There’s so much more to diamond education than the mere understanding of the 4 C's of diamonds (color, cut, carat, clarity) and the factors that impact its quality and price.
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Pretty things may come in small boxes, but what’s in those boxes better be big. That is, yes, size does matter. However - carat weight is not the same thing as size - how large a diamond appears is also dictated by other factors such as shape and cut, so it is important to understand carat weight beyond the value it is generally and often mistakenly ascribed.
Instead of grams or kilos, diamonds are weighed in carats (not to be confused with gold’s Karat which signifies purity). This simply denotes a measuring scale where each 1 carat = 0.2 grams (0.50 carat = 0.1 gram and 5 carats = 1 gram).
As the carat weight increases, so does the size of a diamond. However, confusingly, this relationship is not a linear but rather a curve - so a 2.0ct diamond will not appear twice as big as a 1.0ct diamond as shown below.
The term carat originates from the Greek and Arabic names for the carob tree - Keration in Greek and Qirrat in Arabic. The dried seeds of the Carob (or Locust) tree were once widely used by trading merchants as counterweights for weighing gold, diamonds, gemstones and pearls due to their relatively consistent weight and size. It is important to note however, that the term “carat” with reference diamonds is different to “karat” which is the value used for the purity of gold.
The Byzantine era used glass pebbles, based on carob seeds, for weighing coins, which weighed in at 196 mg, consistent with the average weight of an individual carob seed. However their use eventually diminished as it was discovered that despite their visual uniformity, the seeds were not actually consistent in weight. Many attempts were made to standardise the measurement of gemstone weight and it was only in 1907, at the Fourth General Conference on Weights and Measures that the “carat” was adopted as the official metric measurement for gemstone weights.
In 1913 the United States officially accepted the ‘carat’ as the gemstone measurement, and in 1914 the United Kingdom and Europe followed suit. By the 1930s, the majority of the diamond and gemstone industry had agreed to the standardised measurement, which is still in use today.
Dimensions play an important role in the appearance of a diamond. In addition to the carat weight, the distance across the top of the diamond must also be taken into consideration. A common misconception is that half a carat is half the size of one carat. In fact, a half carat is half the weight of one carat, but the millimetre difference on a round stone is only 1.35mm. The average measurement for a 0.50ct stone is 5.00mm, while the average 1.00ct stone measures at 6.35mm.
While carat weight may indicate a diamond’s size, the shape and cut of a stone also play a large part in determining how large or small the stone appears. An elongated shape such as the Marquise cut may appear larger than a rounded shape such as the round brilliant even if the two stones share the same weight. When comparing two stones of the same shape however, it is important to look at the cut grades and table and depth percentages, as shallower stones will tend to appear larger than deeper ones. Other aspects such as girdle width can also affect how large a stone appears, while not necessarily affecting the quality of the stone.
Far more than simply what shape a rough diamond has been polished into, the cut is the most important determiner of a diamond’s brilliance and light dispersion. Diamond cutting is an art requiring meticulous precision, and knowing how it all works is essential to making the right choice.
Often confused with a diamond shape, the cut is actually the grading that determines how well the diamond sparkles. It encapsulates Brightness (white light reflecting from the top surface), Fire (flares of colour) and Scintillation (flashes of light).
The cut grading currently only applies to Round diamonds as they are technically easier to measure in terms of light performance. Other shapes – such as Princess cuts, Cushions cuts, Emerald shapes, do not have a cut grading on their certificate but 77 Diamonds provide an estimated cut grading based on equivalent parameters.
Cut grades range from Excellent, Very Good, Good, Fair and Poor. The grading takes into account various attributes of the diamond that cannot be seen or measured with the untrained eye. An excellent cut grading will have the best light performance, mainly influenced by the relationship of surface table and the depth of the diamond (not too deep or too shallow).
D is the highest colour grade attributed to a diamond, denoting that the stone is completely colourless (white); as such, they are extremely rare and command the highest prices.
The colour difference between a D and an E graded stone is usually only visible to an expert gemmologist using master stones as a comparison, although E graded stones are slightly cheaper.
The colour difference between an E and an F is only visible to an expert gemmologist using master stones as a comparison. F grades are the lowest and therefore least expensive of the premium colours.
G graded diamonds are nearly colourless and a slight colour difference only become perceptible when compared to diamonds of grades D or E. G stones appear colourless especially once set and therefore offer excellent value for money.
H coloured diamonds are near colourless diamonds which still appear totally white or colourless if they are not compared side by side with higher colour graded stones. The H colour is generally considered the watershed between colourless diamonds and slightly tinted diamonds.
I coloured diamonds are very slightly tinted diamonds, however, once set in jewellery, these stones may appear colourless. If you are looking to maximize your budget, then an Icoloured diamond offers great value for money.
J coloured diamonds are very slightly tinted diamonds, however, once set in jewellery, especially in yellow gold, it is harder to see the slight yellow tint which the J grade produces.
K coloured diamonds are slightly tinted diamonds, however, once set in jewellery, especially in yellow gold, it is harder to see the slight yellow tint which the K grade produces.
Seventy Seven Diamonds currently offers only stones in the higher range of D-J, as these are the only grades we recommend, however, lower clarity grades can be made available on special request.
Almost all diamonds have small impurities or “inclusions” but they are not always visible to the naked eye. The size and location of the inclusions play a significant role in determining the price of a diamond so it is important to understand clarity grades in order to make the most suitable choice.
