Loose diamonds' education guide: cut, color, clarity, shape, value

Learn all about Wholesale Loose Diamonds at our
Diamond Education Center.

How to get a great value in diamond engagement rings,
wedding rings and bands, and other diamond jewelry...

When dealing with a commodity as precious as diamonds, one should be aware of all factors affecting the true value of a given stone. Most "Jewelers" will promote carat weight as the primary determination of value when, in fact, cut, color and clarity can all have greater influence on the value of a loose diamond than carat weight alone.

The Gemological Institute of America (GIA) has taken great strides in developing a grading system to standardize value in diamonds. These diamond grading standards are applied to cut, color and clarity by professionally trained gemologists worldwide.

CUT

The most important yet least understood aspect of a diamond. Just like water, glass or any other transparent medium, the density of diamond will "bend" light at a specific angle as it passes through. In the 18th century, a mathematician named Marcel Tolkowski developed a mathematical model that calculated the behavior of light as it passed through a diamond. He used this model to determine the optimum angles of cut that would reflect and refract the greatest amount of light back out the top of a diamond. These "Ideal" proportions are alternately referred to as "Tolkowski Cut", "GIA Class 1 Cut" and "AGS 0 Cut". True "Ideal" proportions have only been calculated for Round Brilliant Cuts. They are listed in the Table and Depth Percentage Chart below, as well as the best or "preferred" cut proportions for the other shapes. Unfortunately, these ideal cut diamond proportions require a great amount of the diamond to be cut away, minimizing the remaining carat weight. Since loose diamonds are priced and sold by carat weight, this creates a natural contradiction in priorities: cut quality or carat weight? A properly cut diamond will virtually explode with dazzling brilliance and color. An improper cut, often for the sole purpose of leaving added carat weight, will leave dark, glassy or watery looking areas in the diamond. Less than 10% of all Round Brilliant diamonds qualify for true Ideal Cut, and only about 20% of all loose diamonds qualify as Preferred Cut. That leaves 80% of the market cut with carat weight as the priority as opposed to brilliance.

COLOR

Diamonds vary in color from colorless to slight tones of yellow or brown. Colorless diamonds are most brilliant, most rare and most valuable. The following scale shows the GIA loose diamond color rating systems. The D-J ratings are most desirable.

Color Chart
Colorless	Near Colorless	Faint Yellow	Very Light Yellow	Light Yellow
D E F	G H I J	K L M	N O P Q R	S T U V W X Y Z

CLARITY

Practically all diamonds contain naturally occurring internal characteristics called inclusions. The size, nature, location and number of inclusions determine a diamond's clarity grade and affect its value.

The following scale shows the GIA diamond clarity gradings:

Clarity Chart
FL	IF	VVS1 - VVS2	VS1 - VS2	SI1 - SI2	I1 - I2 - I3
Flawless	Internally Flawless	Very Very Small Inclusions	Very Small Inclusions	Small Inclusions	Imperfect

All ratings are based upon expert inspection of the loose diamond under 10X magnification. By GIA standards, diamonds of 1.0 carats or less with clarity grades of SI2 or better should have no inclusions visible to the naked eye. Remember, not all grading labs grade to GIA standards. The Absolue Diamond Exchange only quotes diamonds graded by labs that strictly adhere to the GIA diamond grading standards.

Why choose a GIA Certified loose diamond?

Like snowflakes, no two loose diamonds are exactly alike. Through the forces of nature that create the crystals to the skill of the cutters that shape and polish the finished diamonds, no two diamonds will turn out exactly alike.

However, the VALUE of the diamond is determined by what nature created and what the cutter finished. GIA Certified loose diamonds tell you exactly what nature created: primarily the color, clarity and fluorescence. GIA Certified loose diamonds also tell you what the cutter finished: primarily depth, table, carat weight, polish, symmetry, girdle and culet.

"GIA Certified" is recognized world wide as the standard for diamond grading. Unfortunately, not all labs adhere to GIA's strict diamond grading standards. There can be wide discrepancies in grading for color and clarity between labs. And since color and clarity are two of the "Four C's" that determine a loose diamond's value, it is important to have your diamond "GIA Certified" or graded by a lab that adheres to GIA Certified diamond grading standards on a consistent basis.

