Asking about HCA theory

[Newgirl87]

Hi Gurus!!

As I'm reading more on diamond cut, more question has come to my mind.
I do possess 2 diamond that in my eyes were:
1. GIA 0,4ct F VS2, HCA score 0,9
This diamond is white all the time, but not as sparkly and sometimes can be flat. When it's dirty the edges loose it's sparkle which I found very weird.
2. GIA 0,6ct F VVS2, HCA score 3,8
This diamond is very lively and the fire oh wow. But somehow can look bit yellowish on some lightning (home/office lightning mostly).
I rarely clean this one as it always sparkles. And I do wonder if the yellowish tint I see is because of the halo (melee was F, but looked very2 white)

Butttt,
3. I also have a heart cut GIA 0,9ct D VS2, set on WG solitaire
that are very very sparkly with crisp facet, but also easily looks yellowish. Which is impossible right? since it's a D!

I also read somewhere that well cut diamond is like a chameleon as they are reflecting colors around. Good cut stone will throw more colors than the bad one.
My question is:
- Is it possible for the second diamond outperforming the first one as it score very bad on HCA tools?
- Is well cut diamond change color more easily than the bad one?
- What is the best cert range if I want diamond that look white most of the time and still sparkles?

Btw I'm in Asia where we has no knowledge on ASET, so I'm relying on HCA tools and my untrained eyes =D

Thank you!!!

 

[MissGotRocks]

Hi Gurus!!

As I'm reading more on diamond cut, more question has come to my mind.
I do possess 2 diamond that in my eyes were:
1. GIA 0,4ct F VS2, HCA score 0,9
This diamond is white all the time, but not as sparkly and sometimes can be flat. When it's dirty the edges loose it's sparkle which I found very weird.
2. GIA 0,6ct F VVS2, HCA score 3,8
This diamond is very lively and the fire oh wow. But somehow can look bit yellowish on some lightning (home/office lightning mostly).
I rarely clean this one as it always sparkles. And I do wonder if the yellowish tint I see is because of the halo (melee was F, but looked very2 white)

Butttt,
3. I also have a heart cut GIA 0,9ct D VS2, set on WG solitaire
that are very very sparkly with crisp facet, but also easily looks yellowish. Which is impossible right? since it's a D!

I also read somewhere that well cut diamond is like a chameleon as they are reflecting colors around. Good cut stone will throw more colors than the bad one.
My question is:
- Is it possible for the second diamond outperforming the first one as it score very bad on HCA tools?
- Is well cut diamond change color more easily than the bad one?
- What is the best cert range if I want diamond that look white most of the time and still sparkles?

Btw I'm in Asia where we has no knowledge on ASET, so I'm relying on HCA tools and my untrained eyes =D

Thank you!!!

Can you post the GIA grading reports? Ideally, you would reject diamonds that scored over 2 on the HCA and look further at those that score 2 and under. HCA is more of a rejection tool rather than a selection tool.

 

[Newgirl87]

Can you post the GIA grading reports? Ideally, you would reject diamonds that scored over 2 on the HCA and look further at those that score 2 and under. HCA is more of a rejection tool rather than a selection tool.

Tbh I forgot where I put the GIA report =p

Yes I heard, that's why I'm asking if there's a possibility that low score HCA diamond still perform brilliantly.

 

[Ibrakeforpossums]

I like your question. I have an O-P diamond ~.70 that got a dismal HCA score but I think it sparkles beautifully.

 

[Bianca201]

Tbh I forgot where I put the GIA report =p

Yes I heard, that's why I'm asking if there's a possibility that low score HCA diamond still perform brilliantly.

How do you know what the HCA score is if you don't have the certs with the measurements?

And if you have the stones in your possession, isn't the question moot? I mean, you are literally looking at them, so you can answer this?

A diamond can score poorly on the HCA but be cut so precisely that it's everything you would look for in a stone. Those are hard to find, but they exist. There are specific measurements/ ratios (hence the request for the GIA report) that are known to be in this great performing but not a great HCA area.

But again, if - to you - the diamond that scores poorly on the HCA is super amazing.... I think that answers your question? Or what am I missing?

 

[Newgirl87]

How do you know what the HCA score is if you don't have the certs with the measurements?

And if you have the stones in your possession, isn't the question moot? I mean, you are literally looking at them, so you can answer this?

A diamond can score poorly on the HCA but be cut so precisely that it's everything you would look for in a stone. Those are hard to find, but they exist. There are specific measurements/ ratios (hence the request for the GIA report) that are known to be in this great performing but not a great HCA area.

But again, if - to you - the diamond that scores poorly on the HCA is super amazing.... I think that answers your question? Or what am I missing?

I have the first diamond for 10 years and test the HCA score back then. The second one is only months old but the cert is in the safe.

