Sign in or Register Home
DiamondRing.comYour Online Jewelry Shopping Network
 Ideal Cut Diamond Studs at James Allen 
Buy Sell Education Forum Directory Blog  
View Recent Products View Posts Ask Us Ask our Network Jewelers for a quote on a diamond/gemstone/jewelry




 
Post Reply New Thread
 
Thread Tools Search this Thread
Old 1scorpion
 
My Profile
Registered User : offline
Joined: 12-23-06
Posts: 3
Years:
 
My Karma
Power: 0
Points: 10
1scorpion is on a distinguished road


Proportions vs cut grade
Quote this post and reply to it Post#1 @ 12-23-06 , 05:08 PM


I have a diamond which has all ideal proportions (table, length, crown angle, pavilion angle) except it has been rated by GIA as "very good" instead of "excellent". Using GIA's Facetware™ Cut Estimator I found the "lower half" value of my diamond to be causing the lower cut rating, all other values were well within "excellent" parameters. From my diamond learning experience I have never heard of "lower half" as being an important cut indicator, but GIA apparently thinks it's important. Should I be concerned about this? Does AGS look at "lower half"? Is my diamond really not ideally cut?

Diamond Search:

Carat:  to  Color:  to  Clarity:  to  


Old JohnQuixote

    JohnQuixote's Avatar
 
My Profile

Joined: 09-29-04
Posts: 124
Years:
 
My Karma
Power: 0
Points: 2158
JohnQuixote has a reputation beyond repute JohnQuixote has a reputation beyond repute JohnQuixote has a reputation beyond repute JohnQuixote has a reputation beyond repute JohnQuixote has a reputation beyond repute JohnQuixote has a reputation beyond repute JohnQuixote has a reputation beyond repute JohnQuixote has a reputation beyond repute JohnQuixote has a reputation beyond repute JohnQuixote has a reputation beyond repute JohnQuixote has a reputation beyond repute
Hits: Out=445, In=0


Re: proportions vs cut grade
Quote this post and reply to it Post#2 @ 12-23-06 , 07:41 PM


Quote:
Originally Posted by 1scorpion
I have a diamond which has all ideal proportions (table, length, crown angle, pavilion angle) except it has been rated by GIA as "very good" instead of "excellent". Using GIA's Facetware™ Cut Estimator I found the "lower half" value of my diamond to be causing the lower cut rating, all other values were well within "excellent" parameters. From my diamond learning experience I have never heard of "lower half" as being an important cut indicator, but GIA apparently thinks it's important. Should I be concerned about this? Does AGS look at "lower half"? Is my diamond really not ideally cut?


Hi Scorpion. I'd offer several comments. Most importantly: It sounds like you have the diamond in-hand, so you're the best authority on how it performs. Do you love it? If so, you can skip the rest of this post unless it interests you technically.

By "ideal proportions" you may mean the range of measurements AGS used from 1996-2005 as part of grading cut for rounds. Those numbers are still used in places, but AGS has moved to grading based on light performance so "ideal proportions" are a bit outdated. What's more, traditional AGS proportions grading did not take stars or lower halves into account, so your diamond may conform to the old "ideal proportions" range, but the lower half length could knock it down to VG with GIA. Frankly I wouldn't worry too much about the lower half number, unless it's extremely low or high. I've seen GIA VGs which perform at the top and GIA EX configurations that don't.

About lower halves: A round brilliant's lower halves do have great influence on the life and character of its performance, particularly if the diamond has good patterning.

Here is info on lower halves.

Cheers.

Last edited by JohnQuixote : 12-23-06 at 07:43 PM.
Old shopsc
 
My Profile

Joined: 11-15-06
Posts: 135
Years:
 
My Karma
Power: 0
Points: 10
shopsc is on a distinguished road


Re: proportions vs cut grade
Quote this post and reply to it Post#3 @ 12-26-06 , 11:39 PM


Quote:
Originally Posted by JohnQuixote
Hi Scorpion. I'd offer several comments. Most importantly: It sounds like you have the diamond in-hand, so you're the best authority on how it performs. Do you love it? If so, you can skip the rest of this post unless it interests you technically.

By "ideal proportions" you may mean the range of measurements AGS used from 1996-2005 as part of grading cut for rounds. Those numbers are still used in places, but AGS has moved to grading based on light performance so "ideal proportions" are a bit outdated. What's more, traditional AGS proportions grading did not take stars or lower halves into account, so your diamond may conform to the old "ideal proportions" range, but the lower half length could knock it down to VG with GIA. Frankly I wouldn't worry too much about the lower half number, unless it's extremely low or high. I've seen GIA VGs which perform at the top and GIA EX configurations that don't.

About lower halves: A round brilliant's lower halves do have great influence on the life and character of its performance, particularly if the diamond has good patterning.

Here is info on lower halves.

Cheers.


I guess I learned my something new today!

Read Messages in: DIAMONDS All forums
Newer:
Up a Topic Advice needed on Emerald cut by JerseyAlex
Up a Topic Join me in my freak out posted in Chit Chat by yogimel
Older:
Down a Topic She Said Yes by JAY13
Down a Topic What does ZEI mean posted in JEWELRY by Kimah5202
Thread Tools Search this Thread
Search this Thread:
 
Advanced Search

Contact Us - Guidelines - Privacy Policy - Refer a Friend - Top^


Google Custom Search

XHTML | CSS
Logged in as Unregistered
Powered by: vBulletin®
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright © 1998 - Present, DiamondRing.com. oHraDaco.
All times are GMT -4. The current time is 10:15 PM.
Validation #365a56e7.