Why do H&A brands reject diamonds with large lgfs and stars?

[Daniel S.]

I have noticed that most top level Hearts & Arrows brands from the major PS vendors reject diamonds with larger lower girdle facets and larger stars. Why do they do this? Most of the online literature I have come across and even GOG's minor facet guide espouse the beauty and great light performance of large ldfs and large stars yet others avoid them. Why is this?

 

[stone-cold11]

Re: Why do H&A brands reject diamonds with large lgfs and st

Just because that is not how it was defined.

As GOG noted, larger lgf will have a modified looking hearts, deeper cleft than what is acceptable in the traditional definition. Not necessary a hit on performance, Karl has some simulation on DiamCalc that shows certain proportions works better with larger lgf.

No idea on the star size.

 

[Lula]

Re: Why do H&A brands reject diamonds with large lgfs and st

Stones cut with those parameters have a different look to them and don't meet strict H&A criteria. But they can be very beautiful diamonds. I would love to have a pair of earrings cut with those specs.

If you like the look of longer lgf's and stars > 55, send Good Old Gold an e-mail or give them a call. Jonathan has often stated on PS that he is a fan of stones with these characteristics, and I've seen many stones in his inventory with this "look" (skinny arrows and lots of "hot spots"). Also, because stones cut with longer lgfs and stars > 55 fall outside of the "perfect" H&A specs, they may be less expensive -- always a plus, in my mind.

 

[Rhino]

Re: Why do H&A brands reject diamonds with large lgfs and st

Just to clarify, what we term "modified Hearts & Arrows" are not cut any less precise than a traditional Hearts & Arrows. What is sold and photographed as "Hearts & Arrows" represents a certain level of precision in the cutting which is demonstrated through the H&A viewer. Traditional H&A is only 1 pattern of precise cutting of a 57 facet diamond. Longer lgf's (and shorter as well seen in August Vintage OEC's) do not represent a worse level of precision. The same care in craftsmanship is given to these as there are in traditional H&A. The patterning is different from traditional H&A but that is all. I have them cut because I like variety and enjoy all their appearances.

 

[CharmyPoo]

Re: Why do H&A brands reject diamonds with large lgfs and st

I like the short ones. Jon - if you have an extra AV OEC that you don't need .. send it my way

 

[yssie]

Re: Why do H&A brands reject diamonds with large lgfs and st

Most H&A brands advertised here on PS have, in addition to optical symmetry, a tight set of requirements for different parametres that accepted stones must meet (these determine how the 'hearts' look as SC and Jon described). Not all of these have a causal relationship with performance.


I will say I imagine that the non-PS consumer who simply wants the most sparkly stone likely infers that the brand with the tighter set of requirements is more selective (true), more luxurious (totally subjective), and more consistently outputs diamonds of superior quality (neither true nor correlated, as A) people interpret beauty in different ways, and for example a 60/60-lover's perfectly valid preferences are not addressed, and B) no less care went into cutting one of GOG's modified hearts stones, but that's likely the image).

 

[Andelain]

Re: Why do H&A brands reject diamonds with large lgfs and st

I'm still learning a lot and getting familiar with looking for certain thing in H&A pics, so I'd like the opinions of some of you about these 2 pics here. Would this be considered an H&A stone by the strictest specs. Or even by 'modified' specs?

Note to Rhino; This is NOT a "Should I have bought this diamond" question. I'm just trying to learn what to look for and compare numbers here.

 

[stone-cold11]

Re: Why do H&A brands reject diamonds with large lgfs and st

Modified. The deep cleft in the hearts.

 

[Andelain]

Re: Why do H&A brands reject diamonds with large lgfs and st

Modified. The deep cleft in the hearts.

OK. By the cleft do you mean the top center of the heart? What part of the cut causes those deeper clefts?

And thanks for the response.

 

[stone-cold11]

Re: Why do H&A brands reject diamonds with large lgfs and st

larger lower half, around 80%.

 

[yssie]

Re: Why do H&A brands reject diamonds with large lgfs and st

LW this tutorial may help http://www.wtocd.be/DiamondInfo/article ... _of_HA.pdf

 

[Andelain]

Re: Why do H&A brands reject diamonds with large lgfs and st

larger lower half, around 80%.

I see, said the blind man. You nailed it too, the LGF on that stone is 81%.

Yssie, thanks for the link. Still more reading to do. This stuff will all make sense someday.

 

[Daniel S.]

Re: Why do H&A brands reject diamonds with large lgfs and st

Modified. The deep cleft in the hearts.

Is this modified H&A image a produce of solely the large lower half or larger lower girdle facets (I'm assuming they are the same) or do the stars play a part in this as well.

