Please help reviewing this stone

[winterbaby520]

Hi,
Please see attached images. The HCA score for this diamond is excellent, so I'm confused by all the black areas next to the arrows.
I'm new at reading these images. Any feedback is greatly appreciated!

GIA Ex, 7.49 - 7.51 x 4.54 mm
Color I, VS2
Depth: 60.6 %
Table: 58 %
Crown Angle: 34.0°
Pavilion Angle: 40.8°
Girdle: Thin to Medium, Faceted, 3.0%
Culet: None

 

[Krod]

HCA is a rejection tool, not a selection tool. Something that scores well on HCA can be a terrible diamond and something that scores poorly on the HCA can be a sensational diamond. ASET and Ideal Scope images are the selection tools. This is where you can see that though the proportions of this diamond may be good, the cuts within it arent the most desirable. Personally, I would keep looking for other diamonds.

 

[winterbaby520]

Thank you for your reply!
What about this one? It also has excellent HCA scores, but seems to have a large light red area in the middle.
Is this one better than the first?

Thanks!

 

[Krod]

This one appears to have the "ring of death" from the light leakage in the center. I would keep looking.

 

[diamondseeker2006]

These are GREAT examples of why we recommend getting ASET images!

This is what you want to see (or close to it), keeping in mind that all photography won't be the same.

 

[HobeyB]

I'm still quite new to all this but can someone explain what's wrong with the first diamond in the OP's original post? The IS and ASET look pretty good to my untrained eyes.

 

[teobdl]

Hobey--the IS and ASET were fine. A couple thing about the proportions might be just barely different from some people's taste-the lower facets are a little longer than some people prefer (translation: arrows are a little skinny for some people), and that's paired w/ table that's a little larger than people prefer, especially for those arrows.

Basically no one would notice these things in real life except if someone who knew lots about rings came over and inspected that diamond.

As far as the second Idealscope and ASET that was posted, that is not definitely leakage. It looks more like the diamond wasn't photographed 100% correctly. It's actually quite hard to get lined up perfectly. It looks like the diamond was in the EXACT same orientation relative to the camera in both pics (in terms of roll, pitch, and yaw), which is interesting in itself. I'd ask if they could take either the idealscope or ASET again for that one and see if they can get the white half-ring to become red.

 

[ghostm42]

It looks like the diamond was in the EXACT same orientation relative to the camera in both pics (in terms of roll, pitch, and yaw), which is interesting in itself.

It's in the exact position because they are using a DiBox unit. The reflection at the bottom is a giveaway.
http://www.lexusindia.in/products/gb-dibox.aspx

Basically, you mount the diamond on the platform, then spin the viewer of your choice (located within that carbon fiber middle unit) into place. It can do regular lighting, ASET, IdealScope and H&A. Of course, for hearts view, you do have to flip the diamond upside down. The diamond and camera don't move. That's good if you get the position right, but if it wasn't perfectly aligned to begin with, then all the images will be misaligned.

 

[teobdl]

Thanks, ghost. That makes a lot of sense.

Since they took the pictures in a standardized environment, then I think it's way more likely that the diamond was misaligned to start w/ than there being leakage. In fact, given the hypothesis that the diamond is tipped, the asymmetry in virtual facets left vs right makes a lot more sense. My guess is that if it were aligned better, that diamond would have made perfect IS and ASET images.

WinterBaby--I'm very confident that the second diamond you posted is the better one. Can you post the report number or at least the pavilion angle , crown angle, and table%? Looks like it has dimensions right in the PS sweet spot 40.8 34.5 ~56%, may even be AGS0.

 

[HobeyB]

Hobey--the IS and ASET were fine. A couple thing about the proportions might be just barely different from some people's taste-the lower facets are a little longer than some people prefer (translation: arrows are a little skinny for some people), and that's paired w/ table that's a little larger than people prefer, especially for those arrows.

Basically no one would notice these things in real life except if someone who knew lots about rings came over and inspected that diamond.

As far as the second Idealscope and ASET that was posted, that is not definitely leakage. It looks more like the diamond wasn't photographed 100% correctly. It's actually quite hard to get lined up perfectly. It looks like the diamond was in the EXACT same orientation relative to the camera in both pics (in terms of roll, pitch, and yaw), which is interesting in itself. I'd ask if they could take either the idealscope or ASET again for that one and see if they can get the white half-ring to become red.

