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»  » Diamond Prices and Grading »
 » RockyTalky
»  » AGA vs. HCA
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AGA vs. HCA |
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| P: 9/7/2004 9:15:15 PM | |
aj55 Rough Rock Total Posts: 70 Last Post: 12/2/2004 Member Since: 7/25/2004 |
HEY GUYS, i'm in the final stages before i make my purchase. i have run a couple of stones thru the HCA and AGA. the specs are below. Out of experience which tool should i trust? 1) CANADIAN AGS TRIPLE IDEAL CUT 0.604 VS2 F $2790 USD $4150 CDN 5.43-5.47*3.33 DEPTH: 61.1% TABLE: 57.0% CROWN: 35 DEGREES PAVILLION: 40.7 DEGREES GIRDLE: 0.9-2.2 HCA: 1.2 LIGHT RETURN: EXCELLENT FIRE: EXCELLENT SCINTILLATION: EXCELLENT SPREAD: VERY GOOD AGA: 1B 2) CANADIAN AGS TRIPLE IDEAL CUT 0.607 VS1 F $2825 USD $4225 CDN 5.45-5.49*3.33 DEPTH: 60.9% TABLE: 57.0% CROWN: 34.4 DEGREES PAVILLION: 40.9 DEGREES GIRDLE: 0.9-1.6 HCA: 1.9 LIGHT RETURN: EXCELLENT FIRE: VERY GOOD SCINTILLATION: VERY GOOD SPREAD: VERY GOOD AGA: 1A |
| Posted: 9/7/2004 9:15:15 PM | |
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There are 22 replies to this message. There are 22 replies on this page. |
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| P: 9/7/2004 10:19:50 PM | |
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aj55 Rough Rock Total Posts: 70 Last Post: 12/2/2004 Member Since: 7/25/2004 |
need some advice from the experienced ones on this forum please
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| Posted: 9/7/2004 10:19:50 PM | |
| P: 9/8/2004 12:33:36 AM | |
Rank Amateur Ideal Rock Total Posts: 1,547 Last Post: 5/5/2009 Member Since: 2/26/2003 |
The two men who created these tools both post here regularly. I think they will both say that their tools help weed out the stones which are likely to be less-than-stellar but when comparing two stones as fine and as close as these two the tool can't be the final judge. Odds are both are very pretty. In my very limited experience, the AGA grading gets more play in the industry, but the HCA is coming up fast on the outside. The AGA is more empirical while the HCA attempts to apply more optical science.
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| Posted: 9/8/2004 12:33:36 AM | |
| P: 9/8/2004 2:44:00 AM | |
Garry H (Cut Nut) Ideal Rock Total Posts: 11,567 Last Post: 11/21/2009 Member Since: 8/16/2000 |
What is canadian AGS?????
Garry Holloway FGAA DipDT |
| Posted: 9/8/2004 2:44:00 AM | |
| P: 9/8/2004 10:54:59 AM | |
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aj55 Rough Rock Total Posts: 70 Last Post: 12/2/2004 Member Since: 7/25/2004 |
it is a canadian diamond. cut and polished in canada.
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| Posted: 9/8/2004 10:54:59 AM | |
| P: 9/8/2004 11:10:31 AM | |
Wacky Rough Rock Total Posts: 37 Last Post: 9/11/2004 Member Since: 9/19/2003 |
Don't trust any gimmicky marketing tool! Put your trust in a person to look at and compare the diamonds.
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| Posted: 9/8/2004 11:10:31 AM | |
| P: 9/8/2004 11:37:07 AM | |
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aj55 Rough Rock Total Posts: 70 Last Post: 12/2/2004 Member Since: 7/25/2004 |
ive looked at both CDN and non CDN stones. they look the same but i just want one that i know is from canada. Comes with a govt cert. i know ill be paying a little bit more for it...
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| Posted: 9/8/2004 11:37:07 AM | |
| P: 9/8/2004 1:54:38 PM | |
oldminer Ideal Rock Total Posts: 4,964 Last Post: 11/20/2009 Member Since: 9/4/2000 |
Neither the HCA or the AGA charts are gimmicky or marketing tools. If they were, then they would have been only successful in very minor ways. These are tools that Garry and I designed independently to assist consumers to better be able to judge diamond quality. Garry and I don't sell diamonds on Pricescope although he has a retail store group in Australia and I buy and sell old cut diamonds, to the trade, only in the USA.
