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Diamond Grading

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Carat
 
This is the Unit in which the weight of a Diamond is determined. Being simple and objective its the most easy to follow part of the 4 C's grading system.

 
Ancient traders used the seeds of the carob tree as a unit of weight. Such a seed weighs approx. 0.197gr.
In 1907, the carat weight was adapted to the metric system and now equals to 0.200 gram and Diamonds weighing less than a carat are measured in points or hundredths.

 

In practice the weight of a diamond is measured with an accurate balance to a thousandth of a carat and recorded to a hundredth of a carat. On certificates the third decimal is ignored for all numbers except 9. In this case the weight is rounded up to the nearest hundredth.

 

Example:                      Weight:             Notation:

 

    0.528                  0.52ct.

    0.529                  0.53ct.

 

 

Clarity
 
Almost all rough Diamonds contain impurities or so called "inclusions". Traces of non-diamond materials that were trapped in the mineral during the stone's formation by nature in the upper mantle of the earth, whilst crystallization took place millions of years ago.
 
Some of these inclusions can be removed during the Diamond Cutting process, but only rarely does this process produce a Flawless Diamond, as retaining maximum yield is an important decision making factor.
 
The judgment of a diamond's clarity is based on the visibility of its inclusions, determined by five parameters:
 
 

SIZE

TYPE

COLOR

LOCATION

QUANTITY 

 

 

The highest clarity grade is “loupe clean”, literally meaning, “clean when viewed through a loupe”.

A diamond is called loupe-clean if, after examination by an experienced grader with a 10x-magnification loupe it has been found free of internal characteristics under standardized light conditions.

 

The following is the clarity rating system used by diamond laboratories:

I.F.: internally flawless:
free from internal blemishes visible under 10x magnification (small external details tolerated);

V.V.S.1: very very slightly included:
minute inclusions extremely difficult to locate under 10x magnification;

V.V.S.2: very very slightly included:
minute inclusions very difficult to locate under 10x magnification;

V.S.1: very slightly included:
very small inclusions rather difficult to locate under 10x magnification;

V.S.2: very slightly included:
very small inclusions rather easy to locate under 10x magnification;

S.I.1: slightly included:
small inclusions easy to locate under 10x magnification;

S.I.2: slightly included:
small inclusions obvious under 10x magnification;

P.1- I.1: imperfect:
Large and/or numrous inclusions noticable with the naked eye, without effecting the brilliance of the diamond;

P.2- I.2: imperfect:
Large and/or numrous inclusions visible with the naked eye and decreasing the brilliance slightly;

P.3- I.3: imperfect:
Large and/or numrous obvious when viewed with the naked eye, not only decreasing the brilliance slightly but also its durability;

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Inclusions are a diamonds unique "fingerprint" and no two stones have exactly the same inclusions. Even though many inclusions are removed during the various stages of Diamond Cutting (including cleaving, sawing, bruting, cutting and polishing) pure diamonds remain extremely rare.

 

Color

 

The color of a Diamond is determined by comparing it to an approved series of samples, so called master-stones, under standardized light conditions.

Most laboratories use D 65-lamps in line with the CIE standard (International Commission on Illumination), which have a color temperature of 6,500 Kelvin and posses the same strength as natural polar - daylight.

 

As the color nuances between two adjoining color stones are practically unnoticeable when viewed through the table, the subtle difference can only be accurately judged by comparing them through the pavilion side. To determine the color, a stone is placed between the master-stones on a neutral white background and a grade is given according to an alphabetic scale ranging from D, the purest white color, to S-Z.

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Approximately 90% of gem diamonds have a basically yellowish color, caused by its natural contents of Nitrogen. These Diamonds are referred to as Type 1 Diamonds, sub-classed according to Nitrogen content intensity into A and B.

Whilst Type 1A Diamonds show a lesser Nitrogen content, resulting in white to increasingly yellowish Diamonds, Type 1B Diamonds are relatively Nitrogen rich, causing a more intense Yellow to Orange color.

