Chapter 1
Understanding ASET, HCA, Hearts & Arrows and
Fluorescence
ASET
ASET is the abbreviation for Angular Spectrum Evaluation Technology (also known to many as Angular Spectrum Evaluation Tool).
The ASET scope is currently the most scientific and accurate measure of a diamond’s light performance. The simple version consists of the ASET Scope and a lit background device. The ASET scope is highly regarded in the diamond industry as a reliable tool to assess a diamond’s light performance. In fact, the ASET it is more accurate in assessing a diamond’s light performance than by looking at the actual diamond with the unaided eye! Luzure Jewelry is highly dependant on the ASET Scope to determine a diamond’s light performance before any purchase.
HCA
HCA is used as an exclusion tool, not inclusion tool. It is used to exclude diamonds that do not meet a certain proportion or angular requirement and include those that do.
However there are diamonds that exceed the HCA score of 2.0 but has exceptional Light Performance on ASET. There are also diamonds in which their HCA scores are below 2, but exhibit unacceptable light leakages on ASET assessment.
We may provide HCA scores to requesting customers as a source of additional information, however as a professional diamond trading company that trades in high quality diamonds, Luzure Jewelry will not rely on semi-accurate tools for diamond analysis and as such we do
not grade diamonds based on their HCA score.
Hearts & Arrows Scope
The Hearts & Arrows Scope is used to measure the symmetry of a diamond, not light return. You will
not be able to judge any light return by using a Hearts & Arrows Scope.
At Luzure Jewelry, we want our customers to pay for the light return, not factors that cannot be observed with the unaided eye. We have a simple analogy below:
If an apple looks and tastes good, it doesn’t matter how the seeds are lined up in the core. Surprisingly, there are consumers who prefer an apple with its seed lined up perfectly in the core, and are not very concerned whether the apple taste or looks nice. In this case, just look at the Hearts & Arrows Scope and ignore the ASET scope.
There are diamonds that have perfect Hearts & Arrows and also exhibit exceptional light performance on ASET assessment. However, these diamonds are extremely rare (A rough approximation will be less than 1 in 10,000 57-facet Round Brilliant Cut diamonds) and will command a high premium (in terms of pricing) over the Rapaport. However the price that goes into paying for these diamonds goes into paying for their rarity. The light return of the diamond is still as good as only what the ASET says and not more than that. Hearts & Arrows measures symmetry, not light return, remember?
Fluorescence
Fluorescence is due to the presence of boron attaching itself to the carbon atoms during the diamond’s formation. Under UV light, the boron gets excited and emits a beautiful blue glow. Take note that sunlight contains UV.
There is no known effects of fluorescence on a diamond’s light return.
GIA did report in a publication that less than 0.2% (Less than 2 in 1000) of diamonds with fluorescence does exhibit a blue haze effect. However these diamonds belong to those with exceedingly “very strong blue” fluorescence grading in GIA’s certification. Only a rare few with Very Strong Fluorescence on the GIA certificate may exhibit this effect. That means if someone told you he has seen the blue haze effect on a diamond graded as Strong Blue Fluorescence, without even checking further, we know this person is acting under the influence of a phycological effect because the blue haze effect may only occur (though still rare) on diamonds graded “Very Strong Blue” fluorescence.
These occurrences are very rare and having assessed thousands of diamonds, and having sold diamonds with “Very Strong Blue” Fluorescence, we have not yet to see even one with a blue haze effect. If you have one, please show it to us for us to learn something new!
Why then, so many people reported seeing “hazy diamonds”?
One of the reasons is that many consumers are unable to differentiate a cloudy/milky diamond with that of blue haze. Many of those diamonds that consumers say have a hazy effect don’t even have any fluorescence in them when tested under direct UV light! A Cloudy or milky diamond is due to inclusions or misalignment of the crystal lattice during its formation and these are separate issues from the blue haze effect.
The second reason is due to a physiological effect due to misreporting in the first place. Just because a rare few diamonds (with overly strong fluorescence) were reported to have a blue haze effect, consumers start to believe that all diamonds with fluorescence have a blue haze effect. It’s like someone told you that he has been bitten by a white cat when he was young and you start to believe that all white cats bite people and you carry this psychological phobia with you for life – information that is not true to even begin with.
When filming is done on a diamond with very strong blue fluorescence, some people also reported seeing a blue haze effect. However, the lightings used are LED or spot lights and not UV light. Under ordinary circumstances, no sane person will do filming of diamonds items using UV light, and in the absence of UV, no fluorescence can be emitted to create any blue haze effect. Hence we are very certain that many consumers, who claimed they saw the blue haze effects, are psychologically affected by incorrect reports about fluorescence in diamonds.
Although GIA has corrected the facts about fluorescence in diamonds in their publication, consumer’s confidence did not return and that is actually a good thing. Now the smart consumers can buy high spec (GIA certified) and high light return (Assessed by ASET Scope) diamonds at the cheaper price by selecting those with fluorescence in them. At Luzure Jewelry, we work closely with suppliers for our diamond checks and the rare blue haze effect is one of the checks we do when getting diamonds with “Very Strong Fluorescence”.
