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The 4 Cs of Diamond Quality

The 4Cs of Diamond Quality

A diamonds value is based on rarity, and it varies greatly from one diamond to another. However, a diamonds rarity isn't solely based on size, but many other factors as well. Until the middle of the twentieth century, there wasn't an industry agreed-upon standard by which diamonds could be graded. The 4C's, created by GIA (Gemological Institute of America) became the first, and now globally accepted standard for describing diamonds in terms of Color, Clarity, Cut, and Carat Weight.

The creation of the 4C's, has meant that diamond quality could be communicated in a universal language, and the consumer could know exactly what they were purchasing.


Stuller's Red Box Diamonds

Gem-quality diamonds are rare; having spent billions of years in the making at depths over 100 miles beneath the surface. The 4C's information helps you to identify the quality of the diamond you are purchasing as well as its rarity. Understanding the 4Cs can make the difference between a sound purchase and one of regrets.



Contrary to what many people believe, cut doesn't refer to a diamonds shape, but how the light is returned due to the quality of a diamonds facets. Of the 4Cs, cut is the most important characteristic when it comes to a diamonds light performance.

Diamond Cut Quality

Fire, brilliance and scintillation are the three factors used to describe the interaction of light with your diamond. Brilliance refers how much light is returned back into your eyes while viewing your diamond. Fire refers to the many flashes of color you see from your diamond. While scintillation is the flashes of light you see when the diamond, the light source, or the observer moves about. For the best results, the proportions and symmetry of a diamonds facets along with the quality of its polish have to come together in just the right way.

GIA Diamond Cut Scale


The most widely accepted system for grading diamond color is the GIA D-to-Z diamond color grading system. Diamond color is all about what you can’t see; where a diamond is valued by how closely it approaches colorlessness. The less color, the higher its value. (The exception to this is fancy color diamonds, such as fancy yellows, pinks and blues; all of 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 Diamond Color Scale

The GIA color scale begins with the letter D, representing colorless, and continues with increasing presence of color to the letter Z, or light yellow or brown. 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.

The GIA Diamond Color Scale
So... Why does the GIA color grading scale start with D?

Before GIA developed the D-Z Color Grading Scale, a variety of other systems existed. 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, as well as descriptions such as “gem blue” or “blue white.” The result of all these grading systems was inconsistency and inaccuracy. The creators of the GIA Color Scale wanted to start fresh, without any association with these earlier systems. Therefore, they chose to start with the letter D—a letter grade normally not associated with top quality.



Diamonds are the only gem made up of just 1 element - carbon. However, few things in nature are absolutely perfect, and diamonds are no exception. Diamonds have internal features, called inclusions and surface irregularities, called blemishes. Together, they're called clarity characteristics. Diamond clarity refers to the absence of these inclusions and blemishes. Diamonds free of these characteristics are rare, which increases a diamond’s value. The GIA clarity grades range from flawless (FL) to diamonds with visible inclusions (I3).

GIA Diamond Clarity Grades

The GIA Clarity Scale contains 11 grades. In determining a clarity grade, the GIA system considers the size, nature, position, color or relief, and quantity of clarity characteristics visible under 10× magnification.

  • Flawless (F) - No inclusions or blemishes are visible to a skilled grader using 10× magnification

  • Internally Flawless (IF) - No inclusions and only blemishes are visible to a skilled grader using 10× magnification

  • Very, Very Slightly Included (VVS1 and VVS2) - Inclusions are difficult for a skilled grader to see under 10× magnification

  • Very Slightly Included (VS1 and VS2) - Inclusions are minor and range from difficult to somewhat easy for a skilled grader to see under 10x magnification

  • Slightly Included (SI1 and SI2) - Inclusions are noticeable to a skilled grader under 10x magnification

  • Included (I1, I2, and I3) - Inclusions are obvious under 10× magnification and may affect transparency and brilliance

The GIA Diamond Clarity Scale


Diamonds and other gemstones are weighed in metric carats where one carat is equal to 0.2 grams; about the same weight as a paperclip. (It's important not to confuse carat with karat, as in “18K gold,” which refers to gold purity.)

Diamond Carat Weight Comparison Chart

Contrary to what some people believe, carat refers to a diamonds weight, not its size. However, when diamonds are properly cut within certain parameters, carat weight correlates to approximate size ranges. For example, the size of a 1-carat round brilliant diamond can range from approximately 6.20 mm to 6.80 mm in diameter. A deeper cut will be smaller in diameter and a shallower cut will be wider in diameter. For smaller melee diamonds (those accent diamonds used to dress up a ring), jewelers use the point system. With the point system, a carat is divided into 100 points. For example, a 50-point diamond weighs 0.50 carats.

One thing to keep in mind is that 2 diamonds of equal weight can have very different values, as value is determined by the combination of the 4C's. When the other 4C's are similar, carat weight can have a dramatic effect on the price of a diamond.


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