IYO, Is this a true H&A stone? Please notice the tiny clefts on the hearts.

[Dancing Fire]

Here's my wife's 80% LGF stone. We usually start to see a tiny cleft on the hearts at 79% or >.
What are the PSer rules for true H&A stones?

 

[Karl_K]

Yes as I was taught it by Brian Gavin.
https://www.pricescope.com/articles/hearts_and_arrows_diamonds_and_basics_diamond_cutting
Quick Guide

• 8 equal uniformed symmetrical hearts.
• 8 distinct symmetrical Hearts that separate from the Arrowheads above. If above is correct check the following.
• Check if the hearts are split, measure length of heart then the length of the split.
• Calculate the % of the length split, if it is greater than 8% and there are more than 2 of them IT FAILS.

 

[AV_]

Remind me how the clefts form...

 

[Karl_K]

Remind me how the clefts form...

lower girdle %, when they get near 80 they start to cleft.

 

[Dancing Fire]

Yes as I was taught it by Brian Gavin.
https://www.pricescope.com/articles/hearts_and_arrows_diamonds_and_basics_diamond_cutting
Quick Guide

• 8 equal uniformed symmetrical hearts.
• 8 distinct symmetrical Hearts that separate from the Arrowheads above. If above is correct check the following.
• Check if the hearts are split, measure length of heart then the length of the split.
• Calculate the % of the length split, if it is greater than 8% and there are more than 2 of them IT FAILS.

So, IYO is my wife's stone a true H&A ? How do you do the calculation?

 

[Karl_K]

So, IYO is my wife's stone a true H&A ? How do you do the calculation?

Yes, I know what 8% looks like, there are samples on that page.

 

[Karl_K]

It cracks me up that you are even worried about it.
The goal of h&a images is to show if the stone has optical symmetry and yours has a very high level of optical symmetry.

 

[sledge]

Hey @Karl_K, what causes half the heart to be brighter white than the other half?

See below and item #3. Appears to be minor. Just curious why it happens.

https://beyond4cs.com/hearts-and-arrows/guidelines-for-optical-symmetry/

3. Ideally speaking, coloration of the hearts is not permitted. While this feature is relatively minor, you should see a single color tone instead of 2 different shades of colors.

 

[sledge]

Yes, I know what 8% looks like, there are samples on that page.

Posting for future readers...

2.Calculating the accuracy and Hearts you can measure the length as shown X_to_Y in 1a (A template tool can be used) say this is 10mm. If you see any splits in the cleft this is measured and it can be no longer than 8% of the total length of the heart as shown by Z to C in 2A. If there are more than 2 hearts split at more than 8% then it will not make the grade of True Hearts, in addition the arrow head must separate from the actual Heart.

 

[Karl_K]

Hey @Karl_K, what causes half the heart to be brighter white than the other half?

See below and item #3. Appears to be minor. Just curious why it happens.

https://beyond4cs.com/hearts-and-arrows/guidelines-for-optical-symmetry/

I am having a hard time not being snarky. Not at you but at the source of that drivel.
Where does diamond color on a diamond come from when it isn't the material itself and it isn't fire?
Placement in the scope and or using the the pocket small diameter h&a scopes.

 

[Dancing Fire]

It cracks me up that you are even worried about it.
The goal of h&a images is to show if the stone has optical symmetry and yours has a very high level of optical symmetry.

I'm not...just wondering what PSer's opinion on the tiny clefts, b/c some members say if there are tiny clefts then the stone can't be label as a true heart stone.

 

[Karl_K]

I'm not...just wondering what PSer's opinion on the tiny clefts, b/c some members say if there are tiny clefts then the stone can't be label as a true heart stone.

There are no universally accepted standards out there and there is a lot of drivel out there.
The term hearts and arrows is all marketing wank of the scientific concept of optical symmetry, it just happens that one range of optically symmetrical MRBs that are in one of the sweet spots for the design form hearts and arrows in a viewer.
Personally I think that optical symmetry matters to some degree but the marketing terms are just marketing.

Anyway for the marketing wank Brian's standards are good enough for me.
To me optical symmetry is optical symmetry.

 

[Karl_K]

For example these virtual oec like and long lgf% models are optically symmetrical and have those advantages but are not h&a.

