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Diamond

Diamond Grading 

A diamond's cost is based on its characteristics commonly known as the "4 C's". Clarity, Colour and Cut are the quality elements which together with the Carat Weight determine the value of a stone. The better a diamond grades on one or all of these scales the rarer and the more costly it will be. While clarity is frequently assumed to be the most important factor of all the "C's", in fact, colour and cut (especially cut) have a more profound affect on the visual appearance of a diamond.  More...

 

Carat Weight

Carat is the unit of weight for all gemstones. One carat is subdivided into 100 "points" or "cents". Therefore a diamond measuring 75 points is 3/4 carat in weight, or 0.75ct. There are five carats in a gram. The word "carat" comes from the seed of the carob tree pod which is found in tropical climates. These seeds were used until this century to weigh precious gems. More...

 

Clarity

Because they are formed deep within the earth, under extreme heat and pressure; virtually all diamonds contain "birthmarks"; small imperfections inside the diamond (called inclusions), or on its surface (called blemishes). Clarity refers to the degree to which these imperfections are present.  More...

 

Color

Though Diamonds come in a variety of colors, some of them highly prized (pinks, blues, even yellow). However in a white diamond, the presence of a yellow tint will lower the price of a diamond. The less body color in a white diamond, the more true color it will reflect, and thus the greater its value. More...

Cut

Cut refers not to a diamond's shape (e.g. round, oval, pear, etc.) but to a diamond's proportions, symmetry and .  More...

 

 

A diamond's cost is based on its characteristics commonly known as the "4 C's". Clarity, Colour and Cut are the quality elements which together with the Carat Weight determine the value of a stone. The better a diamond grades on one or all of these scales the rarer and the more costly it will be. While clarity is frequently assumed to be the most important factor of all the "C's", in fact, colour and cut (especially cut) have a more profound affect on the visual appearance of a diamond.

Carat Weight

Carat is the unit of weight for all gemstones. One carat is subdivided into 100 "points" or "cents". Therefore a diamond measuring 75 points is 3/4 carat in weight, or 0.75ct. There are five carats in a gram. The word "carat" comes from the seed of the carob tree pod which is found in tropical climates. These seeds were used until this century to weigh precious gems.

Clarity

A diamond's clarity is determined by the number, nature, position, size and colour of internal characteristics called "inclusions" and surface features called "blemishes". These irregularities occured in the liquid magna (volcanic rock) within which the diamond was created. Diamonds are mostly pure carbon, however, during crystallization other minerals nearby, or even other bits of carbon forming more quickly may have become trapped within the cooling mass. These show themselves as the various characteristics which make up the clarity of a diamond (included crystals, feathers, clouds etc). Clarity is measured on a scale ranging from pure (flawless) to heavily included (I-3). The clarity of a diamond is graded by using 10X magnification under good lighting by an experienced grader. The final clarity grade is usually determined by how easy the inclusions and blemishes are for the grader to see.

Colour

Ideally, a diamond should have no colour at all, like a drop of spring water. Increasing degrees of body colour are measured on a scale ranging from no colour at all (D) to deeply coloured (Z). Beyond "Z" is the range where the diamond's colour is vivid and rich, called "fancy colours". Diamonds of known colour are used as comparison stones for colour grading. Grading is done by comparing the diamond to be graded against these "master stones" under either artificial or natural north daylight ( in the Northern Hemisphere). A machine called the "Colorimeter" can be used for colour grading but there is no substitute for the trained human eye.

Cut

Cut, ensures that a given stone has maximum brilliance and sparkle which would not be the case were the stone cut for weight alone.

We use the following scale to grade a stone on it's overall appearance. Simply put, when looking at a diamond, if it doesn't catch your eye or if it doesn't flash in the light, it's probably not well cut. Good cutting is what brings fire to the stone. Cut Grades

Ideal/ Excellent – Excellent light performance. Reflects almost all of the light that enters. Rare and extremely beautiful cuts.

Very Good – Very good light performance. Reflects almost all of the light that enters. Very Good diamond cuts are considered to be an outstanding value.

Good – Good light performance. Reflects most of the light that enters. Good diamond cuts are far less pricey than Very Good cuts.

Fair – Not as brilliant as a Good cuts or above, Fair diamond cuts are still considered good quality diamonds.

Poor – Poor cut diamonds are typically cut too shallow or too deep causing much of the light to leak out of the diamond's sides and base.

 

Cut refers not to a diamond's shape (e.g. round, oval, pear, etc.) but to a diamond's proportions, symmetry and polish. The beauty of a diamond depends more on cut than any other factor. Though extremely difficult to analyze and quantify, diamond cut has three primary effects on appearance: brilliance (the brightness created by the combination of all the white light reflections from the surface and the inside of a polished diamond), fire (the dispersion of light into the colors of the visible spectrum, seen as flashes of color), and scintillation (the flashes of light and dark, or sparkle, when a diamond or light source is moved).