The founder of Luzure Jewelry is actually quite fond of diamonds with “Very Strong Blue” fluorescence for that out-of-this-world blue glow when UV light is shone directly onto them!
Factual Effects Of Blue Fluorescence On A Diamond’s Colour
Blue cancels out yellow on the light spectrum to become colourless.
When getting a diamond graded G colour and beyond (H, I, J, K, L, M and so on), the smart consumers always choose a diamond with a certain fluorescence grading. When viewed under direct sunlight where the UV activates the fluorescence in diamonds, a near colourless or faint yellow diamond will appear colourless depending if you have the right amount of fluorescence to neutralise the yellow! This fact is proven scientifically and not a misreport.
Do note that the above effects will not be visible under direct sunlight when the fluorescence is graded “Faint”. It has to be graded at least Medium or above for the above effects to become visible under direct sunlight.
A colourless diamond (D,E or F) will appear bluish in colour under direct sunlight if the graded fluorescence at least medium or above. Some people actually prefer this effect.
Fluorescence is a measure of taste, not quality.
Take-aways:
1) ASET is currently the most scientific and accurate measure of a diamond’s light performance.
2) HCA is a semi-accurate tool to judge a diamond’s light return.
3) Hearts & Arrows is a measure of symmetry,
not light return.
4) Fluorescence in diamonds neutralises yellow when activated by UV light.
Chapter 2
The 3 Light Performance Indicators
At Luzure Jewelry, Light Performance Score of a diamond is determined by the following 3 factors on an ASET image:-
a) Light Return – Refers to the intensity of the light return in terms of brilliance and fire. How much red and green, and how deep are the reds on each facet of the ASET image is taken into account before a Light Return Grade can be given. There is a scoring system involving shades of red and green.
Light Return makes up 50% of the overall score that determines Light Performance Score of a diamond.
Basic Red Spectrum Chart (Scoring System intentionally Omitted):
b) Scintillation – Refers to the
total area of the diamond in which light is returning from.
Every facet that is supposed to return light to the observer is taken into account for the purpose of scoring.
White, very faint pinkish red and green colours on an ASET image are critically taken into account for this assessment.
At a later stage, there is a formula to merge results obtained from
(a)Light Return and
(b)Scintillation to make up another part of the scoresheet.
This means to say that intense light return from indicator
a), coupled with high areas of leakage (low scintillation) will give this diamond a low score.
Scintillation makes up 34% of the overall score that determines Light Performance Score of a diamond.
c)
Contrast – Refers to the contrast of light that a person sees when rotating the diamond from the crown-down perspective.
Every one of the 8 arrow’s body and head are taken into consideration for this assessment.
How blue and vivid is every part of the 8 arrows must be assessed to determine the diamond’s contrast
There are only 8 arrows in the modern round brilliant cut 57 facet diamond (or 58 with culet).
Other special modified round cuts may have more arrows.
Contrast is not very important when compared to the aspects of light return and scintillation,
but when 2 diamonds of exceptional light return and scintillation are assessed visually side-by-side,
proper contrast may make one stand out over the other.
Contrast makes up 16% of the overall score that determines Light Performance Score of a diamond.
At Luzure Jewelry, the assessment of ASET is a rather complex process and it begins with examination of the 32 Crown Facets
(Includes the 8 Star Facets, 8 Bezel Facets & 16 Upper Girdle Facets but excludes the Table Facet).
Every one of these 32 Facets will be given a score based on a formula involving it’s
(a)light return and (b)scintillation and this outer region of the crown
will make up 32% of the overall score for Light Performance.
The next assessment will be for the region within the Table Facet.
It is further subdivided into 16 sections (Centre Spot not assessed here) for a closer analysis for
(a)light return and (b)scintillation. Facets of a diamond that makes up these 16 sections will be parts of the
Lower Girdle Facets and Pavilion Mains.
These are are the facets that you will see directly under the Table Facet and they have to work well in order
to provide the diamond with nice light return from “within” the Table Facet.
Light leakages under the Table Facet (Also known as Table leakages) are common even in “GIA Triple Excellent” diamonds.
Table leakages are undesirable and unacceptable by the high standards of Luzure Jewelry and this is why
a more critical emphasise needs to be placed in this section by awarding it with a higher weightage.
This region within the Table Facet will make up 48% of the overall score for Light Performance.
The centre spot within the Table Facet, which is green or red or a combination of both, will make up
4% of the overall score for Light Performance if the right conditions are met for (a)light return and (b)scintillation.
Finally, the 8 arrows are assessed for the amount of blue and vividness of the arrows’s shape,
taking into account the arrow’s body and head. The arrows can be blue in colour only.
The arrows shouldn’t be overlapped or replaced by any other colours with the only exception
being the green outlining the Star Facets.
The body of the arrow must be connected to the arrowhead and cannot be broken or misaligned.
In the next few chapters, you will learn the complex scoring and grading system for
Light Return, Scintillation & Contrast in order to perform Light Performance Grading.
Download Luzure Jewelry's Light Performance Grading References
Using The Link Below:
Luzure Jewelry - Light Performance Grading Chart
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