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few questions for a newbie about cut and optics

C

Chloegal

Rough_Rock
Joined
Jan 1, 2012
Messages
83
Hi just want to ask if the painting and digging that we sometimes hear about is listed on any of the reports? I would like to know how can you tell if a stone has been sort of trick cut into being in the top excellent category. I suppose if painting or digging has no observable darkness or reduction of light then it`s not really important. However I`m sure it`s something built into the price and consumers like me would like to know.


A second thing that I have in my mind is that the diamond dealer I`m dealling with told me that the `smile` of a diamond also depends on the rough. Logic being that not all rough has the same potential to be sparkly, or said differently, some rough is just known to have superior optics.

Can any of the experts comment on this rough issue. I`m guessing some rough from certain parts of the world are better than others?

Last question (for now) why does it state that some people prefer the look of a diamond with HCA score above 1 ? What does under 1 usually look like?

Thanks Chloe
 
Chloegal|1331542504|3146718 said:
A second thing that I have in my mind is that the diamond dealer I`m dealling with told me that the `smile` of a diamond also depends on the rough. Logic being that not all rough has the same potential to be sparkly, or said differently, some rough is just known to have superior optics.

Can any of the experts comment on this rough issue. I`m guessing some rough from certain parts of the world are better than others?


Thanks Chloe
Click to expand...
your diamond dealer is so full of B.S.... :!:
 
Sorry, I can't answer your questions but I have to add one more - what the heck is the smile of a diamond? :confused:
 
Hi- I couldn't tell you anything about what the "smile" of a diamond might be, if there is any such thing...but Good Old Gold has LOTS of info. He does have information about painting and digging, and has ASET images of what it looks like in his articles:

http://www.goodoldgold.com/4Cs/
 
alene|1331599207|3147277 said:
Sorry, I can't answer your questions but I have to add one more - what the heck is the smile of a diamond? :confused:
Click to expand...
sparkles?? i think that's what he meant.
 
Oh, I should have mentioned I have been silently lurking and following this site on and off for years and just reading up just out of interest for one day!

I`m not asking for lack of my own effort to read up on these things. I`m just interested in perhaps an explaination from some others who might simplify some of the very complex things I have read.

The `smile` of a diamond is not my dealer`s words,( and I`m sure he is not full of shit!). In fact he explained about how the cut is the most important part of a diamond. The `smile` is a word that stuck in my head from an article I read here infact. It was to do with the fact that each diamond does seem to have it`s own `look` as a result of everything that goes into it, the cut, the starting point of the rough etc etc. It was an article by a diamond industry expert which made perfect sense to me. It is clearly a word that describes the appeal or not of a diamond, also pointing out that each one has its own unique characteristics. The `smile` was just the sum total of the end result that was observable to the eye!

I agree that most well cut diamonds look the same or painfully similar to me (to have to look for differences), but I`m sure experts dealing with them all the time can see these differences very clearly. So it`s not out of my comprehension to imagine a diamond cutter or grader or dealer would refer to this `smile`.

And I was told that rough from different parts of the world do perform differently and are better or worse for different sizes and color grades. Some are better than others etc. This he seemed certain of and I`m guessing it would be true. Every other precious gem has differences or unique characteristics depending on where it is mined in the world.
 
thbmok|1331613618|3147461 said:
WF and GOG posted very detailed articles if you are interested in reading more about painting and digging. GIA/AGS downgrades the cut grade if painting and digging is severe enough. GIA appears to be a bit more strict in this regard.

https://www.pricescope.com/journal/visible_effects_painting_digging_superideal_diamonds
http://www.goodoldgold.com/4Cs/NewCutGrading/PaintingandDigging/
http://goodoldgold.com/4Cs/NewCutGrading/GIAExAGSIdeal/
Click to expand...


Thanks for these. I have read them but boy is it a lot to take in as a new consumer!

What I wanted to know is if the `painting` or `digging` is ever mentioned on the diamond reports?

Also, correct me if Im wrong but does a GIA triple excellent report imply that this hasn`t occured?

My confusion is from what I read that showed examples of not great cut diamonds that manage to get into the top cut reports (AGS0) by sort of tricking the system?
 
Chloegal said:
What I wanted to know is if the `painting` or `digging` is ever mentioned on the diamond reports?
Click to expand...

No. Painting and digging is not explicitly stated on GIA/AGS reports. Stones with severe enough painting and digging would simply not get the top GIA Ex / AGS0 cut grade.

Chloegal said:
Also, correct me if Im wrong but does a GIA triple excellent report imply that this hasn`t occured?
Click to expand...

