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Cut Question

JMB5383

Rough_Rock
Joined
May 29, 2011
Messages
5
Hello everyone. I have been researching here for a long time but have never before posted.

I have a specific opportunity through a family friend jeweler who just bought a stone back from a private buyer and is willing to sell it to me for not much more than what it cost him to buy it back. The stone is round and the size, color and clarity are all great by my standards. The issue is the cut. The stone's cut rating is only very good, but according to him it has GIA excellent proportions (table, angles, depth). I am told the reason it is rated very good is because symmetry is only "good" and the cut grade can only be, at most, one grade above the lowest grade of symmetry and polish. Supposedly if the symmetry were very good, it would have been graded excellent cut. The problem with the symmetry is that the variation in the stone's diameter is .13 mm. Incidentally, I checked on blue nile and did find stones of the exact same proportions with better symmetry that were graded excellent cut (table is 57%, depth is 62.3%, crown angle is 35 degrees and pavilion angle is 41.2 degrees).

Also, it's not a hearts and arrows stone but I can plainly see arrows when I look at it.

Does this explanation about the cut rating sound right, and does this kind of issue with the symmetry affect the sparkle and light reflection in a diamond like this?

Thanks.
 

Stone-cold11

Super_Ideal_Rock
Joined
Sep 9, 2008
Messages
14,069
Proportions are based on the average of 8 or more measurements for a round brilliant, so variation in symm can result a larger variation in angles.

Based on the numbers, the proportions are iffy at best, probably have slight leakage even with very good symm.

I would buy an idealscope and take a look at the stone with it. Relatively cheap and easy to use.
 

Dancing Fire

Super_Ideal_Rock
Premium
Joined
Apr 3, 2004
Messages
32,405
did you compare his asking price vs online prices?
 

dreamer_dachsie

Super_Ideal_Rock
Joined
Dec 16, 2007
Messages
24,364
Can you post the GIA report number so we have more information? And what is the price he is asking?
 

JMB5383

Rough_Rock
Joined
May 29, 2011
Messages
5
I don't have the GIA report at the moment. When I was there I wrote down this info from the report and our discussion. I could get it, I am sure. As far as asking price, I compared only to Blue Nile and he woudl give it to me for $5,000 less for what comparable stones are going for on there.
 

dreamer_dachsie

Super_Ideal_Rock
Joined
Dec 16, 2007
Messages
24,364
JMB5383|1306720238|2933425 said:
I don't have the GIA report at the moment. When I was there I wrote down this info from the report and our discussion. I could get it, I am sure. As far as asking price, I compared only to Blue Nile and he woudl give it to me for $5,000 less for what comparable stones are going for on there.
We can't help you if you are going to be coy about price my friend ;)) . This is a diamond website, we talk prices and we talk value here. Tell us all the stats you have and the price and we can help you out. $5000 less is nothing if the stone costs $60k. It is a lot if the stone costs $10k. Also, there are comparables, and there are comparables. Clarity carat and color are not the only considerations to find a comparable. Anyways, spill the beans and we can help you better 8) .

This all matters because when you assess the diamond you need to take into account whether you can get better elsewhere for less or the same. It *might* be worth risking the slight imperfections in cut that Stone Cold pointed out *if* the price is really a good deal, you have seen the stone in person and have compared it to more ideally proportioned stones in lots of different lighting and like what you see. With more information, we can help you to judge if the price is really a good deal or not, and with more information from the cert we can have a better idea of the cut -- there are some factors that can perhaps ameliorate the potential issues Stone mentioned.
 

dreamer_dachsie

Super_Ideal_Rock
Joined
Dec 16, 2007
Messages
24,364
JMB5383|1306717936|2933400 said:
I have a specific opportunity through a family friend jeweler who just bought a stone back from a private buyer and is willing to sell it to me for not much more than what it cost him to buy it back.
And not to be alarmist, but we see a lot of stories start out with a sentence like this on PS. Most are not the great deal they seem, and many end unhappily for the consumer. You may be the exception, but don't let the personal relationship influence you dealings with the vendor. You need to cover your bases no matter what -- For example. do not pay cash in exchange for no taxes and no receipt; get his refund and return policies in writing; and make sure there is at least a 7 day no questions asked 100% refund policy in place.

