New HCA uses report #'s

[Serg]

Would you like to do a better job?
Steep Shallow stones have very small spreads and so do not work well for earrings and pendants. Any advantage they have in the fire department is more or less lost because the main attribute observers see is brightness and apparent size.

Hi Garry,
I believe Fire is important for many consumers. If consumers do not care about Fire and prefer just Brightness they need buy melee, Princess cuts,... instead RBC

 

[Garry H (Cut Nut)]

Re: #5 are sure it's trade members or just loyal PS'ers? I know I try a few dozen or hundred a day

5,000 to 20,000 in a day????

 

[Garry H (Cut Nut)]

Hi Garry,
I believe Fire is important for many consumers. If consumers do not care about Fire and prefer just Brightness they need buy melee, Princess cuts,... instead RBC

Sergey I have rarely seen fire when people are wearing earrings or pendants.

Do others see fire in those cases? Maybe only in very large stones?

 

[Karl_K]

Sergey I have rarely seen fire when people are wearing earrings or pendants.

Do others see fire in those cases? Maybe only in very large stones?

In the right lighting I have seen ear rings and more often pendants shoot fire across the room even if they were small.
Bright lighting at the right level is what is needed, ceiling light is not conductive to it.
Light from tvs in a dim room, bright floor/table lamps, bathroom mirror lights, spotlights and windows will set off a fire show even in smaller diamonds.
It is true a larger diamond will do it more often but even small diamonds can put on a light show.

 

[whitewave]

5,000 to 20,000 in a day????

Wow!

 

[Serg]

Sergey I have rarely seen fire when people are wearing earrings or pendants.

Do others see fire in those cases? Maybe only in very large stones?

Garry, what is typical diamond size you see in pedants?
Have you to develop different HCA depends from size?

 

[prs]

Gary, could you please explain exactly what a "symmedivical" diamond is?


Also, is it at all possible for a diamond with a GIA cut rating of "Very Good" to score well on the HCA because of a particular combination of crown and pavilion angles?

 

[gm89uk]

Yes, particularly Gia very good with pavilion <40.5. it will be dinged on proportion with GIA but may have decent light return.

GIA might give a Very good for brillianteering which HCA wouldn't know about, or if the girdle was too thick. There are many scenarios

 

[Garry H (Cut Nut)]

Gary, could you please explain exactly what a "symmedivical" diamond is?


Also, is it at all possible for a diamond with a GIA cut rating of "Very Good" to score well on the HCA because of a particular combination of crown and pavilion angles?

OMG, that is a supercalafragalisticexpeladoshish symmetriacl diamond - surely you knew that?

GM answered your other question perfectly. But the shallow pavilion stone has some limits when combined with a shallow crown - there is an inverse proportion ratio of around 5:1 - for every 1 degree of extra pavilion angle over an optimum #, reduce the crown by 5 degrees.

 

[prs]

OMG, that is a supercalafragalisticexpeladoshish symmetriacl diamond - surely you knew that?

GM answered your other question perfectly. But the shallow pavilion stone has some limits when combined with a shallow crown - there is an inverse proportion ratio of around 5:1 - for every 1 degree of extra pavilion angle over an optimum #, reduce the crown by 5 degrees.

Gary, I hope you cornered the market before posting that explanation, now most of the people on this board are going to want one of those stones!

Sorry I'm not an expert, and while I understood gm89uk to say that good HCA scoring stones might be found in the GIA VG cut gategory, and particularly those with pavilion angles below 40.5°. I couldn't quite figure out the rest of the answer; are those HCA scores true or do those stones have too thick a girdle and may not be as good as the HCA score suggests?

 

[Garry H (Cut Nut)]

PRS find a few large spread for weight GIA VGs with Ex HCA and poat them

 

[Karl_K]

Once you get much below 40.5 your going to start seeing some issues in a ring.
A diamond with 40.5 on the report can go either way.
If its tight and each individual main is right close to 40.5 it could be awesome.
If it has wide ranging main angles and the majority of them dip close to 40.4, maybe not so awesome.
Longer lowers can cover some of it so it still comes down to the overall combo.