The HCA and the AGA charts don't always agree perfectly. This is fine and not a problem. Both tools point out pretty clearly what the best cut diamonds are and pretty clearly denote poor quality stones. Garry Holloway looked at the matter of light performance and created his system to predict the quality of light performance based on parameters measured. With AGA, I looked at parameters and grouped those that are found in well crafted diamonds in meaningful clusters so that they could be readily defined. The AGA charts lower the grades on diamonds that are too thin, too thick, too small, too spready and for a number of other faults in ways similar to the AGS system, but with what I believe to be a little more accurate approach although not quite as commercial as the AGS system. AGA is not quite as liberal at the top end as AGS chose to be. It makes only a small difference, but it is a material one, I think.
Diamonds that score high in HCA and AGA are absolutely going to be super stones. Ones that score high in one and pretty high in the other will also probably be very nice. Any that score low in either or both must have issues of appearance or durability.
I believe both systems compliment eachother and are rarely in conflict. Nothing is as good as just looking at a diamond and loving it, but we are attempting to give consumers good advice on diamonds we have never seen.
David S. Atlas |
| Posted: 9/8/2004 1:54:38 PM | |
| P: 9/8/2004 3:01:02 PM | |
CaptAubrey Ideal Rock Total Posts: 862 Last Post: 3/23/2009 Member Since: 3/28/2004 |
----------------the question is, trust who? there's something to be said for an objective approach. a "person" you enlist to pick your diamonds is going to impose their personal preferences for diamond appearance. there's no more guarantee that this person will pick the stone you would like best than there would be with other guidelines.
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| Posted: 9/8/2004 3:01:02 PM | |
| P: 9/8/2004 3:40:28 PM | |
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oldminer Ideal Rock Total Posts: 4,964 Last Post: 11/20/2009 Member Since: 9/4/2000 |
An expert can be of substantial assistance in eliminating diamonds that have problems. An expert can also help make smart choices about choosing one diamond out of several possible stones based on a myriad of things that need a degree of expertise which can include price and cut quality.
What you really don't want is anyone telling YOU what is beautiful. This is very much a personal thing, but while advice is helpful, it remains a personal decision.
David S. Atlas |
| Posted: 9/8/2004 3:40:28 PM | |
| P: 9/8/2004 7:03:46 PM | |
quaeritur Ideal Rock Total Posts: 1,238 Last Post: 2/3/2005 Member Since: 3/12/2004 |
---------------- |
| Posted: 9/8/2004 7:03:46 PM | |
| P: 9/9/2004 12:47:40 AM | |
Sasori Cut Rock Total Posts: 100 Last Post: 10/24/2007 Member Since: 7/21/2004 |
Totally agree! these tools are definitely not gimmicky. These tool have actually helped me weed out poor performing AGS triple '0' and got me a great stone. The difference in scores is due to the different approach by the 2 grading methodology. AGA as David mention is by parameters. HCA is by light performance.(very scientific I would say) These 2 tools should be use to compliment each other rather then compared against. Try this experiment: Take the % of the pavilion and crown for the HCA instead of angles. You will notice the performance under HCA will change. But does this means the light performance of the stone has changed? My 2 cents worth, dont get too obsessed on the scores. Both are good I would say. 
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| Posted: 9/9/2004 12:47:40 AM | |
| P: 9/9/2004 7:36:45 AM | |
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oldminer Ideal Rock Total Posts: 4,964 Last Post: 11/20/2009 Member Since: 9/4/2000 |
The HCA takes PARAMETERS and cooks them into a result based on science. The AGA Cut Class takes PARAMETERS and cooks them into a result based on experience with diamonds. HCA is based on the accuracy of the measurements, which often can be a little inaccurate and based on scientific study. The Sarin and Ogi are not perfect, so the output of the HCA isn't going to be prefect..... AGA uses parameters, based on experience with physical diamonds, to give people the quality of craftmanship, not a prediction of brilliancy. It just happens that when diamonds are cut correctly, well crafted, they do exhibit super performance. Why else would they be of interest? It is this fortunate accident of nature that gives beauty and durability within certain constraints of cutting. Since the measurements provided by the Sarin and Ogi are not perfect, the AGA result is not totally perfect.... Both tools seem to approach getting the job done pretty well although they may appear to take different approaches. Garry's system will also predict excellent light return that could be present in otherwise not well cut diamonds. I don't think that matters a whole lot, but if you want a strangely cut diamond that happens to be brilliant, then that's okay with me. I would just give it a lower AGA grade. I feel it is a matter of popularity, stone shape, performance and durability all coming together to make the very finest stones, so light perfomance ALONE does not make an "IDEAL" cut stone. In truth, both systems together works the best. Great craftmanship and a high prediction of light return.. Sounds like a winner. In the next few months we will begin to offer a higher degree of accuracy in measurements not found in the Sarin or the Ogi. Light behavior will be measured, by scientific means, combined with the AGA parameters in a very advanced mode and will encompass a new grading of symmetry, as well. I don't offer this quite yet, but it will be something of great interest. Of course, Pricescope participants will be among the very first to know more. David S. Atlas |
| Posted: 9/9/2004 7:36:45 AM | |
| P: 9/9/2004 10:49:08 AM | |
fire&ice Ideal Rock Total Posts: 7,827 Last Post: 3/30/2009 Member Since: 7/22/2002 |
Back from the rock you crawled under, Wacky, and with your infinite wisdom.  You'd think you could get some better material. And, actually help consumers instead of running around like chicken little all the time.
