This article is about gem variety of topaz with yellow color. Topaz is a mineral, a beautiful gemstone. Its name takes its roots from the name of the island of Topazos, which today is called Zebirget, on which were found peridot. But since at the time of Pliny the Elder mineralogy as a science did not exist, confusion arose. Another version of the meaning of the name is the word “tapaz”, which in sanskrit means “fire”.
Color of the mineral is diverse. It can be colorless, gray, blue, green, red, orange, yellow and brown (sherry, tea). Yellow is one of the most valuable color types of that gemstone. It can be called Imperial or Royal topaz. In addition yellow, it can be honey, fiery orange, red, purple.
Topazes have properties that create the image of a popular and sought-after gemstone. This and high hardness, with wear resistance is good for everyday wear. There are pleasant colors and shades. It’s good in polishing, but need to choose right direction because of the perfect cleavage. Topaz has a high specific gravity, due to which it is assigned the nickname “heavyweight”. The yellow variety is characterized by a color from light yellowish to saturated orange-golden hues. Pleochroism is expressed in yellow, orange, less often – in red tones, especially in crystals of intense color.
Suitable for cutting and jewelry applications yellow topazes are mainly mined in Brazil. Well-known deposits are located in the states of Minas Gerais, Espirito Santo, Bahia and Goias. The extraction of crystals from light yellow to orange and orange-red is conducted near Ouro Petru, Virgen de Lapa and other areas. Large crystal finds are rare and highly valued. There is also a noble topaz of gem quality at deposits in Africa and Asia (including Sri Lanka, India, Pakistan, Afghanistan, Tajikistan), but in much smaller volumes. In Russia in the Urals there were finds of golden topazes suitable for cutting.
Mohs scale hardness:
perfect in one direction
3.49-3.60 g / cm3
1.606 to 1.688
Light Yellow to Orange Yellow
There is no consensus in the gemological community whether yellow topazes belong to the Imperial variety. Some experts believe that only expensive pink, purple, and red-orange varieties deserve the name Imperial topaz. In some cases, an untreated condition is added, which means that heated specimens of bright shades cannot be considered Imperial variety. In other cases, yellow specimens are recognized as Imperial, regardless of treatment.
Yellow topazes are sometimes confused with sherry topazes (brown, cognac), which have a golden brown color and can fade in the light. In contrast, the yellow variety is stable.
The refractive index of a particular instance may be different depending on the fluorine content in the composition.
Topaz in Europe appeared in the 18th century, when in 1737 manifestations of this gem-grade mineral were discovered in Saxony (Germany). This field is called Schnekkenstein. For more than a century, it has been mining sherry-yellow stones, and today it has been assigned the status of a reserve. Around the same period, finds began to appear at various fields in Brazil.
Yellow topaz was and remains a rare gem worthy of taking center stage in sophisticated jewelry. Yellow topaz can be found in antique jewelry of the last century and in the modern works of famous jewelers and fashion houses.
Golden yellow color is characteristic of topazes from certain deposits, therefore untreated natural samples are found on the market.
Yellow color can also be obtained by irradiating of more light samples. For this, gamma irradiation with cobalt isotopes is used. This treatment method is safe for later wearing in jewelry. Including color can be changed due to heat treatment.
Another way to treat the mineral is to apply solid colored films and with an optical “rainbow” effect (mystic) on the verge of an already faceted stone. Such film coatings look spectacular, but short-lived, since the films are scratched from constant wear.
In the photo: jewelry sketches for yellow topaz
Image of large topaz with needle-like inclusions
On the photo: a pair of faceted topazes in the form of elongated pears