Topaz - How to Identify

by Ardamun

Citrine is mostly, and erroneously, called topaz, though both are two distinct species. Citrine is quartz, and is much lighter than topaz, which is Hydroxyl Fluorosilicate of Aluminum.

How To Identify Different Topaz?

Topaz is the hardest silicate mineral and one of the hardest minerals in nature, and a very popular gemstone for jewelry. In the ancient past, topaz was always associated with the yellow color, and all yellow and golden-hued gems were called topaz. Fine topaz normally occurs as a colorless crystal, though other colors, such as pink, blue, green, 'sherry', brown, etc are known to occur as well. You will find a variety of yellow gems wrongly being sold as topaz, such as:

Topaz
image courtesy: theimage.com

Citrine is mostly, and erroneously, called topaz, though both are two distinct species. Citrine is quartz, and is much lighter than topaz, which is Hydroxyl Fluorosilicate of Aluminum. Quartz has a Specific Gravity of 2.65 and the Refractive Index of 1.540 to 1.550, whereas topaz has a Specific Gravity of 3,54 and a higher Refractive Index of 1.620 to 1.630.

True topaz is correctly labeled and some are preceded by two words - Precious or Imperial. Natural color topaz is known as precious topaz and imperial topaz, whereas the Imperial Topaz was the topaz with pink tones which were discovered in the 19th century Russia. Imperial topaz is now mined at the Imperial Topaz Mines in Minas Gerais, Brazil.

Topaz is an aluminum fluorite silicate - Al2F2SiO4 - and is found in cavities in granite and rhyolite lava rocks, pegmatites, high temperature quartz veins, and as worn pebbles in alluvial deposits.

The Origin and Colors of Topaz

The name topaz is thought to come from the Sanskrit word - tapas - which means fire. In 1 A.D. it was thought that the name was derived from the Greek word topazos or topazion - meaning to seek - and which was the name of an island - Topazos Island - in the Red Sea. Today, this island is known as 'Zeberget', or the 'Island of St. John'.

Clear or colorless topaz is quite common and has little value. Blue topaz, which is very rare in nature, can be made by irradiating clear topaz. Natural blue topaz is very light in color and irradiation produces blue topazes of darker hues. Treated blue topaz is available from very light, to sky-blue, to almost an inky dark blue. These flawless gemstones are relatively less expensive. The pale or clear topaz that is enhanced to produce blue topaz is mined in Brazil, Sri Lanka, Nigeria, and China. Blue topaz is often confused with aquamarine.

The mines in Utah and Mexico produce the reddish-brown topaz. Though not of high value, they are still more expensive than citrine. Pink topaz is quite rare and hence is highly valued and occasionally found in jewelry. It is found in Pakistan and Russia. Pink topaz is also created by irradiating the common yellow topaz.

Another topaz that is rare is the green topaz, and is highly valued also. The most prized is the Imperial Topaz, which ranges from red-orange to pink-orange color. This topaz normally contains many flaws and is very heat sensitive. Presently, it is mined in small quantities in Brazil.

The other colors of topaz are yellow, brown, orange, beige, and red.

The Deceptive Names of Topaz

Certain unscrupulous jewelers sell other gemstones, with deceptive names, as topaz. The names, such as gold topaz, Madeira topaz, Brazilian topaz, Bahia topaz, citrine topaz, Indian topaz, and smoky topaz are not the names of topaz. These are just names to deceive you into thinking they are topazes.

Citrine is also sold as topaz under the names - Bohemian topaz, Madeira topaz, Colorado topaz, Quartz topaz Saxon topaz, Jeweler's topaz, Scotch topaz, Palmyra topaz, Salamanca topaz, and Occidental topaz. Few more trade names are Hyacinth topaz, Nevada topaz, and Hawaiian golden yellow topaz.

A variety of quartz are also enhanced and sold as topaz. They go under the name - Palmeira Topaz, Madeira Topaz, Gold(en) topaz, Rio Topaz, Hinjosa topaz, Smoky Topaz, Spanish topaz, Scottish topaz, Topaz quartz Orange topaz, and Topaz saffronite. Poor quality sapphire is also enhanced and sold as topaz. They go by the names - as Indian topaz, Palmeira topaz, Star topaz, King topaz, and Topaz cat's eye.

Enhancement of Colorless Topaz

Topaz is found on most of the continents, with the colorless variety being the most common. Due to its availability in abundance, it has a very little value. The colorless topaz is enhanced either by radiation and/or by heating. The natural blue topaz is of a very pale blue color. Today, a mass production of a desirable and darker blue color is done through electron beam enhancement or radiation of colorless topaz. The most common blue topazes produced by radiation are:

Sky Blue Topaz - which is a moderately strong light blue topaz resulting from treating colorless topaz with gamma rays from Cobalt 60 or electrons by electron accelerators. The treatment is then followed by heat treatment.

London Blue Topaz - this slightly grayish medium dark to dark blue topaz results from treating colorless topaz with neutrons produced in nuclear reactors. This process is also followed by heat treatment.

Swiss Blue Topaz - is a vivid medium, to medium dark blue topaz produced by combining neutron treatment with electron treatment, followed by heat treatment.

After the electron beam treatment, the heat treatment is carried out at 200ÂșC for many hours. This achieves strong blue colors. After neutron irradiation, topaz needs a cool off time as it becomes radioactive.

The common yellow topaz, when irradiated converts to pink topaz. Typically, yellow topaz ranges from wine to straw-colored, and heat-treated yellow topaz turns reddish-pink. Heating is one of the most common treatments for topaz. The process can cause the gemstone to change completely, or either lighten or darken. Normally the heat treatment is irreversible. Heat-treated topazes are widely available in blues and pinks.

Topaz is not a very expensive gemstone, and with a variety of colors and sizes available can be an exquisite addition to your wardrobe.

 
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