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| Posted: 9/9/2004 10:49:08 AM | |
| P: 9/9/2004 11:05:22 AM | |
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Wacky Rough Rock Total Posts: 37 Last Post: 9/11/2004 Member Since: 9/19/2003 |
That's what I do sweetie! Help people!!! Did I miss something has the ideal scope been scientifically proven to be a measure of a diamonds light leakage?? My point is miss mouth.... Work with someone like Jonathon at Good Old Gold, and forget all the Whacks trying to sell you tools to play armature gemologist. Wacky
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| Posted: 9/9/2004 11:05:22 AM | |
| P: 9/9/2004 11:27:26 AM | |
Regular Guy Ideal Rock Total Posts: 5,315 Last Post: 11/20/2009 Member Since: 7/7/2004 |
Dear David, Care to share any thoughts on the specific typology of BIC, TIC, FIC? Would you characterize 2/3 of them as strangely cut? I'm genuinely curious! With warm regards, and with some regrets I hadn't succeeded in staying away, for very long, Ira (Ruffles have Ridges) Z. |
| Posted: 9/9/2004 11:27:26 AM | |
| P: 9/9/2004 12:04:14 PM | |
valeria101 Ideal Rock Total Posts: 14,048 Last Post: 4/30/2006 Member Since: 8/29/2003 |
---------------- This is one nice statement! For once, GOG website if rife with 'scope pictures. And there is at least one piece of elegant critique about the AGA system along the differences that "Old Miner" pointed out. There is allot of knowledge summarized in the AGA tables and the Ideal Scope project. But does any of these urge buyers to give up common sense? Maybe these would need sort of a disclaimer like the pills sold over the counter have "ask your doctor's counsel before use" (or so, at lest EU labels read like this). Small letters... Still an amateur with an Iscope is better than one without. One needs to do some reading before using that toy, and that's good Aspirin still works a bit on a headache even with no doc on toe.Do you think this analogy works at all ?  Ana "The greatest experts are only as good as the sum total of what they have seen." [Souren Melikian] |
| Posted: 9/9/2004 12:04:14 PM | |
| P: 9/9/2004 1:02:52 PM | |
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CaptAubrey Ideal Rock Total Posts: 862 Last Post: 3/23/2009 Member Since: 3/28/2004 |
---------------- you may have missed something: http://www.austgem.gil.com.au/ab21-10.html (scroll to the bottom) i offer no opinions on the value of this study, but the AG is a well-respected gemological journal.
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| Posted: 9/9/2004 1:02:52 PM | |
| P: 9/9/2004 1:42:22 PM | |
.JPG)
christarose Rough Rock Total Posts: 35 Last Post: 1/25/2005 Member Since: 3/20/2004 |
---------------- I find most people in this forum to be very helpful, humble and insightful...but I have to admit, this "armature" (immature?) remark made me laugh...did you mean to say "armchair" gemologist?
