Turquoise is one of
the most ancient gems. Archaeologist found royal jewellery made in turquoise
older than 7000 years ago. Chinese artisan carves it since 3000 year ago and is
the national gem of Tibet. Is considered a stone that guarantees health,
fortune and protection from evil.
In southwest US,
native American tribes was used as medium of exchange, and also for jewellery
and amulets. The apaches believed that turquoise enhanced a warrior’s accuracy.
The gem’s name comes
from the French expression pierre turques, Turkish stone, because the gem first
arrived in Europe from Turkish source.
The stone can be
translucent to opaque, and has a unique light blue color. The blue is not
always uniform, it’s actually often mottled and with dark splotches. It might
also have veins of matrix. The quality
is judged on color, texture and absence of matrix.
The blue color is
caused by the presents of copper, while the iron makes the stone look more
greenish and lower the quality.
The color can be
unstable, it can darken, fade or became green, depending on the other foreign
substance that are absorbed from the stone.
The color changing is
caused by the porous surface, that can also affect the durability. On the Mohs
scale its hardness is 5 to 6, perfect to be worn but with care.
Matrix veins are often
visible, even though cutters always try to fashion the final gems without it.
Turquoise gem is not
so rare, but is very difficult find really high quality (that are highly priced
on the market). Treatments are very common either to enhance beauty and to make
them resistant to foreign agents.
Wax impregnation is
the most used treatment. The wax improve luster, seal the pores and avoid
contact with skin, perfume and water; if
you have any jewel in turquoise please pay attention when you wear it: contact with sweat or cosmetics
may damage them irreversibly.
Gem with light color
are dye impregnated , but this technique is actually not used often, because
the result looks unnatural and it doesn’t last.
The first historical
source of Turquoise is Persia, but now the most important mines are in southwest
US and China, where comes the specimen of highest quality.
Like any other gem ,
even turquoise has its synthetics and imitations. we said that the market is
full of turquoise, but not of high quality samples; which is why in the ’80 was
created the Gilson synthetic Turquoise. The material is produced by a ceramic
method and has an artificial appearance, actually it was never widely available
on the market. Instead, the imitation
are very common in the market, both natural and synthetic. The natural gems
that most resemble the turquoise are: Variscite, dyed howlite and chrysocolla.
Among the most widely synthetic used are glass and plastic.
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| dyed Howlite |
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| Variscite |
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| Chrysocolla |