The Absolute Diamond Exchange quotes only GIA Certified Loose Diamonds, or loose diamonds graded by the following labs that we have found to adhere strictly to GIA Certified diamond grading standards on a highly consistent basis: AGS, AGA, and HRD.

A diamond is forever! Take the time to make sure your diamond is a GIA certified loose diamond or graded by an equivalent lab.

SHAPE

In addition to the traditional Round Brilliant shape, the most common Fancy Shapes are: Oval, Pear, Marquise, Princess, Radiant, Emerald and Heart.

Less common shapes include Trillion (or Triangular), Flanders and Asscher.

Layman's Guide to Loose Diamond Grading by Table and Depth Percentage, Polish, Symmetry, Fluorescence, Girdle and Culet

Table and Depth Percentage are two critical measurements for loose diamonds. The angles of cut will affect a diamond's natural ability to both reflect and refract light - that is, the diamond's ability to virtually explode with brilliance. If a diamond is cut too deep, light leaks out the sides, brilliance is lost and the center of the diamond will appear to be dark. If a diamond is cut too shallow, light leaks out the bottom and the diamond appears watery, glassy and dark. If the proportions are good, the sides and bottom of the diamond will all reflect their light back out the top of the diamond, which creates the brilliance diamonds are famous for.

The Table percent is the width of the top facet of the crown compared to the diamond's total width. Table width between 53% and 64% are considered Preferred in Round Brilliant Cut diamonds. The Depth percent is the total depth or height of the diamond compared to the total width. Depth measurements between 58% and 63% are considered Preferred in Round Brilliant Cut Diamonds. The Preferred range for these measurements will change as the shape changes, i.e. a Marquise cut diamond will have different ranges for Premium Table and Depth percentages. The following table shows the Ideal ranges for depth and table for Round Brilliant diamonds as well as the Preferred ranges for Rounds and all other shapes:

Table and Depth Percentage Chart

IDEAL SHAPE

DEPTH RANGE

TABLE RANGE

Round Brilliant 59% to 62.6% 53% to 57%

PREFERRED CUTS

Round Brilliant 58% to 63% 53% to 64%

Marquise, Oval, Pear 58% to 66% 56% to 64%

Emerald, Radiant 59% to 69% 60% to 69%

Princess 60% to 75% 60% to 79%

Heart Shape 55% to 65% 51% to 65%

Naturally, diamonds with measurements within those ranges will be more expensive than diamonds with measurements outside those ranges. You need to balance that decision yourself. A few %'s one way or the other are minimal.

Besides Table and Depth Percentages, there are several other minor grading factors that combine to affect the diamond's beauty and value.

Polish measures the quality of finish on the facets.

Symmetry refers to the proper alignment of the diamond's sections, the proper shape for the cut (circular for round brilliants, rectangular for emerald, etc.) and the uniformity in size and angles of similar facets.

Both Polish and Symmetry are rated as: Excellent (EX), Very Good (VG), Good to Very Good (GVG), Good (G), Fair to Good (FG), Fair (F), Fair to Poor (FP), or Poor (P). An excellent rating is very rare. The Very Good, Good to Very Good, and Good ratings are common and desirable. They will also affect the price, though not as much as Table and Depth.

Fluorescence, normally blue, can naturally occur in diamonds and becomes visible under Ultra Violet light. Fluorescence can be clear or cloudy. Cloudy Fluorescence is undesirable. Fluorescence can be rated as: Nil or None, Very Faint, Faint, Medium, or Strong. Nil to Faint Fluorescence will have negligible impact on a diamond. Medium to Strong Blue Fluorescence can actually be an asset in Color Grades I, J, K, L and up as it will tend to enhance the diamond's brilliance and make it appear "whiter".

The Girdle is the spacing between the upper and lower portions of the stone. Girdles can be rated from extremely thin to extremely thick. Extreme gradings should be avoided. The girdle finish can be natural, polished of faceted. Finer diamonds will normally have faceted girdles.

The Culet size refers to the smallest polished facet at the very bottom of the diamond. Avoid large or chipped culets.

Absolute Diamond Exchange

Suncoast Accredited Gemological Laboratories
4016 Cortez Road West, Suite #1201 • Bradenton, Florida 34210
Phone: 941-756-8787 • FAX: 941-751-6698

For more information contact: Dave Stieglitz, Internet Sales Manager

This page last updated on: Monday September 29, 2003 04:57 AM