Amethyst Chemical PropertiesBy:Ritika Changrani
Summary: Amethyst is a macro crystalline variety of Quartz with the chemical formula SiO2 (Silicon Dioxide). Mostly occurring as purple, lilac or mauve in colour, the purest form is colorless. Experts attribute the purple color of amethyst to small amounts of iron (Fe4+) impurities (approximately 40 parts per million) at specific sites in the crystal structure of quartz.
Once adorned on the Crown Jewels of England, Amethyst is a royal gem - a
symbol of sincerity, security, spirituality and peace of mind.
A purple variety of quartz, amethyst is a semi - precious yet popular
gemstone. If it were not for its abundance in nature, amethyst would be very
expensive. Its royal colour makes it desirable and can be compared to the
most expensive of purple crystals. So if you want a gem that is easy on your
pocket and yet glamorous, amethyst is the perfect choice.
Although it must always be purple to be amethyst, it is available in an
expansive array of purple shades. Intensely colored amethyst may have red
flashes. It may also have color zones. By looking at its color,
transparency, crystal habit, occurrence, hardness, and lack of cleavage, one
can determine the authenticity of an amethyst.
In nature, amethysts appear long and prism-like with a six-sided pyramid at
either end or as crystalline crusts with only the pointed terminations (druzes).
The amethyst is appreciated for its imperial shades and variety of cuts that
lend it a dazzling look.
A premium amethyst is purple, bluish purple to reddish purple in hue, vivid
in intensity and medium dark in tone. Heating the amethyst removes the
colour or converts it to yellow Citrine, depending on the site and original
oxidation state of the iron impurities present and the intensity and
duration of heating. The iron impurities need to be re-oxidized to return
the original colour. The process is called irradiation. Irradiation may be
done by two means: natural and synthetic. As a rule the process is
reversible, but there are exceptions. Application of extreme or
disproportionate heat may alter the existing pattern of iron impurities. In
that case the amethyst is lost and cannot be retrieved by any chemical
process. However, it is not possible to state whether an amethyst has
undergone irradiation or not. Therefore, buying from your trusted Jeweler or
getting it checked with a gemstone laboratory first, is the safest way to
go.
Amethyst in its purest form is colorless and transparent. Experts are of the
opinion that the rich purple colour of the amethyst is to its high content
of Iron Oxide (Fe2O3) impurities. It contains more iron than any other form
of quartz. Quartz makes up about 12% of the earth's crust, making it the
single most abundant mineral on earth. It is present in an extensive range
of igneous, metamorphic and sedimentary rocks. Based on the size of
crystals, quartz is mainly divided into two categories: macro crystalline
quartz, in which the individual crystals are easily distinguishable and
cryptocrystalline quartz, in which the crystals can be distinguished only
under a powerful light microscope. All forms of quartz (including amethyst)
are piezoelectric, which have important applications in electronics. This is
a rare property, possessed by only one other gemstone called tourmaline.
Found in abundance, amethyst is a variety of macro crystalline quartz. It
has been found in quartz veins and siliceous volcanic as geodes. However, it
is not the same everywhere. Amethysts are unique to geographical regions or
even mines. Different areas have different types of formations and iron
distribution patterns. Experts can often identify the source mine that a
particular amethyst came from. The key to this is the color, shape of
crystal, inclusions, associations and formation of the amethyst.
Properties At A Glance:
|
Mineral |
Quartz |
|
Chemical
Composition |
SiO2 (Silicon Dioxide) |
|
Class |
Tectosilicate |
|
Colour |
Clear, Lilac, Mauve,
Purple, Rose |
|
Luster |
Vitreous |
|
transparency |
Transparent to Translucent |
|
Crystal
System |
Hexagonal-R; 32 (Trigonal-Trapezohedral) |
|
Hardness |
7 |
|
Specific
gravity |
2.65 |
|
Index of
Refraction |
1.54-1.55 |
|
Birefringence |
0.009 |
|
Cleavage |
None |
|
Pleochroism |
Distinct |
|
Fracture |
Conchoidal |
The characteristic hardness of amethyst makes it an ideal choice for
almost any type of jewelry setting. Normal plating and pickling solutions do
not alter its nature. While it poses no significant problems, care must be
taken while soldering, as amethyst is sensitive to sudden temperature
changes. A persistent or sudden application of heat could cause a crack or
colour alteration in the gem.
The amethyst is sufficiently durable and can be worn confidently without
worry. It does not break easily due to absence of cleavage planes. However,
sharp blows must be avoided. Clean your amethyst with warm water, soap and a
soft bristle brush. Extended exposure to sun must be avoided or else the gem
will become pale.
Amethyst is the trendiest purple gemstone. Its distinctive colour
complements almost any complexion and wardrobe. Designers advocate amethyst
as the chic choice for jewelry because of its regal hue, affordability, and
variety in sizes, shapes and tones.
Since no two amethyst crystals are alike in colour or composition, its
uniqueness makes it a covetable gem. So go ahead and get yours!
Related Links :
|
| |
Belly Button Piercing The Egyptians, the Indians and many other cultures pierced this humble button to show the significance of the person sporting a pierced navel - Royalty, Warriors, exceptional Beauty. |
|
|
|
|
|
|
|