 

[prs]

I appreciate you all trying to answer my question but, although I'm an engineer, the terms you are using that are specific to diamond cut are beyond me. I guess maybe I should rephrase my question; Given that GIA VG stones might be less expensive than GIA EX, is it worthwhile looking thru VG stones to find a good HCA scorer or would it be like searching for a needle in a haystack?

The fact diamond dealers usually don't list crown and pavilion angles means you have to click on each individual stone to get those details, so a search that yields only a minimal hit rate would be very time consuming.

 

[whitewave]

I appreciate you all trying to answer my question but, although I'm an engineer, the terms you are using that are specific to diamond cut are beyond me. I guess maybe I should rephrase my question; Given that GIA VG stones might be less expensive than GIA EX, is it worthwhile looking thru VG stones to find a good HCA scorer or would it be like searching for a needle in a haystack?

The fact diamond dealers usually don't list crown and pavilion angles means you have to click on each individual stone to get those details, so a search that yields only a minimal hit rate would be very time consuming.

You can try. I use these parameters for advanced search

Depth 60.5-62.1

Table 55-57

Pavilion 40.6 40.8

Crown 34 34.5



Gia excellent:

Depth 60-62.3

Table 54-58

Pavilion 40.6 to 40.9

Crown 34-35



For instance, this very good cut comes out 1.6 hca: https://www.bluenile.com/diamond-details/LD09448332?refTab=DIAMONDS

But again, remember HCA only kicks out duds. There still may be problems with the stone...

 

[Texas Leaguer]

I appreciate you all trying to answer my question but, although I'm an engineer, the terms you are using that are specific to diamond cut are beyond me. I guess maybe I should rephrase my question; Given that GIA VG stones might be less expensive than GIA EX, is it worthwhile looking thru VG stones to find a good HCA scorer or would it be like searching for a needle in a haystack?

The fact diamond dealers usually don't list crown and pavilion angles means you have to click on each individual stone to get those details, so a search that yields only a minimal hit rate would be very time consuming.

Generally speaking finding a VG that will be a top performer is a needle in a haystack. But gm89uk made an astute comment above. Due to the way GIA applies a broad brush penalty for any significant painting or digging out (tweaking of the upper and lower girdle facets), it is actually possible to find super ideals with GIA VG cut grade! Some precision cut stones have crown painting designed not to swindle the stone (keep extra weight), but rather to eliminate virtually all leakage. These stones, which would otherwise have zero deductions even in the more restrictive AGS cut grade system, get dinged by the GIA system.

This has nothing to do with HCA however since it does not factor this aspect into it's calculations.

 

[prs]

You can try. I use these parameters for advanced search

Depth 60.5-62.1
Table 55-57
Pavilion 40.6 40.8
Crown 34 34.5

Gia excellent:
Depth 60-62.3
Table 54-58
Pavilion 40.6 to 40.9
Crown 34-35

For instance, this very good cut comes out 1.6 hca: https://www.bluenile.com/diamond-details/LD09448332?refTab=DIAMONDS

But again, remember HCA only kicks out duds. There still may be problems with the stone...

Thanks Whitewave, what search engine do you use that includes crown and pavilion angles?

 

[whitewave]

Thanks Whitewave, what search engine do you use that includes crown and pavilion angles?

Most only have depth and table, so set those parameters

 

[prs]

PRS find a few large spread for weight GIA VGs with Ex HCA and poat them

Gary, was this your way of telling me to go take a hike?

I can assure you I meant no disrespect, in fact I think the HCA is a tremendous tool. I don't know if you were around in the 1980s when Robert Parker took the wine world by storm when he introduced his 100 point rating scale? Of course it helped that his ratings were right most of the time!! I just feel the output of the HCA, with zero being the best score, is counterintuitive. Just think what it would mean if first class diamond vendors could market stones as HCA 100 pointers!!!

In reality Parker has a scale of 87-100 pts for the wines he rates, he doesn't publish ratings for wines that score below 87 points and the vast majority of wines are unrated. However producers of wines that are rated, market the heck out of their scores, and consumers buy based on those scores. A wine that scores 93 points is generally regarded as an excellent wine, an 87 pointer, at the right price, would be a good daily drinker. Wine producers all over the world have improved their wine making in order to achieve better Parker scores. Your HCA rating system is almost identical except for the output.

