Topaz has an exceptionally wide colour range that includes various tones and saturation's of blue, green, yellow, orange, red, pink, purple and most commonly brown. Colourless topaz can also be found, but is often treated by irradiation and heating to give it a blue colour.
Where is Topaz found?
Topaz stones can be found in countries such as the USA, Mexico, Nigeria, Botswana, Madagascar, Afghanistan and Thailand.
Quality factors of Topaz
Topaz is allochromatic, meaning that its colour is caused by impurity elements or defects in its crystal structure rather than by an element of its basic chemical composition. The element chromium causes natural pink, red, and violet-to-purple colours in topaz. Imperfections at the atomic level in topaz crystal structure can cause yellow, brown, and blue colour. Brown is a common topaz colour, and is sometimes mistaken for âsmoky quartz.â
Topaz is also pleochroic, meaning that the gem can show different colours in different crystal directions.
Red is the most sought after of all 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 gemsâlike pears and ovalsâthat have an otherwise yellow-to-orange bodyÂ colour.
Polished topaz gems are often free of visible inclusions or flaws. This is especially true for blue, colourless and yellow topaz.
Topaz is cut in a wide variety of shapes including all the standard gem shapes such as ovals, pears, rounds, emerald, cushion, triangle and marquise shapes. You may also see bespoke shapes in designer pieces.
Because topaz crystals are usually elongated or columnar, theyâre often cut as long oval or pear shapes. If the rough gem has a strong colour, the cutter often chooses the emerald cut because this style maximises colour and retains the most weight.
Because there is an abundant supply of treated blue topaz, itâs often cut into calibrated sizes for use in mass market and multi-stone jewellery.
Topaz comes in some of the gem world's largest crystals, the largest been in kilos, not carats. This therefore means the gem can come in various sizes, the smaller ones being inexpensive but prices rise for those above 10 x 8 mm.
- Chemical Composition: fluorine aluminium silicate
- Refractive Index: 1.61 to 1.64
- Birefringence: 0.008 to 0.010
- Specific Gravity: 3.50 â 3.60
- Mohs Hardness: 8
Like most gemstones Topaz can be treated using different processes in order to change or improve its colour. Some colourless topaz is coated with metal oxides to create the appearance of a variety of different colours. Colourless topaz is also often treated using irradiation followed by heating to produce a desirable blue colour. Since the 1970's, this has brought blue topaz to a broad market. Heating of yellowish pink topaz sometimes has the effect of removing the yellowish colour component and intensifying the pink colour.
Send AnchorCert Gem Lab your Topaz for testing!
Topaz can be mistaken for other gems such as quartz and surprisingly you will find imitations of topaz. It is therefore beneficial to ensure that you request a Gemstone Identification report to ensure that you are supplying or buying the material you think you are. AnchorCert Gem Lab, which is a division of Assay Office Birmingham, has the required experts, knowledge and equipment to provide you with just that!
Gem Identification from AnchorCert Gem Lab is available for all gemstones. A stone will be assessed visually by qualified gemmologists and also tested for the basics such as its refractive index and specific gravity to help identify the material. Gemmologists have the knowledge and experience to detect the tell tale signs of imitations and treatments giving you complete reassurance.
To find out more about Gem Identification from AnchorCert Gem Lab, please visit our website www.anchorcert.co.ukÂ or get in touch with the team today on 0121 236 2122.