HCA vs Stone Algo

[togal]

I'm searching for a lab diamond and using the HCA to weed out the 'worst' IGI certified 'Ideal' cut stones. I've just learned of the StoneAlgo free online cut calculator.

One stone that I looked at rated 2.3 (Very Good, Very Good, Very Good, Good) on the HCA, but received very high cut score of 9.2 on StoneAlgo. Another stone that I have actually purchased, and is available, but hasn't been shipped yet rates a 0.7 on the HCA (Excellent, Excellent, Excellent, Very Good) and 8.5 on StoneAlgo.

I'm confused. I understand that the HCA is a tool to weed out duds, but it seems that the score of the first stone (the one that rated 2.3 on the HCA) is somewhat at odds with the 9.2 rating on StoneAlgo.

I guess my question is, with a HCA score of 0.7 and a StoneAglo score of 8.5, will the stone I purchased be as beautiful as the one that rated 9.2 on StoneAlgo, but low(er) on the HCA. Hope this makes sense!

And one more question for anyone who knows: I reached out to StoneAlgo to ask a question, and they tell me that LooseGrownDiamon.com is NOT one of their recommended jewellers, so this worries me. Is LooseGrownDiamond.com trustworthy/reputable with members of the PriceScope community? This is where I purchased my stone, that hasn't been dispatched yet (but they assure me that's it's available and mine, as I've paid for it).

 

[lovedogs]

stonealgo isn't reliable with cut numbers--it's just random opinion. I would ignore it entirely.

The HCA tool isn't designed to choose stones. Rather, it's designed to "reject" or "potentially look into/accept" a stone.

Also, anything under 2 on HCA is "maybe good--look into more", and over 2 (especially over 2.5) is usually a "reject".

Loose grown diamonds is used all the time to buy lab diamonds.

 

[togal]

stonealgo isn't reliable with cut numbers--it's just random opinion. I would ignore it entirely.

The HCA tool isn't designed to choose stones. Rather, it's designed to "reject" or "potentially look into/accept" a stone.

Also, anything under 2 on HCA is "maybe good--look into more", and over 2 (especially over 2.5) is usually a "reject".

Loose grown diamonds is used all the time to buy lab diamonds.

Okay...I get that HCA is a tool designed to 'reject or potentially accept' a stone. Why then would the rating scale on HCA put 0.7 higher than a 2.3?... If the parameters of of the HCA are as you say, then why isn't that made more clear when using the HCA? When the score says 'EX, EX, EX'...it seems to me that those ARE the parameters of the HCA, and should be interpreted as such. The diamond I've chosen rates well on both the HCA and StoneAlgo, according to THEIR ratings. Why even bother with the HCA, if the results they show to 'weed out the bad' are subject to interpretation? Again, I understand that they are 'rejection tools'....but if anything under a 2 on the HCA is not as good as a rating between 2 to 2.5, as you suggest, than the scale itself is giving misinformation to the consumer. It's like turning the volume up to 11...

 

[togal]

...And while I'm questioning everything, I'm wondering if anyone can explain to me the disparity between prices of lab diamonds with similar IGI ratings? (eg: Ideal cut, VVS1, E color, ranking well on the HCA, etc)...A 1500 - 2000 difference in price between seemingly identical stones (on paper)... Does price equal a better cut stone? How are they justifying the price differential?

 

[lovedogs]

Prices for lab stones are all over the place. Sometimes it's completely random, other times its based on the quality of the material.

The HCA doesn't quite work the way you are assuming. It's literally "under 2, you should consider; over 2 probably don't". Although some folks will consider stones between 2 and 2.5. Lower score doesn't = better.

 

[lovedogs]

In theory, stones with a score under 2 (any score under 2) is "better" (e.g. the angles are more complimentary) than stones with scores over 2. That's the entire idea of the HCA.

 

[Vladovici]

easiest way put - if the scores are bad then the cut of the stone is bad.
If the scores are good - not necessarily means that the cut is good but it can further be evaluated with pictures/videos.

You can just filter bad cut stones using that scores.

Not sure what the threshold of StoneAlgo is. I'll do some testing in the evening if I find the time today to see what most HCA <2 score get on StoneAlgo, what 2 to 2.5 HCA get on stone algo and what 2.5 + HCA get there.