I think that almost everyone in the diamond world agrees that cut is of primary importance but, at present, there is no accepted rating system that satisfactorily measures cut quality. It seems you have that system, all you need to do, IMNSHO, is tweak the scoring system a tad.

 

[OoohShiny]

I can't answer for Garry with regards to the scoring choices, I don't think he was telling you to 'take a hike' - rather, I think he was suggesting that if you can find some VG stones and post them up, we can review them and offer comment

 

[John P]

Gary, was this your way of telling me to go take a hike?

I believe Garry's offer to assess some examples was genuine. In any case, an Ozzie would tell you to go on walkabout.

I can assure you I meant no disrespect, in fact I think the HCA is a tremendous tool. I don't know if you were around in the 1980s when Robert Parker took the wine world by storm when he introduced his 100 point rating scale? Of course it helped that his ratings were right most of the time!! I just feel the output of the HCA, with zero being the best score, is counterintuitive. Just think what it would mean if first class diamond vendors could market stones as HCA 100 pointers!!!

Parker's system is great, but the reason you get a detailed 50-100 score is because wines of the same type have actually been smelled/tasted against each other.

The HCA doesn't get enough info to 'taste' the diamond: It does not take 40 minor facets into consideration (of 57 total on the diamond). It does not account for cut-consistency. It does not account for 3D optical precision. It does not account for indexing variations such as painting or digging. None of that information is present. There isn't a taste, or even a full picture. In essence, the HCA is imagining a "chalk outline" of averaged (possibly rounded) Table, Crown and Pavilion data, and predicting whether the basic geometry is one proven conducive to light return. It's useful in that context: It will reject diamonds with basic geometries considered too dark, and ID others worth further consideration.

It explains why an HCA rating of 1.0 versus 2.0 is irrelevant. It's like putting two cars on a "HCA radar gun." One is going 55. The other 45. Neither is speeding, so the HCA qualifies them as "safe" drivers, but there is not enough info to know which one is ultimately the SAFER driver, which one navigates curves better, which driver gets from 0-60 fastest, etc. You need to get to know the drivers and put them through many more paces to make a more detailed determination.

Revisiting your Parker comparison: If wines came with standard numeric values on the bottle (sweetness, acidity, tannin, fruit and body, etc.) maybe an adviser could be developed where you enter those numbers and a rating gets returned. That rating could be useful in a broad sense, but it could not possibly communicate the complexity involved in tasting...

By the way, if you develop a "PRS Wine Adviser" and make gazillions, please remember the gentle folks here who sparked the idea.

ETA: Similar discussion in this thread from 2014.

 

[prs]

Yes, sorry Gary. It's never a good idea to post after drinking a glass or two of wine with dinner! Particularly on a board that severely limits the time you have for editing!

Here's one of the needles I found:
GIA: VG, HCA: 1.4
https://www.jamesallen.com/loose-di...-h-color-vs2-clarity-very-good-cut-sku-321279

This one ia an HCA: 0.6
http://www.eternitybyyoni.com/diamond_detail.php?id=2753058&ref=pricescope

 

[John P]

GIA: VG, HCA: 1.4
https://www.jamesallen.com/loose-di...-h-color-vs2-clarity-very-good-cut-sku-321279

No combination of PA 40.6 with table size 60+ will earn EX. If you bring a little more height to the crown (make CA steeper and table size smaller) there are diamonds with average 40.6 PA which reach EX. The 60% table gives this one no hope in GIA's system, although it's a candidate for AGS 0-1 in light performance. Using pavilion angle as a basis, many diamonds with average PA of 40.6 and less cannot qualify for GIA Excellent, even though some have better light return potential than an abundant range of steep-deep combos which do qualify.

This one ia an HCA: 0.6
http://www.eternitybyyoni.com/diamond_detail.php?id=2753058&ref=pricescope

This is a great specimen for discussion: The basic numbers plugged into HCA earn the top rating. But the stars were polished down to 60% average, which is a bit irregular. Those are usually the last facets polished on the diamond, by the way. Sometimes the brillianteerer runs the stars in a way that cleans up mistakes made in cross-working. In any case, that detail causes the diamond to earn VG instead of EX from GIA. But since there is no entry-box for stars (as well as 32 other facets) the HCA doesn't account for it.