We're discussing the effects on the hearts image but will these changes have a large effect on what the consumer will see? Will the diamond with the larger stars and large lower girdle facets possibly have less brilliance as a result of the larger fire?

 

[stone-cold11]

Re: Why do H&A brands reject diamonds with large lgfs and st

Modified. The deep cleft in the hearts.

Is this modified H&A image a produce of solely the large lower half or larger lower girdle facets (I'm assuming they are the same) or do the stars play a part in this as well.

We're discussing the effects on the hearts image but will these changes have a large effect on what the consumer will see? Will the diamond with the larger stars and large lower girdle facets possibly have less brilliance as a result of the larger fire?

Solely. The hearts image only sees the facets on the pavilion.

Already stated before, certain combination of angles favors a larger lower half for better performance.

 

[Paul-Antwerp]

Re: Why do H&A brands reject diamonds with large lgfs and st

Most cutting houses, offering 'H&A'-diamonds to, amongst others, the 'H&A'-brands known on PS, cut their production for various markets worldwide, based upon a traditional, hystory-based approach of H&A.

One of the aspects is the integrity of the hearts, which are generally cut without clefts, thus not with long LGF's and big stars.

Another side-aspect is that they pay more attention to the actual pattern and less to the crispness of the pattern. In my view, the latter is a clear error, since it is the crispness of the pattern that will have the most positive effect on the observed scintillation and fire.

Live long,

 

[Rhino]

Re: Why do H&A brands reject diamonds with large lgfs and st

Modified. The deep cleft in the hearts.

Is this modified H&A image a produce of solely the large lower half or larger lower girdle facets (I'm assuming they are the same) or do the stars play a part in this as well.

Just comes from the lower havles/girdles and yep ... they are the same. The trade tends to use the term "lower half" or "lower halves" rather than "lower girdles" though either is fine really.

We're discussing the effects on the hearts image but will these changes have a large effect on what the consumer will see? Will the diamond with the larger stars and large lower girdle facets possibly have less brilliance as a result of the larger fire?

The will definitely not have less brilliance. When observing in diffuse or natural ambient daylight (and when cut properly like Andelain's) they are equally as bright, sometimes moreso than traditional H&A's. In cases where they may be moreso is when the pavilion mains on an H&A reflect more head/body shadow (if pav main angles fall on the shallow end). This is reduced in longer lgf's because the mains do not take up as much real estate on the pavilion.

In spot lighting there is no reduction in fire and arguably has more pin flash. In the realm of round brilliant cuts its flavor lies between traditional H&A and Solasfera.

I have documented most of what I'm saying here in our clip on Understanding the Lower Half Facets.

Hope that helps.

Kind regards,

 

[Lula]

Re: Why do H&A brands reject diamonds with large lgfs and st

larger lower half, around 80%.

I see, said the blind man. You nailed it too, the LGF on that stone is 81%.

Yssie, thanks for the link. Still more reading to do. This stuff will all make sense someday.

Ha-ha, be prepared for a steep learning curve, LW-Andelain (I changed my screen name, too, this is sarap333 )

There are some fascinating old threads in the archives about lower halves, going back to 2003-2005. I read a lot of very interesting threads on the 35 crown angle / 41 pavilion angle combination and the effect of longer lower halves on this combination. I'll see if I can dig out some old threads.

 

[Lula]

Re: Why do H&A brands reject diamonds with large lgfs and st

larger lower half, around 80%.

I see, said the blind man. You nailed it too, the LGF on that stone is 81%.

Yssie, thanks for the link. Still more reading to do. This stuff will all make sense someday.

Ha-ha, be prepared for a steep learning curve, LW-Andelain (I changed my screen name, too, this is sarap333 )

There are some fascinating old threads in the archives about lower halves, going back to 2003-2005. I read a lot of very interesting threads on the 35 crown angle / 41 pavilion angle combination and the effect of longer lower halves on this combination. I'll see if I can dig out some old threads.

found a few old threads:
https://www.pricescope.com/community/threads/long-stars.32120/?hilit=lower halves
https://www.pricescope.com/community/threads/star-facets-percent-info.27601/?hilit=lower halves
https://www.pricescope.com/communit...needless-perfection.10184/?hilit=lower halves
https://www.pricescope.com/communit...he-numbers-on-a-h-a.62901/?hilit=lower halves
https://www.pricescope.com/community/threads/lgf-and-stars.36793/?hilit=lower halves

Happy reading!

 

[Daniel S.]

Re: Why do H&A brands reject diamonds with large lgfs and st

Thank you for posting these links Portree, I have quite a lot of reading to do!

