Tanzanite Cape Town jewellery.
Tanzanite was discovered in 1967 in the Merelani Hills in Tanzania
which is the only locality where this unique gemstone is found. It was
added to the Birthstone List in 2002 – the first new gem to be honoured
with such a status since 1912.
Tanzanite exhibits rich violet-blue colours that are often due to heat-
treatment. Colours range from blue to purple and from medium to dark
in tone. Those with a predominantly blue colour command a premium
price. The clarity of most tanzanite can be described as eye-clean.
Tanzanite can be less expensive than sapphire and is often purchased
as an alternative. Prins and Prins offers Tanzanite jewellery in Cape Town.
“the most beautiful stone to be discovered in 2000 years.”
Harry Platt, president of Tiffany and Co.
THE HISTORY OF TANZANITE
In July 1967, Manuel de Souza, a part-time gold prospector, found blue
and blue-purple gem crystals in the Merelani Hills, about 40 km
southeast of the town Arusha, in Tanzania. The crystals were shown to
John Saul, a geologist, who sent it to the Gemological Institute of
America, where it was identified as a variety of the mineral zoisite.
Scientifically called “blue zoisite”, the gemstone was renamed as
tanzanite by Tiffany & Co., who wanted to capitalize on the rarity and
single location of the gem, and thus named it after the country where it
was discovered. Prins and Prins offers Tanzanite jewellery in Cape Town.
GEOLOGY OF TANZANITE
Tanzanite occurs in an area approximately 7 km (4.3 mi) long and 2 km
(1.2 mi) wide near the town of Arusha, in a relatively complex geological
environment. It was formed around 585 million years ago during the
collision of tectonic plates that formed the supercontinent of Gondwana.
The intense heat produced by the collisions and the unusual chemistry
of the rock caused tanzanite to crystallize. About 400 million years later,
the massive Gondwanaland broke up and the continents as we know
them today, drifted away from Africa. Vulcanism in the area created the
well-known Kilimanjaro Mountain which overlooks the much older
tanzanite deposits. Prins and Prins offers Tanzanite jewellery in Cape Town.
MINERALOGY OF TANZANITE
The mineral zoisite is a calcium aluminium hydroxyl sorosilicate and the
blue colour is caused by small amounts of the rare element vanadium.
Tanzanite is noted for its strong triochroism, which is an optical
characteristic that causes the crystal to have different colours, ie, blue,
violet or burgundy, when viewed in different directions.
Tanzanite can also have different colours when viewed under different
lighting conditions. The blues appear stronger under fluorescent
light and the violet hues can be seen readily when viewed
under incandescent (yellow) illumination. See below.
The Mohs Hardness of tanzanite is 6.5 – 7, which is similar to that of
emerald. Not being the hardest of gems, it needs to be worn with care.
In 2002, the American Gem Trade Association chose tanzanite as a
December birthstone, the first change to their birthstone list since 1912.
HEATING
Heating, either naturally by underground metamorphic processes, or
artificially – to about 370-3900C in a furnace – remove the
burgundy(brown) colour component and produce a stronger violet-blue
colour. Rarely, a green primary hue accompanied by a blue or violet
secondary hue can be produced by heating.
Since heat treatment is universal, it does not affect price, and finished
gems are assumed to be heat-treated. The GIA has stated that the
source of heating cannot be detected by gemmologists.
MINING HISTORY
From 1967, an estimated two million carats of tanzanite were mined in
Tanzania before the mines were nationalized by the Tanzanian
government in 1971.
After a devastating monsoon flooded the mines in 1998, the Tanzanian
Government split the mining area into Blocks A, B, C and D. A and B
were reserved for local miners. The important block C was leased to
AFGEM, a South African company, which was sold to TanzaniteOne in
- In 2010, the company was forced to cede 50% of its production
to the Tanzanian State Mining Company.
For security and to prevent smuggling, a 24km perimeter wall was built
around block C in 2011. Thereafter production rose from 480kg to a
record 781.2kg in 2019.
