ABOUT
TANZANITE GEM
Tanzanite is an extraordinary gemstone. It occurs in only one place worldwide.
Its blue, surrounded by a fine hint of purple, is a wonderful colour. Thanks to
its unusual aura and the help of the New York jeweller's Tiffany, it has
rapidly become one of the most coveted gemstones in the world.
It is named after the East African state of
Tanzania, the only place in the world where it has been found. Africa is a
continent which provides the world with a multitude of truly magnificent
gemstones, like tanzanite for example. On its discovery in 1967, it was
enthusiastically celebrated by the specialists as the 'gemstone of the 20th
century'. They held their breath in excitement as they caught sight of the
first deep-blue crystals which had been found in the Mererani Hills
near Arusha in the
north of Tanzania. Millions of years ago, metamorphic schists, gneisses and
quartzites formed impressive, flat-topped inselbergs on a vast plain in the
shadow of Kilimanjaro. The precious crystals grew in deposits on the inside of
these unusual elevations. For a long, long time they were hidden from the eye
of Man, until one day some passing Masai shepherds noticed some sparkling
crystals lying in the sun and took them along with them.
In Merelani today, the search is carried on
for the coveted crystals in several, smallish mines, in some cases using modern
methods. As a rule, only small grains are found, but now and again the
mineworkers succeed in fetching out a larger crystal – to the joy of the mine
owners and that of the large number of tanzanite fans.
Really just
a blue zoisite ...
Tanzanite is a blue variety of the gemstone
zoisite. It consists of calcium aluminium silicate and is not particularly
hard, having a value of 6.5 to 7 on the Mohs scale. For that reason, it should
always be worn carefully and never placed in an ultrasonic bath for cleaning or
brought into contact with acids.
But what a
fantastic colour?
The deep blue of the tanzanite is fantastic,
and runs from ultramarine blue to light violet-blue. The most coveted colour is
a blue surrounded by a delicate hint of purple, which has a particularly
wonderful effect in sizes of over 10 carats. The well developed
polychromaticity of the tanzanite is typical: depending on the angle from which
you look at it, the stone may appear blue, purple or brownish-yellow. Having
said that, most raw crystals are somewhat spoiled by a brownish-yellow
component, though it can be made to disappear by the cutter if he heats the
stone carefully in an oven to approximately 500°. During the procedure he must
pay careful attention to the moment at which the colour turns to blue. This
burning is a method of treatment which is regarded as customary in the trade,
but the raw stones must be as free of inclusions as possible, since otherwise
fissures may occur.
In fact working with tanzanite can sometimes
give even the most experienced cutter a bit of a headache, the cleavage of this
gemstone being very pronounced in one direction. This exclusive gemstone is cut
in every imaginable shape from the classical round shape to a number of
imaginative designer cuts.
A tanzanite will continue to fascinate with
its unusual, captivating aura. Its deep blue with the slightly purple tinge is
one of the most extravagant colours known to Man. It personifies immaculate,
yet unconventional elegance. A person who acquires one of these exclusive gems
is someone who wishes to set himself apart from the hoi polloi. A person who
wears it exudes confidence and individuality. The almost magical colour of a
perfectly cut tanzanite is one that not only suits confident young women; it is
also excellently suited to underlining the individuality of the more mature
woman.
In the meantime, almost any price you care to
name is being asked - and paid! - for tanzanites of good quality and large
size. What makes this stone so popular? Is it simply that fantastic colour? No,
it is also the exclusivity of its origin. The stone is particularly highly
prized because it is found in only one place in the whole world. The idea of
possessing something that not everyone has has always been one of the main
criteria in the way we esteem special gems.
Difference
between Tanzanite and Sapphire
The sapphire has long been treasured for its
deep blue color. It is now being rivaled in popularity by the similarly colored
tanzanite, which appeared on the marketplace in the late 1960s.
1. Color
Sapphires are made of corundum and are
generally blue, but can also come in yellow, pink or green. Most sapphires are
heat-treated to enhance their deep midnight-blue color. Tanzanite, made of the
mineral zoisite, is also heat-treated to achieve its medium to deep violet
blue.
2. Durability
With a hardness only slightly less than that
of the diamond (sapphire is 9 on the Mohs hardness scale; diamond is 10),
sapphire is exceptionally durable. It stands up well to everyday wear in a ring
or a bracelet. Tanzanite rates 6.5 on the Mohns scale; its softness and
brittleness require that it be worn with care so it does not crack or shatter.
3. History
Sapphire, the birthstone for September, is a
legendary gemstone from ancient times, when it was worn by kings. Because of
its relatively recent discovery, tanzanite does not yet have much lore. It was
originally called blue zoisite, until Tiffany and Company christened it
tanzanite after the country of its discovery.
4. Relative
Value
Prices for tanzanite have been rising while
prices of sapphire have fallen, meaning costs for the two gemstones may
overlap.
5. Cleaning
Sapphire can be cleaned in a variety of ways,
including ultrasonically or with a little ammonia added to warm water.
Tanzanite is sensitive to temperature changes and should be cleaned with
lukewarm water and a mild liquid detergent, never in an ultrasonic cleaner.
Five
Properties of Tanzanite
By Liz Tomas
Tanzanite is a gemstone that is typically bluish-purple in color.
Lesser-quality stones tend to be more blue than purple. These stones were first
discovered in Africa and can be mistaken for blue sapphires. The stones
properties can be used to determine if the stone of interest is tanzanite or
another stone.
1. Hardness
Tanzanite is a six to seven on the Mohs scale
of hardness. This hardness refers to the scratch resistance of stones. The
hardest stone is a diamond which is a 10 on the Mohs scale. At the bottom end
of the scale, a one, is talc, which is easy to scratch. Tanzanite is a harder
gemstone though it can be scratched by using a sharp knife.
2. Refractive
Index
The refractive index refers to how much light
will bend when it passes through the tanzanite gem. The amount of bending is
the different between the air density and gem density. The refractive index can
be used to tell tanzanite gemstones from other similarly colored stones, as
frequently tanzanite can be mistaken for sapphire. The refractive index of
tanzanite is 1.691 to 1.7
3. Pleochroism
Tanzanite is strongly trichroic when
referring to the gemstone's ability to absorb different light wavelengths. This
property is how a gemstone can appear to have different colors. The difference
in mineral and mineral density in the gemstone will cause light to be absorbed
and reflected in different ways. Tanzanite is a plechroic mineral that will
change color as it is rotated on a stand. Trichroic means that it can be seen
as a different color when looking in three different directions. Tanzanite can
be seen as blue, purple and brown. The brown color is removed using heat
treatments of temperatures that reach 500 degrees Celsius.
4. Specific Gravity
The specific gravity refers to the density of
tanzanite when compared to the specific gravity of water. This is another way
to tell similar-looking gemstones apart, as they all have different specific
gravity. Tanzanite has a specific gravity of 3.35. Therefore, it is a bit more
than three times denser than water. This density is slightly denser than the average
of rocks found on the surface of the earth.
5. Molecular
Composition
The molecular formula of tanzanite is
Ca2Al2(SiO4)3(OH). This shows that tanzanite is made of silicon, Si, calcium,
Ca, oxygen, O, hydrogen, H and Aluminum. The molecular weight of this gemstone
is 427.38 gm.
