Tanzanite

Tanzanite

Tanzanite is the blue and violet variety
of the mineral zoisite (a calcium aluminium hydroxyl sorosilicate),
caused by small amounts of vanadium. Tanzanite belongs to the epidote mineral
group. Tanzanite is only found in Simanjiro District of Manyara
Region in Tanzania, in a very small mining area approximately
7 km (4.3 mi) long and 2 km (1.2 mi) wide near the
Mererani Hills.

Tanzanite is noted for its remarkably strong trichroism,
appearing alternately blue, violet and burgundy depending on crystal orientation. Tanzanite
can also appear differently when viewed under different lighting conditions. In
its rough state Tanzanite is colored a reddish brown to clear, and it requires
heat treatment to remove the brownish veil and bring out the blue violet of the
stone.

The gemstone was given the name Tanzanite after
Tanzania, the country in which it was discovered.

From 1967, an estimated two million carats of Tanzanite
were mined in Tanzania before the mines were nationalized by the Tanzanian government
in 1971.

Untreated tanzanite gemstone

Tanzanite mining developments.

In 1990, the Tanzanian government split the Tanzanite mines
into four sections: Blocks A, B, C and D. Blocks A and C were awarded to large
operators, while Blocks B and D were reserved for the local miners.

In June 2003, the Tanzanian government introduced legislation
banning the export of unprocessed Tanzanite to India. (Like many gemstones,
most Tanzanite is cut in Jaipur.) The reason for the ban is to attempt to
spur development of local processing facilities, thereby boosting the economy
and recouping profits. This ban was phased in over a two-year period, until
which time only stones over 0.5 grams were affected. In 2010, the government of
Tanzania banned the export of rough stones weighing more than one gram.

Following the construction of a 24 km (15 mi)
perimeter wall around the mines, to improve security and prevent
smuggling,production rose from 147.7 kg (325.6 lb) in 2018 to a
record 781.2 kg (1,722 lb) in 2019.

Total reserves of Tanzanite are estimated at 109,000,000
carats (21,800 kg; 48,100 lb), according to a report published in
2018. Block C, by far the largest site, has been estimated at 87,100,000
carats (17,400 kg; 38,400 lb) with a Life of Mine (LOM) expected to
last until the 2040s.

There is no universally accepted method of grading colored
gemstones. TanzaniteOne, a major commercial player in the Tanzanite market,
through its non-profit subsidiary, the Tanzanite Foundation, has
introduced its own color-grading system. The new systems color-grading
scales divide Tanzanite colors into a range of hues, between bluish-violet,
indigo and violetish-blue.

The normal primary and secondary hues in Tanzanite are blue
and violet. Untreated tanzanite is a trichroic gemstone, meaning that light that
enters this anisotropic crystal gets refracted on different paths,
with different color absorption on each of the three optical axes. As a result
of this phenomenon, a multitude of colors have been observed in various
specimens: shades of purple, violet, indigo, blue, cyan, green, yellow, orange,
red and brown. After heating, Tanzanite becomes dichroic. The dichroic
colors range from violet through bluish-violet to indigo and violetish-blue to
blue.

Clarity grading in colored gemstones is based on the eye-clean
standard, that is, a gem is considered flawless if no inclusions are visible
with the unaided eye (assuming 20/20 vision). The Gemological Institute of
America classifies Tanzanite as a Type I gemstone, meaning it is normally
eye-clean. Gems with eye-visible inclusions will be traded at deep discounts.

Heat treatment.

A rough sample of Tanzanite.

Tanzanite forms as a brownish crystal and is trichroic, which
means it shows three colors – brown, blue and violet – concurrently. Heating,
either underground naturally by metamorphic processes, or artificially, removes
the brown or burgundy color component to produce a stronger violet-blue color
and makes the stone dichroic, which means it only reflects blue and
violet. Rarely, gem-quality Tanzanite will heat to a green primary hue,
almost always accompanied by a blue or violet secondary hue. These green Tanzanite
have some meaningful value in the collector market, but are seldom of interest
to commercial buyers.

Heat-treating in a furnace is usually carried out at between
370 and 390 °C (698 and 734 °F) for 30 minutes. The stones should not
have any cracks or bubbles, as they could shatter or the cracks/ bubble could
increase in size during furnace heating.

Some stones found close to the surface in the early days of
the discovery (in an area now called block D) were gem-quality blue without the
need for heat treatment – probably the result of a wildfire in the area which
heated the stones underground. This gave rise to the idea that block D stones
were more desirable than Tanzanite found in other areas of the small Tanzanite
mining area.

Since heat treatment is universal, it has no effect on price,
and finished gems are assumed to be heat-treated. Gemological
Institute of America states that the source of
heating is gemologically undetectable, but is assumed because of its
prevalence.

Pleochroism in Tanzanite.

Pleochroism has a physical property in which the gemstone will
appear to have multiple colors based on the angle of the light hitting the
stone. Tanzanite is a pleochroic gemstone. Most Tanzanite are blue when viewed
from one direction but can vary from violet to red when seeing from a different
angle.

The physical characters can make cutting process difficult
due to the problem of selecting the perfect color. The finished color of the
gemstone will vary depending on how the table cut reflects the light.

As of 2020, Tanzanite has never been successfully synthesized
in a laboratory, so all genuine Tanzanite is naturally occurring. However,
because of its rarity and market demand, Tanzanite has been imitated in several
ways. Among the materials used for this are cubic zirconia,
synthetic spinel, yttrium aluminium
garnet, and colored glass. A test of the
stone with a dichroscope can
easily distinguish these from genuine Tanzanite, as only Tanzanite will appear
doubly refractive: the two viewing windows of the dichroscope will display
different colors (one window blue, the other violet) when viewing genuine Tanzanite,
while the imitation stones are all singly refractive and will cause both
windows to appear the same color (violet).

Tanzanite Shape:

The Tanzanite cutting comes in different shapes from Oval,
Pear, Heart, Round, Cushion, Square, Trilliant and Emerald.

COLOUR
CLARITY:

Clarity
refers to any natural inclusion in a Tanzanite running from internally flawless
to heavily included, with a strong to vivid- Blue, purplish blue,and violet ish
blue.

TANZANITE
WEIGHT: CARAT.

Carat
weight is the terminology used to measure a Tanzanite weight. One carat has 100
points and weighs 1/5 of a gram.

LME
Company provides  all Tanzanite along
with cutting and all legal documentation and certification will be sent all
over the world.