Diamond Quality and Diamond Ratings

What is Diamond Quality?

Diamond quality refers to a combination of factors known as the 4Cs of Diamond Carat Weight, Diamond Clarity, Diamond Color, and Diamond Cut. Diamonds are graded by diamond laboratories, and then ultimately rated and priced accordingly. Diamond quality is somewhat subjective, and the final quality value is up to the consumer.


The 4Cs and Diamond Quality

D color and Internally Flawless are among the highest priced diamonds. Does that mean those diamonds are the best quality? The answer is up to you. Diamond quality preference is personal. The trade prices diamonds based on the 4Cs. D color and F/IF clarity are the rarest, so they are generally priced the highest among diamonds within the D-Z color scale. Savvy consumers, like those who post on our forums, understand how to manipulate the 4Cs to get the diamonds they desire within their price ranges. There is a diamond out there for everyone, and it is up to consumers to arm themselves with information to make the best choices about diamond quality to suit their needs.

Take a look at how different combinations of the 4Cs affect diamond prices via the pricescope diamond search. The comparisons below reflect well cut diamonds with a focus on color and clarity.

Compare a 1.01 carat D IF to a 1.01 carat D SI1 well cut round brilliant diamond.

You will pay $20K+ for the D IF and approximately $6,500-7,500 for the D SI1 of similar cut quality.

Compare a 1.00 carat J VVS1 to a 1.01 carat H SI1 well cut round brilliant diamond.

You will pay about $5,300-6,500 for the J VVS1 and $5,400-6,500 for the H SI1 of similar cut quality.

*Diamond prices are approximate and reflect the current prices from 03/11/2011

Diamond Cut Quality

Diamond cut deserves an honorable mention when it comes to the 4Cs and diamond quality. Cut, which is not to be confused with shape, refers to the proportions and relative angles of a diamond. Diamond cut has the greatest impact on sparkle, fire, and brilliance. Well cut diamonds are brighter and livelier than those that are poorly cut. Please visit our diamond cut tutorial for more information.

*Remember, it is up to you to decide which quality factors you prefer according to your lifestyle and budget. Please read through the tutorials and get familiar with the 4Cs and beyond. Ultimately, the choice is yours.


Assessing Diamond Quality

Diamond grading laboratories will assess the quality of your diamond. Labs are independent institutions, which offer objective evaluations of diamond quality.

The AGS Laboratory Diamond Quality Document

AGS Laboratories offer a variety of different documentation to address diamond quality. In addition to diamond grading of color, clarity, and carat weight, AGSL will also asses a diamond’s light performance as a part of its cut grade, which is based on proportions, polish and symmetry. AGS Labs offer cut grades for round brilliants, princess, emerald and oval shaped diamonds. To learn more about AGSL diamond quality reports, please visit: AGS Laboratories Products.

GIA Diamond Grading Reports

GIA grades a diamond’s color, clarity, cut (round diamonds only), finish (polish and symmetry) and assesses carat weight and proportions via micro-balance and an optical measuring device. For more information on GIA Diamond Grading please visit: How GIA Grades Diamonds

EGL Diamond Grading Reports

EGL and EGL USA grade a diamond’s color and clarity and assess carat weight and cut. For more information on EGL’s diamond grading practices, please visit: Grading a Diamond – EGL USA

HRD Antwerp Diamond Certificates

HRD Antwerp grades a diamond’s color, clarity, carat weight and cut based on proportions. Please visit HRD Antwerp Certificates for more information.

IGI Laboratory Reports

The Institute of Gemology’s grading reports assess a diamond’s color, clarity, carat weight, and cut. IGI also issues a grade for Hearts and Arrows and utilizes H&A viewers to assess optical symmetry. For an example of an IGI diamond grading report, please visit: IGI Laboratory Reports.


Diamond Ratings

Rating Diamond Cut – The 4Cs are assessed by diamond grading labs and skilled diamond appraisers, but there are tools to help you rate the cut of diamonds you are considering.


The Holloway Cut Adviser (U.S. Patent 7,251,619) estimates a round diamonds appeal based on its potential Light Return, Fire, Scintillation and Spread.

Diamond Calculator is a system of modeling cut gemstones, which enables precise calculation of the diamond weight and determination of the cut proportions. The real (photo-realistic) image of a polished diamond created by the system makes it possible to determine the cut parameters and optimal combinations to obtain the best brilliance, fire and scintillation of a stone.

AGA Cut Grading system for round diamonds developed by D. S. Atlas and his laboratory Accredited Gem Appraisers. This system has been adopted by the National Association of Jewelry Appraisers (NAJA).

The Ideal-scope is based on a principle discovered by Mr Okuda in the 1970’s. A 10x lens with a hot red / pink reflector in front of the diamond has a central viewing hole, which allows you to see just how much of the red / pink light refracts back from the diamond.

The GemAdviser is a free read-only software to model polished gemstones allowing anybody to ‘view’ and analyze the diamonds and gems created by Diamond Calculator. GemAdviser also allows to evaluate visual performance of a diamond such as Light Return and Leakage.

A basic guide to Princess, Radiant, Emerald, Asscher, Cushion, Oval, Marquise, Pear, Heart, and Triangular brilliant cut diamonds.


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