DIAMOND ANATOMY

Once cut and polished, all diamonds possess a shared set of characteristics, often referred to as the anatomy of the diamond. While the individual proportions, angles and placement of these common characteristics vary for diamonds of different shapes, their definition is the same

 

 

To properly understand a diamond's cut, it is important to understand the terminology of basic diamond structure as it relates to proportion, symmetry and polish.

Diameter: The diameter is the width of a polished diamond from one side of the girdle to another 

Table: The table is the largest polished facet of the diamond on the top face of the stone

Crown: The crown is the top part of the diamond that is measured from the surface of the table to the girdle

Girdle: The girdle is the widest edge of the diamond where the crown ends and meets the pavilion

Pavilion: The pavilion is the bottom part of the diamond that begins at the girdle and extends downward to the point of the culet

Culet: The culet is the tiny flat facet at the bottom tip of the diamond

Depth: The depth of a diamond refers to the total length of a diamond, measured from the culet to the table

Proportion, Symmetry and Polish

  • Diamond Proportion

The Diamond's depth percentage and table percentage are also key factors that contribute to the quality of a diamond's cut. Depth percentage refers to the depth of the diamond divided by its diameter. Shallower diamonds have low depth percentages whereas deeper diamonds have higher depth percentages. A good target depth percentage for a round diamond is considered to fall between 59 and 62.5%. Table percentage refers to the width of the table divided by the diameter. Again, diamonds with a higher table percentage have larger tables, and diamonds with a smaller table percentage have smaller tables. A good target depth percentage for a round diamond is considered to fall between 53 and 59%.

  • Diamond Symmetry

A diamond's facets must be symmetrical in order to maximize the amount of light that enters and exits the stone. Diamonds with poor symmetry look slightly distorted, unbalanced and improperly shaped. Moreover, they will affect brilliance, scintillation and fire. Many asymmetrical round stones are not completely round, or have misshapen facets or off-centre culets.

  • Diamond Polish

Once a diamond is cut, each facet of the diamond is polished. If the polishing is done improperly, it can leave scratches and streaks. An Excellent diamond polish is a diamond which has very few or no scratches.

A note of caution:

Unlike the other "Cs" (carat weight, color, and clarity), the various Cut grades in existence today were not originated by GIA, and are not uniformly applied. In fact, GIA has only been assigning cut grades since 2005, and only to round diamonds.
Even though retailers use common terms to describe Cut (such as Excellent, Very Good, Fair, Poor) the terms are not uniformly defined or applied. In fact, a diamond seller may assign any cut grade they choose, based on any set of factors they wish. One retailer will use terms such as "Signature Ideal", "Ideal", and "Excellent"; while another uses "Ideal" to describe all three, and another uses "Excellent" for all. Be cautious when comparing cut grades from different sources, as they are most likely inconsistent.

Cut grade should be a primary consideration when evaluating a diamond. Only when comparing two diamonds of identical Cut grade should the individual components of Cut (such as girdle width, symmetry, polish, depth%, table %, and culet size) be used as further refinements or tie breakers.

 

Though Diamonds come in a variety of colors, some of them highly prized (pinks, blues, even yellow). However in a white diamond, the presence of a yellow tint will lower the price of a diamond. The less body color in a white diamond, the more true color it will reflect, and thus the greater its value. The Color of a Diamond actually refers to the degree of its colourlessness.

A Diamond is assigned a color grade in a viewing environment specially designed to eliminate color from surrounding surfaces as well as the light source itself. This allows the color of the diamond to be accurately measured. Minor differences in diamond color detected in this environment are very difficult if not impossible to detect in a normal environment. The diamond industry has adopted the GIA diamond color scale; almost every diamond sold today is rated using the GIA color scale, whether it was actually certified by the GIA or not.

Diamonds of D, K, and Z GIA color Grade

The GIA grades diamonds on a scale of D (colorless) through Z (light color). All D-Z diamonds are considered white, even though they contain varying degrees of color. True fancy colored diamonds (such as yellows, pinks, and blues) are graded on a separate color scale.

Below is the GIA diamond color chart with definitions, accompanied by further explanatory comments

GIA DIAMOND COLOR SCALE

Colorless 

While there are differences in color between D, E, and F diamonds, they can be detected only by a gemologist in side by side comparisons, and rarely by the untrained eye. D-F diamonds should only be set in white gold / platinum. Yellow gold reflects color, negating the diamond's colorless effect.

Near Colorless

While containing traces of color, G-J diamonds are suitable for a platinum or white gold setting, which would normally betray any hint of color in a diamond. Because I-J diamonds are more common than the higher grades, they tend to be a great value.

Faint Color

Beginning with K diamonds, color (usually a yellow tint) is more easily detected by the naked eye. Set in yellow gold, these warm colored diamonds appeal to some, and are an exceptional value. Others will feel they have too much color.

Very

Light Color

Diamonds in the N-R color range have an easily seen yellow or brown tint, but are much less expensive than higher grades.

Light Color

For almost all customers, S-Z diamonds have too much color for a white diamond.

