that allows the stone to show different colours depending on what angle you look at it. All transparent matter refracts light as the wavelengths are slowed down when travelling through a thicker medium. When there is a distinct crystal structure, these wavelengths are split into the slow and fast ray. If it’s a large enough split, different colours distinguishable to the human eye will be expressed. For most topaz, these colours are just deeper or light versions of the body colour. However, in some stones the stone will appear pinkish from one viewpoint and orange from another, giving it a real fiery dance of colour.
Alright, now to dive into the source of these colours and how to detect your topaz is a true topaz. As topaz is relatively abundant, there are not synthetic varieties to worry about. Treatments and imitations are a different story. There are several varieties of topaz, such as the blue ones that cannot be easily made by nature. This is the case with deep blue topazes, properly named Swiss and London blue. The lighter blue usually referred to as “Sky Blue” can appear natural or be created through treating a clear stone. Now here is what is really cool about these coloured topazes. The colour is created through radiation. The process involves pelting the stone with gamma rays (this deforms the crystal lattice) turning the stone to a brown colour. Then they heat the stones to 250℃ to produce a deep, beautiful, stable blue. Unfortunately, there is no easy way to detect this treatment so it has been agreed upon that unless indicated with evidence, all blue topazes have been treated. Still, I find it hilarious thinking about the mad scientist who discovered this treatment.
While clean and grey topaz can be transformed into a captivating blue, yellow-brown stones can be heat treated and transformed into a pink topaz. Interestingly, this is only true if there is chromium within the crystal, otherwise, the treatment turns the topaz colourless. Interestingly they have discovered that the magic temperature is 550℃ to optimal pink. The stone first goes clean and then as it cools the pink starts to shine through. Higher temperatures cause the stone to remain colourless as it cools. Many ‘Imperial” topazes are treated with this treatment to help emphasize the pink tones within the stone. Again it is hard to distinguish the difference between natural and treated stones. Unless indicated, treat all of these stones as treated as well. Gold, brown, orange topaz are less suspicious as they’re the less desired colours.
The only known imitation stone I know used to imitate topaz in cubic zirconia. They can be easily distinguished from topaz as they lack pleochroism and have a much brighter sparkle. Instead, it’s topaz that is used as the imitator. Little fun fact but if you freeze a topaz, it will pass as a diamond with a thermal conductor tester used for diamonds. Thus colourless topaz has been used to imitate diamonds since there is no pleochroism. They also share very similar blue hues and have been mixed up but topaz is easy to tell from diamond again due to the pleochroism. Other stones that are mistaken for topaz are citrines and lighter garnet colours.
One topaz I want to really make sure you watch out for is the topaz known as Mystic topaz. This is a beautiful stone but the colours are not from the stone. This polychromatic effect is created from baking a titanium oxide coating onto the crystal and then anodizing that oxide. This coating is applied to the pavilion or underside of the crystal to protect the coating from wear. The issue I have with this stone is that I have seen it dubbed many names, such as Caribbean Topaz, Azotic Topaz, Rainbow Topaz and more. It’s a very beautiful and colourful stone but not natural. Also, beware the misnomers, topaz is a common name used for less expensive citrines and smoky quartz
Now as I have always stated, there are always unique outliers and that if you are ever curious about your stones, bring them to a certified gemmologist. They know best and can tell you if you have a topaz or not and MAYBE if it’s treated. Again most are assumed to be treated unless specified. Otherwise, if you want a relatively inexpensive but equally beautiful stone that can stand up to everyday wear, then the November birthstone might catch your eye.
I have attached a few links for you to look through at your leisure if you are interested in learning more about opals and their patterns.
Wikipedia – never to be quoted for a research paper but still a great source of information to start.
Geology.com – another great website that goes into more of the geological details of gemstones and really anything geological.
GIA – another great source for gemmological information.
Till next time, Peter