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Help Needed-Finding A Good Tolkowsky/hearts And Arrows


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#1 95girl

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Posted 16 April 2017 - 08:49 AM


Hi.So,I've been seeing that websites don't offer options to search based on star facet % crown angle,pavillion angle etc. they omit them from their options.The thing is,I wish to buy a diamond with tolkowsky's proportions,plus girdle,but every ASET I see has some "side effects" at the bottom of arrows,while some diamonds close to the tolkowsky model,don't.I understand that a good Hearts and arrows has a VERY narrow range of possible proportions,so can you please tell me how to search that options OR a reliable website where I could buy tolkowsky diamonds?Thanks in advance!
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#2 davidelevi

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Posted 16 April 2017 - 10:49 AM

I'm not sure I understand - you seem to conflate "Tolkowsky proportions" (whatever that means - he indicated a huge range as providing good visual results) with H&A, which is a symmetry pattern having very little to do with what Tolkowsky wrote.

 

You then mention "side effects" at the bottom of arrows in ASET (which is not a reflector technology designed to display arrows, though it often does) without actually explaining what these are... which adds to the confusion.


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#3 Furqan Shafi

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Posted 16 April 2017 - 08:58 PM

As far as I remember Tolkowsky family does produce diamonds but they don't sell to online retailers.

Can you upload a picture of what you're seeing as side effects on ASET maps?

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#4 95girl

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Posted 17 April 2017 - 01:24 AM

[url="[url]http://www.briangavindiamonds.com/diamonds/diamond-details/0.730-g-si1-round-diamond-ags-104084692004"]http://www.briangavindiamonds.com/diamonds/diamond-details/0.730-g-si1-round-diamond-ags-104084692004[/url][/url]

[url]http://www.briangavindiamonds.com/diamonds/diamond-details/0.534-g-vs1-round-diamond-ags-104091064031[/url]

At the bottom of the arrows,blue represents contrast.I've seen patterns of perfect ASET scopes,without that additional spots below/around the arrows.And I found out this didn't happen with tolkowsky proportions

Edited by 95girl, 17 April 2017 - 01:27 AM.


#5 davidelevi

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Posted 17 April 2017 - 03:11 AM

OK, that makes one part of the question clearer. Easier to click links below, for others to comment/check:

 

http://www.briangavi...gs-104091064031

http://www.briangavi...gs-104084692004

 

1) "Tolkowsky proportions" have nothing to do with that. The extremely simplified 2-D ray tracing proposed by Tolkowsky in 1919 did not take anything into account beyond table, pavilion mains and crown kites. The pattern that bothers you is created by the interactions of other facets...

 

2) In his analysis, Tolkowsky specified a 53% table. Which I believe is too small (or right at-the-edge of what's possible) to form a proper hearts pattern (which, incidentally, uses fairly arbitrary proportions in its definition). The other problem with a 53% table is that it's decidedly out-of-fashion, so not many are cut.

 

3) I'd be very cautious about the "ASET" images without those extra contrast areas - as far as I know, the only "legitimate" way to eliminate them is to re-orient the angles of the upper and lower girdle facets in what is known as 'painting'. If done correctly, there is nothing wrong with it, but since it can be used to retain weight, GIA frowns upon it and penalises cutters that use the technique, so it's no longer popular either. The early (say until ~2007) Hearts-on-Fire used this style of cutting.

 

The other reason for being cautious is that taking good photographic ASET images is not easy, and a lot of details can be obfuscated by poor technique (deliberate or otherwise), and some methods for producing an ASET (e.g. some types of scan-and-compute software) may simply not be accurate enough to reproduce the issue.

 

4) The most interesting question for me remains: have you actually seen one of these "faultless" diamonds? And compared it to something like the two "defective" ones you have linked above?