The photo below shows a master set used by gemologists to grade color in diamonds. Each diamond to be graded is compared to the master set to determine where it should fall on the diamond color scale. The colors you see below are slightly exaggerated, since viewing diamonds face down makes their body color more pronounced. The face down orientation makes the detection of body color easier because brightness and fire are minimized when the diamond is face down.

           

 

 

 

Because they are formed deep within the earth, under extreme heat and pressure; virtually all diamonds contain "birthmarks"; small imperfections inside the diamond (called inclusions), or on its surface (called blemishes). Clarity refers to the degree to which these imperfections are present. Diamonds which contain numerous or significant inclusions or blemishes have less brilliance because the flaws interfere with the path of light through the diamond.

The position of an inclusion affects how easily it can be seen. Diamond cutters make every effort to cut a stone so that inclusions are not visible through the table of the finished diamond. The preferred position for inclusions is under the bezel facets or near the girdle because they are harder to see there.

Almost all diamonds are graded for clarity using the 11 point diamond clarity scale created by the GIA, including diamonds which were not actually graded by GIA. In grading diamond clarity,  the number, size, color, reflectivity, and position of every flaw visible under 10x magnification, is considered. Below is a reference diamond clarity scale.

DIAMOND REFERENCE CLARITY SCALE

 

FL

Flawless: No inclusions or blemishes are visible to  a skilled grader using 10x magnification

Extremely rare, less than 1 in 5000 jewelry quality diamonds are rated FL.

IF

Internally Flawless: No inclusions, only blemishes are visible to a skilled grader using 10x magnification.

FL and IF diamonds appear identical unless viewed under 10x magnification by a skilled grader.

VVS1

VVS2

Very, Very Slightly Included: Inclusions are difficult for a skilled grader to see under 10x magnification.

VVS1 inclusions are typically only visible from the pavilion, while VVS2 inclusions are visible from the crown. In each, the inclusions are invisible to the eye, appearing identical to the higher grades unless viewed under 10x magnification by a skilled grader.

VVS1

VVS2

Very Slightly Included: Inclusions are clearly visible under 10x magnification but can be characterized  as minor.

Inclusions are not visible to the naked eye. Perhaps 1 in 100 untrained observers can detect VS2 inclusions with the naked eye, on close inspection under ideal conditions.

SI1 

SI2

Slightly Included: Inclusions are noticeable to a skilled grader using 10x magnification.

SI1 is the lowest grade with flaws often invisible to the naked eye. SI2 inclusions are usually visible to the naked eye, although they will require close inspection.

I1

I2

I3

Included: Inclusions are obvious under 10x magnification and may affect transparency and brilliance.

I1   diamonds have inclusions that are almost always visible to the naked eye. Because I2-I3 diamonds have prounounced inclusions, and in the case of I3 may even affect the diamond's durability.

 

 

Just as a dollar is divided into 100 pennies, a carat is divided into 100 points OR cents. For example, a 50-point diamond weighs 0.50 carats. But two diamonds of equal weight can have very different values depending on the other members of the Four C's: clarity, color and cut. The majority of diamonds used in fine jewelry weigh one carat or less.

Because even a fraction of a carat can make a considerable difference in cost, precision is crucial. In the diamond industry, weight is often measured to the hundred thousandths of a carat, and rounded to a  hundredth of a carat.  Diamond weights greater than one carat are expressed in carats and decimals. (For instance, a 1.08 ct. stone would be described as "one point oh eight carats," or "one oh eight.")

Just as a dollar is divided into 100 pennies, a carat is divided into 100 points OR cents. For example, a 50-point diamond weighs 0.50 carats. But two diamonds of equal weight can have very different values depending on the other members of the Four C's: clarity, color and cut. The majority of diamonds used in fine jewelry weigh one carat or less.

Because even a fraction of a carat can make a considerable difference in cost, precision is crucial. In the diamond industry, weight is often measured to the hundred thousandths of a carat, and rounded to a  hundredth of a carat.  Diamond weights greater than one carat are expressed in carats and decimals. (For instance, a 1.08 ct. stone would be described as "one point oh eight carats," or "one oh eight.")

HOW DID THE CARAT SYSTEM START?

The carat, the standard unit of weight for diamonds and other gemstones, takes its name from the carob seed. Because these small seeds had a fairly uniform weight, early gem traders used them as counterweights in their balance scales. The modern metric carat, equal to 0.2 grams, was adopted by the United States in 1913 and other countries soon after. Today, a carat weighs exactly the same in every corner of the world.

As the carat size of a diamond increases, the diamond's price increases at an increasing rate. Why? This is simply because along with the weight the Per Carat Price of the diamond increases.

Because the larger the diamond, the more increasingly rare it is. Fewer than one in one million  mined rough stones are large enough to produce a finished 1 carat diamond. So, as carat weight increases, you will typically pay more not only in total, but on a price Per carat basis as well. The table below illustrates the typical relationship between diamonds of equal quality and increasing carat weights:

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