Tanzanite Identification

Natural tanzanite is known for its brilliant blue shade which has shades of purple in it. It is one gemstone which displays Pleochroism; which means it can put on show different colors in different light. Tanzanite gem has a range of shades from blue to purple to burgundy and that’s why it is the most desired stone.

Crystals of this stone before undergoing the heat treatment are not very impressive to look at. They are reddish brown in appearance. The heat treatment makes the vanadium present in it more permanent and stable and brings out the astonishing blue shade which tanzanite is known for.

Natural tanzanite

As with any other gemstone the cut is very important to bring out the brilliance of color. A perfectly cut natural loose gemstone is a sight to behold. If the stone is poorly cut; either too shallow or too deep, the radiance is lost. A lot depends on the skill of the gem cutter. Size is also a key factor in determining the color. Color is very important for identification of this gemstone. Smaller stones are paler in comparison to bigger stones which have deep blue shade.

Is There Synthetic Tanzanite?

It is widely believed that there are no synthetic tanzanites made by man till date; but the jewelry market is full of its replicas. Mostly colored glass. With growing popularity of this stone as well as its value increasing, no wonder that synthetic and man made gems which looks similar to it are available in the market these days. Tanzanion is synthetic tanzanite and it is found to be harder than the natural gemstone thus making it more feasible for daily wear. It is not that hard to identify tanzanite that is synthetic.

Synthetic Tanzanite

Simulants of tanzanite are used extensively by the jewelry industry as they are much cheaper than genuine stone. Tanzanique is synthetic forsterite which is man made gem but it does not display pleochroism. Natural tanzanite belongs to Zoisite family of minerals having chemical composition of calcium aluminum silicate where as forsterite is magnesium silicate. Natural forsterite can not be cut into gemstones and for this purpose synthetic forsterite is used.

How to Spot a Fake

There are techniques available to distinguish between a fake and a genuine tanzanite stone and identify gemstone that is genuine:

Hanneman Tanzanite filter, a combination of color filter and dichroscope, is one of the methods to separate synthetic forsterite with tanzanite. When viewed through this filter the synthetic forsterite displays greenish color while genuine stone has a pinkish color. So tanzanite identification using this filter is very easy.

Certification by international gemological authority is a must when buying high grade stones. Certificate must include important data as carat weight, color, cut shape as well as cut grade (quality of cutting), refractive index, color including grade and hue.

Digital refractometer is device used to calculate refractive index of faceted gems. Refractive index of tanzanite is from 1.69 to 1.70 so digital refractometer is one of methods that can be used to determined if certain gem is genuine.

Trichroism can be also used as tanzanite identification method. Genuine gemstone when observed under different light should display different colors. You can examine tanzanite for example under incandescent and fluorescent light and you should observe different colors most of the time if it's real genuine stone.

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Tanzanite Identification Methods

Hanneman filter - is used to distinguish between genuine tanzanite and synthetic forsterite

Certification - is essential when buying high grade tanzanite gemstone

Digital refractometer - can be used to determine refractive index of gemstone and therefore can exclude some fakes

Trichroism - as one of tanzanite properties can be used to determine if it's genuine stone (observe gem under different light sources, color should be different as well)