GIA grading for Cut?????

[wannabsure]

This may be a silly question, and I'm not sure if I'm just missing something. I notice the GIA certs do not refer to cut except in regards to the shape. Is the only way to tell by looking at proportions, table and depth % etc.? Or does GIA have a grading scale for cuts? If so, what are the scales, and what are the defining attributes of each scale?

I find when I go to see jewellers and they show my a few diamonds with the certs I start to get confused, and I'm hoping to make the process easier when looking. Does anyone have any hints, or does it just take a lot of practice?

I know that cut is the most important, but have found that translation is lost with jewellers when I say I want a good cut. Everyone seems to define the cut terms a little bit differently, thus only adding to my confusion.....

 

[oldminer]

You are right. GIA leaves off some very important data. Jewelers will attempt to avoid the issue, but the truth and the facts are well known and widely discussed. Search around and you will find out lots about proper diamond cutting.

 

[pricescope]

GIA abandoned ideal cut term in 1999 because their study shown many combinations of proportions can produce beautiful diamond. Now GIA is working on a new cut grading system.

Sometimes though it is possible to say when diamond is inferior cut by table and depth only. For example 62% depth and 60% table combination is most probably a poor cut. However, in most cases table and depth alone are not enough to evaluate the cut.

David, you posted while I was typing

 

[wannabsure]

AAAARGH!

So then can anyone offer some hints that I can keep in mind?

I'm not sure if its very good etiquette to take along a notebook and write down specs, and say "I'll get back to you", then come home and plug numbers into the computer.

When my jeweller asks what kind of cut am I looking for, what am I supposed to tell him to avoid confusion?

 

[wndrful]

How about telling him AGS000 ideal cut? I know, I know not all AGS000 are good but this could be a good first start.

Four simple points to eliminate really bad stones at a glance and not even bother to enter the info on the computer.

Depth:
Try to stick with depth of around 60% and try not to go over 62%. Otherwise most weight is added to the bottom.

Diameter:

When given two ideal cut diamonds of same weight to compare, look at the diameter. A diamond with 62% depth will be less in dia than 60% depth. Thus to 60% depth stone would look bigger and will be a little more expensive. In other words, shallower the better. But don't go below 59% (my two cents here)

Make sure max-min diameter is close to each other. For 3/4 carat to 1 1.2 the variation shouldn't be around 0.05mm or so. A well-cut diamond should be round not oval

Table: Stick to tables b/w 53-58. This would really make a difference in fire of the diamond.

In general well-cut stones will be in this specs. If you see something really off from these four checkpoints, then stay away. By doing this you will eliminate most not-well-cut GIA stones. After you short list, you can start working on the remaining few, get sarin information and plug it in HCA.


Hope this helps.

 

[Derek]

Don't worry about bringing a notebook along. If the jeweler is offended that you are doing your homework, then you probably don't want to be buying anything from him. A simple method that I have been using to get a rough estimate of overall quality is to compare carat weight to diameter. Example a 1.25 carat stone should be around 7 mm in diameter (I've seen as low as 6.5 mm and it wasn't pretty). Remember carat is a measure of weight not size.
I'm not going to buy based on this but it gives me a good idea of the general quality of the stones I'm being offered at a particular store. My theory being that since the cutter controls the final weight of a stone, if he cut a 7 mm stone to be 1.25 carats instead of 1.3 or greater, then it is probably of better quality. (See diamonds 101 on dirtcheapdiamonds.com for a chart)
You'll know that you have found a jeweler who knows diamonds when he asks you what size you are looking for, you respond with 7 mm and he brings out the appropriate stones. Most times I get furled brow responses, it's quite funny!

A bonus to bringing along your notebook is that typically the jeweler will ask to see what you have on your list. You'll be surprised when you get quoted much lower prices as compared to the numbers written on the paper the diamond was wrapped in. I'm most likely going to be buying my diamonds on the web though, much better prices and more avaiable information (and no tax).
Good luck!
-D