When diamonds are formed, deep underground and under extreme pressure and heat, imperfections in the crystal structure can form and mineral impurities become trapped inside the stone.
The size of these impurities and imperfections determine the clarity grading of a diamond. Diamonds without such impurities are very rare.
The grading scale starts from Flawless / Internally Flawless (FL/IF), Very Very Slightly Included (VVS1/VVS2), Very Slightly Included (VS1/VS2), Slightly Included (SI1/SI2) to Included (I1, I2 and I3). 77 Diamonds does not sell diamonds below SI2 as they are not considered suitable for jewellery. Generally, diamonds below a VS2 grading are likely to have visible inclusions to the naked eye however this is on a stone by stone basis.
Internationally Flawless: These rare high clarity diamonds are 100% flawless inside the diamond with no blemishes or inclusions.
Very Very Slightly Included 1: There will be one minor inclusion within a diamond of this grade but only visible under 20x magnification or more.
Very Very Slightly Included 2: There will be minor inclusions within a diamond of this grade but only visible under 20x magnification or more.
Very Slightly Included 1: Diamonds of this clarity will have several inclusions that are only visible with magnification of 10x but remain clean to the naked eye.
Very Slightly Included 2: Diamonds of this clarity will have several groups of inclusion that are only visible with magnification of 10x. A small percentage of these are not eye clean.
Slightly Included 1: Only 50% of diamonds of this clarity have no visible inclusions so it is important your selected diamond is eye clean.
Slightly Included : 85% of diamonds of this clarity have some form of visible inclusion or blemish to the naked eye.
Included 1: Due to the high level of inclusions here, we do not recommended this clarity grade for diamond jewellery.
Diamond certificates are issued to confirm a stone's technical characteristics, value and identity, but it is important to know and understand the differences between the grading bodies as they operate on difference standards.
Ensuring your diamond is certified by one of the leading independent and recognised certification laboratories is essential for an unbiased assessment of the stone's quality. GIA, AGS, HRD, IGI & EGL are the leading grading bodies in the diamond industry, and are listed here in order of strictness. Today, expect most diamonds over 0.20ct to be graded by one of these.
Elegant or eccentric, sparkly or subtle? From the ever popular round brilliant to the more unusual Marquise cut, diamonds come in all shapes and sizes and there is sure to be one to suit every taste and style.
It is often said that diamonds are a girl’s best friend, but perhaps less often pointed out that there is one to suit each and every kind of "girl". Every diamond has its own story and it is up to you which one you will choose to tell yours.
From the classic and versatile round brilliant which accounts for more than half of all diamonds sold today, to the more unusual and eccentric Marquise cut which harkens back to the glory of the age d’or, choosing a diamond can be as elaborate a task as choosing the man who will give one to you. For a change though, it’s not about who but what you know, and what you know about diamond shapes can help you through one of the most significant decisions you will ever make.
Beyond the fact that each shape specifically caters to an individual or personal taste, each one is also meticulously and mathematically cut to highlight a diamond’s best features, and which girl wouldn’t want all the best for her best friend?
Clean, classic, versatile and with more fire and brilliance than any other shape, it would be difficult to persuade anyone against this choice—as proven by the fact that it accounts for more than half of all diamonds sold today. (For men wishing to surprise their ladies and unsure of what they might like, one could hardly go wrong here).
Much like the round brilliant, the Princess cut is a classic and elegant shape, although with its sharp corners boasts more of a contemporary edge. This shape is ideal way to capture the brilliance and simple elegance of the round and still be "à la mode".
Speaking volumes of vintage glamour and old world charm, and favoured by such style icons as Grace Kelly and Jackie O, the emerald cut was one of the first cuts to be used in jewellery design, and with its broad flat plane highlights the clarity and natural crystalline growth of a diamond to unparalleled measure.
Replete with timeless elegance and Art-Deco cool, the Asscher cut is a rectangular shape similar to the more well-known emerald cut, with prismatic brilliance, tremendous lustre and a fascinating optical illusion known as the "Hall of Mirrors" effect.
Infamously given to Elizabeth Taylor by two-time-husband Richard Burton, the pear, or teardrop as it is sometimes called, is a unique and feminine shape with one rounded and one pointed end that makes for a delicate and stunning choice.
A square- or rectangular-shaped hybrid cut that combines thebrilliance and depth of the round, emerald and princess cuts, the radiant is the most brilliant of all the squared shapes making it both a beautiful and dramatic choice.
Somewhere in between the round brilliant and the pear shape,the oval cut is the perfect choice if you’re wishing to savour the sparkle of the round brilliant in a slightly rarer and more elongated form.
As its name suggests, the cushion cut is a square or rectangular shape with rounded corners, resembling a pillow shape. One of the rarer and more unique choices, the cushion cut’s large facets allow for great light dispersion, giving birth to a much larger range of spectral colours and making for a highly scintillating stone.
Originally commissioned in 18th century Paris by King Louis XV to emulate the smile of his mistress the Marchioness Madame de Pompadour, the Marquise harkens back to the glory of the age d’or, and is also an ideal way to optimise carat weight and elongate the finger.
Though most often used for a side or accent stone, with its stunning brilliance and fire, this triangular cut could make for a bold and dramatic solitaire, and has been increasingly appreciated for its impressive effect as a center stone.
There are various factors that affect the pricing of a diamond and a perfect balance of these will ensure you get the ideal diamond for your price range.
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