In June 2020, the world’s largest tanzanite crystals were discovered by a
small-scale miner, who sold a 9.72kg and a 5.1kg crystal to the
Tanzanian government for a total of US$ 3.35 million.
WHAT DETERMINES THE VALUE OF TANZANITE?
As with most gemstones, a combination of its beauty, durability, rarity
and consumer demand determines the value of tanzanite.
Tanzanite is, without a doubt, one of the most beautiful gemstones ever
discovered. Its variable violet-blue hues and the colour intensity of
larger gems have made it one of the most sought-after gemstones.
The colour of tanzanite has been described as: “the colour sapphire
can only wish for.” And that it occurs in one locality only, adds to its uniqueness, rarity and the consumer’s need-to-have. No wonder the price of tanzanite has increased since mining activities were brought under control in the early 2000s. Prins and Prins offers Tanzanite jewellery in Cape Town.
HOW IS THE QUALITY OF TANZANITE DETERMINED?
The 4 C’s of tanzanite are graded as follows:
- Carat weight. As with all gemstones, the weight of polished
tanzanite is determined by electronic scales and described in
carat. (1 carat = 200 mg) - Colour
Tanzanite ranges in colour from pale lavender with light blue hues
to a dark velvety blue with violet hues. Unfortunately, there is no
universally accepted grading system for tanzanite. The following
three colour grading systems are in use.
i) The Tanzanite Foundation has introduced its colour-
grading system. It divides all tanzanite into two colour
groups, i.e., those with a dominant violet hue called the
blueish-Violet Group (vB) and a group with blue the dominant
hue called the violetish-Blue Group. The intensity and
saturation of the stone, i.e., the intensity of colour and the
darkness of the stone is indicated by a number 5 to 1+. 1+
indicates the most beautiful and vivid colour.
For example; Violet dominates: bV1+, bV1, bV2, bV3, bV4 and bV5
Blue dominates: vB1+, vB1, Vb2, vB3, vB4, and vB5
ii) The Gemological Institute of America (GIA) has a grading
protocol for describing the colour and clarity of gemstones
that differs from the above scheme.
Firstly, the colour (hue) of the gem is described, as the eye sees it in a
face-up position under daylight, for example: violetish-blue, or blueish-
purple, greyish-blue, etc.
Secondly, the tone, i.e., the darkness of the stone, and its saturation, i.e.,
the intensity of the colour, are described on scales from 1 – 6, with 6 the
better value.
The diagram below shows that a grade of violetish-Blue 6/6 is
considered the most appealing. Stones with a 6/6 tone and saturation
grade often have a deep velvety violetish-blue appearance. If the tone is
darker than 6, the gem absorbs so much light it appears blackish and
with poor brilliance, and thus less expensive.
iii) The original Colour Grading System that miners and cutters
used in Tanzania in the last century, is still promoted by
some sellers today. From the weakest to the strongest the
terminology they use is as follows:
Poor colour A – AA – AA – AAAA – D – SD darkest colour
The tanzanite in jewellery most often seen in mall stores is of lighter
pastel colour and more affordable than the velvety deeply saturated
violetish-Blue stones in up-market tanzanite stores.
Tanzanite has also the unique quality that smaller stones are normally
paler in colour and that the intensity of the colour increases as the gem
gets larger.
Tanzanite of 50 or more carats are usually a deep dark colour,
extremely rare and sought after by investors and collectors
iv) Clarity
The clarity grading of tanzanite is based on the eye-clean standard, which
means, 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
v) Cut
As with all gemstones, the cut and the proportions of a gem determine
its sparkle (brilliance). Tanzanite is mostly cut and polished into fancy
shapes, such as trilliant, pear, oval and elongated cushion cuts. (see
below.) A greater loss in material is suffered in cutting round
tanzanite, which, understandably, is thus more expensive than the fancy
shapes.
Other factors such as the quality of the polish and the symmetry of the shape is combined with the proportions to give an overall cut grade for
the stone.
Cut grades can vary from Excellent, Very good, Good, and Fair.