Got it, thanks!!

 

[WinkHPD]

Hobey--the IS and ASET were fine. A couple thing about the proportions might be just barely different from some people's taste-the lower facets are a little longer than some people prefer (translation: arrows are a little skinny for some people), and that's paired w/ table that's a little larger than people prefer, especially for those arrows.

Basically no one would notice these things in real life except if someone who knew lots about rings came over and inspected that diamond.

As far as the second Idealscope and ASET that was posted, that is not definitely leakage. It looks more like the diamond wasn't photographed 100% correctly. It's actually quite hard to get lined up perfectly. It looks like the diamond was in the EXACT same orientation relative to the camera in both pics (in terms of roll, pitch, and yaw), which is interesting in itself. I'd ask if they could take either the idealscope or ASET again for that one and see if they can get the white half-ring to become red.

There things about that diamond that might not be noticed in real life, until it was seen next to a diamond that was cut for maximum sparkle and maximum beauty rather than maximum weight retention from the starting crystal. If one such properly cut diamond was seen next to this one, with its larger flashes of both white and colored light, it would be quite well noticed in real life. (Assuming both diamonds are clean of course.)

The diamond with the skinnier arrows images is going to produce smaller flashes of both white and colored light, and the number of scintillation events visible to the human eye will be fewer than those that will be visible with the larger virtual facets.

With its 57 facets the inside of a diamond is a virtual facet factory. Here are some screen captures from DiamCalc to illustrate.

Here is the basic wire frame of a diamond. This one has a crown angle of 34 degrees, a pavilion angle of 40.75, a table of 56 degrees, with a star of 51 and the lower girdle of 76 and has an AGS0 cut grade.



Same diamond plus one reflection.



Same diamond plus 2 reflections.



As you can see, the virtual facets get much much smaller with each reflection.

According to a presentation given by Pete Yantzer to the Crafted by Infinity Symposium some years ago in Dallas, there are approximately 200,000 scintillation events in a one carat round brilliant cut diamond as it is rocked from side to side through a 40 degree arc. The Scintillation events are classified as Very Large, Large, Medium, Small, Very Small and Too Small To See With The Human Eye.

As you might imagine, the larger the starting virtual facets, the more scintillation events you can see with the human eye. I do not remember the maximum number considered to be visible to the unaided eye, but even in the best stones it is a small number compared to the total. I believe it was approaching 15,000 in a one carat diamond. In a poorly cut diamond, it was less than half of that. This is why it is important that you have a well cut diamond if you want to enjoy maximum sparkle and beauty.

I will grant you that there are those who like the longer narrower lower girdle facets with the concomitant smaller flashes of white light, and less dispersion. That is a matter of taste. That the difference can be easily observed with the unaided eye is a matter of only a little practice and knowing what you are looking for.

With the comment in blue, I am largely in agreement with you. It is exceedingly hard to align the diamond and the viewing scopes perfectly unless you are using specialized and expensive equipment. However, it is important to recognize that the ASET as taken is the ASET for that diamond from that angle. From this angle the diamond is clearly showing leakage that will be occurring any time the diamond is seen from that angle. As a diamond is moved, even minusculy, some of the facets will turn on, turn off (via obscuration) show leakage, or reflect the color of the blouse that the observer is wearing. It is this constantly changing appearance that makes diamonds exciting to wear and to see. If the diamond's reflections were static, they would be boring after only a short time. Would that diamond show leakage if lined up perfectly? I do not know. It does from this ASET. Is that a reaction from diamond not being properly aligned or from a tilted table? We do not know. All we know for sure, is that it is not a very good looking diamond in that ASET, and your advice to the OP to request a new one was excellent.

Wink

 

[HobeyB]

Wink,

Wow, that was SUPER informative. Thank you so much. This all is absolutely fascinating to me, I appreciate it very much.

 

[ghostm42]

Wink,

Great insight into some of the science behind it all. It makes me wonder though, is there actually a single set of proportions that maximizes those scintillation events. I know we deal with a range most of the time, but if we can make these calculations, isn't there a single set or multiple sets of exact proportions. I realize part of it is based on personal preference and what's actually noticeable to the unaided eye, but it's be interesting to know the "perfect" numbers.

