The birthstone for the month of November, topaz, occurs in
a variety of colours. The Egyptians believed that topaz got its colour from the Sun God, while others believed that the gemstone changed colour in the presence of poisonous substances. In the 19th century, only the Czar, his family, and those whom the Czar gifted were allowed to own pink topaz in Russia. Said to strengthen intellect and drive away sadness, Indians believe topaz assures long life and beauty.
Tanzanite, a variant of the mineral zoisite, was discovered by a Masai tribesman looking for sapphires in the 1960s. The exotic blue gem, christened tanzanite by Tiffany & Co., has fast become a sensation in the gem world and has joined the list of coveted gems. So much so that the American Gem Trade Association added tanzanite to the list of birthstones for December in 2002 – a first since the list was last changed in 1912. Legend has it that the land was struck by a bolt of lightning which transformed
brown stones to a shimmering violet-blue.
Read on as the Gemological Institute of America (GIA), the world’s foremost authority in gemmology, uncovers the facts and legends that surround these alluring gems in our concluding part of the birthstones series.
A Rainbow of Topaz Colours
Associated with strength and protection against one’s enemies, topaz is admired for it’s beauty and splendour.
Did You Know?
Many consumers know topaz simply as an inexpensive blue gem, but you might be surprised to learn that its blue colour is rarely natural – it’s almost always colourless topaz that’s been treated to give it a blue colour.
You might also be surprised to learn that topaz comes in a variety of colours, including pinks and purples that rival the finest fancy sapphires. In fact, topaz has an exceptionally wide colour range that, besides brown, includes various tones and saturations of blue, green, yellow, orange, red, pink and purple.
Topaz is allochromatic, which means that its colour is caused by impurity elements or defects in its crystal structure rather than by an element of its basic chemical composition. The element chromium causes natural pink, red and violet-to-purple colours in topaz. Imperfections at the atomic level in a topaz crystal structure can cause yellow, brown and blue colour. Brown is a common topaz colour, and the gem is sometimes mistakenly called “smoky quartz”.
The colour varieties are often identified simply by its hue – blue topaz, pink topaz, and so forth – but there are also a couple of special trade names. Imperial topaz is medium reddish orange to orange-red. This is one of the gem’s most expensive colours.
History and Lore
Most authorities agree that the name topaz comes from Topazios, the old Greek name for a small island in the Red Sea, now called Zabargad. The island never produced topaz, but it was once a source of peridot, which was confused with topaz before the development of modern mineralogy. Some scholars trace the origin back to Sanskrit and the word topas or tapaz, meaning ‘fire’.
The ancient Greeks believed topaz gave them strength. Renaissance Europeans believed topaz could break magic spells and dispel anger. For centuries, many people in India have believed topaz when worn above the heart assured long life, beauty and intelligence.
The 4Cs: Clarity, Colour, Cut and Carat Weight
Red is one of the most sought-after topaz colours and represents less than one-half of 1% of facet-grade material found. Medium reddish orange to orange-red topaz, which the trade calls imperial topaz, is highly prized and very rare.
Some say that pink topaz, often called rose topaz, resembles a pink diamond or a bright pink sapphire. Pink topaz has certain advantages over these two gems. It’s much less expensive than pink diamond, and it’s often available in larger sizes than either diamond or sapphire.
Dealers often use the trade term “sherry topaz” for yellowish brown or brownish yellow to orange topaz. Golden or yellow topaz lacks the prized red overtones of imperial topaz. It’s also much more abundant and therefore less valuable. Although brown topaz is also less valuable, it has been used in striking pieces of jewellery and ornamental art.
In nature, topaz is most commonly colourless, and naturally strong blue gems are extremely rare. In the marketplace, however, strong blue shades are plentiful because colourless topaz is treated with a combination of radiation and heat.
A fashioned topaz that displays a combination of two colours is called bicolour topaz. The most valued topaz colours are orange-red to red. Blue gems are widely available.
