Properties of TurquoiseBy:Ashutosh Roy Summary: The chemical name of Turquoise is Hydrated Copper Aluminum Phosphate. The chemical formula is CuAl6(PO)4(OH)8*5(H2O). According to the formula, it comprises of three primary ingredients Copper, Aluminum and Phosphorous. Turquoise has got occasional presence of Zinc, Iron and Chromium as impurities.
Turquoise - The Insight
Mother earth has stored marvelous treasures in her belly and Turquoise is
one of the most precious stones that her sons have been digging out since
6000 BC. Aren't you inquisitive to know all about it?
This modern yet one of the most ancient gemstone is said to be the result of
nature's whims. Before we delve deeper into its properties and attributes,
lets understand clearly that Turquoise is not a primary mineral. It's rather
a collection of several minerals from the earth's crust, formed under
special weathering effects. The entire process is controlled by the nature
itself to produce the ever-growing popular stone - the turquoise. A simple
example will make it clear. As soon as Phelp Dodge had changed his way of
extracting Copper ore, nature refused to produce Turquoise, due to the
change in the weathering effect, in the same Tyrone mine, which had been
producing turquoise for quiet some time.
The mother stone of Turquoise is called Matrix, which means Turquoise
resides on the Matrix and is carefully cut as the method of extraction. The
best colour dazzles when the colour of the matrix contrasts with the colour
of the Turquoise. A thin and evenly spaced layer of Matrix, called Spider
Web, eventually enhances the look and feel of Turquoise. As a secondary
material, when meteoric or groundwater percolates through rocks that contain
copper, Turquoise is formed. Copper may come from varied sources, which
affect the quality and colour of the Turquoise. If Copper comes from Copper
Sulphides, then it produces bluish shades and if Copper comes from
carbonated malachite, the colour turns greenish. Now, if we look at its iron
component, if it is from apalite, the colour becomes black, iron oxide
produces golden-brown while rhyolite produces the yellow colour. If
Turquoise is not cut carefully from the Matrix, impurities remain affecting
its colour.
The chemical name of Turquoise is Hydrated Copper Aluminum Phosphate. The
chemical formula is CuAl6(PO)4(OH)8*5(H2O). According to the formula, it
comprises of three primary ingredients Copper, Aluminum and Phosphorous.
Turquoise has got occasional presence of Zinc, Iron and Chromium as
impurities. The presence of these impurities results in deviation from the
elegant Turquoise blue colour. According to physical chemistry it belongs to
the Class Phosphate.
As it belongs to the class phosphate, Turquoise is fragile and sensitive to
solvents. The hardness of Turquoise ranges between 5 and 6, which is even
lesser than a window glass. The hardness of a deeply mined turquoise is just
above 2. That's why Turquoise are always advised not to keep close to the
other stones or other rough ornaments, which may result cracks in this
auspicious stone. So, the rough and tough people should think twice!
Even Perfumes and other cosmetics may be detrimental, because of its super
sensitivity to solvents. If you wear a Turquoise, be careful of your skin
oil also. The "skystone" should not be exposed to direct sunlight. Heat is
to be strictly avoided. But then how to maintain it? Cleanse it with a
little warm water and dry it with some soft material like woolen clothes.
Various techniques have been evolved to increase its hardness and decrease
its porosity. Light waxing and oiling enhances the colour and luster of
Turquoise. This technique is widely used today to increase the durability of
Turquoise. Some more technologies have come up today like "pressure
technique" by water glass, epoxy and plastic to produce an artificial
wetting effect to reduce the porosity.
Now lets take a quick look at the different colours of turquoises. Turquoise
had first been found in Copper mines in Persia, which produced Sky Blue
colour and the colour has become a symbol of reference and named as
"Turquoise Blue". The effect of Copper results the original blue colour. The
variety in blue colour is a result of geographical location and other
natural factors. Most of the Turquoise is concentrated near the
copper-aluminum, and finally lands up in the iron or zinc-aluminum end. This
natural phenomenon turns most of the turquoises to various shades of blue
and green or bluish green and greenish blue. Some Turquoises have been found
in Gold mines and Diamond Mines also. The presence of Iron and Chromium
leads to Green colour. For example, Indian mines produce green colour
turquoise due to the adequacy of Iron. Again, excessive heat can dehydrate
the Turquoise to turn its colour to Green. Zinc changes the colour to
yellowish but more importantly increases its hardness. Some Nevada and
Tibetan Turquoise contain zinc.
Turquoise is opaque by its nature. The hardness of turquoise, measured by
the Mohs scale of Physical Science, varies remarkably. The lower limit
starts from 2 and the upper limit is 6. Hardness varies due to several
natural factors like environment and its mother stone, matrix. The hardness
also depends upon the processing or treating of Turquoise. Silicification
process, which involves minute Quartz particles, increases the hardness to a
large extent. Its softness makes it very difficult to use the gem directly
by the Jewelers. Turquoises, which have not undergone the silification
process, at the least, undergo stabilization treatment before being mounted
on a necklace.
Properties at a glance
|
Associated Minerals |
Pyrite,
limonite, quartz, chert, cuperite, manganese oxide, apatite,
chalcopyrite, chalcedony, and clays |
|
Birefraction |
0.04 |
|
Chemical
Formula |
CuAl6(PO4)4(OH)8*5(H2O), |
|
Chemical
Name |
Hydrated
Copper Aluminum Phosphate |
|
Class |
Phosphates |
|
Cleavage |
None |
|
Colours |
Mainly in
shades of blue and Green |
|
Crystal
System |
Triclinic
Bar 1 |
|
Crystal
system |
Triclinic |
|
Density |
2.6 to 2.8
|
|
Fracture |
Conchodial |
|
Luster |
Dull to Waxy
|
|
Refractive
Index |
1.61 to 1.65 |
|
Specific
Gravity |
2.60 to 2.80 |
|
Transparency |
Opaque |
The best stones are almost natural but they are fragile and prone to
color fading. But the nice look and the royal colour attract everybody.
These stones are cut, shaped and polished to mount on your third finger.
As the popularity grows up, faking becomes an integral part. People have
been faking for centuries. Fake turquoises are made up of ceramics, bone,
colored minerals, celluloid, plastic etc. A hot pin will give out smell of
resin from a synthetic turquoise. But, this is not the only kind; other
faking methodologies may also deceive your eyes. So, you may prefer to visit
Zach-Low Turquoise Museum, New Mexico, to test the Turquoise before
investing your hard-earned dollars.
You may not be a student of Physics or Chemistry to comprehend all the
properties in details. So what? Go ahead! After all, the taste of pudding is
in the eating. So, why to restrain yourself from a glittering third finger
with an original Persian Blue Turquoise before the next board meeting, which
may turn your luck (!) also.
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