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lunedì 1 ottobre 2012

Topaz


Topaz


The Topaz has always been part of many cultures with different significance all over the world.



Topaz crystal
The ancient Greeks believed that it gives them strength. During renaissance people used it to break magic spells and in India, for centuries, people worn topaz above the heart to have a long life.
In US is the November birthstone, with the Citrine, and it is a talisman for the sign of Sagittarius.
Some research believe the origin of the name comes from the Sanskrit “Tupaz” which means fire.
Some other says it comes from the island S. John, once called Topazios, in the red sea, were was abundant of an olivine stone, confused with Topaz.





Imperial Topaz
sherry Topaz
Always, the topaz has been associated with the yellow color, so all yellow stones were topaz. But Now we know the topaz comes in a wide color range which includes different shades of red, pink, orange, yellow, purple, green and blue. Can also be colorless.
When the stone is found in peachy orange color, in the trade is called Imperial topaz.
But if is found in yellow to orange color is called Precious Topaz.
In the shades of brownish yellow is called sherry topaz, from the color of the sherry wine.



Topaz crystals have an elongated shape, that’s why usually the stone is cut as long ovals, pears or emerald cut. Most colors are available in some standard shapes, but there is a difference in size from color to color.
Is commonly colorless, but treatment can produce the blue color. Naturally blue gems are extremely rare. From ‘70s those treatments gave to the market a big quantities of uniform blue gems that matches the manufacturers demand.





The most used treatment is heat, alone or in combination with some irradiations.
Usually, yellow stones are heated to make pink colors, and colorless topaz are heated and irradiated to create blue shades.
Of course the final colors depend from the original shade and saturation.
In the Mohs scale topaz’s hardness is 8, which is perfect for an everyday jewellery. Topaz is an hard stone but be careful anyway, its toughness is poor, it can be broke due to its cleavage.

Usually does not have specific inclusions, big stones can easily be eye clean and bright clear.

The most important source of fine quality topaz is in Brazil, in the Ouro Preto area. Since the middle age to the XIX century, topaz price was really high, till the brazil’s source was discovered.
Other sources are Pakistan and Sri Lanka.
The Crystal can be very big, we can find 2 famous examples displayed in New York (300kg) and in Florence (150 kg).
Is very often confused with Citrine and smoky quartz, its inexpensive substitutes, the color yellow is similar but in topaz has a warm undertone. Because very often exchanged with its substitute some people get surprised when see a topaz jewel with an expensive price, Citrine is so abundant that is very easy get a big nice stone with a low budget, topaz is more rare.



Treated Topaz

Is important to know that topaz can change its color due to irradiation and heat, but don’t be worried to wear it during summer, the heat must be over 400° C to see some changes. But if anyway you prefer to have back the original color, you have just to expose the stone to the UV irradiation.

Is improbable find in the market a synthetic topaz, some lab made few samples only for scientific purposes; is actually more common see substitute such as natural quartz and Spinel, or even synthetic Spinel, glass and synthetic sapphire.