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#6 95girl

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Posted 17 April 2017 - 04:02 AM

I'm aware that Tolkowsky did not mention star length,which does affect the hearts and arrows,nor lower girdle percentage.to me,the following values are ok

55% table
34.5 crown angle
40.7,40.8 pavillion angle
76-77% lower girdle halves
43.1% depth
16.2% crown
Star 45-50% (sometimes I ran into 47,48 and 50)

Girdle: any type except bruted,and any %

What I mean by ASET is not the one which is posted on briangavin as photos,along with other images,but the AGSL digital image on the certificate.THAT one shows additional defects when compared to just ASET
And yes I have seen "faultless" diamonds before...after countless minutes of searching.one had these exact proportions.I will post the image when I find one again



EDIT example of Good ASET but with "noisy" pattern on certificate. http://www.briangavindiamonds.com/diamonds/diamond-details/0.534-g-vs1-round-diamond-ags-104091064031
Example of mostly clean digital pattern (I have seen even better,but I only found this in my bookmarks). http://www.briangavindiamonds.com/diamonds/diamond-details/0.701-j-vs2-round-diamond-ags-104084684032#!prettyPhoto%5Bgallery2%5D/1/

Edited by 95girl, 17 April 2017 - 04:09 AM.


#7 davidelevi

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Posted 17 April 2017 - 04:44 AM

My question was specifically whether you had seen with your eyes, in real life, one of these (supposedly) faultless diamonds, and compared it to a "faulty" one... I would bet you $100 to a button that you cannot tell the difference without a loupe and other accoutrements.

 

The digitally-derived ASET images are - in my opinion - suspect, if nothing else because of the successive approximations introduced by scanning and then ray-tracing.


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#8 95girl

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Posted 17 April 2017 - 07:47 AM

My question was specifically whether you had seen with your eyes, in real life, one of these (supposedly) faultless diamonds, and compared it to a "faulty" one... I would bet you $100 to a button that you cannot tell the difference without a loupe and other accoutrements.
 
The digitally-derived ASET images are - in my opinion - suspect, if nothing else because of the successive approximations introduced by scanning and then ray-tracing.


I wish I had seen one in real life,I would have enjoyed an experience like this.I surely would have asked to see it.My trusted jeweler,who sold me my first diamond (not hearts and arrows) said he didn't have any of those (unless I ordered one) and that they were expensive compared to other diamonds.Most jewelers in my town usually have very small diamonds already available or even none unless preordered,but no hearts and arrows.I'm a mineral lover,and that type of diamonds is my ultimate goal.

#9 davidelevi

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Posted 17 April 2017 - 08:18 AM

I don't find the last two examples significantly different from the other two - which makes me think I'm looking at the wrong things, perhaps? Do I understand correctly that what worries you are the two "things" highlighted in here (set of 8 for solid and set of 8 for dashed)? Apologies for picking a Whiteflash stone, but BG makes it very difficult to access their images... it's a 0.7 G/SI1, so comparable to the other 4, I think.

WF H&A.jpg

 

Both Brian Gavin and Whiteflash have good return periods, and so do most other online merchants. I'd be extremely wary of anyone that wants to sell you a "special" diamond without a decent return policy on the account that it is "special".

 

BTW - any definition of H&A I have ever seen would consider those "faults" irrelevant - what matters is whether the shaft and head are well-formed, distinct but not separate. And any read-out based on a reflector image that does not contain enough contrast would leave me distinctly cold: a flat mirror held at the appropriate height shows up all red in an ASET, but it's hardly as interesting as a diamond.


Edited by davidelevi, 17 April 2017 - 08:18 AM.

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#10 95girl

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Posted 17 April 2017 - 08:38 AM

Err,no,look at this. http://www.briangavindiamonds.com/diamonds/diamond-details/0.222-i-vs1-round-diamond-ags-104092458036 What I call a defect are the blue patches at the center of the stone,around the arrows.

#11 Furqan Shafi

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Posted 17 April 2017 - 09:18 AM

I think she means the blue contrast areas around the table reflection at the shaft of the arrows.

Edited by Furqan Shafi, 17 April 2017 - 09:26 AM.

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#12 Furqan Shafi

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Posted 17 April 2017 - 09:21 AM

Those happen because of the slightly shallower pavilion angle. And it appears to be only visible in the computer generated ASET map on the certificate and not on the actual ASET image on that 0.222 ct I coloured diamond.

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#13 davidelevi

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Posted 17 April 2017 - 09:25 AM

Ah... these (x 4 or 8, depending on what you consider being in the highlight)? I was looking at the wrong end of the arrow, then! Sorry!