Please mind that I'm in Asia where diamond IS diamond, we don't talk about cut. So this is a question from someone with very untrained eyes, so most likely I cannot differentiate good cut vs ideal cut diamond? Just looking for more info on HCA score and what is ideal cut?
Is the behavior of reflecting light is relate with how good a diamond is cut? What about the yellowish I see on my F and D diamond that IMO is better cut ones?

 

[MissGotRocks]

I have the first diamond for 10 years and test the HCA score back then. The second one is only months old but the cert is in the safe.

Please mind that I'm in Asia where diamond IS diamond, we don't talk about cut. So this is a question from someone with very untrained eyes, so most likely I cannot differentiate good cut vs ideal cut diamond? Just looking for more info on HCA score and what is ideal cut?
Is the behavior of reflecting light is relate with how good a diamond is cut? What about the yellowish I see on my F and D diamond that IMO is better cut ones?

Color that you see in diamonds often depends on the environment it is reflecting. If you are indoors, with beige walls and yellow lighting, the diamonds reflect that color. The D and F appearing yellow should have nothing to do with their cut. They may not be bright and lively due to their cut, but the color should not be yellow. Take the diamonds outdoors - not in the direct sun - but in daylight. You should be able to get a better idea of their color.

Why did you buy the second diamond? I assume you liked what you saw in it? If so, why question it now? If you love the diamond, just enjoy it - particularly if it is too late for return.

 

[Karl_K]

Diamonds reflect what is around them and different combinations draw light from different locations.
That is why 2 diamonds same color, different proportions can return different colors from the environment to the eye when in the exact same location.

 

[Newgirl87]

@MissGotRocks yes I do love the second diamond. I'm just newbie at learning about cut and wondering if my eyes can be trusted since it's not aligning with the HCA theory. Or, is it better for me to stick to the cert and HCA score.

@Karl_K I was observing both diamond side by side in my bedroom, which has warm white light and white walls. IMO the better cut F VVS2 looks yellower (while sparkler) than the F VS2 diamond which look very white (but kinda flat). So is this relate to the cut? Is better the cut the more 'surrounding' colour it will show?

Here's a photo of a second diamond (F VVS2) on warm white light and white walls. The center looks yellower to me rather than the halo (IRL it's more buttery yellow rather than gray in the photo). While the first diamond (F VS2) looks more white like the halo.
Can you also determine a good cut vs bad cut from pic like this?



Thanks you so so much!

 

[Newgirl87]

Adding more photo


Under table:

 

[Karl_K]

Cant tell much from the pics.
What color is your camera?

 

[Newgirl87]

Cant tell much from the pics.
What color is your camera?

My phone case is white, ceiling also white.

Sorry i know it's very hard to give advice with so little detail.
But I'm dying to know if the yellow I see is relating to the cut or not.
I'm very overwhelm the first time I see the D heart IRL and it looked yellowish. So when my new diamond behaving the same, I'm wondering why. Is it normal behavior with a good cut diamond? Or is it because my eyes always pick the bad one?

 

[Karl_K]

what you can try is take a compact mirror
put it same place as the diamond and rotate it to see what light the diamond is seeing.
You could also do the same looking at the back of a shiny spoon.

 

[Newgirl87]

what you can try is take a compact mirror
put it same place as the diamond and rotate it to see what light the diamond is seeing.
You could also do the same looking at the back of a shiny spoon.

Will do!
So in your opinion there is no relation between the yellowish tint I see with the cut?

 

[Karl_K]

Will do!
So in your opinion there is no relation between the yellowish tint I see with the cut?

F color looking buttery yellow is environmental or something on the stone.
Ruled out bad cut in yellow gold prongs.

 

[GemView]

Will do!
So in your opinion there is no relation between the yellowish tint I see with the cut?

Do they have fluorescence? Usually that's blue but not always…

 

[kenny]

...
But I'm dying to know if the yellow I see is relating to the cut or not.

In your first post you stated the two diamonds in question are graded F color by GIA.
There is no way the source of the yellow is the diamond material itself.
It has to be something yellow in the room, your clothing, nail polish, eyeglass frames, wig, your Halloween mask (LOL) that the mirrors (aka diamond facets) are reflecting.
It has to be.
GIA F is GIA F!

BTW, I know a politician who always sees orange in diamonds.
That's nice, because Fancy Colored Diamonds of pure orange are very rare and very expensive.

 

[kenny]

... You could also do the same looking at the back of a shiny spoon.

Oh @Karl_K
You mean I could have gotten the same excitement from a spoon!
If I knew that before, I wouldn't have spent all that money on diamonds.

