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Topaz Buyer's Guide
 

Topaz is the name for the mineral species that is number 8 on Mohs’ scale of hardness. There is some uncertainty regarding the name. Some say it comes from the Sanskrit word meaning “fire.” Others link it to the Red Sea Island of Topazios (Zabargad or St. John’s Island), where peridot has been found.
For the general public, topaz means a yellow gem, and much citrine and smoky quartz has been sold as “golden topaz” and “smoky topaz.” The terms “imperial” and “precious” topaz are often used to distinguish between true topaz and the quartz look-alikes.
The name “imperial topaz” is said to have originated in the 19th century in Russia, where the Ural Mountain mines were an important source. According to some sources, pink topaz from those mines was restricted to the family of the Czar. Today, the gem trade generally uses the term for pink, orange and red topaz, which comes mainly from Ouro Prêto, Brazil. Fine pink topaz also comes from the Katlang area of Pakistan.

 
Color

Topaz commonly occurs in colorless and brown colors, it is the rare golden, orange, pink, red and purple colors, which are often termed “precious” or “imperial” topaz, that are the mainstay of the fine gem market. While blue topaz is found in nature, most of the material is produced by a combination irradiation/heating treatment.

Yellow and brown topaz owe their color to color centers. The impurity chromium produces pink to red colors. A combination of color centers and chromium produces orange topaz. Blue topaz is colored by color centers.
   :: Note that the color of some brown topaz may fade with time.

 

Lighting

Due to its orange to red-orange color, topaz generally looks best under incandescent light. In contrast, blue topaz looks best under daylight or fluorescent light. When buying any gem, it is always a good idea to examine it under a variety of light sources, to eliminate future surprises.

Clarity

Topaz from most sources is reasonably clean. Thus eye-clean stones are both desirable and possible. The exception is with pink and red topaz, where only small stones are normally available. In those colors, a slightly higher degree of inclusions are tolerated.

Shape & Cut

Due to the shape of the rough (elongated prisms), topaz is generally cut as elongated stones, typically emerald cuts, elongated ovals, cushions and pears. To save weight, pears in particular are often cut with overly narrow shoulders. Due to the huge production, blue topaz is cut in virtually any shape and style one can imagine. Cabochon-cut topazes are rarely seen.

While topaz does have a perfect basal cleavage, it is not an easy cleavage, and so does not present too much difficulty to the cutter. Nevertheless, cutters will often try to ensure that no facet is parallel to the cleavage direction and jewelers try to mount valuable stones in settings that protect the stone.

Stone Sizes

Topaz sometimes occurs in enormous sizes, where clean gems of even 1000 cts. are known. Indeed, faceted stones of tens of thousands of carats have been produced from some monster crystals. However, cut stones of the prized “imperial” colors (orange, pink and red) are more rare. Fine pinks and reds above 5 cts. are scarce. Fine oranges above 20 cts. are also rare.

Sources

Gem topaz has been found at a number of localities around the world, including Brazil, Nigeria, Sri Lanka, Russia, Burma, Pakistan, USA and Mexico. The premier source is near Ouro Prêto in Brazil’s Minas Gerais state.

 
Properties of Topaz

Composition

Hardness (Mohs)

Cleavage

Specific Gravity

Refractive Index

Crystal System


Colors

Pleochroism

Dispersion

Phenomena

Handling

Topaz has the following composition: Al2(F,OH)2SiO4

8

Perfect (but not that easy) basal cleavage

3.53 ± 0.04

1.619–1.627 (±0.010)

Orthorhombic; usually occurs as vertically striated elongated prisms topped by domes

Orange, yellow, brown, blue, pink, colorless, rarely red

Weak to moderate, dichroic

0.014

None

Ultrasonic: not safe; never clean topaz ultrasonically
Steamer: not safe
The best way to care for topaz is to clean it with warm, soapy water. Avoid exposure to heat, acids and rapid temperature changes. Strong heat may alter or destroy color.

Various
Most blue topaz is made by irradiation and then heat; this treatment is undetectable and extremely common.
Blue topaz irradiated with in nuclear reactors can emit dangerous levels of radiation; it must be allowed to cool down to safe levels before sale.
Some orangy topaz is heated to destroy the color centers, leaving behind the chromium-caused pink color.

No

 

Enhancements

Synthetic available?
 
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