 

[WinkHPD]

Wink,

Great insight into some of the science behind it all. It makes me wonder though, is there actually a single set of proportions that maximizes those scintillation events. I know we deal with a range most of the time, but if we can make these calculations, isn't there a single set or multiple sets of exact proportions. I realize part of it is based on personal preference and what's actually noticeable to the unaided eye, but it's be interesting to know the "perfect" numbers.

So, you seek the Holy Grail my son. Step right up, put your money down and let me provide you the deep and secret handshake.

Ah, but that it was that easy.

First there are the 2 dimensional numbers that we all know and love. Of course, GIA has the widest of those and accepts much in the way of steep and deep measurements that many of us love to hate. AGS has a much narrower set of numbers that excludes much of the steep deep realm of GIA, but has some at the shallow end of the scale that GIA would not accept.

Then there are some of the branded diamonds with numbers much tighter than either AGS or GIA. Surely these must be what you seek.

Nope!

"But wait!" you say. "What do you mean they are not? After all you are constantly bragging about your diamonds, have you been misleading us?"

Well, no, I have not been misleading you. It is just that there is more afoot than the game of numbers, and angles and percentages and star and lower halves lengths. "But wait," you say, "you promised me numbers that I could count on."

Sorry, there are no numbers you can count on. If I told you that a 34 degree crown angle coupled with a 40.75 pavilion angle with a 56 degree table, 51% star and 76% lower girdle (or lower halves, they are often used interchangeably) was the perfect set of numbers and you decided to have your cutter only cut those for you, you would soon find out that even if he/she could always hit those numbers, that the result would not always be what you wanted. If the facets were not placed precisely, and with perfect optical balance, you could have non existent arrows or arrows with so many tiny virtual facets that the large sparkle and dazzling dispersion would be almost non existent. Your cutter might be working with a diamond that simply refuses to meet those exact proportions, but might well have gone willingly to a 35 degree crown angle and a 40.9 pavilion angle, still well within the range of an AGS 0 cut diamond. Diamonds are the hardest natural substance on planet and sometimes they just laugh at the efforts of the cutter to bend them to the cutter's will.

There might be an inclusion that would lover the clarity grade from a VS1 to an SI2 or even an I1 if you used that 35 degree angle. John Pollard wrote an excellent article about three actual diamonds that were cut to make weight, and why cutters who wanted to cut them to be fantastic could not purchase the starting crystal because to cut the gem properly it was going to weigh less than the magic cut off weight. One of the stones was cut to an angle to the normal cutting plane in order to miss an inclusion near the bottom of the original crystal that would have made the finished diamond a D-I1 instead of the D-IF it became. It was forced to finish at 3.01 carats and was sold for more than $100,000 more than a properly cut 2.72 ct diamond D-IF would have sold for. Maybe Mr. Pollard can share some of his information and photos from that article with us. But, I am now getting away from your original question, sorry. I do love a good ramble from time to time...

It is simply MORE THAN NUMBERS! It is an entire package. Proper numbers help, but it also requires precision in the placement of the facets and perfect placement means you have considered where it will be in relation to many other facets, and oops, what if there is some optical aberration within the crystal? Is your cutter skilled enough to adjust? If not, too bad, great numbers, lousy diamond performance. It is, in fact, a three dimensional project, magnificently more complex than the numbers that you seek.

Those of us who have been around many years and seen tens of thousands of diamonds will all have stories to tell you of the stone that was perfect, on paper, yet just did not excite in real life. It is why I constantly harp on YOU MUST SEE IT WITH YOUR EYES, as even if I love love love it, you may not. I once showed some of my branded diamonds together with a diamond that I use to show just how crummy a diamond can look when not cut properly. My client loved the crummy one, as it just was more properly sedate and proper, not all sparkly like a teen aged giddy girl. (Her words, not mine.)

For those of you wondering why I am so buzzed on a late Saturday night, it is not booze. I just got back from taking my grand kids to The Jungle Book. Wow, what an exciting and thoughtful movie. I am now back down to earth having thought long and hard about your question, so I am going to post it now and go to bed. I am really excited for you to think deeply on this Ghost and I hope you will accept the truth that there are great numbers, but there are no perfect numbers, unless the things that are not included in the measurements of the report are also done correctly in conjunction with those numbers.

Wink