Is HCA relevant for colored diamonds?

[Lizabeth]

Is HCA relevant for yellow diamonds or just white ones?

 

[Rockdiamond]

Hi Lizabeth,
I see no reason why HCA would not work the same way for a round brilliant colored diamond, if one had the CA/PA/ Table/ Depth
BUT the results are not really relevant as-
1) colored diamonds use light differently than colorless in a broad sense so you'd be looking at other parameters on a Fancy Colored Diamond
2) most FCD's are not round.....

 

[kenny]

HCA will work for any round diamond D - Z or Fancy Colored.
... but good luck finding many round FCDs.
The round does not jack up the color strength in the top view, like other cuts such as radiant.

Next, even if you do find a round FCD it will likely have been cut to save weight to maximize profit, and cut deep to maximize the material the light must pass through, which increases color strength, which may get it a higher GIA color grade, which will maximize profit - all at the expense of light performance.

Lastly, the HCA needs crown and pavilion specs but good luck determining the Crown and Pavilion angles, or even the Crown and Pavilion percentages of depth; GIA reports those on some D-Z reports but not on either of their FCD reports.
This is further evidence that light performance takes a back seat in FCDs.

That said, if you are patient enough you may eventually find a round FCD that's well cut.
I found one.
GIA reports: 0.26 ct Fancy Intense Green round OEC, VS2 with natural material and color origin.
It ain't no ACA but it sparkles like crazy for an FCD.
So you can find these needles in the haystack.



One option, if you don't care that you are lowering the value of the diamond by losing carat weight, face up size, and possibly color strength and a GIA color grade ... is to buy a larger round and send it to someone like www.briangavindiamonds.com for a recut.

 

[cflutist]

HCA will work for any round diamond D - Z or Fancy Colored.
... but good luck finding many round FCDs.
The round does not jack up the color strength in the top view, like other cuts such as radiant.

Couldn't resist,

Paul Slegers (Crafted by Infinity) sourced an entire 8.94 ctw parcel of 20-pointer round Fancy Intense Yellow diamonds for me. They were used to make a bracelet and an a pendant.

[URL='https://www.pricescope.com/community/threads/my-8-94-tw-parcel-of-fancy-intense-yellow-round-brilliants.204007/']https://www.pricescope.com/community/threads/my-8-94-tw-parcel-of-fancy-intense-yellow-round-brilliants.204007/[/URL]

[URL='https://www.pricescope.com/community/threads/19-ctw-of-diamonds-from-wink-including-a-new-fiy-bracelet.204589/']https://www.pricescope.com/community/threads/19-ctw-of-diamonds-from-wink-including-a-new-fiy-bracelet.204589/[/URL]

[URL='https://www.pricescope.com/community/threads/1-79-ctw-fancy-intense-yellow-diamond-pendant-from-wink.204846/']https://www.pricescope.com/community/threads/1-79-ctw-fancy-intense-yellow-diamond-pendant-from-wink.204846/[/URL]

 

[MelisendeDiamonds]

HCA will work for any round diamond D - Z or Fancy Colored.

The HCA was designed to be applied to colorless modern round brilliants where the goal is to optimize brightness as well as provide balanced contrast and fire.

It does not apply where the goal is to intensify color in a round FCD. It does not apply when a balance of sparkle and color entrapment is preferred in a FCD. It does not work on cuts Old Cuts with shorter lowers where the CA/PA combination and table size can be dramatically different than a MRB.

Practically it doesn't apply to the majority of FCDs, theoretically the singular goal of optimizing brightness might apply to dark rough like dark brown (and very few other colors and saturations) but even then the lack of information on the grading report would limit its usefulness.

The goal balance for most FCDs even from deeply saturated rough (which does not require color entrapment techniques) are balanced differently most of the time thus its output is not applicable.

 

[kenny]

HCA will work for any round diamond D - Z or Fancy Colored.

The HCA should only be applied to colorless modern round brilliants where the goal is to optimize brightness as well as provide balanced contrast and fire.

It does not apply where the goal is to intensify color in a round FCD. It does not apply when a balance of sparkle and color entrapment is preferred in a FCD. It does not work on cuts Old Cuts with shorter lowers where the CA/PA combination and table size can be dramatically different than a MRB.

Practically it doesn't apply to any FCD, theoretically the singular goal of optimizing brightness might apply to dark rough like dark brown (and very few other colors and saturations) but even then the lack of information on the grading report would limit its usefulness.

The goal balance for FCD even from deeply saturated rough (which does require color entrapment techniques) are balanced differently, thus its output is not applicable.