 

[sledge]

I am having a hard time not being snarky. Not at you but at the source of that drivel.
Where does diamond color on a diamond come from when it isn't the material itself and it isn't fire?
Placement in the scope and or using the the pocket small diameter h&a scopes.

Sorry. I understand your POV.

I was being a geek and thinking maybe they were inferring the shade difference was created by twisted facets, thereby reflecting the light slightly different.

 

[Athena10X]

For example these virtual oec like and long lgf% models are optically symmetrical and have those advantages but are not h&a.

With this in mind, what are your recommended lgh lengths for a great performing diamond that is optically symmetrical, but not necessarily an ideal H&A (which I believe fall within 76-78?). I am assuming all other PS-recommended facet proportions would remain the same. Also, how would an optically-symmetrical non-H&A compare visually irl to an H&A (same crown, pavilion, table, depth)-more/less fire, brilliance, scintillation? Or does lgh length not affect these?

 

[WinkHPD]

For example these virtual oec like and long lgf% models are optically symmetrical and have those advantages but are not h&a.

Karl, am I remembering these from a long ago cutting discussion on Pricescope? If I am, I believe it was John Pollard who labeled the “Hearts and Darts.” A reflective function of lower-half choices.

Wink

 

[Karl_K]

Karl, am I remembering these from a long ago cutting discussion on Pricescope? If I am, I believe it was John Pollard who labeled the “Hearts and Darts.” A reflective function of lower-half choices.

Wink

Yep :}
We have had this conversation several times over the years on PS.
I figured it was time to do it again.

 

[Karl_K]

Sorry. I understand your POV.

I was being a geek and thinking maybe they were inferring the shade difference was created by twisted facets, thereby reflecting the light slightly different.

Nada to be sorry about. :} its a fair question.

 

[Karl_K]

With this in mind, what are your recommended lgh lengths for a great performing diamond that is optically symmetrical, but not necessarily an ideal H&A (which I believe fall within 76-78?). I am assuming all other PS-recommended facet proportions would remain the same. Also, how would an optically-symmetrical non-H&A compare visually irl to an H&A (same crown, pavilion, table, depth)-more/less fire, brilliance, scintillation? Or does lgh length not affect these?

H&a generally falls within 74 to 80
Below is 73 and 81


There really is no ideal lgf% but some combinations match up better with certain ranges of lgf%.

 

[gm89uk]

Lgf will affect fire brilliance and scintillation, not necessarily any less than 'true' H&A. The values that give the H&A you know and love strikes a good balance of those features.

 

[Karl_K]

For example: With slightly deep pavilions under table leakage can be eliminated by longer lgf% and borderline obstruction issues can be helped by a longer lgf%.

 

[Karl_K]

Lgf will affect fire brilliance and scintillation, not necessarily any less than 'true' H&A. The values that give the H&A you know and love strikes a good balance of those features.

Even within the h&a range there is some difference.
Shorter lgf% within the h&a range have a larger % of the under table dark under obstruction, larger flashes off the mains and smaller flashes off the lowers.
Longer lgf% with the h&a range have a smaller % of the table dark under obstruction, smaller flashes off the mains and larger flashes off the lowers.
In the end it comes down to personal preference and a large portion of the population would probably take a look at them side by side and say your nuts when your explaining the difference.

 

[Athena10X]

For example: With slightly deep pavilions under table leakage can be eliminated by longer lgf% and borderline obstruction issues can be helped by a longer lgf%.

If I’m understanding correctly, a 34,41 combo could have less light leakage and obstruction with longer lgf% > 80? Conversely, could a 36,40.6 combo perform decently with lgf% < 75? Just trying to figure out “sweet spots” for those who want optical symmetry, but may not want to pay a premium for H&A or the gold standard of 34-35, 40.6-40.8 combos.

 

[Karl_K]

If I’m understanding correctly, a 34,41 combo could have less light leakage and obstruction with longer lgf% > 80? Conversely, could a 36,40.6 combo perform decently with lgf% < 75? Just trying to figure out “sweet spots” for those who want optical symmetry, but may not want to pay a premium for H&A or the gold standard of 34-35, 40.6-40.8 combos.

it depends on what is in the averages.
If the 40.6 average has a few mains below ~40.45 the 75% could be an issue. ASET or IS will not show it.
If the 41 average has some steep mains it could have less leakage at 80% lgf%. ASET or IS will show this.
One of my favorite h&a combos is a tight 55-56t/34/41/80lgf combo.