Topaz
from the Antique Jewelry University
Topaz is a gemstone which throughout history had to share its name with all other yellow gemstones. It was not until the mid 18th century that the name was assigned to the aluminum fluor-silicate that we know it as now. Even in the 16th century Cellini described a - most probably - yellow sapphire as "topaz". Due to its close resemblance in color to citrine, the yellow to orange topazes were termed "precious topaz" to distinguish between the two. Topaz comes in many hues, from colorless through yellow, blue, brown, red and everything in between. Mostly these are rather pale and only few are of a saturated color. In modern days all these saturated stones are termed "precious" in contrast to the original assignment to just the yellow to orange stones. The colorless and pale blue stones are most abundant in nature, followed by yellow and brown stones, while the golden-orange, pinks and reds are most rare. The latter ones mostly being mined in Brazil.
One particular color - or color range - is of special interest to collectors. It is the saturated golden-sherry or quince-jelly hue with often a brown modifier and yellow or pink undertones that is named "imperial topaz". How the imperial demarcation came about is subject to speculation and two theories are most common with the second one being the most plausible version. The first one states that it was in honor of the Russian Tsar who owned the mining fields of topaz in the Ural mountain range and the best quality topazes were reserved for the emperor and his family. A second version attributes it to the Brazilian Empire. When the Brazilian/Portuguese Emperor Peter II visited the town of Ouro Preto in 1881, he was presented a reddish topaz by Professor Henry Gorceix and this color was hence termed "imperial". Although nowadays almost every topaz with a hint of red or orange is denoted as imperial, it only applies to the saturated colors of a small range in hues. The boundary where precious becomes imperial however is thin.
Topaz' its name is derived from the island Topazus, just on the coast of Egypt. It is the same island where historically the best peridots were mined (present day Zagbargad). The word topaz comes from the Troglodytae language, an ancient Ethiopian tribe, and means to seek due to the fact that the island was always covered in a fog.
The mining of topaz is strongly associated with tin mining, a mineral needed to create bronze (an alloy of copper and tin) and it is almost certain that the people in the middle-eastern bronze age would have known about this gemstone [1]. In Europe the stone became highly popular after the topaz discoveries in Brazil during the 18th century and by the turn of the 19th century yellow and pink topazes were all the fashion. Although the fashion declined after approximately 1850, it was used throughout most of the 1800's. While from the end of the 1700's open a jour setting were used more and more often, many topazes were still set in closed settings with a back foil. This was especially true when several stones were set in a cluster or when a complete riviere was to be crafted. For smaller individual stones, as used in the dearest jewelry from around 1840, this was less necessary. The letter t was of course represented by a topaz, either pink or yellow.
Pink topaz does exist in nature, but they are rare and mostly of a pale color. In order to improve the color these stones were pinked by back foiling them with a red foil[2]. Colorless topaz was also used in this fashion[3]. Another way of pinking topaz is through the slow heating of yellow stones up to a temperature of 500 degrees Celsius, followed by slow cooling. This latter method were practiced since the 18th century and one can safely assume that many of the pink stones have gone either of the treatments.
Many blue topazes that we see in jewelry today have undergone an irradiation treatment to produce a stable color of varying saturation. The lighter shades are termed sky blue, the medium range Swiss blue and the darker toned blue topazes are sold as London blue. White topaz is readily available and they have a high luster which comes close to diamond and they are so clear that they were described as water drops by the Brazilian miners. The Portuguese - who owned the mines - termed them slaves' diamond due to the slaves who were employed for the mining in the region around Ouro Preto.
Topaz is a relative hard stone, harder than quartz but softer than corundum, which makes it very suitable for jewelry. This gem however suffers from a perfect cleavage in one direction (the basal plane) which makes it a stone to be handled with care. A hard knock in the right - or wrong, depending which viewpoint you take - direction will split the stone in half. In that regard it is in good company as diamond also suffers from this. Colorless and blue stones are usually cut with the table a few degrees of this cleavage direction so it can take a good polish. The more costly imperial topazes are cut with the cleavage plane perpendicular to the table of the gemstone, mostly for weight retention of the rough material which can be very costly (a multitude of a 100 compared to the costs of blue topaz). This poses a problem during setting of a stone as it can easily break. The wearer should be aware of this problem. It is best not to expose topaz to heat or ultrasonic cleaning.
| Gemological information for topaz | |
|---|---|
| Color | Colorless, blue, pink, yellow, green, "mystic" colors |
| Crystal structure | Orthorhombic |
| Refractive index | 1.619-1.627 |
| Durability | Perfect cleavage |
| Hardness | 8 |
| Treatments | Irradiation, heat treatment, coatings |
| Country of origin | Brazil |
| Topaz care | |
| Ultrasonic cleaning | Not safe |
| Steam cleaning | Not safe |
| Warm soapy water | Safe |
| Chemical attack | Avoid |
| Light sensitivity | Usually stable |
| Heat sensitivity | May fracture |
Notes
Sources consulted
- Donald B. Hoover, Topaz, Butterworths, 1992. ISBN 0750610875
- Pliny the Elder, Historia Naturalis.
- Cellini, Benvenuto (translated by C.R. Ashbee), The treatises of Benvenuto Cellini on goldsmithing and sculpture, 1967, Dover publications, NY. ISBN 0486215687
- Marquardt, Brigitte. Schmuck, Klassizismus und Biedermeier 1780-1850 Deutschland, Osterreich, Schweiz. Verlag Kunst & Antiquitaten GmbH, Munich, Germany, 1982. ISBN 3921811260
- Amstel-Bos, E.G.G van. Sieraden uit de negentiende eeuw. Lochem, The Netherlands: De Tijdstroom, 1981
- Bennett, David & Daniela Mascetti. Understanding Jewellery. Suffolk, England: Antique Collectors' Club, 1989. ISBN 1851494308 (3rd edition, 2007)
- Romero, Christie. Warman's Jewelry. Iola, WI, USA: Krause Publications, 2002
- Robert Webster/ B.W. Anderson. Gems Their Sources, Descriptions and Identification 4th Edition. 1990.