Education

Carat

Diamonds and other gemstones are weighed in metric carats: one carat is equal to 0.2 grams, about the same weight as a paperclip. (Don’t confuse carat with karat, as in “18K gold,” which refers to gold purity.)

Just as a dollar is divided into 100 pennies, a carat is divided into 100 points. 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.


Color

Diamond color is all about what you can’t see. Diamonds are valued by how closely they approach colorlessness – the less color, the higher their value. (The exception to this is fancy-color diamonds, such as pinks and blues, which lie outside this color range.)

Most diamonds found in jewelry stores run from colorless to near-colorless, with slight hints of yellow or brown.

GIA’s color-grading scale for diamonds is the industry standard. The scale begins with the letter D, representing colorless, and continues with increasing presence of color to the letter Z, or near-colorless. Each letter grade has a clearly defined range of color appearance. Diamonds are color-graded by comparing them to stones of known color under controlled lighting and precise viewing conditions.

Many of these color distinctions are so subtle as to be invisible to the untrained eye. But these slight differences make a very big difference in diamond quality and price.

WHY DOES THE GIA COLOR GRADING SYSTEM START AT D?

Before GIA developed the D-Z Color Grading Scale, a variety of other systems were loosely applied. These included letters of the alphabet (A, B and C, with multiple A’s for the best stones), Arabic (0, 1, 2, 3) and Roman (I, II, III) numerals, and descriptions such as “gem blue” or “blue white.” The result of all these grading systems was inconsistency and inaccuracy. Because the creators of the GIA Color Scale wanted to start fresh, without any association with earlier systems, they chose to start with the letter D—a letter grade normally not associated with top quality.

Clarity

Diamonds that are absolutely clear are the most sought-after and therefore the most expensive. But many diamonds have inclusions — scratches, trace minerals or other tiny characteristics that can detract from the pure beauty of the diamond. The GIA and EGL use a detailed system of rules and standards to summarize the number, location, size, and type of inclusions present in a diamond.
diamond clarity

FL, IF Diamonds: Flawless: No internal or external flaws. Internally Flawless: No internal flaws. Very rare and beautiful diamonds.

VVS1, VVS2 Diamonds: Very, Very Slightly Included: Very difficult to see inclusions under 10x magnification. An excellent quality diamond.

VS1, VS2 Diamonds: Very Slightly Included: Inclusions are not typically visible to the unaided eye. Less expensive than the VVS1 or VVS2 grades.

SI1, SI2 Diamonds: Slightly Included: Inclusions are visible under 10x magnification, and may be visible with the unaided eye. A good diamond value.

I1, I2, I3 Diamonds: Included: We do not carry diamonds of I-grade clarity.

We recommend that you select an "eye-clean" diamond — one that has no inclusions visible to the unaided eye. An excellent value, diamonds of this clarity are much less expensive than IF- or FL-grade diamonds and typically do not contain visible inclusions that detract from the beauty of the diamond. If you're considering an SI grade diamond, call to speak to a diamond and jewelry consultant who will review the diamond to ensure the inclusions are not visible with the unaided eye. But, if you'd rather not compromise on clarity yet are budget conscious, choose a diamond with a good cut and G or H color.

The table to the right compares the prices of diamonds with the same carat weight, color, and cut grades.

Cut

Cut is the factor that fuels a diamond’s fire, sparkle and brilliance.

The traditional 58 facets in a round brilliant diamond, each precisely cut and defined, are as small as two millimeters in diameter. But without this precision, a diamond wouldn’t be nearly as beautiful. The allure of a particular diamond depends more on cut than anything else.

Though extremely difficult to analyze or quantify, the cut of any diamond has three attributes: brilliance (the total light reflected from a diamond), fire (the dispersion of light into the colors of the spectrum), and scintillation (the flashes of light, or sparkle, when a diamond is moved).

An understanding of diamond cut begins with the shape of a diamond. The standard round brilliant is the shape used in most diamond jewelry. All others are known as fancy shapes. Traditional fancy shapes include the marquise, pear, oval and emerald cuts. Hearts, cushions, triangles and a variety of others are also gaining popularity in diamond jewelry.