 

[Karl_K]

Oh @Karl_K
You mean I could have gotten the same excitement from a spoon!
If I knew that before, I wouldn't have spent all that money on diamonds.

lol that cracked me up.
No but if you see yellow light reflected from the spoon you know that's where your diamond is getting it from.
Why its important is someone could stand in front of a yellow wall, look at the diamond and see yellow and look up and say there is no yellow. Most people don't know/understand the concept that its drawing light from behind you.

 

[Garry H (Cut Nut)]

HCA does not know about the symmetry of the stone - it is a rejection tool. So your 0.9 shallow stone may be wonky.
Your deeper 3.8 stone will show more colour for this reason - there could be a yellower area donut shaped just inside the table.

 

[Garry H (Cut Nut)]

Oh @Karl_K
You mean I could have gotten the same excitement from a spoon!
If I knew that before, I wouldn't have spent all that money on diamonds.

The reflection on the back of a spoon is the easiest and cheapest way to identify the color temperature of the lights in a room.

 

[kenny]

HCA ... is a rejection tool. So your 0.9 shallow stone may be wonky.
Your deeper 3.8 stone will show more colour for this reason - there could be a yellower area donut shaped just inside the table.

But she's talking about a GIA F.
So where exactly could that yellow originate, if not a reflection of something outside the diamond?

Are you referring to the light bouncing back and forth more times before exiting out the top?
If so, could a GIA F really show noticeable yellow, especially in a round this small, 0.6 ct?

If the answer is yes, how many paths through the faintly-yellow-tinted diamond material be making? 3, 4, 5, 6, more?

 

[kenny]

The reflection on the back of a spoon is the easiest and cheapest way to identify the color temperature of the lights in a room.

True, but a decent camera, operated by a competent photographer, will white-balance out the color temperature of the light source.

Unfortunately good cameras and competent photographers today are a fast-dying breed.

 

[Garry H (Cut Nut)]

But she's talking about a GIA F.
So where exactly could that yellow originate, if not a reflection of something outside the diamond?

Are you referring to the light bouncing back and forth more times before exiting out the top?
If so, could a GIA F really show noticable yellow, in a small round like this 0.6 ct?

If the answer is yes, how many paths through the faintly-yellow-tinted diamond material be making? 3, 4, 5, 6, more?

Not simple to answer Kenny - I am not sure. the left is Tolkowsky 57% table. The right is a 41.2 pavilion. As the pavilion gets deeper - or the symmetry gets messed up the is more leakage out the pavilion and longer ray paths. But don't shoot me - trying to be a messenger - see the ray paths slightly rotated stones elow

 

[kenny]

If the diamond is graded E through Z by a legit lab it has some color, usually yellow.
And the longer the lights through the material the more color it pics up.
Cutters of FCD often choose radiant shape to keep the light bouncing around as long as possible to get the stronge$$$$$t color grade possible.

But is there enough yellow in a GIA F of only 0.60 ct?
I doubt it based on how yellow the pic looks, but as always accurate color is pics are as rare as chicken teeth.

 

[Garry H (Cut Nut)]

Another issue is the color of the dirt and grime on the pavilion.

 

[Newgirl87]

Thanks to all answer!! It's been interesting, although I'm still not sure if I can understand lol.

So my take is that it's possible for low HCA score diamond to outperform the higher ones since HCA tools is used for guidelines, not rule. Correct?
Is anybody can answer this one? -- Is well cut diamond will look more yellowish than the bad ones in warm room?

Another issue is the color of the dirt and grime on the pavilion.

No the diamond is completely clean.

 

[Garry H (Cut Nut)]

So my take is that it's possible for low HCA score diamond to outperform the higher ones since HCA tools is used for guidelines, not rule. Correct?
Is anybody can answer this one? -- Is well cut diamond will look more yellowish than the bad ones in warm room?



No the diamond is completely clean.

The HCA proportions and the 4 tables and other rules are complex the way they interact - and there is no easy answer to your question.
The direction a diamond returns light from is the issue here. A shallower diamond from higher angles (blue and red in ASET) and a deeper stone (red and green in ASET) from lower angles.
Symmetry variations can have various effects.
Since we know little about your stones we really can not help.
Here is the original HCA development pages and data used:
www.diamond-cut.com.au

 

[Newgirl87]

The HCA proportions and the 4 tables and other rules are complex the way they interact - and there is no easy answer to your question.
The direction a diamond returns light from is the issue here. A shallower diamond from higher angles (blue and red in ASET) and a deeper stone (red and green in ASET) from lower angles.
Symmetry variations can have various effects.
Since we know little about your stones we really can not help.
Here is the original HCA development pages and data used:
www.diamond-cut.com.au

Noted Garry, thank you so much for your time answering! It's always a pleasure reading your thoughts.

 

[Garry H (Cut Nut)]

Noted Garry, thank you so much for your time answering! It's always a pleasure reading your thoughts.

If only my wife thought the same about my thoughts