The will definitely not have less brilliance. When observing in diffuse or natural ambient daylight (and when cut properly like Andelain's) they are equally as bright, sometimes moreso than traditional H&A's. In cases where they may be moreso is when the pavilion mains on an H&A reflect more head/body shadow (if pav main angles fall on the shallow end). This is reduced in longer lgf's because the mains do not take up as much real estate on the pavilion.

In spot lighting there is no reduction in fire and arguably has more pin flash. In the realm of round brilliant cuts its flavor lies between traditional H&A and Solasfera.

If a Diamond with lower halfs larger than 80% really has the potential more brilliance and more fire, then why limit ourselves? Do we limit ourselves solely for the sake of a prettier heart image? It seems ludicrous to limit performance potential which you see all the time just for a heart image that most will see only once on a vendor's website.

For stars and lower halfs alike, when are they too big? Is there a point where it becomes physically impossible to cut them so big or they will begin to hurt performance? In the case of stars, will making them excessively large will require some sort of brillianteering to avoid the turning the crown mains into triangles rather than kites? In the case of lower halfs, what is stopping a cutter from cutting them at 85% or 90%?

 

[Andelain]

Re: Why do H&A brands reject diamonds with large lgfs and st

Portree/Sara, as I mentioned in your other thread that gorgeous ring in your avatar kind of gave you away... The Eightstar/ACA sandwich in my avatar probably does the same thing for me.

Thanks for posting those links, I've got some reading when I have time. I'm just starting to put the picture together beyond the basic crown/pavilion angles.

Daniel, you bring up a good point about sacrificing the hearts and arrows in favor of a more brilliant diamond. I was also wondering how muchh difference this would make in lower color stones as opposed to colorless ones. Would it not make something in the L-N range face up a little more white if it was cut with longer LGF's to give more brilliance?

 

[stone-cold11]

Re: Why do H&A brands reject diamonds with large lgfs and st

As I said before, certain proportions work better together, there is no one proportions that work for everyone.

 

[Lula]

Re: Why do H&A brands reject diamonds with large lgfs and st

Portree/Sara, as I mentioned in your other thread that gorgeous ring in your avatar kind of gave you away... The Eightstar/ACA sandwich in my avatar probably does the same thing for me.

Thanks for posting those links, I've got some reading when I have time. I'm just starting to put the picture together beyond the basic crown/pavilion angles.

Daniel, you bring up a good point about sacrificing the hearts and arrows in favor of a more brilliant diamond. I was also wondering how muchh difference this would make in lower color stones as opposed to colorless ones. Would it not make something in the L-N range face up a little more white if it was cut with longer LGF's to give more brilliance?

Ha-ha, yes, Andelain, our avatars give us away! Love the "eightstar" sandwich! Enjoy your reading. There's a lot to learn. The interesting thing is, as Stone notes, there are many combinations that produce beautiful diamonds. If you hang around here enough -- and in your case, if you keep adding to your collection -- you will learn to discern the finer details between the stones. I'm sure you will notice the difference between your eightstars and a stone cut with longer lower halves right away.

 

[Lula]

Re: Why do H&A brands reject diamonds with large lgfs and st

Thank you for posting these links Portree, I have quite a lot of reading to do!

The will definitely not have less brilliance. When observing in diffuse or natural ambient daylight (and when cut properly like Andelain's) they are equally as bright, sometimes moreso than traditional H&A's. In cases where they may be moreso is when the pavilion mains on an H&A reflect more head/body shadow (if pav main angles fall on the shallow end). This is reduced in longer lgf's because the mains do not take up as much real estate on the pavilion.

In spot lighting there is no reduction in fire and arguably has more pin flash. In the realm of round brilliant cuts its flavor lies between traditional H&A and Solasfera.

If a Diamond with lower halfs larger than 80% really has the potential more brilliance and more fire, then why limit ourselves? Do we limit ourselves solely for the sake of a prettier heart image? It seems ludicrous to limit performance potential which you see all the time just for a heart image that most will see only once on a vendor's website.

For stars and lower halfs alike, when are they too big? Is there a point where it becomes physically impossible to cut them so big or they will begin to hurt performance? In the case of stars, will making them excessively large will require some sort of brillianteering to avoid the turning the crown mains into triangles rather than kites? In the case of lower halfs, what is stopping a cutter from cutting them at 85% or 90%?

You are welcome, Daniel -- happy reading. I cannot find the thread right now, but I seem to remember a thread that explained that there is a point (somewhere around 85% maybe?) where longer lower halves significantly change the appearance of the diamond. I just can't find the thread right now. But have you read this article by Karl K https://www.pricescope.com/journal/do_pavilion_mains_drive_light_return_modern_round_brilliant? I learned a lot from reading this -- though I had to read it about 35 times!