need help in choosing diamonds

[spellinbee]

i went shopping today and found one stone which "seems" good value but since i do not know anything about diamonds..i would appreciate if anyone can spare 2 cents to help me.

Details are from GIA report

Round Brilliant
6.46-6.53X3.89mm
1 carat
depth: 59.9%
table: 58%
Girdle: very thin to thick, faceted
cutlet: None
Polish ; VG
Symmerty: VG
Clarity grade: SI1
Color Grade: F
Flourescence: None
cost: USD 4360

I look at the stone and it looks great and i cannot detect any defects from naked-eye. Since this is my aunt's close friend, i do not want to challenge her for too many questions. Is this a good deal/price?
I also wonder if i can tell the report matches the stone = does all the diamonds have identification label on the stone itself? i dont seemed to be able to see it even with the loupe.

Pls advise. Thanks

 

[valeria101]

Two cents...

One

Two: the big variation of girdle thickness indicates rather poor cut quality

The price seems in line with non-ideal cuts, no tremendous bargain. It is likely that some account of light return would add quite bit of value to this purchase. Not sure if that extra notch in color compensates for non-descript cut, but this is your choice to make. Did you ever see an ideal cut RBC for reference ?

Here's the virtual pedegree of such a stone, for example. And another...

And one more: 1cts G, SI1, $5.4k HCA Ex-Ex-Ex-Ex (unusual top rate)

I would love to see some simmilar tests done on your stone, but if light return ("sparkle") is not your priority, any round diamond would work out nicely, including the one you found... I guess.

 

[spellinbee]

hm... does it also makes the diamond looks smaller than it should be???

 

[phoenixgirl]

Your stone is not overly deep, so it will face up like the best cut one carat stones. 6.5 is around the diameter that you expect for a one carat stone.

However, the question is how well your stone returns light. Is it sparkly and firey, or is it dull and lifeless? The range in the girdle thickness indicate that the angles of the crown and pavilion (which affect brilliance) probably vary too much.

Don't let the fact that this is your aunt's friend keep you from asking important questions. To find out if this stone is well cut, see if the jeweler can do a sarin analysis on it. Or, at the very least, follow the links on this site to buy an "Ideal Scope" so that you can eyeball cut quality yourself.

Here are some comparable stones:
1.00 F SI1 great cut for $5345

1.00 F SI1 average cut for $4228

Stones that are 1.00 carats command a premium, so cutters will fudge and turn what would have been a great 0.94 carat stone into a compromised 1.00 carat stone. That may be what is "up" with your stone's girdle.