Prins and Prins offers Tanzanite jewellery in Cape Town.
BEWARE OF IMITATION (FAKE) TANZANITE
Tanzanite cannot be made in the laboratory, so all genuine stones
are mined from nature. Because of its popularity, imitations, a.k.a.
‘look-a-likes,’ have been made by man. For instance:
Cubic zirconia, synthetic spinel, synthetic yttrium aluminium garnet
and glass with a purple-blue colour are readily available as fake
tanzanite.
A purplish-blue lab-grown forsterite(Mg2SiO2) is sometimes sold
as tanzanite.
Poor and pale-coloured tanzanite is enhanced by a thin layer of
cobalt to give it a deeper shade of blue, which will rub off over
time. The process of cobalt coating is deceptive and should be
declared by sellers of such treated stones.
Identification of fakes:
A qualified gemmologist will have no problem identifying fake or cobalt-
coated tanzanite. There are various gemological tools and techniques,
such as the determination of pleochroism, refractive index, birefringence
and typical inclusions of lab-grown stones, that can be used to separate
natural tanzanite from its many imitations.
Unfortunately, the normal retail jeweller often has not the expertise or
equipment to identify fake tanzanite.
NOTE: Unmounted tanzanite or tanzanite must be set in
jewellery be accompanied and sold with a grading report from a
qualified gemmologist.
HOW TO CARE FOR TANZANITE JEWELLERY.
Because tanzanite is about as hard as emerald, active people should
take care when wearing it. Tanzanite is an ideal gem for earrings,
pendants, and brooches. The gem is stable to light but can be damaged
by hydrochloric and hydrofluoric acid.
Sudden temperature changes can cause cracking and undue pressure,
as during the setting of the stone in jewellery, can cause damage. Your
tanzanite jewellery should be cleaned with warm soapy water, and under
no circumstances should an ultrasonic or steam cleaner be used.
HEALING PROPERTIES OF TANZANITE
Some people believe most gemstones have a specific energy of
a vibration that aids metaphysical healing. Tanzanite is said to be helpful
in all stress-related illnesses and that its high crystal energy can
transform negative energies into positive ones which can help to overcome
fear and anxiety.
Others believe they are magical stones that can connect you with
ancient wisdom and increase your spiritual awareness.
These traits are not supported by scientific evidence and are not supported
by Prins & Prins.
GRADING SERVICES FROM PRINS & PRINS GEMMOLOGICAL
LABORATORY
The Prins & Prins Gemological Laboratory offers identification and
grading service for tanzanite and other coloured gemstones.
SOME CUTTING STYLES
Cushion Oval Triangle Pear Round
GEMMOLOGICAL SPECIFICATIONS
Mineral Zoisite
Chem.Composition: Ca 2 A1 3 O 12 (OH)
Specific Gravity 3.35
Hardness 6-7
Refractive Index 1.691 – 1.700
Birefringence .008 – .013
Fluorescence UV light Inert (LW/SW)
Pleochroism Strong Trichroic
Optic character Bi-axial positive
This certificate is the opinion of the grader at the specific time of
inspection. It is not an evaluation. The customer shall have no
claim against the grader, its principal, distributor or retailer for
any inaccuracies or errors contained herein. Please Note: Most
gemstones have been heated to improve their colour.
GRADERS Dr Petré Prins PhD(Geochemistry) MBA
Riana Courtis Graduate Gemologist. (GIA)
Date………………………Signature……………………..
TANZANITE
the item graded
GEMOLOGICAL
GRADING REPORT
No. T3121
PRINS & PRINS
GEMSTONE LABORATORY
Huguenot House, 66 Loop Street, Cape Town, South Africa.
www.prinsandprins.com / Tel: 0027 21 422
Member of the S.A Jewellery Council
GRADING REPORT
Identification … NATURAL TANZANITE ………..
Origin ………….. Merelani Hills, Tanzania …….…
Weight …………..…… 12.48 ct ……………..…………
Dimensions………. 16,23 x 13.37 – 8.58 mm ……..