No. Most stones have some degree of painting and digging, whether by design or by lack of cut precision. As shown in Photo Compilation 5 from https://www.pricescope.com/journal/visible_effects_painting_digging_superideal_diamonds , a stone with average crown painting of 4 degrees can still get GIA EX, and a stone with average crown painting of 6.2 degrees can still get AGS0.

Chloegal said:
My confusion is from what I read that showed examples of not great cut diamonds that manage to get into the top cut reports (AGS0) by sort of tricking the system?
Click to expand...

As with all systems and standards a line has to be drawn somewhere, and it's unavoidable that some people will simply aim to meet the minimum standard. That is why some of us stress that not all GIA EX / AGS0 are comparable and that ASET/IS images are really helpful if you cannot see the stone in person.
 
Chloegal|1331542504|3146718 said:
...

A second thing that I have in my mind is that the diamond dealer I`m dealling with told me that the `smile` of a diamond also depends on the rough. Logic being that not all rough has the same potential to be sparkly, or said differently, some rough is just known to have superior optics.

Can any of the experts comment on this rough issue. I`m guessing some rough from certain parts of the world are better than others?

Last question (for now) why does it state that some people prefer the look of a diamond with HCA score above 1 ? What does under 1 usually look like?

Thanks Chloe
Click to expand...

Hello Chloe,

As for your rough-question, optics in the sense of sparkle, brilliance, fire or life of a diamond (whatever name you want to give it) is a result of the interaction of light with the polished diamond. Rough as such has no optics.

More specifically, optics are a result of light and the specific refractive index of the diamond. Where textbooks mostly give one specific refractive index for diamond, it actually is a range (a very narrow range) with the theoretic possibility of each diamond actually having its own refractive index.

In reality however, we are talking about such minor theoretical differences that I have never seen proven or exhibited in real-life-examples.

I must add, however, that only yesterday, I have heard about Canadian scientists claiming that such differences in rough could be a basis to prove that Canadian rough is by far superior. I am extremely skeptical about this.

Live long,
 
As thb and Paul said - difference in RI is what makes the "fire" - and each stone will have its own absorption spectrum.


Whether painting/digging for the sole purpose of tweaking appearance/weight is "good" or "bad" depends on extent, proportions of the specific stone in question, who you ask... it's basically changing the angles at which crown and pavilion facets meet at the girdle - altered girdle profile and altered angle differences between adjacent facets are byproducts. GIA has something of a zero-tolerance policy, AGS is much more laid back, and Eighstar specializes in crown-painting...

http://www.youtube.com/watch?v=glnGcuzEzO4&ad=8132676332&kw=diamond+information&lr=1&feature=pyv
(PS thread for video) [URL='https://www.pricescope.com/community/threads/which-stone-would-you-choose-photos-video-included.169210/#post-3077281?hilit=no%20question#p3077281']https://www.pricescope.com/community/threads/which-stone-would-you-choose-photos-video-included.169210/#post-3077281?hilit=no%20question#p3077281[/URL]
 
Paul-Antwerp|1331654918|3147632 said:
Chloegal|1331542504|3146718 said:
...

A second thing that I have in my mind is that the diamond dealer I`m dealling with told me that the `smile` of a diamond also depends on the rough. Logic being that not all rough has the same potential to be sparkly, or said differently, some rough is just known to have superior optics.

Can any of the experts comment on this rough issue. I`m guessing some rough from certain parts of the world are better than others?

Last question (for now) why does it state that some people prefer the look of a diamond with HCA score above 1 ? What does under 1 usually look like?

Thanks Chloe
Click to expand...

Hello Chloe,

As for your rough-question, optics in the sense of sparkle, brilliance, fire or life of a diamond (whatever name you want to give it) is a result of the interaction of light with the polished diamond. Rough as such has no optics.

More specifically, optics are a result of light and the specific refractive index of the diamond. Where textbooks mostly give one specific refractive index for diamond, it actually is a range (a very narrow range) with the theoretic possibility of each diamond actually having its own refractive index.

In reality however, we are talking about such minor theoretical differences that I have never seen proven or exhibited in real-life-examples.

I must add, however, that only yesterday, I have heard about Canadian scientists claiming that such differences in rough could be a basis to prove that Canadian rough is by far superior. I am extremely skeptical about this.

Live long,
Click to expand...

Paul, thanks for your thoughtful answer.

Maybe I`m wording it wrong about the optics etc.

Can I ask whether some rough is just superior to work with for cutters in general? My diamond dealer believes that rough from South Africa is the best (hardest) especially for larger stones. He had found that rough from some areas did not cut and polish up to the same sandard due to the rough being inferior (softer?).
 
Yssie|1331661742|3147739 said:
As thb and Paul said - difference in RI is what makes the "fire" - and each stone will have its own absorption spectrum.


