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Diamond education

The Four C’s

The value of a diamond is based on four characteristics; cut, color, clarity and carat weight.  This grading system was developed by the Gemological Institute of America (GIA) in the 1930’s.  Today this system is used worldwide to grade diamonds.

Of the four C's, cut is perhaps the most important factor affecting a diamond's overall beauty.  Cut refers to the angles and proportions of each facet of the diamond, not the shape of the diamond.  A diamond's brilliance is determined by how much light is reflected back to your eyes.  Light enters the stone through the crown, which is the portion of the diamond above the girdle.  The crown is made up of the table, which is the large flat facet on top of the diamond, and many crown facets.  It then travels to the pavilion, or body, of the stone, where it is reflected from one side to the other and then back through the top and to an observer's eye. 


A well cut, well proportioned stone evenly reflects and refracts light within the stone, thereby producing an eye-catching, fiery spectrum of color.   A poorly cut diamond, on the other hand, allows more light to pass through or "leak" from the sides or bottom of the stone, which results in a lifeless appearance with reduced sparkle. 


The science behind diamond cutting is more or less an exercise in proportion.  Changing the proportion of a diamond's depth and width is done in order to maximize the stone's brilliance.  If the cut adheres to certain "ideal" proportions, the results can be spectacular.  Because cut is so important, gemologists have developed grading methods to assist consumers in determining a diamond's cut.  In general, they are:  Ideal, Excellent, Very Good, Good and Fair.

The ideal proportions shown below are known as the Tolkowsky Theoretical Brilliant cut.  In 1919, Marcel Tolkowsky published a paper detailing ideal proportions for a round brilliant diamond.  Modern cutters offer a wide range of opinions on the "ideal" cut, but Tolkowsky's findings are mathematically indisputable and remain the basis for these modern ideal proportions.



Color refers to the absence (or presence) of a diamond's body color.  The most desireable diamond has no color at all.  The measurement and comparison of diamond color ranges from colorless to slightly tinted.  However, discerning the subtle differences between sequential color grades can be almost impossible with the naked eye.  For this reason, a letter scale, such as the GIA professional color scale which ranges from D to Z, was created to assist in distinguishing a diamond's color grade.   

Diamonds that are in the "D-F" range are considered colorless.  These diamonds are rarer and more expensive.   Diamonds in the "G-I" range are considered nearly colorless, and appear completely white to most observers and for this reason can be a better value than colorless diamonds.  Color grades beyond "J" exhibit a yellowish or brownish tint, which is increasingly discernable by the untrained eye as you approach the extreme end of the spectrum. 



Clarity is most often mistaken as being the factor that determines a diamond's sparkle and brilliance.  This is not true.  Clarity describes the presence (or absence) of imperfections both on and within a diamond.  Most imperfections are microscopic flaws, or "inclusions," formed inside the diamond during the formation process known as crystallization.  Other flaws, however, appear on the surface of a diamond and may have appeared during the cutting process. 

Essentially, the clarity grade describes the flawlessness of a diamond; the fewer the imperfections, the higher the clarity grading.  Naturally, these imperfections have an impact on the value of a diamond, particularly those that may be viewed by the naked eye.  In order to find and plot a stone's flaws, gemologists use at least 10x loupe magnification when grading for clarity.  Clarity grades range from Flawless, which are diamonds that reveal no imperfection even under 10x magnification, to Imperfect 3, which are stones with distinct blemishes visible to the naked eye.  See the chart below for a description of each clarity grading.


Flawless or Internally Flawless.


Very, Very Slight Inclusions. Requires 60X magnification to clearly see inclusions.

VS1 / VS2

Very Slight Inclusions. Requires 30X magnification to clearly see inclusions. A good choice for those wishing to balance quality and affordability.

SI1 / SI2

Slight Inclusions. Typically requires 10X magnification to clearly see inclusions.  In larger carat weights, SI diamonds sometimes reveal their inclusions to the naked eye.  Nonetheless, as long as you are careful to consider each stone individually, you can often find the best value in an SI1 or SI2 diamond.


Imperfect. Eye-Visible Inclusions.  Often a popular choice for earrings or pendants, as these items are generally scrutinized less than diamond rings.  Also a popular choice for those shopping on a budget.

I2 / I3

Imperfect.  Not recommended for any practical jewelry application.

Carat is the standard unit of weight for diamonds.  The modern carat system started with the carob seed.  Early gem traders used the small, uniform seeds as counterweights in their balance scales.  One carat equals 1/5th of a gram or .007 of an ounce.  A carat is divided into 100 "points".  Carat weight is further divided into decimals.  For example, 1/2 carat is .50 carats and expressed as 50 points; 3/4 carat is .75 carats, or 75 points, etc.  And as stated before, a one-carat diamond is 100 points.  With all other things being equal, the greater the weight of a diamond the greater the rarity and value.