Shape ………..…………… OVAL …………………………
Colour Hue …… blueish VIOLET (bV1) …………
Tone ……….… DARK …………..………..…..
Saturation …….. VIVID …………………….……
Clarity ………… Internally EYE CLEAN ……………..
…. slight abrasion on girdle…….…….…
Cut …………………….. VERY GOOD …………..….….
Brilliance …………….…… 80% ………………….…….
Final Grade ……… PREMIER PLUS ………….…
GRADING REPORT
Identification … NATURAL TANZANITE ………..
Origin ………….. Merelani Hills, Tanzania …….…
Weight …………..…… 12.48 ct ……………..…………
Dimensions………. 16,23 x 13.37 – 8.58 mm ……..
Shape ………..…………… OVAL …………………………
Colour Hue …… blueish VIOLET (bV1) …………
Tone ……….… DARK …………..………..…..
Saturation …….. VIVID …………………….……
Clarity ………… Internally EYE CLEAN ……………..
…. slight abrasion on girdle…….…….…
Cut …………………….. VERY GOOD …………..….….
Brilliance …………….…… 80% ………………….…….
Final Grade ……… PREMIER PLUS ………….…
EXPLANATION OF REPORT
WEIGHT: 1 carat = 200mg = 100 points
COLOUR HUE: “vB” indicates that the colour is predominantly
blue, while “bV” indicates a predominantly violet colour.
bV1 + or vB1 + exceptional bV1 or vB1 = excellent
bV2 or vB2 = very good bV3 or vB3 = good
bV4 or vB4 = moderate bV5 or vB5 = light
TONE: Describes the darkness or lightness of the colour
colourless — light – medium – dark – very dark — black
SATURATION: Describes the strength of the primary colour.
very light – light-moderate – strong – intense – vivid
CLARITY: indicates the amount of internal and external
blemishes visible with the trained naked eye.
eye clean slightly included included
CUT: Describes the quality of the gem’s symmetry, polish and
proportions
excellent very
good good average
BRILLIANCE: The percentage of light reflected to the eye with
the gemstone in the face-up position.
FINAL GRADE
PREMIER PLUS – PREMIER – GOOD – AVERAGE – POOR
SATURATION: Describes the strength of the primary colour.
CLARITY: indicates the amount of internal and external
blemishes visible with the trained naked eye
eye clean slightly included included
CUT: Describes the quality of the gem’s symmetry, polish and
proportions
excellent very
good good average
BRILLIANCE: The percentage of light reflected to the eye with
the gemstone in the face-up position.
FINAL GRADE
Premier plus
Premier
Good
Average
Poor
GRADING REPORT
Identification … NATURAL TANZANITE ………..
Origin ………….. Merelani Hills, Tanzania …….…
Weight …………..…… 12.48 ct ……………..…………
Dimensions………. 16,23 x 13.37 – 8.58 mm
Shape ………..…………… OVAL …………………………
Colour Hue …… blueish VIOLET (bV1) …………
Tone ……….… DARK …………..………..…..
Saturation …….. VIVID …………………….……
Clarity ………… Internally EYE CLEAN ……………..
…. slight abrasion on girdle…….…….…
Cut …………………….. VERY GOOD …………..….….
Brilliance …………….…… 80% ………………….…….
Final Grade ……… PREMIER PLUS ………….…
OWN A TANZANITE – A gem for the future
You can be the proud owner of the world’s most beautiful gemstone.
Contact Prins & Prins Diamonds for a vast selection of loose tanzanite
and already-set tanzanite jewellery. You can rest assure that every
Prins & Prins tanzanite has been bought from sustainable sources and
chosen by their gemologists for its excellent colour, proportions and
clarity.
All of their tanzanite larger than 1 carat is accompanied by a
Gemological Grading Report (see sample above) as well as an
Insurance Valuation Certificate.
Prins and Prins offers Tanzanite jewellery in Cape Town.
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Beautiful Tanzanite Jewelry By The Rare Gemstone Company