Whether painting/digging for the sole purpose of tweaking appearance/weight is "good" or "bad" depends on extent, proportions of the specific stone in question, who you ask... it's basically changing the angles at which crown and pavilion facets meet at the girdle - altered girdle profile and altered angle differences between adjacent facets are byproducts. GIA has something of a zero-tolerance policy, AGS is much more laid back, and Eighstar specializes in crown-painting...

http://www.youtube.com/watch?v=glnGcuzEzO4&ad=8132676332&kw=diamond+information&lr=1&feature=pyv
(PS thread for video) [URL='https://www.pricescope.com/community/threads/which-stone-would-you-choose-photos-video-included.169210/#post-3077281?hilit=no%20question#p3077281']https://www.pricescope.com/community/threads/which-stone-would-you-choose-photos-video-included.169210/#post-3077281?hilit=no%20question#p3077281[/URL]
Click to expand...

Yssie, thank you so much for this simple summary of an otherwise complicated to explain set of diamond treatments.

I`m really glad that this isn`t an IQ test as I find it really hard to follow what is happening in the painting and digging diagrams. So many layers of complexity to the diamond cutting and finishing process. I`m thinking diamond cutters should be much more famous and appreciated for their amazing skill!
 
thbmok|1331653959|3147622 said:
Chloegal said:
What I wanted to know is if the `painting` or `digging` is ever mentioned on the diamond reports?
Click to expand...

No. Painting and digging is not explicitly stated on GIA/AGS reports. Stones with severe enough painting and digging would simply not get the top GIA Ex / AGS0 cut grade.

Chloegal said:
Also, correct me if Im wrong but does a GIA triple excellent report imply that this hasn`t occured?
Click to expand...

No. Most stones have some degree of painting and digging, whether by design or by lack of cut precision. As shown in Photo Compilation 5 from https://www.pricescope.com/journal/visible_effects_painting_digging_superideal_diamonds , a stone with average crown painting of 4 degrees can still get GIA EX, and a stone with average crown painting of 6.2 degrees can still get AGS0.

Chloegal said:
My confusion is from what I read that showed examples of not great cut diamonds that manage to get into the top cut reports (AGS0) by sort of tricking the system?
Click to expand...

As with all systems and standards a line has to be drawn somewhere, and it's unavoidable that some people will simply aim to meet the minimum standard. That is why some of us stress that not all GIA EX / AGS0 are comparable and that ASET/IS images are really helpful if you cannot see the stone in person.
Click to expand...

Thank you thbmok for your time in explaining all this. I`m currently looking at GIA triple ex stones and even with my eyes, an IS and all the theory and cut tables here that I have tried to memorise......a sparkly diamond just looks like a sparkly diamond to me!!!!! But I am having fun trying to see things with an experts eye!
 
Chloegal|1331676600|3147988 said:
Paul-Antwerp|1331654918|3147632 said:
Chloegal|1331542504|3146718 said:
...

A second thing that I have in my mind is that the diamond dealer I`m dealling with told me that the `smile` of a diamond also depends on the rough. Logic being that not all rough has the same potential to be sparkly, or said differently, some rough is just known to have superior optics.

Can any of the experts comment on this rough issue. I`m guessing some rough from certain parts of the world are better than others?

Last question (for now) why does it state that some people prefer the look of a diamond with HCA score above 1 ? What does under 1 usually look like?

Thanks Chloe
Click to expand...

Hello Chloe,

As for your rough-question, optics in the sense of sparkle, brilliance, fire or life of a diamond (whatever name you want to give it) is a result of the interaction of light with the polished diamond. Rough as such has no optics.

More specifically, optics are a result of light and the specific refractive index of the diamond. Where textbooks mostly give one specific refractive index for diamond, it actually is a range (a very narrow range) with the theoretic possibility of each diamond actually having its own refractive index.

In reality however, we are talking about such minor theoretical differences that I have never seen proven or exhibited in real-life-examples.

I must add, however, that only yesterday, I have heard about Canadian scientists claiming that such differences in rough could be a basis to prove that Canadian rough is by far superior. I am extremely skeptical about this.

Live long,
Click to expand...

Paul, thanks for your thoughtful answer.

Maybe I`m wording it wrong about the optics etc.

Can I ask whether some rough is just superior to work with for cutters in general? My diamond dealer believes that rough from South Africa is the best (hardest) especially for larger stones. He had found that rough from some areas did not cut and polish up to the same sandard due to the rough being inferior (softer?).
Click to expand...

Hi Chloe,

Certain cutters prefer certain origins of rough, surely. But that preference has no relations to optics.

Live long,
 
 
 
Oh. I see. Left stone has had some painting and digging done to improve light return. Interesting -- I prefer the right stone myself...
 
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