History & Introduction
Alexandrite is a gemstone hardly available, the gemstone got its name from the name
of the Russian tsar Alexander II (1818-1881). The first crystals of the gemstone
were found in April, 1834 in the emerald mines near the Tokovaya River of the Ural
Mountains. It from the family of Chrysoberyl gemstone. The appearance of the stone
is emerald green during sunlight, while in the presence of luminous light it looks
red.
The utmost sensational and unique feature for this stone is its amazing capability
to change color called the 'alexandrite effect'. The color changes because of the
strong absorption of light in the blue and yellow portions of the color spectrum.
The color change is observed under definite conditions of light, naturally in the
presence of daylight also in incandescent lighting. This amazing feature makes this
semi-precious stone different from others. Green or blue-green in daylight, convert
to purple red or raspberry red in the soft shades of red in the presence of radiant
light. The feature of unique optical gives it the position of most treasured gemstones
of all, especially of good qualities.
Availability - Maximum availability of alexandrite gemstone is
in Russia, it is extracted from the mines of the Urals. However, lately it has been
found in even larger sizes in Brazil. Other locations in world where Alexandrite
is found are Ceylon, Madagascar, Tanzania, India, Zimbabwe, Burma and Sri Lanka.
Recognize - Maximum the chrysoberyl is colored by iron, however
the colour of alexandrite is due to chromium traces. With the spectroscopic analysis
along with the testing of alexandrite is distinguished from other similar stones.
However, ordinary specimens of chrysoberyl might contain chromium coloring agents,
till they present an ability of change in the color, it is identified as chrysoberyl
and not alexandrite.
Usages - Like other gemstones, alexandrite emerged millions of
years ago under metamorphic environment. The chemical element beryllium (a major
constituent in chrysoberyl) and chromium (the coloring agent in alexandrite) have
contrasting chemical characteristics and do not as a rule occur as one, usually
it is found in the rock types that is contrasting. It is the nature that has brought
these contrasting rock types into contact with each other, but the absence of the
chemical element silica is also required to prevent the development of the emerald.
The present geological scenario, which is very rare in the history of the Earth
and is the reason that makes the alexandrite crystals very scarce. This rare and
exquisite gemstone carries outstanding properties of color getting changed, and
is most often faceted into a round and cushion cuts that can bring out the best
in case of color. Alexandrite stone as a jewelry is used in rings and pendant centerpieces.
In fact the stone, which is large size is extremely rare and precious; mainly Alexandrite
is found in 2 carats or less.
Buying Guide
Color - Alexandrite's green hue is because of chromium impurities
and chromium is the same coloring element that is present in emerald, the green
variety of precious beryl. Sri Lanka (Ceylon) alexandrite is known to exhibit a
khaki to brown color change. Alexandrite from Zimbabwe origin shows a very little
color change and they are typically darker in color with tints of purple. Tanzanian
specimens are available with lighter tones and possess moderate to good color change.
Brazilian alexandrite is popular for high saturation tendency and exhibits a blue
to purplish color change. The most desirable alexandrite is those with pure hues
and a strong color change ability.
Clarity and Luster - Alexandrite stones are actually clean as well
as clear once it is cut and polished, they will show a vitreous luster. In case
of rough it ranges from transparent to opaque whereas fine alexandrite is considered
to be more treasured as compared to blue sapphire, emerald and ruby, especially
alexandrite with a weight of over 1 carat. Sri Lanka is a renowned producer of the
cleanest alexandrite, frequently absence of any visible inclusions is there.
Cut and Shape - Hardly, alexandrite is available in large sizes.
Any varieties that weigh above three carats are considered to be particularly rare.
The largest cut alexandrite gemstone available is about 66 carats and is currently
in Washington, D.C.'s Smithsonian Institution. Actually, alexandrite are faceted
in different kinds of shapes like round, marquise, oval, pear and cushion cuts,
however they are even found in fancy shapes such as heart and trillions cuts too.
They are not naturally cut to en cabochon, till they obtain chatoyant characteristics.
Treatment - Alexandrite gemstones are not treated naturally, however
imitation stones still are there. Sometimes, alexandrite stones are oiled or dyed.
There are synthetic (lab-grown) and others may be natural 'simulated' gem stones
alexandrite like the color change garnet, sapphire or spinel. A large number of
lab-grown (synthetic) alexandrite stones are in fact corundum (ruby / sapphire)
that laced or imbued with either chromium or vanadium to give color. It is costly
in preparing a synthetic alexandrite. Alexandrite is in the market since 1960.
Gemological Characteristics: