The allure of precious stones lies in their colour, tone, saturation, inclusions, character, and clarity, which skilled artisans carve into exquisite jewellery. Choosing a coloured precious stone means appreciating millions of years of Earth's history and thousands of hours of craftsmanship. Along with colour, cut, clarity, and carat weight, one must also consider a precious stone's symbolism, values, and personality, which are captured by the six Cs, including certification and character. While personal preferences may lead to deviations from expert opinions, emotions cannot be measured by these guidelines.
CUT PROPORTIONS AND LIGHT
The cut proportion of a precious stone refers to its shape and dimensions, including the depth, angles, and symmetry of its facets. The way a precious stone is cut can greatly affect its overall appearance, as it impacts the way light interacts with the stone.
When white light enters a coloured precious stone, some of its rays are reflected outward while others are absorbed into the gem, creating its body colour. The transmitted rays are then returned to the viewer's eyes.
3 DIMENSIONS OF COLOUR
Colour consists of three aspects: hue, tone, and saturation. When dealing with transparent precious stones, it is useful to think of colour in a 3D system. The most desirable precious stone colour would be located at the "equator of the globe" with a medium tone and high saturation.
PLEOCHROISM
Pleochroism is a gemological term used to describe a doubly refractive gem that exhibits different colours when viewed from different angles. Tanzanites are examples of such gems. A lapidary with excellent skills can cut the gem in a way that reduces the pleochroism effect in the final cut and polished gem. The goal is to create a gem that displays the full colour when viewed face up, with minimal or no secondary hues.
The Six C’s
Character
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Color
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Clarity
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Cut
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Carat
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Certification, Reports and Treatments
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Character
Each colored gemstone is unique and distinct!
The captivating allure of coloured stones lies in their ability to transcend the
confines of perfection, with some possessing a radiant beauty that defines their
character. While diamonds are celebrated for their clarity, their unique charm
emanates
from a blend of inclusions, light reflection, and crystal pigments, creating an
internal
glow that is entirely their own.
Despite their imperfections, these stones exude individuality and distinct
characteristics, making them a perfect reflection of one's unique personality.
Color
Gemmologists characterize the color of a gemstone based on its hue, tone, and saturation levels.
GIA evaluates diamonds by comparing them to known coloured stones under controlled
lighting and specific viewing conditions to determine their colour. Precious stones
have a wide range of hues, each with a unique and distinct colour. Describing a
stone's colour is a complex process that involves examining its hue, saturation, and
tone.
Hue is the visible colour variation in a precious stone and is often used to
differentiate between different shades of the same colour. However, naming
conventions for hues are not standardised. NGE colour cards are commonly used to
identify the hue of precious stones.
Saturation refers to how evenly the colour is distributed throughout the stone
and how strongly it is expressed. Good saturation is characterised by a vibrant and
evenly distributed colour, while poor saturation is characterised by weak and uneven
colour distribution.
The tone of a precious stone is determined by the level of lightness or
darkness of its
colour. Two precious stones with the same colour can appear different due to the
amount of grey mixed with the main hue, resulting in one being lighter and the other
darker. Spinel is an example of a precious stone that can be found in various
colours, such as red, pink, blue, and green, which are determined by its chemical
composition, impurities, and crystal structure. Red is created by chromium, while
blue is produced by iron and cobalt.
Clarity
Clarity in a gemstone is determined by the lack of imperfections or flaws, which amplifies its aesthetic appeal and worth.
To determine a precious stone's clarity, a grading system ranging from "flawless" to
"included" is used. The clarity grade assigned to a precious stone provides a
standard terminology for buyers to compare and assess the quality and value of a
precious stone
Precious stones are graded according to their clarity, which refers to the absence
of inclusions or blemishes. The highest grade is "free from flaws", which
means the stone has no visible imperfections, even under 10x magnification. These
stones are the rarest and most valuable.
The next grade is "eye clean", which means the stone has no visible
inclusions or blemishes to the naked eye. These stones are also considered high
quality and value.
"Slightly included" stones have minor imperfections that are visible under 10x
magnification, but not to the naked eye. These stones are still of high quality and the
imperfections usually do not affect their beauty or durability.
"Included" stones have visible inclusions or blemishes that can be seen with the
naked eye. These stones are considered lower quality and less valuable than stones with
higher clarity grades. Depending on the nature and location of the inclusions, they may
also affect the durability of the stone.
When purchasing a precious stone, it's essential to consider the clarity grade
carefully, as this can significantly impact the stone's value and beauty, as the higher
the clarity grade of a precious stone, the more valuable it is likely to be. The best
way to assess the clarity grade of a precious stone is to examine it under
magnification, such as with a jeweller's loupe or microscope, and to seek the advice of
a reputable gemologist or jeweller.
Cut
The term 'cut' refers to the specific shape and polished form achieved from the raw gemstone.
Gem-cutting is a delicate and intricate art that continues to be practised in
traditional workshops established for centuries. Traditional cuts include faceted
gems with straight-line cuts like round or oval symmetric cuts and non-faceted gems
with rounded surfaces like the ancient cabochon.
The choice of cut is based on the nature of the rough precious stones, with a clean
rough being suitable for faceting to emphasise natural beauty.
For instance, the most popular cut for Tanzanite is the step cut, improving
stability for the relatively soft gem. Round Brilliant cut is preferred for Spinel
as they minimise waste and enhance the precious stone's internal fire and colour.
Carat
Carat refers to the weight of the gem, despite a common misconception that it denotes its size.
When it comes to choosing the perfect precious stone for your jewellery, it is
essential to consider the carat weight in conjunction with the other 5 C's, which
determine the value and quality of a precious stone.
Carat refers to the weight of the precious stone, a single carat is equivalent to
0.2 grams or 200 milligrams, and the higher the carat weight, the more valuable and
rarer the precious stone becomes, While a larger precious stone may catch your eye
but a smaller precious stone with higher clarity, colour, and cuts may be more
valuable.
It's also vital to remember that different types of precious stones have varying
average carat weights, so it's crucial to compare apples to apples. For example, an
8mm round-cut Tanzanite has an average carat weight of 1.80 to 2.30, while a
Tsavorite of the same size weighs about 2.00 to 2.60 carats.
Confidence, Reports and Treatments
Validated information about its quality, origin, and any enhancements it may have undergone, ensuring transparency and trust in its valuation.
To ensure that you are purchasing a responsibly sourced and accurately described
precious stone, it is important to buy from a trusted source. Due to the limited
availability of high-quality precious stones, many undergo treatments to improve
their appearance, which affects their value. Any treatments should be disclosed to
the customer, and if the price seems too good to be true, it probably is.
Do not hesitate to ask any questions that will aid in the comprehension of your
precious stone. Gem Experience is working with industry partners to make laboratory
and chain-of-custody reports a standard for precious stones. This ensures that
purchasers of its precious stones can have confidence in their quality and that the
purchase has a positive impact on the gem's country of origin.
The Mining Process
"The Gem Experience" runs its own mining operations, upholding a rigorous ethical mining code and optimal practices to ensure the preservation of Tanzanite's most valuable characteristics.
Since 1967, a staggering two million carats of Tanzanite have been mined, leading up to the Tanzanian government's nationalization of the mines in 1971.
A significant change occurred in 1990 when the government segmented the mines into four distinct areas: Blocks A, B, C, and D. Large-scale operators were granted Blocks A and C, while Blocks B and D were set aside for local miners.
In an initiative to spur the growth of local expertise and stimulate the economy, the Tanzanian government implemented a law in June 2003 that prohibited the export of uncut Tanzanite to India, a place renowned for its gemstone cutting industry in Jaipur.
Further legislation was enacted by the Tanzanian government in 2010, prohibiting the export of unpolished gemstones weighing more than a gram.
The Art of Shaping Tanzanite
One of the challenges in handling Tanzanite lies in its yield - typically, a raw piece of Tanzanite renders just 25% of usable material. Consequently, immense pressure is placed on the cutter to optimize return on investment by selecting the most suitable shape, which could range from a basic cabochon to a more intricate trilliant or princess cut.
The process begins with mounting the stones onto 'dop sticks', followed by cutting and polishing the facets across the stone's entire surface, guided by a highly symmetrical pattern.
The dop stick is inserted into a specialized handpiece that offers meticulous control over the stone's position. The facets are subsequently ground, sanded, and polished on a rotating lap studded with ground diamond, with water serving as a coolant.
Upon completion of one side (either top or bottom) of the stone, it is then shifted to another dop stick, and the procedure is mirrored on the opposite side.
Assessing Tanzanite's Qualities
Each feature of Tanzanite is scrutinized to guarantee that only the highest quality gemstones are released to the market.
The grading of Tanzanite is conducted using the 4Cs principle, similar to the methodology employed for diamond grading. Factors like the color, cut, clarity, and carat weight of each individual stone are carefully evaluated, and the findings are documented on a unique certificate that accompanies the stone. A superior blend of the 4Cs elevates the quality and, consequently, the value of the Tanzanite gemstone."
The Tanzanite Tale
While the legendary tale may be a part of folklore, the actual history of Tanzanite is equally captivating.
A geological marvel occurred over 585 million years ago in a confined area of merely 14 square kilometers, during the event now known as the Pan-African event. The shifting continents resulted in the formation of Mount Kilimanjaro and the Great Rift Valley. Subterranean minerals underwent metamorphosis under extreme heat and pressure, leading to the birth of Tanzanite.
Famously known as 'a thousand times rarer than diamonds', Tanzanite has also earned the title of the 'single generation' gemstone due to its finite supply. Even experts maintain the odds of discovering another source of Tanzanite on Earth are one in a million.
Another intriguing characteristic of Tanzanite is its trichroic nature, meaning it radiates three different colors—blue, violet, and burgundy—from three different axes in its unprocessed state. However, once gently heated, the burgundy hue fades, leaving behind an intense blue-violet tint.
The discovery of this gemstone dates back only to 1967, initially mistaken for sapphire until its composition revealed it to be a form of blue zoisite. By 1968, the renowned jeweler Tiffany & Co had baptized the gemstone as Tanzanite and introduced it to the world as the new must-have, proclaiming it to be "the most beautiful blue stone to be discovered in 2000 years."
By 2001, in acknowledgement of its widespread popularity, Tanzanite had seen such an increase in demand within the jewelry industry that it ranked as the second most favored colored gemstone in the United States, just behind the sapphire.
Recognizing its acclaim and unique properties, the official birthstone list in the jewelry industry was revised in 2002 to include Tanzanite, along with turquoise and zircon, as the December birthstone. This was a remarkable milestone, considering it was the first modification to the list since 1912!
Tanzanite Knowledge
Origins of the Blue Jewel
The exclusive source of this captivating gemstone is confined to a tiny area nestled at the base of Mount Kilimanjaro. Tanzania, a nation steeped in lore, is home to an age-old Maasai legend where a thunderbolt descended from the heavens, hitting the earth and transmuting all the rocks into a glistening blue hue - the birth of Tanzanite.
Exploring the Depths of Mererani
Tanzanite, a precious gemstone, is industrially mined from a singular, small locale known as the Mererani (or Merelani) Hills in the northern part of Tanzania, nestled at the base of Mount Kilimanjaro. In its early stages, Tanzanite was readily available on the earth's surface, easily picked up by those passing by. However, the surface collection swiftly evolved into the creation of pits and ultimately developed into tunnel systems. These tunnels delve hundreds of meters into the heart of the earth, marking a significant transition from the previous scavenger mining approach.
Expertise Handling
Achieving an 'excellent cut' certification for Tanzanite requires years of specialized training aimed at maximizing the gemstone's radiance. The stone's unique property to exhibit either blue or violet hues, depending on the viewing angle, underlines the significance of the cutting process in unveiling its true colors. The ultimate visual appeal of the gem, predominantly its face-up color, is fundamentally determined by the direction of the cut.
Evaluating Tanzanite's Quality
After the Tanzanite gemstone is expertly shaped and polished, it undergoes a rigorous grading process in a laboratory to ascertain its quality. The Tanzanite Experience Museum houses the Tanzanite Laboratory, a place where each gemstone is meticulously evaluated before being made ready for sale.