Besides white, slightly yellowish and orange, diamonds can have many different colors. These are Type 2 Diamonds, which are free of Nitrogen and again sub-classed into A and B.

The color of Type 2A Diamonds is affected by cracks and graining, resulting in brown, pink and red diamonds, whilst Type 2B Diamonds contain other minerals, such as Boromit, which can lead to gray and blue Diamonds, or Graphite resulting in Black Diamonds.

 

Also some Type 2 Diamonds that are colorless do exist. Besides being free of Nitrogen they are also free of other mineral content, as well as cracks and graining. Some connoisseurs are extremely fond of them and green Diamonds are the only ones that can be found with and without Nitrogen content and are amongst the rarest and dearest.

 

Natural Fancy Color Diamonds as the trade calls these colored Diamonds can be very valuable, depending on color and its intensity

Color treated Diamonds

 

Diamonds with artificially created colors do exist, too. These Diamonds have to be indicated in such a manner, that there can be no doubt concerning the origin of the color. The term used for this indication is treated and in naming an artificial color the words “natural” or “fancy” cannot be used. As they are a creation of modern science their value is significantly lower than Natural Fancy Color Diamonds. Detection of such color treated Diamonds is extremely difficult and requires complex examination. Cases are heard of where Diamonds were “stuck” in the lab for almost two years. We highly recommend to stay away from uncertified Natural colored Diamonds.

Cut

 
 

Quite often the cut of a Diamond is confused with its shape. Diamonds are cut into various shapes depending upon the original form of the uncut Diamond, which is referred to as rough.

The most common shapes are:
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Whilst the other three aspects of the 4 C`s are dictated by nature, the cut is the one directly influenced by man. The Cut Proportions are designed to maximize the amount of light reflected through a Diamond in order to obtain their maximum existence. It is in the hands of the Cutter to create a magnificent Diamond that sparkles noticeably from a distance or to produce a dull Diamond that lacks the very life and shine it is desired for. This makes the Cut perhaps the most important aspect in the grading and evaluation of a Diamond.

For centuries Diamonds have been cut to retain a maximum yield of the rough, sacrificing brilliance for weight, as the value of Diamonds with higher carat weight increases disproportionately due to their scarcity. Frequently meaning four times the price for double the weight in equal color and clarity!

 

It was not until 1919 that this attitude towards Diamond Cutting was questioned, when Marcel Tolkowsky, a member of a Belgian family of Diamond Cutters and an engineer by education, developed as set chart of proportions for Round Brilliant Diamonds.

The Tolkowsky Ideal Cut (1919)
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These proportions were derived from mathematical calculations that considered both, brilliance and fire of Diamonds, hence producing Diamonds superior in sparkle/life. They were published in his book Diamond Design the same year and recommended to the trade. Ever since referred to as “Tolkowsky Ideal round Brilliant”.

 

Nevertheless a vast majority of Round Brilliant Diamond Manufacturers kept parameters that differ from the ideal proportions proposed by Tolkowsky to maintain profitability, by avoiding the additional weight loss and increased production costs through longer working hours.
 

Many had a point as Tolkowsky only offered one specific set of proportions and research has since proven that there are many variants that produce equally brilliant Diamonds.

Over the last decades this research has resulted in grading charts that have modified the “Ideal Cut Range” and produced further proportion grading descriptions. These are in descending order “Ideal Cut", “Excellent”, “Very Good” and “Good”.

 

It should be understood that these proportion grades are for round brilliant cut diamonds only, that no other mainstream laboratory except I.G.I issues certificates with proportion grades for Fancy shapes and that “Hearts & Arrows” is not a proportion grade.

 

Whatever the shape, a diamond cut to well proportions is easy to detect, as it has a higher overall brilliance through its better ability to reflect light. Therefore it can be of considerably higher value than its equivalent in color, clarity and carat weight.

PRINCESS DIAMONDS P/L 
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