Also be aware that the latter part of the sentence I quoted is likely a sales tactic.
 

JMB5383

Rough_Rock
Joined
May 29, 2011
Messages
5
Not really trying to be coy, just didn't have the GIA at that time. Report no is 2125535232. Asking price is $16,500.
 

Todd Gray

Brilliant_Rock
Trade
Joined
Jan 20, 2009
Messages
1,297
Steep / Steep (35.0 / 41.2) wouldn't be my first choice when it comes to the offset for crown and pavilion angle; it would be better if the crown angle were within a range of 34.3 - 34.8 degrees offset by a pavilion angle of somewhere between 40.6 - 40.9 degrees; however if you're going to have a steep pavilion angle, then it would be better offset by something shallow.

It's interesting to me that the GIA didn't drop the overall cut grade of the diamond to the lowest denominator, if the lowest factor of the cut grade is "good" then the diamond would have obtained a grade no higher than "good" on the grading system employed by the AGS Laboratory... So GIA is averaging their cut grade on the new system? I didn't know that...
 

denverappraiser

Ideal_Rock
Trade
Joined
Jul 21, 2004
Messages
8,827
Todd Gray|1306862220|2934553 said:
Steep / Steep (35.0 / 41.2) wouldn't be my first choice when it comes to the offset for crown and pavilion angle; it would be better if the crown angle were within a range of 34.3 - 34.8 degrees offset by a pavilion angle of somewhere between 40.6 - 40.9 degrees; however if you're going to have a steep pavilion angle, then it would be better offset by something shallow.

It's interesting to me that the GIA didn't drop the overall cut grade of the diamond to the lowest denominator, if the lowest factor of the cut grade is "good" then the diamond would have obtained a grade no higher than "good" on the grading system employed by the AGS Laboratory... So GIA is averaging their cut grade on the new system? I didn't know that...
GIA gives a mulligan for symmetry and polish, AGS does not. GIA reports list the crown and pavilion angles as an average of the 8 individual values. They don't report the individual measurements (Neither does AGS). If there's an unacceptable variation between the individual measurements they'll ding the symmetry, but the reported angles will still show as the average.
 

JMB5383

Rough_Rock
Joined
May 29, 2011
Messages
5
FYI, I ran it thru the GIA Facetware program and it came out as "Very Good" when I put it's numbers in. When I changed symmetry to be "very good" the cut changed to excellent, so it seems there is at least some credence to what the jeweler has said about why this stone was graded VG. I guess the issues are whether the stone is a) worth it given price and b) how much is the symmetry really going to affect the brilliance.
 

yssie

Super_Ideal_Rock
Premium
Joined
Aug 14, 2009
Messages
21,118
http://www2.gia.edu/reportcheck/act_printPDF.cfm?r=M%298%2F%24R%24_%24%22%2F[%3CZT%3D%25W%2FL%241K%27ZCO.%27%24XV%3DVL6-2%2C%3B\S0S%223.%26O2-%29%3F%40AE%3E%20%3C%3C*%0A%26!M\%3B3%27Z%3B%0A


lower "physical" (facet meet) symmetry, which is what the labs are grading, will certainly affect light return - physical symmetry is a basis for existence of optical symmetry (can't have excellent radial optical symmetry pattern in an oval stone, say) though the two need not perfectly correlate - we can't start to dissect how without more info/scan/pics. Generally speaking a stone with higher optical symmetry will have larger avg facet size - more difference btwn large and tiny facets, stone of the same size w/ less optical symmetry will have smaller avg facet size from lots of tiny facets and lots of medium facets and less in the way of large facets. Larger facets permit more visible dispersion and bigger, bolder flashes of light.

Neither AGS nor GIA considers optical symmetry patterning in cut quality/light performance determinations
 

dreamer_dachsie

Super_Ideal_Rock
Joined
Dec 16, 2007
Messages
24,364
Price is decent for the specs, about on par with what you might spend online, maybe a little bit less, though it is hard to find an exact comparable.
 
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