Diamond Information

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The Four C's for evaluating Diamonds

Who is GIA?

Today's Leading Edge, Tomorrow's Standard

The Four C’s clearly provide a standard for evaluating diamonds. You should be well informed of the importance of color, cut, clarity, and carat weight. Next, determine how much you plan to spend, or what size or quality you want. This will help guide you to the best value for your money.

Color - Diamonds can cover the entire spectrum of colors. The majority range from a perceptible yellow or brownish tint, up to the very rare diamonds described as colorless. Colorless diamonds are the most desirable since they allow the most reflection of light. Off-white diamonds absorb light, inhibiting brilliance. You can best observe diamond color by placing the stone table side up on a flat white surface or grading trough, and examining it from different angles. Next, place it table-side down with the culet facing you, and examine it through the pavilion facets.

Cut - The only one of the Four C’s affected by human intervention, cut has the greatest influence on the diamond’s fire and brilliance. A round, brilliant-cut diamond has 58 facets. When well proportioned this shape best shows the stone’s brilliance because it allows the most light to be reflected back to the eye of the observer. Stones that appear lifeless or seem dark in the center are probably poorly cut. When the angle relationship between the crown and pavilion facets is correct , rays of light entering the diamond strike the rear facets at an angle greater than the critical angle (24.5 degrees for a diamond) and reflect back to the eye of the observer. 

If the stone is cut too deeply, the light strikes the rear facets at an angle less than the critical angle and the light is lost through the sides of the diamond. If the stone is cut too shallow , the light passes through the diamond without being reflected back.

Clarity - Most diamonds contain minute traces of non-crystallized carbon and internal stress fractures. Called inclusions, most of these are not apparent to the naked eye, but can be seen in loose stones under magnification.  In order to grade the clarity of a diamond, it is necessary to ascertain the number and nature of any inclusions in the stone as well as their size and position.  A diamond is said to be "Internally Flawless" when it presents no internal defect under 10x magnification.  Inclusions greatly affect the beauty and value of a diamond because they absorb the light rather than allowing it to be reflected back through the front of the stone. How much they reduce the value of a diamond depends on their size, number and position within the stone. An inclusion in the center of a diamond beneath the table is more visible than one near the edge. It also may be mirrored many times by adjoining facets.

Internally Flawless	Very Very Slightly included	Very Slightly included
Free from internal blemishes visible under 10x magnification (small external details tolerated).	Inclusions and/or external blemishes very difficult to locate under 10x magnification.	Minor inclusions and external blemishes difficult to locate under 10x magnification.

Slightly included	Imperfect	Imperfect	Imperfect
Inclusions and external blemishes easy to locate under 10x magnification.	Inclusions and external blemishes visible to the naked eye.	Inclusions and external blemishes easy to locate with naked eye.	Heavy inclusions located with naked eye.

A truly flawless diamond is extremely rare. In fact, it’s more important that any blemishes or inclusions do not affect the stone’s attractiveness or durability, than that the diamond is ‘perfect’. It is these identifying characteristics that give each stone its individual character, or fingerprint, making your diamond as unique as you are. As a matter of fact, these distinguishing marks are mapped on a diamond grading report (if your stone came with one), enabling you to identify your stone if need be.

Since clarity in a diamond is so critical, it will of course result in price differences. If a diamond of a particular cut, color and carat weight is moved to the next clarity grade, it’s possible to see a significant increase or decrease in the per-carat price--all other factors being equal.

Carat Weight - The weight or size of a diamond is measured in Carats.  The term carat comes from the ancient practice of weighing diamonds against the seeds of the carob tree. The system was eventually standardized, and one carat was fixed at 0.2 grams. One carat is divided into 100 points (or 200 milligrams per carat), so a quarter-carat diamond is 25 points or 0.25 carat. Although carat is a unit of weight, not size, the carat weight of a diamond has come to refer to particular sizes. If properly cut, diamonds of the same weight should be about the same size. These sizes don’t apply to other gems, however, because they have different specific gravities than diamonds.

Carat	0.05	0.10	0.20	0.25	0.30	0.40	0.50	0.70	0.90	1.00	1.25	1.50	1.75	2.00	2.50	3.00
Øm/ m	2.5	3.0	3.8	4.1	4.5	4.8	5.2	5.8	6.3	6.5	6.9	7.4	7.8	8.2	8.8	9.4
h m/ m	1.5	1.8	2.3	2.5	2.7	3.0	3.1	3.5	3.8	3.9	4.3	4.5	4.7	4.9	5.3	5.6

(sizes shown are fairly accurate on 72 dpi monitors)

GIA – Creators of the International Diamond Grading System™
From 1953, when Richard T. Liddicoat created and introduced the International Diamond Grading System™ – to the position the Institute holds today as the most respected grading and identification authority in the world – GIA has combined the principles of research, education, and service to help gem and jewelry professionals around the globe use science and product knowledge to sustain the public's trust.

An independent nonprofit organization, the Gemological Institute of America (GIA), is renowned for its impartial service as the world's foremost authority in gemology.  The Institute's history of ground-breaking scientific research, education, and gemological laboratory services reads as a virtual chronicle of the industry's own growth and sophistication.  Since 1931, when Robert M. Shipley founded the GIA in Los Angeles, GIA has translated its expert knowledge of diamonds and gemstones into the most respected education available in the gem and jewelry industry. The Institute's world renowned curricula of courses, classes, and seminars are developed to help jewelers and their customers deal in a mutually assured spirit of professionalism and trust.  GIA makes its knowledge available to anyone with an interest in the world of gems.

Today's Leading Edge, Tomorrow's Standard                  
Over the past two decades we have witnessed a transformation of an industry. In a relatively short time the gemstone and jewelry industry has catapulted from the dark ages into the fast paced computer and information age of the 21st century.

For example, where rough diamonds were divided in two by archaic hand operated machinery, today we have automatic sawing equipment and lasers. Where diamonds were and in some instances still are polished by hand, automatic polishing machines have taken over. The cutting of diamonds painstakingly performed by skilled laborers could now be performed perfectly by automatic machinery. Furthermore, where an experienced artisan had to lay out and plan for cutting a rough diamond in order to yield the greatest weight of the finished gem, we now have computers that not only tell one where and how to cut the diamond, but additionally will predict almost perfectly the final weight of the finished stone. There are computers that will predict the final color and clarity of the finished gemstones from the rough material.

These are a few examples of how the computer and information age has affected the diamond industry. Similarly, the colored stone and jewelry industry have been touched. Optimum yield via computer for rough Emerald, Ruby and Sapphire, jewelry design via computer, showing literally thousands of different variations of a particular style are all very real today.

Along with the maturing of both the gemstone cutting industry and the jewelry manufacturing business we have experienced the recognition of parallel industries that were, for loss of better words, not utilized by the gem and jewelry industry before, however, today a necessary component.

Let us look at the field of gemology. Gemology, the study of gemstones. Usually divided into two major categories, that of diamonds and all other gemstones, including colored stones and pearls.

Four decades ago rarely did the gem and jewelry industry require the services of a gemological laboratory, other than to distinguish natural from cultured pearls.  Today various labs are available to lend their expertise in addition to in-house gemologists.

 

 

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