Yes and no.

Yes, the colored diamond industry cuts for weight and color, NOT for light performance.

No, customers are free too look for whatever they want no matter now rare the industry makes it.
There is nothing about optics, physics or any other branch of science that makes the HCA not work when the dimaond material is colored.
You are taking about marketing.

Yes I realize my OEC green may not be favored by the HCA.
I have no idea since, as I stated earlier, GIA does not report crown and pavilion info in their FCD reports.
I have several superbly cut white diamonds and have owned around 25 FCDs and the green round has the best light performance of any.

Still, my point is customers are free to search for that rare round, or any shape, FCD that has good light performance.
My next best FCD when it comes to light performance is a Fancy Vivid Yellow Asscher.

I can understand that vendors of FCDs see my words as anathema when it comes to selling their inventory.
Sorry.

I suspect good light performance in an FCD only happens accidentally when the shape of the rough happens to coincide with good proportions for light performance even though they were just cutting for weight.
A lucky accident.

 

[Rockdiamond]

Interesting discussion.
From my standpoint, brightness is a crucial element in a Fancy Colored Diamond.
Of course how one defines brightness can't be specifically measured per se.
Same for light performance.
The green diamond Kenny posted is obviously beautiful, but with all due respect Kenny -you're basically saying that your diamond "sparkles like crazy" so it's really well cut, yet no one else can make such a claim.

My experience is that the best cutters are very good at producing beautiful desirable FCDs that "Sparkle like crazy".
Sure, there's bad cuts out there. But also really good ones.

I can also say that I've seen quite a bit of improvement in overall cut quality in many fancy colored diamonds over the past five years. That's not happening by accident. Technology is being used to maximize color, weight retention and brilliance. There's so many considerations when plotting and cutting fancy colored rough.

Lets also remember that although round FCD's over 1.00ct are pretty rare, most FCD's below .10ct are indeed round.
In essence, there's far more FCD round diamonds cut, considering the numbers of stones as opposed to overall weight.

 

[MelisendeDiamonds]

HCA will work for any round diamond D - Z or Fancy Colored.

The HCA should only be applied to colorless modern round brilliants where the goal is to optimize brightness as well as provide balanced contrast and fire.

It does not apply where the goal is to intensify color in a round FCD. It does not apply when a balance of sparkle and color entrapment is preferred in a FCD. It does not work on cuts Old Cuts with shorter lowers where the CA/PA combination and table size can be dramatically different than a MRB.

Practically it doesn't apply to any FCD, theoretically the singular goal of optimizing brightness might apply to dark rough like dark brown (and very few other colors and saturations) but even then the lack of information on the grading report would limit its usefulness.

The goal balance for FCD even from deeply saturated rough (which does require color entrapment techniques) are balanced differently, thus its output is not applicable.

Yes and no.

Yes, the colored diamond industry cuts for weight and color, NOT for light performance.

No, customers are free too look for whatever they want no matter now rare the industry makes it.
There is nothing about optics, physics or any other branch of science that makes the HCA not work when the dimaond material is colored.
You are taking about marketing.

Yes I realize my OEC green may not be favored by the HCA.
I have no idea since, as I stated earlier, GIA does not report crown and pavilion info in their FCD reports.
I have several superbly cut white diamonds and have owned around 25 FCDs and the green round has the best light performance of any.

Still, my point is customers are free to search for that rare round FCD that has good light performance.

Sorry.
I can understand that vendors of FCDs see my words as anathema when it comes to selling their inventory.

Kenny,

Advising customer to search for the "holy grail" of optimal LP and color saturation is both impractical(doesn't exist) and may not be the best of both worlds as you think.

Color uniformity is much more important for a fancy yellow and avoiding harsh contrast than is maximizing sparkle. This rebalancing from colorless goals is for aesthetic reasons just as much as for financial ones.

I'm not advising that someone ignore sparkle and brightness when choosing a fancy color but a blunt rejection tool like HCA is not going to be helpful in this task.

Practically with no CA/PA or CH/PH the HCA tool cannot be used so this is purely a theoretical discussion for Fancy color.

Now there may be cases where melee, recuts, or deeply saturated diamond rough(like lab grown) could benefit from strict tolk angles but these cases are few and far between and I doubt a customer would have enough choices to select for optimal angles by HCA anyway.

 

[Rockdiamond]

Really great points Melisende.
Even color is a very attractive aspect in well cut Yellow diamonds.
Very hard to achieve in a round- or step cut for that matter.

if it really was an issue a sarin would give the numbers for an HCA run. CA/PA are not that elusive.