Fri, 22 May 2009

Laboratory Cut Grades: What the report doesn’t show

What the report doesn’t show


To the naked eye a D Flawless diamond can appear identical to an F VS diamond if each has been cut the same way.  Alternately,
less than one degree of variation in two diamonds’ facet measurements
can make a noticeable difference in appearance – yet both could be
issued the same cut grade from a given lab.




thanks to Bryan Boyne G.G, James Ramey and the Whiteflash Photography
Team for their input, assistance and collaboration in the creation of
this article.




Think of a drum.


this moment different people reading this article have conjured up
different drums in their minds.  For example, snare drum, conga,
timpano… 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.


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.


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.




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)



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)



* The 2009 American Gem Society Platinum Report prints an ASET view of the diamond when requested by the seller.



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)



** Some labs identify and print “Hearts & Arrows” views when requested for round brilliants.





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




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




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




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


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]















PAVILION PRECISION IMAGES (“Hearts & Arrows” Viewer)




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








Report data, White background, Black background, Ideal-Scope®, ASET®, Hearts




E. Final Word


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.


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.


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.


discuss on the forum