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diamonds,Laboratory Cut Grades

Laboratory Cut Grades: What the report doesn't show

By John Pollard
Think of a drum.

At this moment different people reading this article have conjured up different drums in their minds. For example, snare drum, conga, timpano/diamonds_info. But each is made differently, sounds different from the other and can be tuned in different ways. Therefore, we must use more than the word “drum” to communicate specifics. In school young percussionists learn the different ‘makes' of drum as a starting point (let's call this Drum 101). For example, the snare drum is ‘made' like this and has this characteristic sound, etc. As students advance they explore what constitutes effective tuning and “quality of sound” on the different ‘makes' of drum. Eventually those at the top of the learning taxonomy set industry standards by evaluating sound quality using scientific-acoustic and subjective methods.


For diamonds this article is like Drum 101. It is meant to illustrate visibly notable subsets of shape, performance and precision which are not communicated on grading reports nor differentiated by grade. While opinions and evaluations of quality are inevitable, it's not the point of this “101” level article: The diamonds used are chosen not to promote or condemn any subset, but to reveal the different appearances possible within many grading labs' top cut grades. This variance is starkly at odds with the uniformity in lab grading of color, clarity and finish grades of polish and meet-point symmetry. For the purposes of this article I will refer to subsets within a given shape as ‘make' - to avoid confusion with other usages of words like ‘proportions.'


A. Same Grade? Different Looks.


Cut quality is the most important “C” for diamond beauty but it's the least consistent category, visually, on laboratory grading reports.


Top Color and Clarity grades are consistent at reputable labs. For example, diamonds of Flawless clarity appear identical (in clarity) to the naked eye. The same holds true for D color. In fact one can descend several grades from the top in either category before a normal human will detect differences in the category being observed.




Many diamonds within a given lab's top cut grade look different from one another even to casual observers. This is not always bad, as appeal can be a matter of taste, but it runs in opposition to what people expect from their experience with the other “Cs.” When it comes to cut grading even the most reputable labs include a wide variety of visible differences in the top grade. Second tier labs often permit an even wider and more varied range.




1. Make is the term I will use to describe subsets of shape. A diamond with a large table and low crown is ‘made' differently than one with a small table and high crown. A steep & deep angular combination is ‘made' differently than a shallow combination. Diamonds of different makes have different visual characteristics but may fall within a single cut grade from a given lab.


Different Makes of Round Brilliant (images generated with DiamCalc software by Octonus)


diamonds,Laboratory Cut Grades


2. Performance is an assessment of visual properties. Commonly described properties include brightness, dispersion, contrast, scintillation and leakage. Within the character of a given ‘make' performance can vary. Different labs approach performance criteria differently when considering cut grade but you can still expect to see notably different visual properties within the same cut grade. *


Different Performance Properties as seen with ASET (images generated with DiamCalc software by Octonus)
diamonds,Laboratory Cut Grades


3. Precision is how well a diamond's facets align in 3D. The presence of crisp symmetrical or chaotic patterns plays a significant role in the personality of a diamond. In diamonds with more light return high precision can boost contrast and improve visible dispersion and scintillation. Less precision results in randomness in pattern and scintillation. Diamonds with different patterning will have different personalities but can be issued the same cut grade. **


Different Precision Patterning as seen with a “Hearts & Arrows” Viewer (images generated with DiamCalc software by Octonus)
diamonds,Laboratory Cut Grades




Many new shoppers are surprised to discover there are differences in visual character (make), balance of visual properties (performance) and patterning (precision) within a top cut grade that aren't differentiated on grading reports. This is of little concern to some shoppers, but there are buyers who wish to learn the distinctions and employ them in their diamond journeys.


B. Making Distinctions




Traditional buyers can use their eyes to identify differences. However, they must be made aware that jewelry stores often have lighting which, logically, is designed to make all diamonds look good. Additionally, many stores stock diamonds of a single make, with similar performance and precision attributes, limiting variety and choice. Buyers interested in making distinctions should seek stores carrying different makes with different visual properties, and observe and compare candidate diamonds in several lighting conditions, focusing on lighting they feel to be “real” in their own lives. Differences in overall make will be the most obvious. The nuances of performance and precision become more visible in diffused, indirect and natural lighting than in bright direct spotlighting. For enthusiasts, there are even hand-held tools which can help reveal differences in performance and precision (see images and scans).