My 2 cents? A justified reduction, since the upper-halves then draw light from slightly lower angles. Although the diamond certainly isn't a train wreck.

 

[Garry H (Cut Nut)]

I appreciate you all trying to answer my question but, although I'm an engineer, the terms you are using that are specific to diamond cut are beyond me. I guess maybe I should rephrase my question; Given that GIA VG stones might be less expensive than GIA EX, is it worthwhile looking thru VG stones to find a good HCA scorer or would it be like searching for a needle in a haystack?

The fact diamond dealers usually don't list crown and pavilion angles means you have to click on each individual stone to get those details, so a search that yields only a minimal hit rate would be very time consuming.

It is rather hard because dealers know the PS buyers are super fussy about cut and only usually list GIA Excellent cut stones. So you cant use the HCA listing on Pricescope.
But you must tell us what you are buying for - if it is a ring, STOP. And buy a stone between 1 and 2 and stop trying to penny pinch

 

[Garry H (Cut Nut)]

Gary, was this your way of telling me to go take a hike?

I can assure you I meant no disrespect, in fact I think the HCA is a tremendous tool. I don't know if you were around in the 1980s when Robert Parker took the wine world by storm when he introduced his 100 point rating scale? Of course it helped that his ratings were right most of the time!! I just feel the output of the HCA, with zero being the best score, is counterintuitive. Just think what it would mean if first class diamond vendors could market stones as HCA 100 pointers!!!

In reality Parker has a scale of 87-100 pts for the wines he rates, he doesn't publish ratings for wines that score below 87 points and the vast majority of wines are unrated. However producers of wines that are rated, market the heck out of their scores, and consumers buy based on those scores. A wine that scores 93 points is generally regarded as an excellent wine, an 87 pointer, at the right price, would be a good daily drinker. Wine producers all over the world have improved their wine making in order to achieve better Parker scores. Your HCA rating system is almost identical except for the output.

I think that almost everyone in the diamond world agrees that cut is of primary importance but, at present, there is no accepted rating system that satisfactorily measures cut quality. It seems you have that system, all you need to do, IMNSHO, is tweak the scoring system a tad.

POAT was meant to be post.
I was seriously helping you

 

[Garry H (Cut Nut)]

I agree with John. But the shallow pav and shallowish crown is greeat for earrings and pendants - not for a ring. My rule is 61% max table for under 3/4ct, 60% for under 1ct, 59% for 2ct and 58% above that otherwise the sonte lacks 'detail'.
But J - that is going to be pretty yellow - that everyone will see - I would personally pefer an SI1 with a hard to see inclusion and a +G preferrably with some good eyes to assure me that strong lbue fluoro is a benefit not a problem

 

[prs]

By the way, if you develop a "PRS Wine Adviser" and make gazillions, please remember the gentle folks here who sparked the idea.

ETA: Similar discussion in this thread from 2014.

John, please don't hold your breath waiting for the gazillions and thank you for the link and explanations. I now have a much better understanding of the HCA.

By the way, on your "Crafted by Infinity" website there is a slight problem on the "Locations" page with the address of the Fresno store. I only spotted that because we have family in Fresno, and I've actually driven on Shaw Ave.

 

[angeljosephy]

Hi Garry (or others),

I tried to use the HCA earlier today but when I entered the report number an error message pops up saying that 'The total Depth % entered suggests the girdle is dangerously thin, or the data entered is incorrect.'

When I checked against my GIA report (1233884445) the girdle should be medium (3.5%). Any idea why that is? Thanks a lot for your help!

 

[Garry H (Cut Nut)]

Hi Garry (or others),

I tried to use the HCA earlier today but when I entered the report number an error message pops up saying that 'The total Depth % entered suggests the girdle is dangerously thin, or the data entered is incorrect.'

When I checked against my GIA report (1233884445) the girdle should be medium (3.5%). Any idea why that is? Thanks a lot for your help!

share the cert please

 

[Garry H (Cut Nut)]

enter the angles not the depth %

 

[angeljosephy]

share the cert please

Here's the report:

1233884445-1

• angeljosephy
• Jan 22, 2018