 

[Garry H (Cut Nut)]

I'm searching for a lab diamond and using the HCA to weed out the 'worst' IGI certified 'Ideal' cut stones. I've just learned of the StoneAlgo free online cut calculator.

One stone that I looked at rated 2.3 (Very Good, Very Good, Very Good, Good) on the HCA, but received very high cut score of 9.2 on StoneAlgo. Another stone that I have actually purchased, and is available, but hasn't been shipped yet rates a 0.7 on the HCA (Excellent, Excellent, Excellent, Very Good) and 8.5 on StoneAlgo.

I'm confused. I understand that the HCA is a tool to weed out duds, but it seems that the score of the first stone (the one that rated 2.3 on the HCA) is somewhat at odds with the 9.2 rating on StoneAlgo.

I guess my question is, with a HCA score of 0.7 and a StoneAglo score of 8.5, will the stone I purchased be as beautiful as the one that rated 9.2 on StoneAlgo, but low(er) on the HCA. Hope this makes sense!

And one more question for anyone who knows: I reached out to StoneAlgo to ask a question, and they tell me that LooseGrownDiamon.com is NOT one of their recommended jewellers, so this worries me. Is LooseGrownDiamond.com trustworthy/reputable with members of the PriceScope community? This is where I purchased my stone, that hasn't been dispatched yet (but they assure me that's it's available and mine, as I've paid for it).

Hi Togal,
Perhaps we could do some research and provide some answers if you posted the two stones proportions?
PS IGI are soon to announce their new round cut grading system that like HCA is based on Ideal-Scope assessment.

 

[Karl_K]

Hi Togal,
Perhaps we could do some research and provide some answers if you posted the two stones proportions?
PS IGI are soon to announce their new round cut grading system that like HCA is based on Ideal-Scope assessment.

Hi Garry,
It has been launched.

Fyi: IGI Scores Diamonds for Light Performance

https://www.idexonline.com/FullArticle?Id=49479

www.pricescope.com

In the process of creating the IGI system we also verified the HCA number scores.
We take into account the minor facets so on the edges of the ranges depending on the minors we diverted from the HCA but overall its good for a rejection filter.

 

[Garry H (Cut Nut)]

And one more question for anyone who knows: I reached out to StoneAlgo to ask a question, and they tell me that LooseGrownDiamon.com is NOT one of their recommended jewellers, so this worries me. Is LooseGrownDiamond.com trustworthy/reputable with members of the PriceScope community? This is where I purchased my stone, that hasn't been dispatched yet (but they assure me that's it's available and mine, as I've paid for it).

I have no opinion (and no right to comment) about that company.
However the reason StoneAglo does not recommend the firm is they do not receive any affiliate fees from them.

 

[togal]

Hi Togal,
Perhaps we could do some research and provide some answers if you posted the two stones proportions?
PS IGI are soon to announce their new round cut grading system that like HCA is based on Ideal-Scope assessment.

Hi Gary,

That would be great!

The stone I purchased is as follows (.07 on HCA and 8.5 on StoneAlgo):

2.29 carat
Size: 8.46 - 8.52 x 5.19
Depth: 61.2
Table: 56
Crown: 33.3
Pavilion: 40.5

Other stone (2.3 on HCA and 9.1 on StoneAlgo):

2.29 carat
Size: 8.43 - 8.46 x 5.21
Depth: 61.7
Table: 58
Crown: 35.1
Pavilion: 40.9

Both stones were created by HPHT method.

Loosegrowndiamond.com do not provide ideal scope images, so I'm relying on these tools to help ensure I get a good stone. I believe the one I've chosen is a good one...hopefully...

I'm interested in your analysis, Gary. Thanks!

 

[togal]

easiest way put - if the scores are bad then the cut of the stone is bad.
If the scores are good - not necessarily means that the cut is good but it can further be evaluated with pictures/videos.

You can just filter bad cut stones using that scores.

Not sure what the threshold of StoneAlgo is. I'll do some testing in the evening if I find the time today to see what most HCA <2 score get on StoneAlgo, what 2 to 2.5 HCA get on stone algo and what 2.5 + HCA get there.

That would be very helpful. Thank you!

 

[Garry H (Cut Nut)]

Hi Gary,

Thank would be great!

