The 4 Cs of Diamond

Abstract:  To evaluate the quality of a loose cut diamond, the 4 Cs of Diamonds are:

  • Carat Weight
  • Color Grade
  • Clarity Grade
  • Cut Grade

The above grading system is clearly defined under the International Diamond Grading System by the Gemological Institute of America, (GIA) in the United States of America:

Carat Weight

This is the weight of a cut diamond.

5ct = 1 gram or 1 ct = 0.2gm

In the diamond trade, 1ct = 100 points. Hence, a 0.30ct stone can be called as a 30 pointer.

Those cut diamonds below 0.20ct are usually referred to as Melee Diamonds. Usually there are used as accent stones for setting into jewelry.

Read the chart below to get some idea of how big a diamond is when it is of a certain weight.  Hence, a 1.00ct Round Brilliant Cut diamond has a diameter of approximate 6.40 to 6.50mm.

The world’s most expensive diamond per carat was sold to an unnamed buyer in Sotheby’s Diamond, London in March 2018. The price sold for the 102.34 carat D-color Flawless solitaire diamond was not revealed by the auctioneer, but it was estimated that it was more than US$35 million.

Color Grade

It is strange to most of us that the word ‘Color’ conjures up images of anything that has color in it, other than white or colorless.  In the GIA color grades, color refers to the absence of color or near absence of color.  Hence, the lesser the color, the higher worth will be a cut diamond.

The GIA Color Grade ranges from D to Z and are defined as follows:

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

The Color Grade that lie outside of this range is called Fancy Color Diamonds, which is graded as Z+. Fancy Color Diamonds are those diamonds which are with vivid (or slightly vivid) natural color of yellow, pink, blue or red. Fancy Color Diamonds are a class of its own and are extremely pricey. 

The Moussaieff Red Diamond is a diamond weighing 5.11 carat with a triangular brilliant cut, and graded as Fancy Red by GIA.  It is the world’s largest known red diamond and its estimated worth is more than US$20 million, that is, if the owner Shlomo Moussaieff, an Israeli Jeweler in London, is willing to put it up on the auction market.

Clarity Grade

Clarity is defined as the degree of blemishes or inclusions within the diamond or on its outer surface.  This is based on examination of a diamond under a 10x loupe. 

The GIA International Diamond Grading System has 11 Clarity Grades. 

These are:

  • Flawless (FL) – 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 (SIand 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.

Cut Grade

Cut Grade is not the shape of the diamond as many people thought it to be. 

Cut is what we call ‘make’ of the diamond.  It defines how well and how proportionate is the cutting to bring out the fire, brilliance and scintillations of a diamond. 

The grades are Excellent, Very Good, Good, Fair and Poor.

The shapes of diamonds refer to the geometrical shape of a diamond as shown in the diagram.

Hence, if you are buying a solitaire diamond, or a diamond jewelry, the above 4 Cs will help you ask better questions to the seller.

In my next post, I will write about the objectivity and subjectivity of a GIA Diamond Report.

Pictures and references credit acknowledgement:


    Infrared Therapy



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