This issue has more implications for internet buyers who are unable to compare differences with their own eyes. Measurements and two-dimensional predictive systems can help with rejection for rounds, but are extremely limited and near-useless for fancy shapes. In all cases one will need more than a typical grading report to make detailed distinctions about make, performance and precision.




Aspects of a diamond's character and appearance can be predicted using images and scans of the target diamond. Reflectors like ASET® and Ideal-Scope® are vetted science and show natural areas of brightness and contrast. “Hearts and Arrows” views reveal cut precision in the pavilion as well as the crown. A 3D scan can be used with software for further predictions. A magnified photo of the subject diamond in diffused light is also useful for verifying what reflector images or scans reveal, but is limited by itself.




Machines have been developed to assess diamond appearance. Their appeal as global assessors is limited since different brands of machine can come to different conclusions for a given diamond. While such devices have largely been dismissed by top labs and the science community, operators educated in their metrics may be able to provide useful interpretation of results, based on skill and experience.


C. Examples


The purpose of this section is not to promote or condemn any diamond, but to reveal the different appearances possible within a lab's top cut grade; especially since this practice runs contrary to the absolute visual consistency of top color, clarity and finish grades.


Examine the nine diamonds below. These diamonds would be issued the same cut grade at many laboratories. This means that despite visual differences in aspects of cut they will be categorized as “the same” on paper. And while an educated person may be able to determine a diamond's make from measurements (when present) it is impossible to interpret nuances of performance and precision without more information, such as the photos below.


[Expert details for examples provided in Section D]



diamonds,Laboratory Cut Grades
diamonds,Laboratory Cut Grades
diamonds,Laboratory Cut Grades
PAVILION PRECISION IMAGES (“Hearts & Arrows” Viewer)
diamonds,Laboratory Cut Grades

D. Expert Details


For interested experts, a summary comparison of the nine diamonds used in this article.

* GIA Facetware or AGS PGS Light Performance Result

** Second PA CA ST and LH numbers taken from onsite scan





Diamonds were photographed in four groups, graduated by size (0.92 0.94) (1.00 1.02 1.09) (1.15 1.16) and (1.29 1.30).


· In groups against White Background


· In groups against Black Background


· Diamonds 1 and 2 against skin
diamonds,Laboratory Cut Grades
diamonds,Laboratory Cut Grades
diamonds,Laboratory Cut Grades




Report data, White background, Black background, Ideal-Scope®, ASET®, Hearts
diamonds,Laboratory Cut Grades


E. Final Word


I feel a need to stress that this document uses Round Brilliant diamonds as examples because RB is the only shape currently issued a cut grade by numerous labs.  In fact, when it comes to fancy shapes there are far more extreme differences in visual appearance.  For example, princess cuts can have pavilion configurations of 24, 32, 40 or 48 facets (no culet), but many people don’t realize this because the different makes are treated without distinction.  In keeping with the above, performance and precision details are not even considerations for fancy shapes at most labs at this time.  In practical terms other shapes are nearly a century behind the round brilliant in terms of global research and development.



In a utopian society we would elegantly standardize communication (not judgments) about all existing diamond shapes and even explore new possibilities.  That day may come but it is not today. For now we can acknowledge that cut is the most important “C” for diamond beauty, but it is the least developed in terms of clear communication about nuances such as those put forward in this article.  Let us remember that the other “Cs” are subdivided to a level which influences category/pricing even when invisible to the naked eye. In that spirit it seems reasonable to expect some notation (if not judgments) about visible make, performance and precision differences.


It is certain that consumers are not becoming less educated. Tomorrow’s shoppers will be even more data-intensive and detailed than today’s.  As our public evolves in their expectations our trade must evolve in terms of communication. With that in mind I urge industry professionals to be proactive in developing strategies to better serve a growing, more demanding, better-educated public.

* GIA Facetware or AGS PGS Light Performance Result

** Second PA CA ST and LH numbers taken from onsite scan


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