As a value factor, though, cut refers to a diamond’s proportions, symmetry and polish. For example, look at a side view of the standard round brilliant. The major components, from top to bottom, are the crown, girdle and pavilion. A round brilliant cut diamond has 57 or 58 facets, the 58th being a tiny flat facet at the bottom of the pavilion that’s known as the culet. The large, flat facet on the top is the table. The proportions of a diamond refer to the relationships between table size, crown angle and pavilion depth. A wide range of proportion combinations are possible, and these ultimately affect the stone’s interaction with light.

In early 2005, GIA unveiled a diamond cut grading system for standard round brilliants in the D-to-Z color range. This system, the product of more than 15 years of intensive research and testing, assigns an overall diamond cut grade ranging from Excellent to Poor.

HOW DOES PAVILION DEPTH AFFECT A DIAMOND'S CUT?

The distance from the bottom of the girdle to the culet is the pavilion depth. A pavilion depth that’s too shallow or too deep will allow light to escape through the sides or the bottom of the stone. A well-cut diamond will direct more light through the crown.

Shape

Virtually all  diamond cuts sold and used in jewelry are one of ten round or fancy diamond shapes. 

Following is an introduction to each shape, including information on how to determine the best combination of size, color, and clarity for your needs. View our  side-by-side comparison of each diamond shape to see how shape affects apparent size as well.



Round Diamonds

The round cut diamond is the most popular diamond shape, representing approximately 75% of all diamonds sold. Due to the mechanics of its shape, the round diamond is generally superior to fancy shapes at the proper reflection of light, maximizing potential brightness.

Princess Cut Diamond

The princess cut diamond, first created in 1980, is the most popular fancy diamond shape, especially for engagement rings. Like round cut diamonds, princess cut diamonds are a good choice for their flexibility in working in almost any style of ring.

Oval Diamonds

Because the oval diamond is a modified brilliant-cut (like virtually all round cut diamonds), the two diamond shapes possess a similar fire and brilliance. However, oval cut diamonds have the added advantage of an elongated shape, which can create the illusion of greater size.

Marquise Diamonds

The marquise cut diamond is a football-shaped, modified brilliant-cut. Because the marquise diamond is long and narrow, it can also create the illusion of greater size. Carat for carat, the marquise diamond has one of the largest surface areas of any diamond shape, making it a good choice when trying to maximize perceived size.

Pear Shaped Diamonds

The modified brilliant-cut pear shaped diamond is a combination of a round and a marquise shape, with a tapered point on one end. Ideally, a pear shaped diamond should possess excellent or very good symmetry. The point should line up with the apex of the rounded end. The shoulders and wings (the upper and lower curves on the right and left side of the diamond) should form uniform, symmetrical curves.

Cushion Cut Diamond

The cushion cut diamond combines a square cut with rounded corners, much like a pillow (hence the name). This classic cut has been around for almost 200 years, and for the first century of its existence was the most popular diamond shape (similar to round cut today). Refinements in cut have led to a recent resurgence in popularity.

Emerald Cut Diamonds

The unique look of the emerald cut diamond is due to the step cuts of its pavilion and its large, open table. Instead of the sparkle of a brilliant-cut, emerald cut diamonds produce a hall-of-mirrors effect, with the interplay of light and dark planes. Often, inclusions or body color are easier to see in an emerald cut diamond.

Asscher Cut Diamonds

The asscher cut diamond was first produced in 1902 by the Asscher Brothers of Holland, an is a forerunner to the emerald cut. The asscher cut diamond is similar to the emerald cut, but in a square shape with larger step facets, a higher crown, and a smaller table. This combination often produces more brilliance than the emerald cut.

Radiant Cut Diamonds

The radiant cut diamond is the first rectangular cut to have a complete brilliant-cut facet pattern applied to both the crown and pavilion, creating a vibrant and lively diamond. The modified square shape is a nice bridge between a cushion and a princess cut, and for that reason looks beautiful set with both rounded or square cornered diamonds.

Heart Shaped Diamonds

The modified brilliant-cut heart shaped diamond is a unique and unmistakable symbol of love, popular in solitaire pendants as well as rings. Heart shaped diamonds less than .50 carats may not be a good choice, since the heart shape is more difficult to perceive in smaller diamonds, especially after they are set in prongs.

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