christarose |
| Posted: 9/9/2004 1:42:22 PM | |
| P: 9/9/2004 1:49:46 PM | |
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valeria101 Ideal Rock Total Posts: 14,048 Last Post: 4/30/2006 Member Since: 8/29/2003 |
---------------- So do I. Is this wrong? I think books are good money-makers too and one can make money from teaching and selling information, in general. Still, even the phone book is not totally unbiased. To me, the Iscope is more like that CD that comes pegged in the back of a book (happens in econ, math and finance, I don't know of others) - it gives you something to play with and an incentive to read the long boring book.   I hope I understand how 'scopes work as branding tools. Here's my take below:Among the 'scopes, Isee2 is the typical branding tool for me: all diamonds could be run through the process, but the associated software only "reads" the type of diamonds (rounds and a branded square, as far as I know) that the maker decided should be called "Isee2 diamonds". Good for them... The Brilliance Scope is somewhat less restrictive - at least one can analyze a range of shapes with it and there is no single associated diamond brand. But only sellers can use this tool and only some do, so if a buyer does what to believe in the Bscope truth it's choices are limited to whatever limited supply of diamonds ever pass through the Bscope at seller's choice. Not a brand per se... but about the same idea of calling names on a limited supply of something. To what degree these two are "black boxes" ( = giving no info on their technology and precision ) I am not so sure. As far as I know Jonathan put some effort into finding an answer That Iscope can be put over any diamond by any seller or buyer and as yet there are no "Ideal Scope" branded diamonds out there. There is no restriction of diamond stock that can be passed under the scope at the buyer's wish. So... it's less of a branding tool. There is a worse part, but mostly about common sense than the Ideal Scope, I think: If you go back a bit on Pricescope posts with comments of Iscope images, it is rather easy to see that using this darn tool does induce some bias: for once, it makes believe that the most brilliant diamonds are the only worthy to look at - so any cut that gives top light return receives higher approval. And then... it is easy to exaggerate seeing flaws where there is none. It is still up to the buyer to do the reality check: what difference does this or that detail make (you will find lots of questions like this). It does not seem fair to demand perfection from any such grading tool. As it is not fair to ask from someone to give up any opportunity to learn something about diamonds aside the address of a jeweler. Nothing personal, hopefully. Ana "The greatest experts are only as good as the sum total of what they have seen." [Souren Melikian] |
| Posted: 9/9/2004 1:49:46 PM | |
| P: 9/9/2004 2:02:09 PM | |
Hest88 Ideal Rock Total Posts: 3,670 Last Post: 11/20/2009 Member Since: 1/22/2003 |
Personally, I wouldn't trust *just* those tools, but if both say the same thing for a RB I think you can be fairly secure. Both of those choices look pretty decent to me. Perhaps it comes down to which vendor you prefer to give your money to?
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| Posted: 9/9/2004 2:02:09 PM | |
| P: 9/9/2004 5:52:24 PM | |
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Rank Amateur Ideal Rock Total Posts: 1,547 Last Post: 5/5/2009 Member Since: 2/26/2003 |
If you are cynical enough to think Garry is in it for the 50 cents (Austrailian, approx 2 cents US) he rakes in from the IS, you must then REALLY give the hairy eyeball to ANY diamond vendor. After all, the vendor might make THOUSANDS off of you, and every dollar of discount he doesn't give is another dollar in his pocket! But who among us could be that cynical? 
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| Posted: 9/9/2004 5:52:24 PM | |
| P: 9/9/2004 11:06:30 PM | |
andrewk Rough Rock Total Posts: 18 Last Post: 9/16/2004 Member Since: 8/10/2004 |
AJ, I'm very much a diamond newbie, but both of your stones sound like winners to me. Bottom line: Make your choice using the best set of equipment ever created, your eyes. HCA and AGA are excellent tools and I am thankful I found PS so that I could have learned about them. They will certainly help you weed out likely duds and the scores you list certainly sound like both are very nice stones. But you can play around a lot with those tools too! Try this: adjust your diamond parameters by 0.1 units at a time (either degree or %) and watch the HCA give you different results. I'm not saying you'll change a 1.9 to a 5, but I recently bought a HCA 2.4 (vg/vg/vg/vg) diamond that I thought to be very beautiful and by changing parameters by only 0.1 units, the HCA varied from 1.6 to 3.2 Why did I bother doing this? Well, very few diamonds (if any) possess the exact set of measurements in all the parameters that are listed on their grading report because no two pieces of equipment will measure the same thing with the exact same precision. Furthermore, very few diamonds (if any) have absolutely perfect axes of symmetry. Just look at the most basic measurement for a round brilliant: Length x Width x Depth. Why do you need both L and W if it is supposedly round? Why not just give a diameter? Answer...because round diamonds are not round! There will be slight variations in lengths and angles along each facet so the values you get from a grading report likely represent the midpoint of a range. I'm not saying this to discount the HCA because when I ran the numbers of stones that my eyes told me did not look quite as nice, they indeed got lower HCA scores. All I'm saying is, HCA and AGA are great tools and I am far better off for having used them because they readily confirmed what my eyes could see. But once HCA and AGA have suggested to you that you have a well cut and sparkly/shiny stone, the rest is up to your peepers. Sorry bout the long winded post. Cheers, andrewk
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| Posted: 9/9/2004 11:06:30 PM | |
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