Fashioned topaz gems are often free of visible inclusions or flaws. This is especially true of blue, colourless and yellow topaz. Other rare colours like imperial and pink may show inclusions more often and still be valuable due to the colour’s rarity.
Because topaz crystals are usually elongated or columnar, they’re often cut as long oval or pear shapes to improve yield. If the rough is strongly coloured, the cutter often chooses the emerald cut because that cutting style maximises colour and retains the most weight.
Topaz can often form as large crystals that yield sizeable cut gems.
Topaz is pleochroic, often displaying different colours in different crystal directions.
How to Care for Topaz
Topaz, which is an eight on the Mohs scale of mineral hardness, requires special care during cutting, polishing and mounting. Because it is not very tough, a hard blow might split it, and extreme pressure or sharp temperature changes might cause it to break. Jewellers prefer to set valuable topaz gems in protective mountings or use it in pieces that aren’t exposed to too much wear, like pendants and pins.
One of the world’s newest gems, the rare deep blue tanzanite is a coveted find.
Did You Know?
Named after Tanzania, the country where it was discovered in 1967, tanzanite is a variety of the mineral zoisite. This blue-to-violet or purple gem can rival sapphire’s blue and is commercially mined in the Merelani hills of Tanzania. Although relatively new to the coloured stone market, it’s become one of the most popular coloured gemstones.
Story and Lore
When blue crystals were first discovered in Tanzania in the 1960s, no one was quite sure what they were. as the story of the tanzanite mining boom goes, in 1967 a Masai tribesman stumbled upon a cluster of highly transparent, intense blue crystals. He alerted a local fortune hunter named Manuel D’Souza, who quickly registered four mining claims. D’Souza hoped that he’d been shown a new sapphire deposit. Instead, the deposit contained one of the world’s newest gems.
The 4Cs: Clarity, Colour, Cut and Carat Weight
A deep saturated “sapphire” blue is tanzanite’s most valuable colour, although some consumers favour gems with an intense violet-blue hue. Tanzanite with a bluish purple body colour is also popular, but less valuable. in any shade, pale colours are less prized than saturated ones. Exceptional tanzanite displays an intense violet-blue with red flashes of pleochroic colour. Tanzanite’s appearance is influenced greatly by its pleochroism, which is the ability of a gemstone to show different colours when viewed in different crystal directions.
Much of the tanzanite sold in jewellery has inclusions that can be seen only under magnification, so any eye-visible inclusions cause a drop in value, particularly in lighter coloured stones, where they’re more visible against the gem’s body colour. Any inclusions that might pose durability problems, such as fractures, lower tanzanite’s value greatly.
Tanzanite is available in a wide range of shapes but cushion and oval cuts are most common. Cutting orientation has a big impact on a gem’s face up colour and price. Cutting to emphasise a gem’s bluish purple colour usually wastes less rough than cutting it to get a pure blue or violet-blue hue. That’s part of the reason face-up bluish purple tanzanite is more plentiful than pure blue specimens.
Tanzanite is available in fine, larger pieces with strong colour or lighter material cut to standard sizes for use in mass market jewellery. Tanzanite colour is less saturated in smaller sizes as most gems must be above 5 carats in size to have fine colour.
Tanzanite is often heat-treated to produce colours that include light to dark violet- blue and bluish purple, as well as pure blue.
How to Care for Tanzanite
Tanzanite, a 6-7 on the Mohs scale of mineral hardness, is somewhat delicate and should be worn with care. Sudden temperature changes or accidental bumps may cause cleavage, a flat break that can have a step-like appearance. You should select jewellery pieces that protect the stone if you are going to wear it every day or are very active. Pendants and earrings are good choices. Tanzanite jewellery should be cleaned with warm, soapy water and wiped with a tightly woven microfibre cloth. Never use an ultrasonic or steam cleaner on tanzanite.