AGA grading

[Acclaim]

http://www.goodoldgold.com/1_00ct_d_vvs2_h&a.htm

Can someone explain why this stone from GoodOldGold only get a cut grading of 3B of AGA scale and great score on HCA.

Thanks,

 

[Richard Sherwood]

Hi Acclaim. That stone grades out to an AGA Ideal Make 1B.

 

[Garry H (Cut Nut)]

Yes - it is a fine stone and recognised by AGA and HCA as such.

Did you miss something?

 

[Acclaim]

Thanks Gary, Can you please comment on this stone.

GIA, 1.21, EX/EX, F, VVS2, Faint

Depth: 61.7
Table: 57.6
Crown Angle: 35.0
Pavillion Angle: 41.1
Girdle: 0.73-1.46 Thin to Medium

It score a 2.9 (Very Good) on HCA and I believe it's a 1B on the AGA scale.

Very Good
Very Good
Good
Very Good

It's kinda disappointing. The vendor claimed that this is one of the ideal-cut H&A diamond out-there. Apparently, it's doesn't have a very good HCA score. Can the expert common on this stone. It's a very good stone or just one of the average stone out-there. Am I expecting too much. That is, Exellence or at least very good for all of the above

 

[Garry H (Cut Nut)]

It is ideal as defined by AGS.

I would pass

 

[Acclaim]

Gary & Dave,

I took your advice and did not buy the last stone. I went and look at 2 new stone. They have HRD certificates. The nice thing about this certificate is that it has crown height %, gridle % and pav depth %. which I can use with HCA and AGA without asking them for a SARIN analysis.

Carat: 1.17
Color: F
Clarity: IF
Sym/Finish: VG/VG
6.67 X 6.78 X 4.12
Table: 61.0%
Crown: 14.5 %
Pav: 43.0
Gridle: 3.5 %
Cullet: Pointed
Proportion: Very Good

HCA: VG,G,G,VG Total: 4.1 Good
ACA: 2B

--------------------------------------

Carat: 1.10
Color: F
Clarity: IF
Sym/Finish: G/G
6.82 X 6.88 X 3.93
Table: 62 %
Crown: 11.5 %
Pav: 43.0
Gridle: 3 %
Cullet: Pointed
Proportion: Very Good

HCA: VG,VG,VG,EX Total: 2.5 Very Good
ACA: 3A

I calculated the crown angle = tan-1(crown%/((100-table%)/2)) for the AGA grading.

Now, the result is opposite for AGA and HCA. To my amature eye, the first stone (1.17) has better proportion. The 2nd stone has shallow crown. They both look brilliant to me.

Thanks in advance for your comments.

 

[Garry H (Cut Nut)]

I would always want non rounded angles, not the % data you have.

It is very hard to get a great look from a >60% table, possible but hard.

On the plus side they have a bigger spread.