 

BG H&A.png

 

Those have also nothing to do with "Tolkowsky" or H&A - nor unfortunately are they detectable through the measurements, whether they are listed on an engine or not: your "best" example (0.701 JVS2) and your "worst" (0.534 G/VS1) have the same reported crown and pavilion angles, and it's not a matter of lower girdle or star length.

 

It's a question of how precisely the facet has been worked and how consistent the angle is through the facet (not between one facet and the next). We are talking thousandths of a mm... and of measurements that are not visible except through direct observation (or high quality 3D scanning).

 

All the observations/comments above about the contrast/leakage at the edge of the stone remain true, but clearly not applicable to your case. I agree that stones with a fully "red" centre exist - finding one is a matter of patience and luck.

 

I still feel that you would not see the difference in real life, and I would invite you to order one of the "bad" ones from BGD (or anyone else) - I think you may be surprised.

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  • BG H&A.png

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#14 95girl

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Posted 17 April 2017 - 09:30 AM

Ah... these (x 4 or 8, depending on what you consider being in the highlight)? I was looking at the wrong end of the arrow, then! Sorry!
 
attachicon.gif [url=http://www.diamondreview.com/forum/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=5104]BG H&A.png[/url]
 
Those have also nothing to do with "Tolkowsky" or H&A - nor unfortunately are they detectable through the measurements, whether they are listed on an engine or not: your "best" example (0.701 JVS2) and your "worst" (0.534 G/VS1) have the same reported crown and pavilion angles, and it's not a matter of lower girdle or star length.
 
It's a question of how precisely the facet has been worked and how consistent the angle is through the facet (not between one facet and the next). We are talking thousandths of a mm... and of measurements that are not visible except through direct observation (or high quality 3D scanning).
 
All the observations/comments above about the contrast/leakage at the edge of the stone remain true, but clearly not applicable to your case. I agree that stones with a fully "red" centre exist - finding one is a matter of patience and luck.
 
I still feel that you would not see the difference in real life, and I would invite you to order one of the "bad" ones from BGD (or anyone else) - I think you may be surprised.



You speak about a facet,which one?I'm relieved that the problem is not all about proportions

#15 Furqan Shafi

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Posted 17 April 2017 - 09:31 AM

Ah... these (x 4 or 8, depending on what you consider being in the highlight)? I was looking at the wrong end of the arrow, then! Sorry!

BG H&A.png

Those have also nothing to do with "Tolkowsky" or H&A - nor unfortunately are they detectable through the measurements, whether they are listed on an engine or not: your "best" example (0.701 JVS2) and your "worst" (0.534 G/VS1) have the same reported crown and pavilion angles, and it's not a matter of lower girdle or star length.

It's a question of how precisely the facet has been worked and how consistent the angle is through the facet (not between one facet and the next). We are talking thousandths of a mm... and of measurements that are not visible except through direct observation (or high quality 3D scanning).

All the observations/comments above about the contrast/leakage at the edge of the stone remain true, but clearly not applicable to your case. I agree that stones with a fully "red" centre exist - finding one is a matter of patience and luck.

I still feel that you would not see the difference in real life, and I would invite you to order one of the "bad" ones from BGD (or anyone else) - I think you may be surprised.


I think that happens because of slight LGF variations and she probably means to ask why this happens? (picture attached)
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#16 Furqan Shafi

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Posted 17 April 2017 - 09:33 AM

This attached picture have more contrast at the shaft of the arrows.

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#17 davidelevi

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Posted 17 April 2017 - 10:30 AM

You speak about a facet,which one?I'm relieved that the problem is not all about proportions

Lower girdle azimuth and possibly (just possibly) pavilion mains azimuth. The fact that it's not about "proportions" is not necessarily good... it means that to find whether it's there you need to see at the very least a good quality ASET, which is not a given for all stones. Before you complicate your life to such an extent, see if you can notice the problem in real life first (and if it's a problem at all - as I said, I tend to like stones with more contrast, not less!)


Edited by davidelevi, 17 April 2017 - 10:31 AM.

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