The stone I purchased is as follows (.07 on HCA and 8.5 on StoneAlgo):

2.29 carat
Size: 8.46 - 8.52 x 5.19
Depth: 61.2
Table: 56
Crown: 33.3
Pavilion: 40.5

Other stone (2.3 on HCA and 9.1 on StoneAlgo):

2.29 carat
Size: 8.43 - 8.46 x 5.21
Depth: 61.7
Table: 58
Crown: 35.1
Pavilion: 40.9

Both stones were created by HPHT method.

Loosegrowndiamond.com do not provide ideal scope images, so I'm relying on these tools to help ensure I get a good stone. I believe the one I've chosen is a good one...hopefully...

I'm interested in your analysis, Gary. Thanks!

Your shallower stone has a larger spread - and will sparkle nearly twice as well when it is dirty than that other stone which will have slight leakage just inside the table.
See the new IGI Light Performance posts popping up - I just posted it on Rocky Talky also.

 

[togal]

Your shallower stone has a larger spread - and will sparkle nearly twice as well when it is dirty than that other stone which will have slight leakage just inside the table.
See the new IGI Light Performance posts popping up - I just posted it on Rocky Talky also.

So I picked a good one!...thus the .07 score on your cut advisor. Thanks...I'll check out the post re IGI light performance.

 

[togal]

Your shallower stone has a larger spread - and will sparkle nearly twice as well when it is dirty than that other stone which will have slight leakage just inside the table.
See the new IGI Light Performance posts popping up - I just posted it on Rocky Talky also.

Am looking forward to the May 15 seminar!

 

[Garry H (Cut Nut)]

Am looking forward to the May 15 seminar!

You may need a linked in account?

Seeing the Light: All You Need to Know About Light Performance in Diamonds | LinkedIn

Join us for our next exciting GEMTalks session on May 15 at 10 a.m. EDT as GEMTalks goes LIVE on LinkedIn. In this exclusive event, Leah Meirovich from Rapaport and Senior Director of Education at IGI, John Pollard and Garry Holloway from Ideal-Scope will explore the differences and uncover the...

www.linkedin.com

 

[togal]

You may need a linked in account?

Seeing the Light: All You Need to Know About Light Performance in Diamonds | LinkedIn

Join us for our next exciting GEMTalks session on May 15 at 10 a.m. EDT as GEMTalks goes LIVE on LinkedIn. In this exclusive event, Leah Meirovich from Rapaport and Senior Director of Education at IGI, John Pollard and Garry Holloway from Ideal-Scope will explore the differences and uncover the...

www.linkedin.com

Thanks. I have a linkedin account and tuned in during the live seminar.. It was very informative, and glad it was recorded, as I rewatched it

 

[Garry H (Cut Nut)]

Thanks. I have a linkedin account and tuned in during the live seminar.. It was very informative, and glad it was recorded, as I rewatched it

Hope it met or exceeded expectations.
Any takeaways ( for my future and Johns to inform).
Much of what I contributed is in my book out in 2 months

 

[togal]

I'll check your website in a few months time for your book, and look forward to reading it. I feel that what you and John presented was very informative and well presented. I had pen and paper in hand whilst watching, and kept some key take-aways. There's so much to learn, especially for people navigating the waters through online purchase...and lab diamonds in particular. I've learned that it's not 'white-glove' service when dealing with online vendors who sell lab diamonds (at competitive prices)...so the consumer is that the mercy of the knowledge that they acquire through people like yourself. I'm still learning. I've spent a good deal of time using the HCA and comparing it against StoneAlgo and trying to answer a lot of my own questions..so every bit of information is extremely helpful. I'm so glad you've written a book. It's easy to find bits of information all over the internet, and try to piece it all together, but a concise, detailed book of reference for consumers is fantastic. I really look forward to learning more from your book. I assume it will be available on your website (and maybe Amazon?).

 

[Garry H (Cut Nut)]

I'm still learning. I've spent a good deal of time using the HCA and comparing it against StoneAlgo and trying to answer a lot of my own questions..so every bit of information is extremely helpf I really look forward to learning more from your book. I assume it will be available on your website (and maybe Amazon?).

The book will be available on Amazon and I expect to have a discount offer for the first week for the digital kindle.
It will be announced here and on my various websites Togal