Topaz Quality Factors
Red is one of the most sought-after topaz colours and represents less than one-half of 1 percent of facet-grade material found. The colour the trade calls imperial topaz is highly prized and very rare. Many dealers insist that a stone must show a reddish pleochroic colour to be called imperial topaz. The reddish pleochroic colour often appears at the ends of fashioned gems—like pears and ovals—that have an otherwise yellow-to-orange bodycolour.
A fashioned topaz that displays a combination of two colours is called bicolour topaz. 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. The term comes from the colour of sherry wine. Stones in that colour range are also sometimes called precious topaz. This helps distinguish them from less expensive citrine and smoky quartz, both of which look similar to, and are frequently misrepresented as, 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. Treatments are the reason for this. Treaters use a combination of radiation and heat to produce blue hues in topaz. Since the 1970s, treatments have brought blue topaz to a broad market.
When it was first introduced to the market, treated blue topaz sold for $20 to $40 per carat. But oversupply led to huge drops in wholesale prices, down to a few dollars or less per carat. Today, blue topaz is basically a mass-market gem, and price is often the most important consideration for many buyers. Uniformity of colour and cut is also important, especially for mass-market jewellery manufacturers.
Fashioned topaz gems are often free of visible inclusions or flaws. This especially true of blue, colourless and yellow topaz.
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 is cut in a wide variety of shapes and cutting styles. Production includes all the standard gem shapes such as ovals, pears, rounds, cushions, triangles, marquise and emerald cuts as well as designer-inspired fantasy shapes.
Cutting styles are also well represented. Brilliant cuts with triangular and kite-shaped facets, step cuts with concentric rows of parallel facets and mixed cuts usually consisting of brilliant-cut crowns and step-cut pavilions are all common. Designer cuts fashioned by hand and machine are popular, too.
Because there is an abundant supply of treated blue topaz, it’s often cut into calibrated sizes for use in mass market and multi-stone jewellery.
Standard topaz cuts for the jewellery industry include a wide range of shapes and sizes. The gem is inexpensive in smaller sizes, but prices rise for gems above 10×8 mm.